Positronics of radiation-induced effects in chalcogenide glassy semiconductors

Using As2S3 and AsS2 glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models

Influence of the composition on the thermoelectric and electro-physical properties of Ge-Sb-Te thin films for phase change memory application

Influence of the composition variation along the quasi-binary line GeTe-Sb2Te3 on the thermoelectric and electro-physical properties of thin films was investigated. GST amorphous thin films have high Seebeck coefficients, which drops nearly on the order of magnitude after the crystallization. Temperature dependences of the resistivities were studied, and it was determined that crystallization temperature increases with moving along the quasi-binary line GeTe-Sb2Te3 from GeSb4Te7 to GeSb2Te4, and then to Ge2Sb2Te5, while the phase transition temperature range decreases. Current-voltage characteristics of amorphous thin films have three voltage ranges with different dependencies due to the different mechanisms of charge carrier transport

NEW DYES BASED ON THIENO[3,2-b]INDOLE WITH AN EXTENDED Π-CONJUGATION SYSTEM FOR DYE-SENSITIZED SOLAR CELLS

This work was supported by the Russian Foundation for Basic Research, project # 22-73-00291

Low power reconfigurable multilevel nanophotonic devices based on Sn-doped Ge2Sb2Te5 thin films

In the past years, Ge2Sb2Te5 has been considered a promising functional material for a variety of reconfigurable multilevel devices, including photonic integrated circuits for the post-von Neumann arithmetic processing. However, despite significant advances, it is necessary to reduce the switching energy of Ge2Sb2Te5 for creation of the on-chip low power all-photonic spiking neural networks. The present work focuses on the effect of tin ion implantation on the properties of amorphous Ge2Sb2Te5 thin films, as well as on the performance of Mach-Zehnder interferometers and balanced beam splitters based on them. As a result, Sn-doping accompanied by the formation of weaker bonds in Ge2Sb2Te5 thin films is an efficient approach to significantly reduce the threshold energy of fs-laser initiated phase transitions and change the effective absorption coefficient. The possibility of using the Sn-doped Ge2Sb2Te5 thin films for fully optical multilevel reversible recording between 9 different levels (3 bits) has been demonstrated by experimental measurements of fabricated on-chip balanced beam splitters. The obtained results show that the Sn doping of Ge2Sb2Te5 layer can be used to optimize the properties of the GST225 thin films, in particular to reduce the switching energy. So, it has the potential to improve the characteristics of reconfigurable multilevel nanophotonic devices using the GST225 thin films, including fully non-volatile memory and developed on-chip low power all-photonic circuits for post-von Neumann arithmetic processin

Novel push-pull thieno[2,3-b]indole-based dyes for efficient dye-sensitized solar cells (DSSCs)

New metal-free sensitizers (IK 3-6), based on the thieno[2,3-b]indole ring system, bearing various aliphatic substituents at the nitrogen atom (electron-donating part), several thiophene units (π-bridge linker) and 2-cyanoacrylic acid (the electron-accepting and anchoring group) have been synthesized for application in dye-sensitized solar cells (DSSCs). The relationship between the IK dye structure and efficiency of the corresponding DSSC has been elucidated. Power conversion efficiency (PCE) up to 6.3% (short-circuit photocurrent density (JSC) 19.0 mA cm-2, open-circuit voltage (VOC) 0.59 V, and fill factor (FF) 56.4%) were obtained for the DSSC, based on 2-cyano-3-{5-[8-(2-ethylhexyl)-8H-thieno[2,3- b]indol-2-yl]thiophen-2-yl}acrylic acid (IK 3), which proved to be a highly synthetic available compound, under simulated AM 1.5 G irradiation (100 mW cm-2), thus indicating that thieno[2,3-b]indole-based organic dyes are perspective candidates for DSSCs. © 2017 Arkat. All rights reserved

Inter-diffusion of Plasmonic Metals and Phase Change Materials

This work investigates the problematic diffusion of metal atoms into phase change chalcogenides, which can destroy resonances in photonic devices. Interfaces between Ge2Sb2Te5 and metal layers were studied using X-ray reflectivity (XRR) and reflectometry of metal-Ge2Sb2Te5 layered stacks. The diffusion of metal atoms influences the crystallisation temperature and optical properties of phase change materials. When Au, Ag, Al, W structures are directly deposited on Ge2Sb2Te5 inter-diffusion occurs. Indeed, Au forms AuTe2 layers at the interface. Diffusion barrier layers, such as Si3N4 or stable diffusionless plasmonic materials, such as TiN, can prevent the interfacial damage. This work shows that the interfacial diffusion must be considered when designing phase change material tuned photonic devices, and that TiN is the most suitable plasmonic material to interface directly with Ge2Sb2Te5.Comment: 23 pages, 8 figures, articl

Pyrimidine-Based Push–Pull Systems with a New Anchoring Amide Group for Dye-Sensitized Solar Cells

New donor–π–acceptor pyrimidine-based dyes comprising an amide moiety as an anchoring group have been designed. The dyes were synthesized by sequential procedures based on the microwave-assisted Suzuki cross-coupling and bromination reactions. The influence of the dye structure and length of π-linker on the photophysical and electrochemical properties and on the photovoltaic effectiveness of dye-sensitized solar cells was investigated. An increase in efficiency with a decrease in the length of π-linker was revealed. The D1 dye with only one 2,5-thienylene-linker provided the highest power conversion efficiency among the fabricated dye sensitized solar cells. © 2021 by the authors.IGIC RAS, (AAAA-A20-120101490004-4)Russian Foundation for Basic Research, РФФИ, (18-29-23045)Ministry of Education and Science of the Russian Federation, Minobrnauka, (AAAA-A19-119011790132-7)This work (optical and electrochemical properties) was supported by the Russian Foundation for Basic Research (Project No. 18-29-23045 mk). E.V.V. is grateful to the financial support for the synthetic part from the Ministry of Education and Science of the Russian Federation within the framework of the State Assignment for Research (Project No. AAAA-A19-119011790132-7). NMR experiments were carried out by using equipment of the Center for Joint Use «Spectroscopy and Analysis of Organic Compounds» at the Postovsky Institute of Organic Synthesis of the Ural Branch of the Russian Academy of Sciences. S.A.K and E.V.K. are grateful to the financial support for the fabrication of DSSCs part from IGIC RAS state assignment (Project No AAAA-A20-120101490004-4). V.V.E. is grateful to the partial financial support from the Ministry of Science and Higher Education of the Russian Federation in the frame of the State Task for 2021 IPCE RAS