Nanooptics and photonics

Properties of fuels and quantum-dimensional structures based on CdTe
Mazur T.M.1, Prokopiv VV.1, Slyotov M.M.2, Slyotov O.M.2
 1State Pedagogical University "Vasyl Stefanyk Precarpathian National University”, street Shevchenko, 57, Ivano-Frankivsk, 76018, Ukraine
E-mail: tatyana.m.mazur@gmail.com
2Chernivtsi National University named after Yuri Fedkovich, street Kotsyubinsky, 2, Chernivtsi, 58012, Ukraine 
CdTe films were prepared by the hot wall method. Substrates of mica, warmed to T ~ 200°C, were used as substrates. The chosen method of deposition at certain optimum temperature modes provided conditions that are as close as possible to equilibrium with the corresponding surface morphology. This is confirmed by studies of the differential transmission spectra T'ω and the reflection of R'ω. According to them, the basic parameters of the band structure, which are Eg = 1.50 eV and spin-orbital splitting Δso = 0.9 eV, are determined. The character of the reflection spectra indicates the uniformity of the sizes and the uniformity of the placement along the surface of the deposited film.
As the annealing is used to increase the efficiency of up to 15% of surface-barrier photocells, under similar conditions, the thermal treatment of the studied films CdTe at 700-1000 K was performed. This allowed to obtain a nanostructured surface. About its formation is the displacement of the maximum transmission T'ω to ħω = 1.3 eV. Note that the differential optical reflection curves R'ω repeat the immutability of the position of the characteristic at ħω = 1.5 eV. This indicates the formation of a modified surface of CdTe films. The formation of a sufficiently intense photoluminescence, which is not observed on the base films, also testifies to their formation. Its spectral distribution is characterized by two bands A and B with corresponding maxima at photon energies ħω1 = 1.5 eV and ħω2 = 2.95 eV. The properties of the radiation of the A band can be explained by the interband recombination of free charge carriers and by the annihilation of excitons. Each of these generation-recombination processes determines the process of forming the corresponding component of the band A. The high-energy band B can be explained by quantum-dimensional processes. The large half-width of the strip and the stretched maximum are due to the dispersion of the size and shape of small grains, which are observed at visual observation under a microscope with a large increase, as well as for atomic force microscopy. It is a diverse form of grains and their size that determines the dimensional quantization of the energy of charge carriers on the formed nanostructures.