Effect of Annealing on the Structural and Optical Properties of Amorphous Ge8Se60Te30Sb2 Thin Films

Thin film of Ge8Se60Te30Sb2 was synthesized by conventional melt quench technique. The structural properties of the pre annealed and post annealed films were studied by XRD characterization. Once the Ge8Se60Te30Sb2 film is annealed in the temperature range of 373–413 K for 2 h, it is observed that there is a continuous change in structure and formation of some polycrystalline structures in the amorphous phases. The optical transmission of these films was studied in the range 300–1000 nm as a function of photon wavelength. The band gap value suggests that sample is a semiconductor. The optical band gap Eg was observed to decrease in the range 373–413 K with increasing annealing temperature. The absorption coefficient (α) and extinction coefficient (k) were also evaluated. Annealing induced effect on the optical parameters was described on the basis of defect states and density of localized states arises from amorphous to crystalline phase transformation.

Перенос заряда в планарных структурах на основе халькогенидной системы (As-=SUB=-2-=/SUB=-Se-=SUB=-3-=/SUB=-)-=SUB=-100-x-=/SUB=-Bi-=SUB=-x-=/SUB=-

The results of investigating charge-transfer processes in thin layers of a vitreous system (As_2Se_3)_100 – _ x Bi_ x are presented. A power-law dependence of the conductivity on the frequency and a decrease in the exponent s with increasing temperature are found. Charge transfer is a thermally activated process with two regions in the temperature dependence of the conductivity with the activation energies E _1 = 0.12 ± 0.01 eV and E _2 = 0.23 ± 0.01 eV, respectively. The results are explained in terms of the correlated barrier hopping (CBH) model of hopping conductivity in disordered systems. The main microparameters of the system are calculated: the density of localized states ( N ), the hopping length ( R _ω), and the largest height of the potential barrier ( W _ M ).

Структура и электрические свойства тонких пленок (ZnO/SiO-=SUB=-2-=/SUB=-)-=SUB=-25-=/SUB=-

Multilayer (ZnO/SiO2)25 thin films with a bilayer thickness of 6 to 10 nm has been synthesized in a single deposition process. The structure of the films consist of nanocrystalline ZnO layers and layers of amorphous SiO2. An analysis of the temperature dependences of the electrical resistivity, showed that a consistent change of the dominant conduction mechanism are realized in (ZnO/SiO2)25 thin films at temperatures 77 – 300 K: variable length hopping mechanism in a narrow energy band near the Fermi level at temperatures 77 – 250 K changed by the thermal activated impurity conductivity at close to room temperatures. The density of localized states and the activation energy of impurity conductivity has been estimated. The effect of heat treatment on the structure and electrical properties of the synthesized films has been investigated. It was found that the chemical interaction between the ZnO and SiO2 layers occurs at 580–600°C. It accompanied by the destruction of the multilayer structure and the appearance of the chemical compound Zn2SiO4 with the tetragonal structure (I-42d space group).