MSc Students Presentations - Drivas Charalampos

Abstract (Περίληψη)
Microelectronics is a continuously developing field, overcoming its limits every day. Its applications are numerous, ranging from high-tech devices to everyday ones, such as the smartphone, which reflects the rapid development of microelectronics the recent years. What’s more, state of the art arrays are used in solar cells to maximize their efficiency to provide sufficient sustainable energy. The trend nowadays is to make arrays as small as possible in order to fit as many of them in a device as possible. Hence, each layer constituting the array is getting smaller as well, up to the nanometer scale. This leads to surface phenomena being dominant and interfaces being “part” of the device.
In order to have a better insight to the properties of the surfaces and interfaces of common oxides used in such applications, the X-ray and Ultra-violet Photoelectron Spectroscopies (XPS and UPS respectively) were implemented as two complementary highly surface sensitive techniques. XPS provides information about the chemical composition of the sample’s surface from up to 10 nm in depth. UPS depth analysis is about 1-2 nm and it provides information about the electronic configuration of the surface.
First, a study has been carried out considering the Electron Extraction Layer (EEL) of organic solar cells upon doping with light and heavy metals in different nanostructures. Doping is a way to properly tune the desired properties, depending of the doping level, enabling the engineering of the EEL. More specifically, Li-doped ZnO films (0%, 2%, 5% and 10% Li) and Sn-doped ZnO (0%, 1%, 2% and 3% Sn) nanowires were studied by XPS and UPS, varying the doping levels. The doping of ZnO was confirmed by XPS and from the UP spectra, a slight variation of the Work Function (WF) of the Li-doped samples was detected, whereas for the Sn-doped ones further hybridization of the Zn orbitals was recorded upon doping.
For the second part, several interfaces between widely used ultra-thin oxide films (Al2O3, HfO2, ZrO2, Ta2O5 and ZnO) and oxide substrates (TiO2 and ZnO) were prepared by Atomic Layer Deposition (ALD). Such interfaces are used in organic solar cells as an addition layer between the EEL and the organic compound and in Metal-Oxide-Semiconductor-Field-Effect-Transistors (MOSFETs) as high-k dielectrics. They were studied by XPS, in order to investigate their possible interaction and the barriers imposed to the electrons and holes by the means of the Kraut et al. model.
Lastly, CoOx - promoted BiVO4 photocatalysts of variable Co content (0, 0.5 and 1.0 wt.%) were synthesized and studied by XPS in order to identify the chemical state of the CoOx and to calculate the Conduction and Valence Band offsets at the interface. The Co oxide was identified as Co3O4 and the offsets promoted separation of the electrons and holes, as desired. What’s more, it was shown that the Kraut et al. model, which is traditionally used for microelectronic devices, can be used in other applications, such as photocatalysis.
Speakers Short CV (Σύντομο Βιογραφικό Ομιλητή)
02/2016–Present |
M.Sc. in Chemical Engineering Department of Chemical Engineering - University of Patras, Patras (Greece) Specialization in Materials Science and Technology Master Thesis: Determination of the chemical composition and electronic structure of oxide thin-films with applications in microelectronic devices by photoelectron spectroscopies. Supervisor: Professor S.Kennou (Surface Science Laboratory) |
09/2010–12/2015 |
B.S. in Materials Science Department of Materials Science - University of Patras, Patras (Greece) First in the graduation order of the academic year 2015-2016. (8.06/10) Bachelor Thesis: Synthesis and characterization of superconducting materials. Supervisor: Professor P. Poulopoulos (Laboratory of High Tech Materials) |
Honours and awards |
· Scholar of the 44th Regular Scholarship Programme for Postgraduate Studies of the Bodossaki Foundation. · Awards of excellence by the Limmat Foundation, Switzerland, Postgraduate Studies - Chemical Engineering - University of Patras. |
Conferences
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· Drivas, C., Kennou, S. · Drivas, C., Mpotzakaki, M.A., Georga, S.N., Krontiras, C.A., Kennou, S. |
Publications
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[1]. Velegraki, G., Miao, J., Drivas, C., Liu, B., Kennou, S., & Armatas, G. S. (2018). [2]. Polydorou, E., Botzakaki, M. A., Sakellis, I., Soultati, A., Kaltzoglou, A., Papadopoulos, T. A., Briscoe, J., Drivas, C., … Vasilopoulou, M. (2017). [3]. Thu, C., Ehrenreich, P., Wong, K. K., Zimmermann, E., Wang, W., Fakharuddin, A., Putnik, M., Drivas, C., … Schmidt-Mende, L. (2018) [4]. Petala, A., Noe, A., Frontistis, Z., Drivas, C., Kennou, S., Mantzavinos, D., Kondarides, D.I. [5]. Drivas, C., Botzakaki, M. A., Georga, S. N., Krontiras, C. A., & Kennou, S. [6]. Balis, N., Verykios, A., Soultati, A., Papadakis, Michael; Kournoutas, F., Drivas, C., ... Vasilopoulou, M. [7]. Vamvasakis, I., Papadas, I.T., Tzanoudakis, T., Drivas, C., Choulis, S.A., Kennou, S., Armatas, G.S. [8]. Patsiouras, L., Skotadis, E., Gialama, N., Drivas, C., Kennou, S., Giannakopoulos, K., Tsoukalas, D., [9]. Polydorou, E., Botzakaki, M., Drivas, C., … Vasilopoulou, M. |