[Paper: Oxide-cladding aluminum nitride photonic crystal slab: Design and investigation of material dispersion and fabrication induced disorder. Melo, EG; Carvalho, DO; Ferlauto, AS; Alvarado, MA; Carreno, MNP; Alayo, MI. Journal of Applied Physics 119, 023107 (2016). DOI: 10.1063/1.4939773.]
Designing structures to manipulate light
Photonic crystals are nanostructures capable of manipulating visible light and other forms of electromagnetic radiation by organizing its structure in periodic patterns.
In addition to the natural materials with these characteristics, such as opal, photonic crystals are man-made and are generally classified as metamaterials. Its characteristics (shape, size and composition) are designed to control light waves. Through nanofabrication processes these become tangible structures and are used in many “nanophotonic” devices. Nevertheless, producing these structures is by no means a simple task.
The authors of the article. From left to right, at the laboratory: Prof. Marcelo Nélson Paez Carreño, Emerson Gonçalves de Melo, Maria Elisia Armas Alvarado and Prof. Marco Isaías Alayo Chávez. At the insets: Daniel Orquiza de Carvalho (left), André Santarosa Ferlauto (right).
With a study based on computer simulations, a team of Brazilian scientists headed by researchers from the Polytechnic School of the University of São Paulo (EPUSP) presented scientific contributions that can be used to improve the production of photonic crystals to enhance their performance of manipulating light. According to Emerson Melo, the first author of a paper on the study that was recently published in the prestigious Journal of Applied Physics (JAP) “the work presents a detailed analysis of the effects caused by nanofabrication processes on the optical properties of planar photonic crystals produced on silicon dioxide-cladding aluminum nitride”.
“The idea emerged from the opportunity of combining the excellent optical and physical characteristics of aluminum nitride (AlN), such as transparency over a wide wavelength range (from the near infrared to the ultraviolet range), its non-linear effects, great stability and temperature variations, with the advantages provided by photonic crystals, such as the construction of high-efficiency waveguides, curves and resonant cavities in nanoscale dimensions, in addition to the various optical effects of photonic crystals, such as very low group velocity and low-intensity nonlinear effects of the materials”, adds Emerson, who is a doctoral student in Microelectronics – Photonics in EPUSP, within the Group of New materials and Devices of the Microelectronics Laboratory of the Department of Electronic Systems Engineering. Emerson`s doctoral research, whose advisor is Professor Marco Isaías Alayo Chávez, enquires into the study, production and characterization of nanophotonic devices such as waveguides, resonant cavities, optical modulators and switches in aluminum nitride photonic crystals.
The study that resulted in the paper published in the JAP began with an experimental stage. Thin films of aluminum nitride and silicon dioxide (SiO2) were manufactured by the EPUSP group, and with the research collaboration from UFMG and UNESP they were analyzed by the Variable Angle Spectroscopic Ellipsometry (VASE) technique to determine the dielectric functions, which was later used as the theoretical research data.
On the left, a diagram of a photonic crystal structure with some of the manufacturing defects studied. On the right, a diagram of the unit cell of the ideal photonic crystal designed by the scientists.
Then, the EPUSP group designed a photonic crystal, ideal in terms of performance and manufacturing possibilities, consisting of a layer of aluminum nitride between two silicon dioxide layers, with round holes arranged in a repeating pattern along the “sandwich” material. Using analytical and numerical methods, the USP researchers simulated some of the “side effects” of the photonic crystal manufacturing processes of this type (e.g., variations of size and location of holes) and theoretically analyzed how these imperfections affect the performance of the photonic crystal.
The theoretical research of Emerson and the other researchers of EPUSP focused on the imperfections generated in the two main stages of the nanofabrication process normally used in photonic crystals such as the one studied: electron-beam lithography and plasma-assisted dry etching. “The results presented allow to assess that the electron-beam lithography process has greater effect on the performance of devices that explore the dispersion of electromagnetic radiation through the photonic crystal, such as prisms, optical switches and modulators”, says Emerson. “However, the quality of the dry etching process has a more profound impact on the characteristics of devices into which linear or exact defects are introduced in the periodic network of the photonic crystal to insert harmonic modes within the photonic band gap. In this case, the dry etching has to be extremely well controlled for manufacturing the devices where waveguides and resonant cavities are among its main elements”.
In addition to making headway in understanding the role of nanofabrication processes of photonic crystals in the performance of nanophotonic devices, the authors of the paper were able to define a method to design planar photonic crystals with core and cover in thin film dielectric materials. “The methodology includes determining the dielectric function of the material by the spectroscopic ellipsometry technique to analyze the dispersion effects of the materials, determining the geometrical parameters that maximize the photonic band gap and the analysis of the impacts caused by deviations introduced in the manufacturing process”, explains Emerson.
The research received financial support from the National Council for Scientific and Technological Development (CNPq) and from the Financier of Studies and Projects (Finep).
The authors of the article. From left to right, at the laboratory:.
Brazilian Materials Research Society (SBPMat) newsletter News update from Brazil for the Materials community
English edition. Year 3, issue 2.
SBPMat news: XV Meeting - Campinas (SP), Sept 25-29, 2016
Plenary speakers: See who are the scientists who will give plenary lectures at our event and enthuse yourself. Here.
Exhibitors: The contact for companies interested in being exhibitors is comercial@sbpmat.org.br (Alexandre).
Symposia: The list of the approved symposia that will compose the event will be posted on the meeting website until March 7.
Important dates: Abstracts submission will be open until May 30. Notifications of accepted abstracts will be sent to the authors until July 10.
Venue: Visit the site of event and watch the video about the city of Campinas and the folder on the Expo D. Pedro convention center.
Organization: This edition of the event is chaired by UNICAMP Professors Ana Flávia Nogueira (Institute of Chemistry) and Mônica Alonso Cotta (Institute of Physics “Gleb Wataghin”). Find the members of the local committee here.
In an article published in Nanoscale, a group of Brazilian scientists and a researcher from Germany reported a “green” method for synthesizing nanoparticles made of a palladium and copper alloy. The authors also reported that the composition of the nanoalloy affects its ability to oxidize and reduce. The results can be used for more efficient nanomaterials design for various applications. See our story about the study.
People in the Materials community
Our interviewee in this issue is Professor Roberto Mendonça Faria (IFSC-USP). Passionate about unraveling mysteries of materials through scientific research, Faria made significant contributions to the study of ferroelectric polymers, electronic polymers and organic solar cells. Besides, Faria was SBPMat president, IFSC – USP director, and coordinator of two Brazilian national research institutes. In the interview, he told us about his scientific career, his achievements as president of SBPMat and his plans for the immediate future within our society and in the international IUMRS, where he is the second vice president. In a message to young people, Professor Faria stressed the importance of “manufacturing knowledge”. See our interview.
Brazilian scientist Ruth Kiminami, professor at DEMa-UFSCar, is included in the book “Sucessful Women Ceramic and Glass Scientists and Engineers – 100 Inspirational Profiles”published by Wiley. See book.
Former presidents of SBPMat Elson Longo and José Arana Varela are among 50 researchers working in Brazil with more citations according to Google Scholar. Find out more.
Special: Brazilian Multipurpose Reactor (RMB)
Several characterization instruments receiving neutron beams to interact with matter will comprise the Brazilian National Laboratory of Neutrons, which, after its inauguration, estimated for 2022, will be open to the scientific community day and night, 80% of the year. The neutrons beams will come from RMB, a research nuclear reactor of 30 MW, currently under development. The laboratory will be in Iperó (São Paulo State). See our report, with an interview with the coordinator of the project, José Augusto Perrotta.
Reading tips
Lithium superoxide stabilization opens possibilities of batteries with better performance (based on Nature paper). Here.
New nanosculpture method for fabrication of 1-2 nm crystalline structures using STEM (based on Small paper). Here.
In the market (or almost): metal didymium is obtained for the first time in Brazil, enabling the national production of super magnets. Here.
Events
5th International Conference on Surface Metrology.Póznan (Poland). April, 4 to 7, 2016. Site.
9th Brazilian-German Workshop on Applied Surface Science. Maresias, SP (Brazil). April, 10 to 15, 2016. Site.
43rd International Conference on Metallurgical Coatings and Thin Films (ICMCTF). San Diego (USA). April, 25 to 29, 2016. Site.
5th School of SAXS. Campinas, SP (Brazil). May, 2 to 6, 2016. Site.
40th WOCSDICE ‐ Workshop on Compound Semiconductor Devices and Integrated Circuits held in Europe & 13th EXMATEC ‐ Expert Evaluation and Control of Compound Semiconductor Materials and Technologies. Aveiro (Portugal). June, 6 to 10, 2016. Site.
Photonic Colloidal Nanostructures: Synthesis, Properties, and Applications (PCNSPA Conference 2016). Saint – Petersburg (Russia). June, 27 to July, 1, 2016. Site.
1st International Symposium on Advanced Photonic Materials. Saint – Petersburg (Russia). June, 27 to July, 1, 2016. Site.
XXV International Conference on Raman Spectroscopy (ICORS2016).Fortaleza, CE (Brazil). August, 14 to 19, 2016. Site.
XV Encontro da SBPMat. Campinas, SP (Brazil). September, 25 to 29, 2016. Site.
Aerospace Technology 2016. Stockholm (Sweden). October, 11 to 12, 2016. Site.
[Paper: Charge transfer effects on the chemical reactivity of PdxCu1−x nanoalloys. M. V. Castegnaro, A. Gorgeski, B. Balke, M. C. M. Alves and J. Morais. Nanoscale, 2016,8, 641-647. DOI: 10.1039/C5NR06685A]
Taming the reactivity of nanoalloys
When, in 2009, the Electron Spectroscopy Laboratory (LEe-) group of the Federal University of Rio Grande do Sul (UFRGS) decided to start developing in-house metal nanoparticles required for their studies, they came across some issues. Many synthesis methods reported in the literature did not provide the expected results when made in the Brazilian laboratory.
Authors of the paper. From the top left: Marcus Vinicius Castegnaro, Andreia Gorgeski, PhD Benjamin Balke, Prof. Maria do Carmo Martins Alves and Prof. Jonder Morais.
Strongly motivated by curiosity, as usual, says professor Jonder Morais, LEe- researcher, the group members were able, after much dedication, to develop new routes of synthesis that, in addition to being reproducible, are environment-friendly, efficient and cost-effective. “The first articles were published in international journals in 2013, initially with palladium (Pd), platinum (Pt) and silver (Ag) nanoparticles applied to the catalytic decomposition of nitric oxide. Subsequently, we published some works focused in “in situ” studies aimed at determining the mechanisms of formation and growth of monometallic nanoparticles. We have recently started reporting the results obtained with more complex systems, such as palladium and copper (Pd-Cu) nanoalloys,” states Professor Morais.
The latter group includes the results recently reported in an article published in the journal Nanoscale, whose main authors are Professor Jonder Morais and Marcus Vinicius Castegnaro, a physics doctoral student at UFRGS, advised by Morais. The research covered the entire process from the production of nanomaterials to the survey of their applications. “It was important to have dedicated students, willing to face the challenge of preparing accurately their own samples, and correlating the electronic and structural properties to understand the final properties in terms of chemical reactivity,” says Morais.
In the article published in Nanoscale, nanoparticles composed of palladium and copper alloys were produced by applying a simple method developed by the LEe- team. This process is carried out under mild conditions to the environment and health (aqueous, ambient temperature and pressure, and use of cheap and innocuous substances, such as ascorbic acid and sodium citrate). Several samples were synthesized by this route, containing three different amounts of palladium and copper atoms.
The synthesized nanoparticles have undergone a series of analyses conducted at UFRGS, in Porto Alegre (Rio Grande do Sul State), they traveled to Campinas (São Paulo State) for another series of analyses on equipment of the National Center for Research in Energy and Materials (CNPEM) and crossed the ocean to Johannes Gutenberg University, in Germany, for some additional measures. From characterization, the authors concluded that the nanoparticles were approximately 4 nm in size and were highly crystalline, among other characteristics. In addition, through experiments conducted by the XANES in situ technique, the team of scientists exposed the nanoparticles to carbon monoxide (CO) at 450 ° C and surveyed the reactivity of the nanoalloys, i.e., their ability to react chemically.
After studying the results of the characterization, the authors of the article were able to conclude that the alloy composition affects the ability of nanoalloys to reduce (gain electrons) and to oxidize (lose electrons). In fact, the greater the amount of palladium, the easier the reduction, and the harder the oxidation.
Representative scheme of the correlation between the partial charge transfer between the Pd and Cu atoms (observed by XPS), and the reactivity after exposure to CO (surveyed by XANES in situ) for Pdx¬Cu1-x nanoalloys. It was observed that the higher is the amount of Pd present in nanoalloys, the greater is the reactivity of the sample after CO reduction, and the greater is the oxidation resistance of the atoms comprising it.
“The published results, obtained by the association of several experimental techniques are relevant to an understanding of the origin of high catalytic reactivity of palladium and copper (Pd-Cu) nanoalloys, as well as to elucidating similar behavior of other bimetallic systems”, highlights Jonder Morais. “Mostly, these results can be used in the “design “of new nanomaterials more efficient for various applications, such as in the petrochemical industry, in fuel cells or in the control of greenhouse gas emissions,” he concludes.
At the end of September 2015, in the context of the XIV SBPMat Meeting, around 40 researchers of the Materials field participated in a symposium about the Brazilian Multipurpose Reactor (RMB), a project that has been developed by the Brazilian National Nuclear Energy Commission (CNEN) and that, when inaugurated in Iperó (SP), will add an important research tool to the current facilities that Brazil has.
As a matter of fact, the RMB will provide beams of neutrons that, when interacting with samples and with the mediation of several experimental techniques, will be able to provide unique information about the structure of the materials. For such, the RMB project envisions the construction of a series of laboratories with diffractometer equipment (of high resolution, of high intensity, Laue, of residual tension); small angle scattering; analysis of prompt gamma; triple-axis spectrometry and neutrongraphy, among other techniques. This research infrastructure must comprise a laboratory open to the scientific community and working day and night, more than 300 days a year: the Brazilian National Laboratory of Neutrons.
As indicated by its name, RMB will meet several goals. Besides providing beams of neutrons for scientific research, it will be used in irradiation tests of materials and fuels used in nuclear power plants for electricity generation and submarines propelled by nuclear reactors, for instance. The reactor will also have the important mission of producing radioisotopes and radioactive sources for health, industry, agriculture and environment, replacing imports and even generating exports.
Interview with the technical coordinator
To further explain the RMB project and, in particular, its applications in materials science and technology, we interviewed José Augusto Perrotta, technical coordinator of the RMB enterprise. Master in Nuclear Engineering by the Military Institute of Engineering (IME), and PhD in Nuclear Technology by the São Paulo University (USP), Perrotta works as technologist at CNEN since 1983.
SBPMat Newsletter: – Briefly comment about all the possibilities that the future RMB will offer to the materials science and technology community.In what way the beams of neutrons can be used for research and development in this area?
Production and research nucleus.
José Perrotta: – RMB is an enterprise that has as its core part a nuclear multipurpose research reactor and several laboratories to perform research, services and products.
The reactor was conceived with a high flow of neutrons to:
i. Produce radioisotopes in the quality and amount needed to Brazilian applications;
ii. Have the ability to irradiate and test nuclear fuels used in the several applications and irradiation conditions within the Brazilian nuclear program;
iii. Have the ability to irradiate materials with neutrons and check its performance under irradiation;
iv. Have the possibility to irradiate samples to perform a chemical analysis via activation of neutrons;
v. Extract beams of neutrons for research on materials structure in several application areas.
Regarding item (ii), the reactor is prepared to receive fuel samples and irradiation circuits that simulate the conditions of PWR reactors, that is, test fuels of the power reactors used or developed in the country.
Regarding item (iii), inside the reactor core there are two positions with high flow of neutrons for irradiations of materials. In these positions, samples can be placed in capsules with a controlled environment (temperature and medium of insertion of the sample). In these positions, samples of structural materials and samples of components of power reactors used in the country can be tested.
The reactor and the infrastructure of the reactor (pools, hot cells and transport shields) are designed to meet the two previous items (ii and iii).
A Post-Irradiation Analysis Laboratory is designed with hot cells and the entire infrastructure for mechanical, physical and microscopy analysis of the irradiated samples, both for the samples of irradiated fuels and for the structural materials.
Regarding item (iv), a laboratory of analysis by activation and radiochemistry is projected. The laboratory is connected to the reactor via pneumatic pipes that allow sending samples for irradiation in the reactor and bring them back to the laboratory for analysis. Several irradiation positions were defined in the reactor, varying the range of flow of neutrons in which the irradiations can be performed. The laboratory has hot cells to receive and handle the irradiated samples before their destination to the analysis equipment (radiochemistry or gamma spectrometry). The laboratory will be managed as a national laboratory, which will allow its use by the Brazilian scientific community.
Regarding item (v), the reactor is designed with a heavy water reflector tank that, mechanically, allows the extraction of beams of neutrons. These neutrons are thermal, and in order to obtain cold neutrons a small tank with deuterium at 19ºK (cold source) is designed. Thermal neutrons will be extracted in two positions and cold neutrons in two other. Each extraction tube may contain up to three neutrons guides. These guides will conduct the beam of neutrons for positions in a lobby of experiments at the building of the reactor, and in a building called neutron guides building. Scientific and technological equipment can be attached to the neutron guides for the analysis of the samples with the beam of neutrons. There is an additional thermal neutron extraction tube to make images with beam of neutrons (neutrongraphy). The experiments lobby in the reactor building and the guides building will form what we call “National Laboratory of Neutrons” (LNN).
SBPMat Newsletter: –Will there be experimental stations for Materials Science and Technology, analogous to the Brazilian Synchrotron Light Laboratory (LNLS)?Which ones?Will they be open to the entire scientific community?Will they operate constantly while the reactor is working?
José Perrotta: – The neutrons lines, as mentioned, are five: three with thermal neutrons and two with cold neutrons. Four of the lines can have up to three guides. In these guides, the experimental instruments (or stations) will be placed.
The following stations might be available since the beginning of the operation of the National Laboratory of Neutrons
i. Neutrons Guides Building.
For thermal neutrons: High Resolution Diffractometer; High Intensity Diffractometer; Laue Diffractometer; Residual Tension Diffractometer.
For cold neutrons: Small Angle Scattering; Prompt Gamma Analysis
The table shows the power of other research reactors worldwide. The Brazilian RMB will have a power of 30 MW. (Data provided by José Perrotta)
The RMB will bring to the country’s research community an important laboratory for utilization of neutrons beams. This laboratory, per its technical characteristics, is complementary to the Brazilian Synchrotron Light Laboratory (LNLS), which also has a large scale project, the Sirius. It is a proposal of the RMB enterprise that the National Laboratory of Neutrons is, like the LNLS, a national laboratory. This will facilitate the access of the Brazilian scientific society to the facility.
The functioning of the neutrons lines is related to the operation of the reactor. The reactor will operate 24 hours a day, in cycles of 25-28 days, in a way to achieve availability higher than 80% of the annual time (more than 300 days in full operation). The LNN can operate during all this time.
An important point is that the LNN will be operationally independent regarding the operation of the reactor, that is, the operation of the reactor offers the beam of neutrons and does not interfere in the operation of the LNN.
SBPMat Newsletter: –From the point of view of materials science and technology, which would be the advantages of the future RMB regarding the other reactors currently existing in Brazil?
José Perrotta: – Brazil has four research nuclear reactors in operation. The oldest one, and also the one with higher power (5 MW), is the IEA-R1 reactor from the Institute for Nuclear and Energy Research (IPEN) in São Paulo, which was unveiled in 1957. Other two low power research reactors, the IPR-R1 reactor of the Center for Nuclear Technology Development (CDTN) in Belo Horizonte (100 kW) and the Argonauta reactor of the Institute for Nuclear Engineering (IEN) in Rio de Janeiro (500 W) were built in the 1960s. These three reactors, of North-American designs, were built inside the university campusesof USP, UFMG and UFRJ, respectively, and originated the main nuclear research institutes of the Brazilian National Nuclear Energy Commission (CNEN), which developed themselves in proportion of the size of the reactors and their applications. These reactors and the CNEN institutes growing around them were essential in the development and use of nuclear technology that we have in the country today, and in the formation of the associated human resources. The fourth research nuclear reactor, the IPEN/MB-01 at IPEN, is an installation of the critical unit type (100 W) and was built in the 1980s, already with national technology, aiming towards the autonomous development of technology for power nuclear reactors.
The RMB reactor´s power is 30 MW and has modern design and conception. The reactors existing today in the country do not have flow of neutrons to ensure commercial operation or adequate characteristics for a high level research. In addition to being a more modern installation, the flow of neutrons of the RMB is one order of magnitude higher than the IEA-R1, and has functions that are not met by this reactor today. The other three reactors have really low flow of neutrons.
SBPMat Newsletter: – Could you estimate when the RMB and its research laboratories would be launched?
The RMB enterprise can be carried out in a period of 6 to 7 years. In the current stage of development, this would occur in 2022, if the full resources for the project are made available. It is important to highlight that, besides the need for intensive financial resources for its execution, the enterprise requires environmental and nuclear licenses for its construction and operation, since it has nuclear and radioactive facilities. This implies additional times for its implementation.
Funders and partners in the development of the RMB
The execution of the RMB project occurs under the responsibility of the Brazilian National Nuclear Energy Commission (CNEN).
The enterprise is coordinated by the Research and Development Directory of CNEN and developed by its research institutes: Nuclear Energy Research Institute (IPEN), Nuclear Engineering Institute (IEN), Nuclear Technology Development Center (CDTN), Northeast Regional Center of Nuclear Sciences (CRCN-NE) and Radiological Protection and Dosimetry Institute (IRD).
Throughout the stages of development of the RMB, CNEN counts and will count on partnerships, as well as contracts of national and foreign companies. Some of the partners participating so far: Brazilian Navy and the São Paulo State government, in the concession of the land where the RMB will be placed; the Brazilian Navy Technology Center in São Paulo (CTMSP); the cooperation of CNEN with the National Atomic Energy Commission (CNEA) from Argentina, which develops in Argentina the research nuclear reactor RA-10, similar to RMB. Contracted companies: Argentine company INVAP, which designed the Australian OPAL research reactor, and Brazilian company Intertechne have developed the basic engineering design of the enterprise.
With an estimated cost of US$500 million, the RMB is sponsored by the Brazilian Federal Government through the Brazilian Ministry of Science, Technology and Innovation (MCTI).
The interviewee of this edition of the newsletter of the Brazilian Materials Research Society Newsletter (SBPMat) is Professor Roberto Mendonça Faria, who has just handed over the SBPMat Presidency after four years in office (although he promises to remain active in the society).
Roberto Mendonça Faria was born in Adamantina, a small town on the west side of the State of São Paulo (Brazil), on May 1952. At the beginning of his secondary studies, already oriented towards “hard sciences” and stimulated by a great physics teacher, he started to look at science as a potential profession. In 1976, Faria concluded his bachelor’s degree in physics at the São Paulo University (USP).
In the same year, still passionate about physics, in which humanity was taking great steps towards knowledge, Faria began his academic career. He started teaching in undergraduate courses at USP and began his master´s course in physics at the same university. There, supervised by Professor Bernhard Gross, a pioneer in Materials research in Brazil, Faria learnt the pillars of scientific activity and developed a fascination for uncovering mysteries of materials (in this case, the conductivity induced via radiation in a polymer known as Teflon). Right after obtaining the master’s degree, in 1980, Faria began the doctorate course in physics at USP, once again having Professor Gross as supervisor. In 1984, Faria defended his dissertation about dielectric absorption and induced conductivity via radiation in the polymer PVDF.
In 1985, Faria started lecturing in postgraduate courses at USP. Between 1987 and 1989, he stayed in France on a post-doctorate internship at Université Montpellier 2. In 1990, he obtained the Associate Professor title at USP after defending a thesis about phase transitions in ferroelectric copolymers. In 1999, he became Full Professor of the São Carlos Institute of Physics (IFSC) at USP, where he occupied several management positions throughout the years, such as the head of the Department of Physics and Materials Science (1994-1996), the coordination of the postgraduate program in physics (1997-1998) and the IFSC general direction (2002-2006).
Roberto Faria also was the coordinator of two large scale projects at a national level. The first project was the “Multidisciplinary Millennium Institute of Polymeric Materials”, one of 17 projects selected within the program “Institutes of the Millennium” of the Brazilian Ministry of Science, Technology and Innovation (MCT). This institute gathered around 140 researchers from 17 institutions from Brazil’s five regions, and existed between 2002 and 2008. The second project continued one of the research focuses of the first one – the study of electronic polymers and their applications. Starting in 2009, the Brazilian National Institute for Organic Electronics was approved and established in the context of the Brazilian National Institutes of Science and Technology (INCTs) from the MCT.
Going beyond the frontiers of his scientific area, Faria was the coordinator, between 2010 and 2014, of the São Carlos pole of the Institute of Advanced Studies (IEA) at USP, an organization intended for broad and interdisciplinary research and discussion of fundamental issues on science and culture. In addition, in the context of his interest in contributing with the economical development of his country through research, Faria coordinated the making of the book “Science, technology and innovation for a competitive Brazil”, published in 2012.
In the last few years, Faria has been having an active participation in international scientific entities in the Materials area. In 2014, he was one of the general coordinators of the “Spring Meeting of the European Material Research Society – 2014”, which took place in the French city of Lille. In 2015, he was elected second vice-president of the International Union of Materials Research Societies (IUMRS).
Faria is a member of the Academy of Sciences of the State of São Paulo and the Brazilian Academy of Sciences and belongs to the editorial board of the journal “Materials Science – Poland”. In 40 years of scientific research on polymeric materials, particularly those with electronic activity and their applications in devices, Professor Faria has produced around 180 articles published in indexed journals, having about 2,000 references, and has supervised 47 master´ss and doctorate thesis.
An interview with the researcher follows below.
SBPMat Newsletter: – Tell us what made you become a scientist and work in the field of Materials.
Roberto Mendonça Faria: – Before High School, I imagined I was going to follow my studies in the “hard sciences” area (engineering, physics, chemistry, mathematics, etc.). But I didn’t have any intention to follow a scientific career, even less so to be a scientist. However, in the first year of High School I started to change my mind, stimulated by an excellent physics teacher, Roberto Stark. I graduated in Physics and soon after I was lucky to be supervised by two great masters: Professor Bernhard Gross and Professor Guilherme Fontes Leal Ferreira. As any newly-graduated person in physics at the time, I was passionate about the extraordinary experimental and theoretical advances of the 20th century physics. However, my first research study was about an apparently modest theme: the interaction of ionizing radiation with thin films of insulating polymers. Under the supervision of Professor Gross, I definitely learnt how to approach a scientific issue and also how to handle the methodological strictness needed to discover the effects and the phenomena arising from the experiments performed. Those first years of research were crucially important to my career. I never again lost the fascination in discovering the properties and the enigmas of the condensed matter, and I’m happy because materials science and engineering is extremely important for the development of Brazil.
SBPMat Newsletter: – In your assessment, which are your main contributions to the field of Materials?
Roberto Mendonça Faria: – There are different ways to measure the contributions made to the advance of scientific and technological knowledge. The most objective and internationally followed view is the bibliometric, conduced by the Journal of Citation Reports (JCR) from Thomson Reuters. This metric has many merits, but it’s too much focused on numbers. Another fact influencing scientific assessments comes from the pragmatism of the present world. Today, it is required that scientific works aim at specific applications. In this context, researches involving more fundamental studies tend to lose the visibility they deserve. That is, many times scientific works of great value have little mentions. An analysis of my production from JCR may lead to the conclusion that my most relevant contributions are connected to applications, but I particularly believe that my greatest contributions are more related to fundamental works in the areas of phase transitions of ferroelectric polymers and electrical transportation mechanisms in electronic polymers.
One of the interesting areas I have been working on in the last few years is the organic solar cells. I believe that, with my research group, we gave a significant contribution to the understanding of phenomena involving the transportation of electrical carriers inside the cell. Since 2013 we published two works where we developed an analytical equation which rules the electrical current curve in function of the voltage of a solar cell when under lighting. This analytical equation works very well in special cases and has explained many of the optoelectronic effects of the devices we built and measured in our laboratories. One of the works was published in the Applied Physics Letters journal in 2013, and the other was published on Solar Energy Materials and Solar Cells in 2015.
On the other hand, I always dedicated myself to assembling research laboratories and forming human resources. I also have been contributing with several post-graduation programs, directly and indirectly, and for more than 20 years I have been dedicating myself to strengthening the area of Organic Electronics in the country, especially in the formation of a research network in this area: the National Institute of Science and Technology of Organic Electronics. Whenever possible, I try to encourage projects in partnership with private enterprises and research institutes that aim towards applied projects. In the public policies area, I believe my greatest participation was coordinating a document from CAPES (the Brazilian agency in charge of post-graduate programs) and SBPC (Brazilian Society for the Advancement of Science), called “Science, technology and innovation for a competitive Brazil”, which has contributed to the creation of the Brazilian Company of Industrial Research and Innovation (EMBRAPII).
SBPMat Newsletter: – You have just finished your tenure as President of SBPMat. Share with our readers an analysis of the results achieved by the boards you have headed during the last four years.
Roberto Mendonça Faria: – SBPMat is a relatively new society, but it has an important mission to fulfill for the development of the country. Brazil has an extraordinary richness offered to it by nature. However, the country does not take advantage of this richness because it places little knowledge over its natural resources. There was a revolution in agriculture after the country decided to put knowledge over this blessing that nature has offered to it. Today, agribusiness is one of the pillars, perhaps the strongest one, of our economy. We have to do the same with the raw matters that abound in our territory. The publication “Science Impact – A special report on materials science in Brazil”, in partnership with the Institute of Physics (IOP), was one of the projects that worked and gratified me very much. This type of initiative helps raising awareness that Brazil has a natural gift to be a leader in several materials-related segments and to generate a lot more richness than it currently does.
Another valuable contribution that the two previous SBPMat administrations gave to materials science and engineering in Brazil was the definite consolidation and internationalization of the annual meeting, which always take place at the end of September.
I must highlight that the creation of the bilingual electronic newsletter was a realization that worked, especially because of the capability it has been produced with.
SBPMat Newsletter: – You just took over, for two years, the second vice-presidency of IUMRS. Talk about your plans, expectations…
Roberto Mendonça Faria: – I’m starting this activity. My plans are, first of all, to increasingly insert the Brazilian Materials Science in the international scenario. At the same time, I intend to use the IUMRS support to stimulate materials research in other Latin American countries. Brazil and Latin America have many problems that come from their still deficient economies. I have conviction that research studies in the materials area are valuable instruments to improve the living conditions of these populations. Today, as a member of the SBPMat council, I want to take this discussion not only in Brazil, but in several Latin American countries with the help from IUMRS.
SBPMat Newsletter: – Leave a message for the readers that are starting their scientific careers.
Roberto Mendonça Faria: – I decided to register here that one of the fulfillments (still in progress) that makes our administration proud was the creation of the University Chapters program. I’m going to ask the council to allow me to work with Professor Rodrigo F. Bianchi within this program. I have no doubts that the more researchers we form, the more Brazil will gain with this.
I believe that the work with young people starting scientific activity is one of the most valuable works for a senior researcher. It is our duty to show young people how important the work of “manufacturing knowledge” is for the country, especially in scientific and technological areas. There isn’t one example of a country that has eradicated poverty without the development of strong education and competitive science and technology. Therefore, the message to young people is: believe in your work and always try to make it in the most competent way possible.
Brazilian Materials Research Society (SBPMat) newsletter News update from Brazil for the Materials community
English edition. Year 3, issue 1.
SBPMat news: XV Meeting - Campinas (SP), Sept 25-29, 2016
Simposia: Symposia proposals on subjects of Materials Science and Technology can be submitted up to February 11 (extended deadline). The submission is open to the international scientific community. Read more.
Venue: Visit the site of event and watch the video about the city of Campinas and the folder on the Expo D. Pedro convention center.
Organization: This edition of the event is chaired by UNICAMP Professors Ana Flávia Nogueira (Institute of Chemistry) and Mônica Alonso Cotta (Institute of Physics “Gleb Wataghin”). Find the members of the local committee here.
Featured paper
The performance of organic solar cells, devices that are able to produce electricity from sunlight, can now be assessed more accurately thanks to research entirely conducted at the São Carlos Institute of Physics of the University of São Paulo (IFSC-USP). The study included a series of experiments and the development of an analytical model, and led to the publication of a paper on the journal Solar Energy Materials and Solar Cells. Read our story about the study.
People in the Materials community
We interviewed Osvaldo Novais de Oliveira Junior, Professor at the São Carlos Institute of Physics (USP), who took office as SBPMat’s president on last Friday. We discussed his life history, career and plans for SBPMat. Osvaldo Novais does not belong to the group of people who discover early a professional vocation, but this has not impede the developing a scientific career with great results, such as an H index of 53. Passionate about knowledge, he made important contributions to the field of Materials, particularly for the study and application of Langmuir films and the development of electronic tongues, in addition to participating in the creation of the first software for grammar revision in Portuguese, as well as studying and promoting how to write good papers in English. In his message to the youth, the scientist stressed the importance of language proficiency (Portuguese, English, Mathematics) as base for lifelong learning. Read our interview.
Edgar D. Zanotto and Victor C. Pandolfelli, both Full Professors of the Materials Engineering Department at the Federal University of São Carlos (UFSCar), received special honors from the Rector,Professor Targino de Araújo Filho, at the closing ceremony of UFSCar’s 45th anniversary celebrations.
Reading tips
Borophene, a two-dimensional metallic, conductive material made of boron atoms (based on Science paper). Here.
Strange, but real: structures that expand volumetrically, both when streched and compressed (based on paper on Nature Materials, section “News and Views”). Here.
Healthcare materials: responding to UV light stimulus, hydrogel capsules can release RNA “on demand” (based on Advance Healthcare Materials paper).Here.
Opportunities
Postdoctoral fellowship in confocal microscopy and cell membrane models. Here.
Events
5th International Conference on Surface Metrology.Póznan (Poland). April, 4 to 7, 2016. Site.
43rd International Conference on Metallurgical Coatings and Thin Films (ICMCTF). San Diego (USA). April, 25 to 29, 2016. Site.
9th Brazilian-German Workshop on Applied Surface Science. Maresias, SP (Brazil). April, 10 to 15, 2016. Site.
40th WOCSDICE ‐ Workshop on Compound Semiconductor Devices and Integrated Circuits held in Europe & 13th EXMATEC ‐ Expert Evaluation and Control of Compound Semiconductor Materials and Technologies. Aveiro (Portugal). June, 6 to 10, 2016. Site.
Photonic Colloidal Nanostructures: Synthesis, Properties, and Applications (PCNSPA Conference 2016). Saint Petersburg (Russia). June, 27 to July, 1, 2016. Site.
XXV International Conference on Raman Spectroscopy (ICORS2016).Fortaleza, CE (Brazil). August, 14 to 19, 2016. Site.
XV Encontro da SBPMat. Campinas, SP (Brazil). September, 25 to 29, 2016. Site.
Aerospace Technology 2016. Stockholm (Sweden). October, 11 to 12, 2016. Site.
[Paper: Influence of charge carriers mobility and lifetime on the performance of bulk heterojunction organic solar cells. D.J. Coutinho, G.C. Faria, D.T. Balogh, R.M. Faria. Solar Energy Materials and Solar Cells, Volume 143, Pages 503-509 (December 2015). DOI:10.1016/j.solmat.2015.07.047]
Analytical contribution to sustainable energy
A scientific study entirely conducted at the São Carlos Institute of Physics from the University of São Paulo (IFSC-USP) has made significant contribution to the assessment of performance of organic solar cells, devices that are able to produce electricity from sunlight – a renewable, clean, safe and practically inexhaustible source of energy. The results of this piece of research were recently published on the journal Solar Energy Materials & Solar Cells, which has an impact factor of 5.337.
Composition of the bulk-heterojunction organic solar cell used in the experiments reported in the paper. In the active layer, the configuration of the electron acceptor (Blue) and donor (Red) materials.
With a structure comparable to a sandwich, the organic solar cell is comprised of layers of nanometric thickness, made of several materials that execute specific functions in the device.
The so-called “active layer”, the one responsible for the main stages of transforming light (flow of photons) into electric current (flow of electrically charged particles), is made of semiconducting organic materials (whose molecules have carbon atoms). In the electronic band structure of traditional semiconductors, electrons located in the so-called “valence band” jump from their state when they absorb photons, leaving vacant spaces, or holes, and occupying new places in the so-called “conduction band”. In organic semiconductors, the mechanism that produces the electron-hole pairs is similar, with the difference that, instead of a direct transition from one band to the other, there is a molecular exciton (a system containing one negative charge, and one positive charge), which is easily dissociated, producing free charges (electrons and holes).
For the next stage in the conversion of light into electricity to occur, the active layer of the organic solar cells must have many interface regions between two types of materials: the donor and the acceptor of electrons (usually an electronic polymer and a fullerene derivative, respectively). If the exciton, in its few picoseconds of existence, manages to reach an interface region, the forces keeping the electron and the hole together are broken, so the donation of the electron from the polymer to the fullerene happens. At this moment, if no traps are on the way to prevent their movement, electrons and holes flow in opposite directions, attracted and collected by electrode elements, producing an electric current that can be used in an external circuit.
In this succession of stages, efficiency losses in the conversion of solar energy into electrical energy may happen due to several factors. One example is the recombination of electrons and holes after the dissociation of the exciton, which prevents these charge carriers to flow freely. Other examples include defects or impurities in active layer materials, which act as traps for the charge carriers, decreasing their mobility.
The paper published on Solar Energy Materials and Solar Cells reports the results of a series of experiments conducted for the purpose of studying, in detail, the mobility and lifetime of charge carriers (electrons and holes), as a function of temperature, in a bulk-heterojunction organic solar cell produced at IFSC. In this kind of device, the electron donor and acceptor materials coexist in a particular configuration (a nanometric film with a dual-phase structure) that increases the interface area between the two, compared to other possible configurations.
The authors also presented in the paper the results of electric current measurements, based on external applied voltage (J-V) under lighting – one of the most relevant experiments in the characterization of solar cells. In fact, this experiment is necessary for assessing the efficiency of a solar cell.
Organic solar cell during electrical characterization under artificial lighting equivalent to sunlight. In the prototype pictured above, on a 5 x 5 cm plate, five devices are connected in series, producing a total of approximately 2V. The individual efficiency of each device studied is around 4%.
In order to adjust and analyze the experimental results, the authors developed a model, based on a set of equations. This model filled a gap in the scientific literature as, up to its release, these analyses were made from approximations, being inaccurate, or using numerical methods, which require hard time-consuming work.
“To this day, there is no formal description of the J-V curve”, says Roberto Mendonça Faria, full professor at IFSC-USP and corresponding author of the paper. “Our research had the merit of developing a J-V analytical expression, which successfully reproduces the characteristics of an organic solar cell in the event the positive and negative carriers have equal mobility”, he points out. With this expression, he adds, it is possible to carry out a more precise assessment of the cells performance, even for cases in which the electrons and holes do not have the exact same mobility.
Left side: Roberto Mendonça Faria corresponding author of the paper). Right side: Douglas José Coutinho (first author).
The paper also features all the analyses the team managed to do from the experimental results and the model, mainly in regard to some factors leading to efficiency loss in the conversion of light into electricity.
This way, the authors of the paper made a contribution to the challenge of producing sustainable energy. “Energy production is crucial for humanity to keep its economic and social development, but it cannot go on with its terrible side effects, polluting the planet and contributing to global warming”, says Faria.
The results reported in the paper comprise the Master’s and Doctoral studies of Douglas José Coutinho, advised by Professor Faria and financed by Brazilian research funding agencies, FAPESP (São Paulo Research Foundation) and CNPq (National Council for Scientific and Technological Development), including through the CNPq National Institute of Science and Technology for Organic Electronics (INEO).
On January 29, 2016, in the city of Campinas (São Paulo State, Brazil), Osvaldo Novais de Oliveira Junior took office in the new executive board of the Brazilian Materials Research Society (SBPMat), acting as president. Novais is a professor of the São Carlos Institute of Physics (IFSC) at the University of São Paulo (USP). He has been a researcher in the field of Materials for 35 years, during which time he has published over 460 articles in indexed journals, 7 patents and 16 book chapters, among other publications. In total, the scientific production of professor Osvaldo has received, so far, over 8,500 citations according to Web of Science (index h=46) and 12,100 (h = 53) according to Google Scholar.
Osvaldo Novais de Oliveira Jr. was born on August 13, 1960 in Barretos, a city of the northern part of the State of São Paulo that, at that time, had approximately 60,000 inhabitants. When he was a teenager, he received the nickname of Chu, which accompanies him to this day, being also part of his professional electronic address.
He began his university studies in the Educational Foundation of Barretos. In 1980, while he was attending courses to obtain a teaching degree in Physics, he transferred to IFSC/USP to pursue a Bachelor degree in Physics, and started to work in research projects in the Electrets Group, nowadays referred to as Polymers Group “Bernhard Gross”. Within such group he began his master’s degree in 1983, supervised by professor Guilherme Fontes Leal Ferreira, obtaining in 1984 the title of Master in Applied Physics. In the following year he began to teach courses in the Bachelor Degree in Physics at USP São Carlos and continued developing research activities in the Polymers Group.
In 1986, he moved from São Carlos to the Welsh city of Bangor, United Kingdom, for doctoral degree studies in the University of Wales – nowadays Bangor University. In 1990, he obtained the title of Doctor in Electronic Engineering by defending his doctoral dissertation concerning electrical properties of Langmuir films, supervised by professor David Martin Taylor.
Back to Brazil in 1991, he added to his teaching activities at USP São Carlos, some classes in the graduation courses in Applied Physics. In 1993, he was named associate professor in that university.
In the same year, he conducted his first academic research works in natural language processing, an area that basically deals with problems related to automatic generation and understanding of texts by means of computers. Professor Osvaldo Novais was part of the team that founded the Interinstitutional Center for Computational Linguistics (NILC) and participated in the development of the first software for grammar revision of Brazilian Portuguese, which was named “ReGra”. The grammar checker was part of several versions of Microsoft Word processor as from 1999. From the work in NILC and scientific writing courses, he produced a book, together with more 7 authors, on scientific writing in English (“Writing Scientific Papers in English Successfully: Your Complete Roadmap”).
Osvaldo Novais was a visiting researcher in the University of Massachusetts Lowell (UMass Lowell), in the United States, between 2000 and 2001, and a visiting professor of University of Aveiro (Portugal) in 2006. Also in such year, he received Scopus Award, granted by Elsevier do Brasil and Capes (the Brazilian agency in charge of post-graduate programs), as one of the 16 Brazilian researchers with greatest scientific production, based on the number of publications, citations and supervisions (nowadays, there are 40 completed master theses and doctoral dissertations).
In 2008, he became a full professor of USP.
Nowadays, in addition to his activities as professor and researcher in IFSC-USP, Prof. Osvaldo Novais is a member of the coordination in Physics at FAPESP (the São Paulo research foundation), regional editor for South America of “Display and Imaging” scientific journal and associate editor of “Journal of Nanoscience and Nanotechnology”.
Here you find an interview with the researcher.
SBPMat Newsletter: – Tell us what made you become a researcher and work in the field of Materials.
Osvaldo Novais: – My professional choices almost always occurred without planning or specific motivation. I began the course for obtaining a teaching degree in Sciences in the Educational Foundation of Barretos, since I did not pass the entrance examination for being admitted in the Electronic Engineering graduation course, which I thought was the career I would like to have. After having decided to change area at the end of the first year and to do the entrance examinations for Philosophy and Psychology courses, for financial and personal reasons, I ended up continuing in the Sciences course and chose a teaching degree in Physics in the third year. There was a major transformation when I transferred to the Bachelor degree in Physics in USP São Carlos, and started participating in research projects. There I decided to become a teacher and researcher. My choice for the area of polymers was the result of a suggestion from a friend, who had great admiration for the faculty members of the Electrets Group at that time. Thus, I began doing research activities in such group, nowadays called Polymers Group “Bernhard Gross”, where I have been for 35 years.
Although I have not chosen a career or a research area due to a vocation or conviction, I was very fortunate because I consider the study of materials both fascinating and essential for society. Researchers in materials may amuse themselves with challenges and contribute to make this world a better place. Research training also allowed me to act in different areas, which is an important factor for those passionate for knowledge, as it is my case.
SBPMat Newsletter: – What are, in your own assessment, your main contributions to the field of Materials?
Osvaldo Novais: – I believe my greatest contribution was to have participated in the construction of a network of research in materials, mainly in nanostructured organic films. Such network nowadays comprehends researchers in many regions of Brazil, and also includes international connections. Concerning specific scientific contributions, I could possibly point out the study of electrical properties of Langmuir films, as well as the use of such films as cell membrane models. It could also be worth to point out sensors (such as electronic languages) and biosensors produced with nanostructured films, noting that the main actors of such contributions have been students and doctoral candidates of my research group.
SBPMat Newsletter: – In parallel to your performance in Materials research, you develop studies concerning natural language processing within NILC, center of which you are founding member. Tell us a little bit about this activity.
Osvaldo Novais: – Out of need, I ended up becoming interested in scientific writing in English, in a work that was, at first, informal and that resulted in projects of software tools for writing aid. Being invited to participate in the team that developed the first grammar checker for Portuguese in the 1990s, NILC was created, which to this date is a reference worldwide for Portuguese language automatic processing. I say that without any embarrassment whatsoever, since all merits for this achievement go to a team of computer scientists and linguists, of several universities of Brazil, who have been conducting research and development of the highest level for years. My participation was merely important in the beginning.
For two decades, my research in natural language processing with NILC was fully disconnected from Physics, but in the last years we have used statistical physics methodologies for text treatment. With the new research paradigm based on intensive use of data (called “Big Data”), now there is the possibility of combining nanotechnology – an area that is predominantly of materials – with natural language processing and artificial intelligence, for example, in the diagnosis systems supported by computer. This is a fascinating topic that allows exercising technological convergence, which will boost research and development in the 21st century.
SBPMat Newsletter: – Briefly tell us what are your plans for SBPMat while president of the society within 2016-2018.
Osvaldo Novais: – I believe that the most relevant plan is to continue the excellent work that the previous executive boards have carried out, which made SBPMat be one of the most powerful scientific societies in Brazil. That includes keeping the excellent level of our annual meetings and strengthening the international insertion that it has achieved. Other goals of the new executive board are: to increase the interaction of materials researchers with the industries installed in Brazil, to encourage the participation of young researchers in the society and to promote scientific and technological popularization programs, emphasizing the key role of research in materials for technological and social development.
SBPMat Newsletter: – We always invite the interviewees of this newsletter section to leave a message for the readers who are beginning their scientific careers. Would you like to say something in particular for the future/ junior scientists?
Osvaldo Novais: – My message is: apply yourself and strive towards obtaining strong scientific training, focusing on languages of knowledge, whatever the natural languages (in our case, Portuguese and English) and languages of mathematical formalisms. Such strong training will allow you to continuously learn, which is essential in an ever-changing society. May you follow your dreams by solving scientific and technological problems, which is one of the most amusing and refreshing activities.
