A. V. Zoteev

Enhancement of the Raman scattering in grooved silicon structures

The Raman effect in grooved silicon structures consisting of an array of cavities (grooves) and silicon layers is studied. It is found that the intensity of the Stokes component increases severalfold when the thickness of the silicon layers (1–2 μm) is close to the excitation wavelength. The results obtained, interpreted as a manifestation of the effects of localization of light, suggest that grooved structures of this kind offer promise as matrices providing for enhanced efficiency of the Raman scattering.

Threshold of inelastic strain formation in Si and GaAs surface layers under multiple pulsed laser irradiation

For the first time, a contactless local photoacoustic technique based on the spectroscopy of laser beam deviation was used to estimate maximal values of elastic shear strains ϕ0 in micrometer-sized surface regions of Si and GaAs; the values obtained fall in the range of 10−5<ϕ0<10−4. The development of irreversible inelastic processes in the surface layers of semiconductors subjected to a series of focused laser pulses under photoinduced quasistatic strains ϕ>ϕ0 is demonstrated. Studying the diffuse and Raman scattering of light near the thresholds ϕ0 suggests that the early stage of the inelastic cyclic strain photoinduced in the surface layers is accompanied by the generation and spatial redistribution of point rather than extended defects (e.g., dislocations). A number of threshold values, such as the photoinduced increase in the temperature and the mean shear stresses that appear in the surface layers of Si and GaAs samples exposed to local submicrosecond radiation, are estimated. The physical nature of the low-threshold effects is discussed.

Low-Threshold Defect Formation and Modification of Ge Surface Layer under Elastic and Elastoplastic Pulsed Laser Effects

Changes in the spectra of fluorescence of dye (rhodamine B) molecules adsorbed on a Ge surface and modification of the parameters of Raman and diffuse scattering of light by a semiconductor surface subjected to elastic and elastoplastic effects of pulsed laser radiation are studied. Using contactless photoacoustic measurements based on the laser beam deflection technique, the amplitude of the threshold surface strain is estimated at ∼5×10−5. An appreciable quenching of the fluorescence of the adsorbed probe molecules, an abrupt broadening of the molecular spectra, and an above-threshold increase in the intensity of the diffusively scattered light are observed upon the transition to the range of energy densities corresponding to the inelastic strain formation. The larger the laser-induced strain, the smaller the frequency and the width of the Raman lines, and the higher their intensities. The physical nature of these effects is discussed.

Nature of Charge Traps in Anode Oxide Films on GaAs

The influence of exposure to a wet atmosphere and vacuum annealing effects on the electron and hole traps in an anode oxide of GaAs by using optical charge method have been studied. Charging of the sample surface by illumination for photon energies of 1.0 to 5.4 eV was recorded from the change in the dark value of the contact potential difference (CPD) between the sample and a transparent nickel net electrode. The CPD was measured using a dynamic capacitor (Kelvin) method. From correlation of the optical charging and mass spectrometry and electron spin resonant method experimental data it has been found that the defects which include arsenic vacancies are traps for the holes. On the other hand, the oxygen atoms localized on gallium vacancies in the anode oxide are responsible for the electron trapping.

Electrochemical Nanostructuring of Semiconductors by Capillary-Cell Method

Wafers of silicon and compound semiconductors are nanostructured by using electrochemical or chemical etching (stain etching) in etching cell with electrolyte kept by capillary forces. Atomic force microscopy, infrared spectroscopy and Raman scattering methods reveale nanoporous and nanocrystalline structure of the treated surfaces. The formed porous semiconductors demonstrate efficient photoluminescence, which is controlled by etching parameters, i.e. current density, electrolyte content, etc. These results indicate good prospects of the employed capillary-cell method for preparing nanostructured porous materials with desired structure and optical properties.

Influence of laser exposure on the luminescent properties of GaP∶S monocrystals

Conclusions1.The action of laser radiation of both the visible and UV bands on the surface of GaP monocrystals results in quenching of PL because of generation of centers of irradiative recombination.2.In addition to quenching of the initial 1.78 eV line under the effects of laser pulses with energies exceeding a certain threshold value, a new band with a maximum at 2.04 eV occurs.