Today, we will discover his fascinating journey in the field of scientific research, the motivations that led him to explore the universe of nanomaterials, and how cutting-edge technology contributes to remarkable discoveries in this domain. Cosmin will share key moments from his career, innovative research projects, and offer valuable advice for young people aspiring to a career in science.
• Can you tell us more about yourself and how you began your journey in scientific research?
I am Cosmin Romanițan, currently a Scientific Researcher, Grade II, at the National Institute for Research and Development in Microtechnology (IMT), where I am responsible for the raze Rigaku SmartLab X-ray diffraction equipment in the institute. My primary activity involves studying the crystal structure of nanomaterials using X-ray techniques such as X-ray diffraction (XRD), X-ray reflectivity (XRR), and small-angle X-ray scattering (SAXS). I completed my studies at the Faculty of Physics, followed by master’s and doctoral studies, and my doctoral thesis, defended at the Condensed Matter Physics Department, is titled “Non-destructive Investigation of Stress in Nanomaterials Using X-ray Methods.” My first encounter with scientific research took place in the second year of my undergraduate studies at the Elementary Particle Physics Department, IFIN-HH, where I started obtaining the first data and results for my thesis.
• What inspired you to follow this field, and what motivates you to continue?
Since my high school years, I was fascinated by the “world that cannot be seen,” and I was very curious about what lies beyond the macroscopic world. Therefore, in the early years of university, I was drawn to fundamental physics, and my studies for my bachelor’s thesis focused on the theoretical simulation of proton-proton collisions at 14 GeV using simulation software. Later, I had the opportunity to explore experimental physics through X-ray diffraction for studying nanomaterials. I was fascinated that the results obtained for the investigated nanomaterials correlated with their physical properties or the performance of devices, which convinced me to continue in this field without hesitation. Furthermore, I am motivated to keep moving forward because of the broad spectrum of new applications that continue to emerge year by year in the field of nanotechnology, and the new challenges associated with highlighting the crystalline structure of new materials for various applications. This type of activity also fits very well with my personality and lifestyle, as it constantly offers me the chance to meet new people and places through participation in various schools, workshops, conferences, and training programs.
• Can you name some of the research projects you have participated in?
Some of the research projects I have been involved in focused on developing new heterostructures based on low-dimensional nanomaterials to improve the performance of energy storage/conversion in supercapacitors. I have also participated in projects aimed at developing III-V materials for high-efficiency solar cells by modifying their electronic structure using dopants or stress. Other projects in which I participated aimed to develop new materials in the context of ferroelectrics, gas sensors, or aromatic hydrocarbons.
• What was the initial context of your projects? What were your main objectives?
Specifically, my research activities focused on investigating the microstructure of epitaxial III-V films with thicknesses on the order of tens or hundreds of nanometers, nanostructured materials such as porous materials or nanowires, metal oxides, or carbon-based materials. My main objective was to highlight the crystalline structure of the materials investigated and to develop new methods and theoretical frameworks to obtain new information about the structure of nanomaterials, beyond the standard methods used in most scientific articles. Additionally, my main goal was to correlate microstructural parameters with the functionality of the developed nanomaterials in order to optimize synthesis processes.
• What were the main technical or scientific challenges you encountered in your projects?
Throughout my research, technical challenges were related to finding the most suitable experimental configuration to obtain diffraction signals with resolutions as close as possible to the theoretical ones. We aimed to develop new methods for the non-destructive study of stress distribution in dense nanowire systems, the degree of porosity in high-surface-area porous materials, or crystalline imperfections in epitaxial materials. On the other hand, scientific challenges involved developing an appropriate theoretical framework to explain the experimental results obtained through X-ray diffraction.
• How has technology influenced the results obtained?
Since the intensity of the diffracted X-rays and the resolution used are central elements in extracting new information, technology has played a decisive role in the development of new study methods for nanomaterials, ranging from epitaxial films with micron-scale thicknesses to porous materials or dense nanowire matrices. The use of appropriate monochromators led to high-precision studies in thin films with thicknesses of 20-30 nm, even in the laboratory. In particular, studies on the distribution of microstructural parameters along the growth direction require multiple degrees of freedom for the source, goniometer, or detector, which involves special technical features for diffraction equipment.
• Can you provide a concrete example/presentation of a study/research?
I would like to describe a recent study conducted on epitaxial indium nitride (InN) films grown on GaN/Al2O3 substrates by molecular beam epitaxy (MBE), in collaboration with the Institute for NanoScience and Engineering at the University of Arkansas, USA. This study focused on obtaining InN with a reduced electron concentration on the surface by controlled nanostructuring of the surface. Epitaxial growth by MBE was performed at different In/N fluxes and growth temperatures to modify surface characteristics. By using Rigaku equipment, we overcame certain limitations regarding the weak signal obtained on (100) planes in wurtzite materials with standard 1.6 or 3 kW equipment without a rotating anode. By obtaining an appropriate diffraction signal, even in films with a thickness of 50 nm, we were able to determine the main microstructural parameters of the grown films, such as the lattice constant, crystalline block size, and stress at the film-substrate interface. Moreover, by obtaining a large signal in high-resolution configurations, we conducted X-ray reflectivity studies in triple-axis configuration to accurately determine the total reflection angle, in order to calculate porosity and the S/V ratio in the investigated materials. The results obtained are featured in the article Electron Accumulation Tuning by Surface-to-Volume Scaling of Nanostructured InN Grown on GaN(001) for Narrow-Bandgap Optoelectronics in the ACS Applied Nano Materials journal, highlighting the decisive role of surface nanostructuring in low-bandgap optoelectronics.
• Is there a discovery or specific progress within your projects that you feel you would not have been able to achieve without this equipment?
The multitude of degrees of freedom in the goniometer had a decisive impact on my studies. The “asymmetric skew” configuration, which allows the modification of the X-ray penetration depth in the material by varying the incidence angle, while simultaneously tilting the sample, led to innovative studies in the nanotechnology field. This configuration allowed for a systematic study of the distribution of the microstructure of gallium nitride grown on an Al2O3 substrate. I proposed a formalism for investigating the distribution of dislocation densities in nitrides, with final results currently in the process of publication. Additionally, this configuration allowed for obtaining important results that contributed to the development of new theoretical frameworks for assessing porosity distribution and stress relaxation processes in porous materials and nanowires. The remarkable results obtained through this configuration have been published in the prestigious Journal of Applied Crystallography and the American journal Spectroscopy. Fortunately, these studies would not have been possible without the “asymmetric skew” configuration provided by Rigaku equipment.
• From a technical standpoint, what features of Rigaku equipment did you find most innovative or useful?
From a technical perspective, I believe that the 9 kW rotating anode and the multitude of degrees of freedom are the innovative elements that can make a difference compared to other X-ray diffraction equipment. Additionally, the in-plane arm for pole figures is very useful for advanced texture studies of materials. It should be noted that without a high-power X-ray tube, it would be necessary to write a proposal to benefit from synchrotron radiation for studies involving thin films with thicknesses under 50 nm.
• Did you encounter challenges in the learning process and use of this equipment? If so, how did you overcome them?
I encountered various challenges in using new configurations, but participating in workshops organized by Rigaku and conferences, as well as discussions with other researchers with similar scientific interests, helped me make significant progress in overcoming those challenges at that time.
• What advice would you give to a student choosing to attend the same university you did?
I would encourage all students to follow their initial goals when enrolling in university and “not to get lost along the way” when other temptations arise, such as easily accessible jobs without completing their studies. One thing I didn’t know at the beginning of my university years is that research is a mix of individual work in the lab, uncovering the secrets of equipment, but also meeting new people, coordinating with other researchers for projects, and having national and international exposure through conferences and workshops, both specialized and of general interest.
• What advice would you offer to other young researchers who wish to use advanced research equipment?
It is important to note that using advanced research equipment generally involves several considerations. For example, the high cost of acquisition and maintenance of such equipment requires careful attention and a comprehensive approach to the various technical components. Furthermore, obtaining new information using these tools requires continuous documentation about new trends and requirements in the field of nanotechnology through specialized journals and participation in international conferences, workshops, training stages, schools, and specialized courses. I believe it would add value for all young researchers to be aware of these aspects before determining what suits them best.
• How do you see the evolution of technology supporting the research field you are active in?
As the complexity of materials continues to grow year by year, due to the increasing complexity of growth and deposition techniques, it is clear that technology plays a crucial role in supporting research. The installation of new generations of 2D detectors in the last decade has significantly reduced acquisition time for reciprocal space maps of epitaxial materials, while analysis software has made substantial contributions to in-situ studies for batteries and supercapacitors, as well as Rietveld refinement in powders. I am convinced that, in the future, research in various fields, as well as artificial intelligence, will lead to work modules and analysis software with superior capabilities, resulting in better resolutions and shorter acquisition times.
We conclude this inspirational interview with young researcher Cosmin Romanițan, who has provided us with a deep perspective on the importance of scientific research and the impact of new technologies in exploring the world of nanomaterials. Thank you, Cosmin, for your openness and valuable advice. We hope that this conversation has inspired young people passionate about science to follow their curiosity and explore new horizons in the research field. We wish you continued success in your innovative projects and in discovering the “world that cannot be seen”!
