Papers by Author: A.N. Tereshchenko

Abstract: ZnO nanoparticles (NPs) formed in (-1012) sapphire substrates have been studied. The NPs were formed by implantation of ⁶⁴Zn⁺ ions followed by furnace annealing in oxygen atmosphere for 1h at elevated temperatures. The radiation defects and Zn implant profiles were investigated by Rutherford backscattering spectroscopy of He⁺ ions with energy of 1.7MeV with scattering angle of 160^o at Van de Graff accelerator using the ion channeling technique (RBS/CT). The surface morphology was studied by atomic force microscopy (AFM) and scan electron microscopy in secondary emission mode (SEM-SE). The distribution of Zn implant profiles was analyzed by secondary ion mass-spectrometry (SIMS). Identification of the phase content of the materials was carried out by X-ray photoelectron spectroscopy (XPS). In as implanted samples, a near-surface amorphization layer was formed, and in this layer the surface voids were created. After annealing in temperature range of 600-900°C the ZnO phase was synthesized in sapphire substrate. After annealing at 900°C one can see the phase variation from ZnO/Zn phases at sample surface to metal Zn phase in sample body at a depth of 40nm. Annealing at temperatures above 900°C leads to disappearing of ZnO phase and creating of ZnAl₂O₄ phase.

Abstract: PL spectra of SOI wafers with buried oxide (BOX) layer were measured after dissolution annealing at 1200°. Depending on mutual orientation of starting base and top wafers different patterns of luminescence bands were observed after annealing. While the small fraction of luminescence clearly originated from dislocation related centers, another intensive band appeared in the range 0.8 – 0.95eV with certain dependence of maximum position on the twist misorientation. TEM investigation confirmed the existence of dislocation net at the interface. On the other hand some peculiarities of PL spectra did not support their relation to dislocations. Though a stepped chemical etch of surface layer confirmed the origin of new band being at the interface too. Therefore a nature of possible defects generated due to dissolution of BOX layer is discussed.

Abstract: We used the DLTS and photoluminescence (PL) techniques to study the deep states due to dislocations and deformation-induced point defects (PDs) in plastically deformed p-type germanium single crystals containing predominantly 60 dislocations with density ND, ranging from 105 to 106 cm-2. The narrow line near the temperature 140K dominates in the DLTS spectra. The ionization enthalpy and the capture cross section for holes traps indicate that the substitution copper atoms Cus are the main type of PDs. A decrease of the Cus atoms concentration and redistribution of the intensity in the PL spectra after the heat treatment of deformed samples at a temperature 500 °C are attributed to the diffusion of copper atoms to dislocations resulting in the appearance of “dirty” regular segments of 60 dislocations.

Abstract: The samples of p- and n-doped Fz Si were deformed in 3-point bending mode in the temperature range 800-950flC. Dislocation related PL (DRL) spectra were measured at temperature in the range 4.2 – 200K. Several features of DRL turned out to be sensitive to donor level doping. First, the low energy components of D1/D2 bands disappear at middle and high doping level. Second, the intensity of D1 band showed much more dependence on the donor doping level than other DRL bands and almost disappeared at the concentration of donors around 1017cm-3. Finally, it has been found that the temperature variation of the D1/D2 line positions depend on the donor doping level. Namely, at the donor concentration higher than 1015cm-3 the D1/D2 bands demonstrate the blue shift when the sample temperature goes up from 4K. At higher temperature the band positions more or less follow the temperature behavior of the band gap. The effect does not depend on chemical nature of donor except a value of ionization energy. No such behavior has been observed for different levels of acceptor doping. Taking into account that the ionization of shallow donors happens in the temperature range of above 30K, the effect of blue shift has been attributed to the influence of free electrons released from donors.

Abstract: Dislocation photoluminescence (DPL) is studied at 4.2K in plastically deformed germanium single crystals containing predominantly 60fl dislocations of “relaxed” morphology. The DPL spectra were deconvolved into Gaussian (Gm) lines of two groups over the range 0.5-0.6 eV. One of these lines corresponds to the radiation of 60fl dislocations with the equilibrium stacking fault width F0. To clarify the origin of the other Gm lines, the effect of both the dislocation density ND, ranging from106 to 109 cm-2, and the annealing at temperatures above 600flC on the intensity of Gm lines was investigated. The origin of different lines in the DPL spectra of germanium and silicon is discussed.

Abstract: In this paper we present a detailed investigation of peculiarities of dislocation related D1/D2 bands behavior in silicon doped with Cu. For this purpose float zone grown (FZ) p-type silicon with B-doping 2.85·1015cm-3 was deformed by 3-point bending method at 950flC up to dislocation density of 2±0.2·106 cm-2. The deformed samples were contaminated with Cu up to several concentrations from 6·1013 cm-3 to 5·1016 cm-3. The variation in dislocation related spectra were traced after different thermal treatments. A decrease of D1/D2 bands intensity in quenched samples was observed even after their storage at room temperature. Taking into account the fact that Cu has a high mobility even at room temperature the decrease of D1/D2 bands intensity can be attributed to passivation of corresponding luminescence centers by Cu atoms. The influence of Cu contamination on D2 band is much more complicated as compared to D1 band. New line in position about 883 meV was observed as a result of storage of samples at room temperature and subsequent isochronous anneals. It was observed that D1/D2 band luminescence sharply increased in 30K – 50K range in samples with high Cu doping level. In addition the line in about 830 meV position became stronger at these temperatures whereas its intensity was negligible at 6K.

Abstract: The samples of Cz Si were subjected to multi-step annealing at different temperatures. After high temperature consequent steps the dislocation related spectra (DRL) were detected from the samples. The main feature of the DRL spectra was the very narrow low energy bands D1/D2, which are unusual for Cz Si. TEM analysis shown that the only candidates for DRL spectra are dislocation loops, punched out from precipitates. To explain the absence of influence of oxygen it was assumed that the distribution of interstitial oxygen is nonuniform in such samples and has some depletion regions in the vicinity of precipitates.

Abstract: The samples of p- and n-doped Fz Si were deformed in 3-point bending mode in the temperature range 800-950°C. The fine structure of dislocation related luminescence in the region of D1 and D2 bands was most pronounced at lowest rate of deformation. The temperature variation of intensity of individual lines did not reveal any thermalization effects. It implies that centers responsible for different individual lines are situated in diverse places. The most narrow lines with maximum positions of 802 meV and 807 meV (D1 band) and 869 meV and 873 meV (D2 band) are rapidly quenched with increase in temperature, while the broader background lines survive at higher temperature. The new line with maximum position at about 882 meV appears in the D2 band with enhanced carbon doping. It was found that at higher P-doping the low energy fine structure lines 802 meV and 869 meV are absent. Besides, the Fz samples with different P doping level from 6×1014 cm-3 to 1.2×1016 cm-3 demonstrate quite a different temperature variation of broad background lines. At lowest level of P-doping they move to low energy side at temperature above 30K, while at P-doping above 1015 cm-3 these lines move to higher energy in the same temperature range. A possible explanation of this observation can be related to distribution of electrons in the cband. It implies that the corresponding electronic transitions occur between the edge of conduction band and deep states.