A.P. Chernushich

Optical properties of Si nanocrystals prepared by magnetron sputtering

Visible photoluminescence (PL), optical transmission, and Raman scattering spectra of Si nanocrystals embedded in SiO2 matrix have been studied. Films were deposited by rf magnetron sputtering of compound SiO2/Si targets. Films containing silicon in the form of nanocrystals clusters show intense luminescence at room temperature. Films containing only amorphous Si clusters show little or no PL. Annealing in vacuum or in specific atmosphere leads to strong change of the PL spectrum and its intensity. Results are explained by strong influence of the Si/SiO2 interface state on integral PL emission.

Superlattice ZnSxSe1−x/ZnSySe1−y on (100) GaAs obtained by a photoassistant metal-organic chemical vapour deposition method

Abstract The influence of radiation in the visible spectral range on the growth rate and composition of ZnSxSe1−x during the usual metal-organic chemical vapour deposition process was observed. This fact was used to grow the superlattice under pulse radiation from a xenon or tungsten lamp directed at a GaAs substrate. Superlattices with periods of 60–1500 A were obtained by this method.

Ultrathin CdSe quantum wells

Abstract We report a survey of samples containing ultrathin layers of CdSe embedded in ZnSe or ZnS0.06Se0.94 matrices. CdSe single quantum wells (SQW) with well widths in the range 0.3–3 ML show several bands in the photon energy range from 1.7 to 2.4 eV. Similar bands have been attributed recently to self-organised quantum dots. Temperature-dependent photoluminescence (PL) shows that the bands in our samples vanish, without significant peak shift, at moderately high temperatures. Preliminary time-resolved PL shows that they also have relatively long lifetimes (ca. 30−250 ns). In all samples, the SQW exciton band lying at higher energies shows line narrowing with increasing temperature. Variations due to quantum-well thickness induce a correlation between the luminescence peak energy and the optical bandwidth which may be used to systematise our observations.

Algorithm for Elimination of Structural Noise in an Image Intensifier with Pyroelectric Array

Signal formation in image intensifier with pyroelectric array is considered. Application of panning regime is substantiated, and impossibility of image obturation is shown. A method for processing of thermal image is proposed to eliminate structural noise and allow operation in the absence of shutter. The method is optimized for pyroelectric arrays and practical applications are presented. Development of the method, in particular, with the aid of calibration of the signal of pyroelectric array is considered.

Photo-MOVPE growth and characterization of ZnSeZnxCd1 − xSe heterostructures

Abstract We have studied the growth of ZnCdSe layers on (1 0 0) GaAs substrates using atmospheric metalorganic vapor phase epitaxy (MOVPE). It was found that surface fluctuations of temperature were the main reason for compositional non-uniformity. The photo-assisted technique and a mechanism for rotational and back and forth movement of the substrates have been used for the growth of the Zn 0.45 Cd 0.55 Se- and CdSe-based heterostructures giving good homogeneity of the width and composition on a 12 cm 2 area at growth temperatures as low as 400–425°C. Strained single Zn 0.45 Cd 0.55 Se layers embedded in a ZnSe matrix were pseudomorphic up to the thickness of 4.5 nm. Strong green emission from a single well and 50 periodic Zn 0.45 Cd 0.55 Se ZnSe superlattices (SL) are observed under 441.6 nm HeCd laser excitation at 77 K.

Excitons in ZnSe1 − xSxZnSe1 − ySy superlattices grown by photomodulated MOCVD

Abstract The superlattices ZnSe 1 − x S x ZnSe 1 − x S y of alternating layers of solid solutions differing in composition were grown by photomodulated MOCVD method. A high quality of our samples was evidenced by the sharp exciton spectra and high intensity of exciton luminescence. The analysis of the band shapes of 1LO and 2LO exciton replica shows that the excitons in our SLs can be considered as free particles with the equilibrium kinetic energy distribution. The exciton motion in the studied SLs has essentially three-dimensional character due to the small height of the barriers. However, the periodic potential of SL perturbs the exciton wave vector, introducing additional elastic exciton scattering which can be detected through the band-shapes of phonon-assisted exciton luminescence.