Papers by Author: Arthur Medvid

Abstract: It was established that irradiation of a semiconductor by nanosecond laser leads to drift of the impurity atoms. The direction of the drift depends on relation between covalent radius of the impurity and of the basic substance atoms. This effect was shown for a wide class of semiconductors, such as: Si, Ge, InSb, GaAs, CdTe, Cd_xZn_1-xTe. This is due to a laser thermal shock effect connected with action of high temperature and pressure gradients formed by strong absorbed nanosecond laser pulse. A new concept was proposed, and the technology has been developed of laser-induced (YAG: Nd ⁺³, wavelength l= 0.532 mm, pulse duration τ_p = 10 ns) nano-fragmentation of metal film, for example, Au with an average size of fragments <δ> = 80 nm, and the concentration on the surface <n> = 2.5×10⁹ cm^-2. The fragmentation is realized by the self organization of surface plasmon-polariton subsystem excited by high power laser pulses at a surface plasmon-polariton resonance. It was shown that the proposed method provides by laser-assisted fragmentation of the metal film (Au) in conditions of the resonance, decomposition of the nanofragments from the substrate, their transfer through an air gap, and implantation in a polymer layer on a separate surface at the same laser pulse.

Abstract: The results of the investigation of stresses relaxation by strain by means of EPR spectra, IR absorption spectra, SEM and samples deflection are presented. It has been shown that stresses relaxation mechanism depended on the oxidation conditions: temperature, cooling rate, oxide thickness. In the Si-SiO₂-Si₃N₄ system the stresses relaxation by the strain occur due to the opposite sign of the thermal expansion coefficient of Si-SiO₂ and Si₃N₄ on Si. Laser irradiation allows to modify the system stresses.

Abstract: For the first time, a new PL band at 1.8718 eV is observed after irradiation of Cd1-xZnxTe (x = 0.1) crystal by Nd:YAG laser at intensity 12.0 MW/cm2. The origin of this PL band we connect with formation of strongly enriched layer by Zn atoms at the irradiated surface of the sample due to a themogradient effect. Self-organizing structures of nanometer size are observed on the surface of a CdZnTe crystal (x = 0.1) irradiated by strongly absorbed Nd:YAG laser radiation at intensities 4.0-12.0 MW/cm2. The effect of exciton quantum confinement manifested by a shift to higher energies of the A0,X exciton line in the photoluminescent spectrum is present in structures of 10–15 nm in diameter at the top of nanohills. A graded band gap structure with optical window is formed on the top of nanohills.

Abstract: The influence of strongly absorbing N¬2 laser radiation on pores formation on a surface of Si single crystal has been investigated using optical microscope, atomic force microscope and photoluminescence. After irradiation by the laser and subsequent electrochemical etching in HF acid solution morphological changes of the irradiated parts of a surface of Si were not observed. At the same time, pores formation on the non-irradiated parts of Si surface took place. The porous part of the Si surface is characterized by strong photoluminescence in red part of spectra with maximum at 1.88 eV and intensity of photoluminescence increases with current density. Suppression of the pores formation by the laser radiation is explained with inversion of Si type conductivity from p-type to n-type. This fact is explained by Thermogradient effect – generation and redistribution of the intrinsic defects in gradient of temperature. It was shown that the depth of n-Si layer on p-Si substrate depends on intensity of laser radiation and it increases with intensity of laser radiation. The results of the investigation can be used for optical recording and storage of information on surface of semiconductors.

Abstract: The results of investigation of the point defect generation and interaction with impurities in the Si-SiO2 system during the process of its formation by means of electron paramagnetic resonance (EPR) and nucleous magnetic resonance (NMR) technique are presented. It has been shown that the diference in point defects interaction with hydrogen at the Si-SO2 interface with n- and p-type conductivity are connected with the sign of hydrogen ions incorporation dependence on the Fermi level position in accordance with the proposed model. The interface properties may be improved by laser irradiation.

Abstract: The aim of this work is to study optical properties of Si nanohills formed on the SiO2/Si interface by the pulsed Nd:YAG laser radiation. Nanohills which are self-organized on the surface of Si, are characterized by strong photoluminescence in the visible range of spectra with long wing in the red part of spectra. This peculiarity is explained by Quantum confinement effect in nanohillsnanowires with graded diameter. We have found a new method for graded band gap semiconductor formation using an elementary semiconductor. Graded change of band gap arises due to Quantum confinement effect.

Abstract: The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. Interaction between the point defects with extended defects and impurities affects the SiO2 structure and Si-SiO2 interface properties. Hydrogen adsorption on n- and p- type wafers is different. One possible reason for that can be the strength of the magnetic interaction between the hydrogen and paramagnetic impurities of the adsorbent. The influence of point defects and impurities may be diminished and the interface properties improved by an appropriate choice of the oxidation conditions and postoxidation laser irradiation.

Abstract: The type and density of the point defects that are generated in the Si surface layer during thermal oxidation depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. The interaction between point defects with extended defects and impurities affect the Si-SiO2 interface properties. The influence of point defects may be diminished and the interface properties improved by an appropriate choice of oxidation conditions.