Дослідження оптичного поглинання та п’єзоелектричного ефекту у монокристалі твердого розчину AgGaGe3Se7.6Te0.4

In present work spectral distribution of absorption coefficient in the range of 100 – 300 K was investigated and band gap values  evaluated. Parameters of Urbach rule were calculated and linearity  of temperature dependence of Urbach energy was showed. Thermo induced piezoelectric effect in a range of 297 ‑ 357 K was investigated. Laser induced kinetics of piezomodule was investigated and absence of irreversible changes was showed. Influence of heating the crystal during laser illuminating on piezoelectric module was adjusted.У даній роботі досліджено спектральний розподіл коефіцієнта поглинання в діапазоні температур 100 – 300 К, оцінена ширина забороненої зони. Показана експоненційна залежність коефіцієнта поглинання в області краю поглинання, розраховані параметри правила Урбаха. Досліджено температурно- та лазерно- індукований п’єзоелектричний ефект. Скорегован

Influence the cationic substitution in AgGaGe₃Se₈ on the electro-optical, IR optical and nonlinear properties

In present article we present results of detailed study of the possibility adapting AgGaGe3Se8 single crystal properties to desired requirements by investigate the influence of the different cationic substitution on the physical properties: optical, nonlinear optical (NLO) - Second Harmonic Generation (SHG) and temperature dependent photoconductivity. We report results obtained for modified crystals based on AgGaGe₃Se₈ by cationic substitution of the elements belong to first - (Ag-Cu), third (Ga-In), and fourth (Ge-Sn) groups of the periodic system. For the convincing observation the effects of various impurities and compare results with obtained for virgin AgGaGe₃Se₈ crystal was conducted replacing at 5 mol. % one element by another

Photoelectric Properties of AgGaGeS4 Crystal

У роботі досліджено кінетику релаксації фотопровідностів в монокристалі AgGaGeS4 Установлено, що час релаксації фотопровідності в кристалах AgGaGeS4 залежить від інтенсивності освітлення та температури. Оцінено глибину залягання пастки. ; Kinetics of photoconductivity relaxation in AgGaGeS4 crystal has been investigated in this work. It has been established that photoconductivity relaxation time in AgGaGeS4 crystals depends on light intensity and the temperature. The depth of trap has been estimated from the experimental data

A Novel Effect of CO2 Laser Induced Piezoelectricity in Ag2Ga2SiS6 Chalcogenide Crystals

We have discovered a substantial enhancement of the piezoelectric coefficients (from 10 to 78 pm/V) in the chalcogenide Ag2Ga2SiS6 single crystals. The piezoelectric studies were done under the influence of a CO2 laser (wavelength 10.6 μm, time duration 200 ns, lasers with power densities varying up to 700 MW/cm2). Contrary to the earlier studies where the photoinduced piezoelectricity was done under the influence of the near IR lasers, the effect is higher by at least one order, which is a consequence of the phonon anharmonic contributions and photopolarizations. Such a discovery allows one to build infrared piezotronic devices, which may be used for the production of the IR laser tunable optoelectronic triggers and memories. This is additionally confirmed by the fact that analogous photoillumination by the near IR laser (Nd:YAG (1064 nm) and Er:glass laser (1540 nm)) gives the obtained values of the effective piezoelectricity at of least one order less. The effect is completely reversible with a relaxation time up to several milliseconds. In order to clarify the role of free carriers, additional studies of photoelectrical spectra were done

Study of Photo and Heat Induced Piezoelectric Effect in Monocrystals AgxGaxGe1-хSe2

У монокристалах AgGaGe3Se8 було досліджено фотоіндукований п’єзоелектричний ефект. Зроблено виміри залежності п’єзоелектричних модулів від температури та визначено п’єзооптичний коефіцієнт. Проана- лізовано внесок різних механізмів у фотостимульовані п’єзоелектричні механізми.; Photoinduced piezoelectric effect in monocrystals AgGaGe3Se8 was found under the influence of continuos irradiation of a laser with wavelength of 523 nm. The changes relatively the main diagonal of piezocurrent components d11, d22, d33 been studied. To study the contribution of thermal and photo-stimulated piezooptic effect made measurements of depending piezoelectric modules on temperature and determined piezooptic coefficient. Analyzed contribution of different mechanisms of photoinduced piezoelectric mechanisms

Laser-induced piezoelectricity in AgGaGe

Photoinduced changes of piezoelectric coefficients for novel chalcogenide AgGaGe3–xSixSe8 (x = 0.15, 0.3, 0.6, 0.9) single crystals are discovered. The measurements were performed during illumination by cw 532 nm laser (above energy band gap) with power about 400 mW. The relaxation after switching off of the laser beam was studied. Additional temperature dependences of piezoelectric diagonal tensor components were recorded to separate the thermal effect with respect to pure electronic contribution to the photoinduced piezoelectricity. In addition to the photoinduced piezoelectric effect FTIR spectra are studied in order to explore the influence of the thermal contribution. The photoinduced changes with taking into account of temperature contribution have achieved magnitude equal to approximately 50–60% for all the studied samples and the changes were found to be completely reversible. The possible mechanisms for the observed effects are discussed and additional quantum chemical DFT simulations for the principal structural fragments were performed

Preparation and photoelectric properties of solid solutions Tl1−x In1−x Sn x Se 2 (х = 0–0,25)

Розроблено технологічні умови вирощування монокристалів твердих розчинів Tl1-x In1-x Sn x Se 2 (х = 0–0,25). Рентгенівським методом порошку розшифровано кристалічну структуру сплавів й запропоновано механізм утворення твердого розчину. Досліджено спектральний розподіл фотопровідності отриманих кристалів при T = 300 K та термостимульовану провідність. Показано вплив катіонного заміщення In 3+ на Sn 4+ у твердих роз-чинах Tl 1-x In1-x Sn x Se 2 (х = 0–0,25) на їх кристалографічні та фотоелектричні властивості. ; he technological conditions for growth of solid solutions Tl 1-x In1-x Sn x Se 2 (х = 0–0,25) single crystals have been developed. The crystal structure of the alloy has been solved by X ray diffraction powder method, the mechanism of the solid solution formation is proposed. Spectral distribution of photoconductivity for obtained crystals at T= 300 K and thermoinduced conductivity have been studied. The effect of In 3+ for Sn 4+ cationic substitution in solid solutions Tl 1-x In1-x Sn x Se 2 (х = 0–0,25) on their crystallographic and photovoltaic properties is shown