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The effect of doping level and illumination on the formation of n-type porous silicon is studied with the help of high-resolution x-ray diffraction. A degradation of the crystal quality, increasing with a decrease of the material doping level is observed.

Several experimental and theoretical studies are conducted to explain the electronic mechanisms associated with the laser desorption and nanosecond-laser ablation of silicon. The system is shown to contain high-energy ions with a narrow energy distribution at low fluences of the laser.

The anomalous phenomenon of the scanning tunneling microscopy-photoabsorption spectroscopy (STM-PAS) spectra of n-type Si in the Fourier transform near infrared (FT-NIR) scheme which exhibit a peaking signal at a sub-bandgap energy is reported. The result suggest that subsidiary suprabandgap lights in addition to spectroscopic lights helps to enhance the sensitivity for tip-probing PAS detection of sub-bandgap centers.

The far-field Raman intensity of strained Si(100) is calculated based on the Raman tensor, Snell's law and Fresnel's equations with the incident angle of 0 and 60 degree. The studies have shown that for Raman active and thin crystalline samples assembled in bulk materials, the depolarization effect has outweighed the field enhancement effect in getting a high-contrast Raman signal.

The time evolution of the density of defect states in tritiated hydrogenated amorphous silicon (a-Si:H:T) thin films are analyzed by using the constant photocurrent method (CPM) and isothermal capacitance transient spectroscopy (ICTS). The studies have shown that the concentration of positively charged dangling bonds [D.sup.+] states has decreased with time in tritiated amorphous silicon, while the concentration of negatively charged dangling bonds [D.sup.-] states has increased.

The existence of tensile stress is highlighted in heavily arsenic-doped epitaxial silicon prepared by low pressure chemical vapor deposition. Positron annihilation spectroscopy has shown the formation of arsenic-vacancies defects during the growth and has also shown that the tensile strain is related to this type of defects involving As atoms.

The Raman spectrometry is used to examine the lattice disorder and strain induced by hydrogen or helium implantation in (001) and (011) Si by light ion implantation. The results suggest that the amount of strain increases with the implant dose.

The effect of laser-induced heating on Raman measurements for different unpatterned and patterned substrates, including pure silicon, strained-silicon-on-insulator and silicon-germanium layers on silicon is examined. The results have shown that heating should be considered for moderate laser intensity when accurate stress measurements on such substrates are performed by Raman spectroscopy.

The strain and defect state of silicon implanted with nitrogen by plasma immersion ion implantation is examined using various spectroscopy methods. The close relationship between the calculated strain profiles and Auger electron spectroscopy (AES) nitrogen concentration profiles outside the amorphous regional signal has indicated interstitial nitrogen as the main source of strain.

The oscillator strength of silicon nanoparticles and its implication on the absorption and photoluminescence spectra are studied. The results have supported the assumption that Si nanoparticles are direct or indirect semiconductors.

Photoexcitation dependent Raman studies were carried out on the optical phonon mode in silicon nanostructures (Si-NS) prepared by laser-induced etching. A broad photoluminescence spectrum from Si NS containing multiple peak behavior reveal the presence of continuum of electronic states in the Si NS which could be applied to the transport properties of the photonic devices and solar cell made of these Si NSs.

The crystallization of amorphous silicon (a-Si) thin films by the self-propagation of copper oxide/aluminum thermite nanocomposites is presented. Raman spectroscopy is used to analyze the crystallization of a-Si.

The photoluminescence (PL) properties changed significantly after porous silicon (PS) was irradiated by low energy nitrogen or argon ions. X-ray photoelectron spectroscopy and Fourier transforms infrared spectroscopy results indicate that the Si-N bonds were formed during low-energy-nitrogen-ion irradiation. On the other hand, Raman scattering spectroscopy suggests the crystal structure of PS did not change during ion irradiation.

The plasma-assisted radio frequency (rf) magnetron sputtering technique is used for the synthesis of optically transparent, highly oriented nanocrystalline AlN(002) films on Si(111) and glass substrates at low temperature. The hydrogenated AlN films have shown an excellent transmittance of almost 80 percent in the visible region of the spectrum.

Silicon nanoparticles are prepared by off axis pulsed laser deposition (PLD) technique and their optical properties are characterized by optical absorption, photoluminescence, Raman and transmission electron microscopy (TEM). The photoluminescence (PL) peak energy and intensity are discovered to be sensitive to the nature of substrate and the mechanism of optical absorption and PL origin is discussed in terms of quantum confinement luminescent center model.