EFFECT OF CURRENT DENSITY ON OPTICAL PROPERTIES OF ANISOTROPIC PHOTOELECTROCHEMICAL ETCHED SILICON (110)

Photoelectrochemical etched Si layers were prepared on n-type (110) oriented silicon wafer. The photoluminescence (PL), Fourier transformed infrared (FTIR) absorption and Raman spectroscopies of etched Si (110) at two different current densities were studied. Both samples showed PL peak in the visible spectral range situated from 650 nm to 750 nm. The corresponding changes in Raman spectra at different current density are discussed. The blue shift in the PL and Raman peaks is consequent of the quantum confinement effect and defect states of surface Si nanocrystallites complexes and hydrogen atoms of the photoelectrochemical etched Si (110) samples. The attenuated total reflection (ATR) results show both hydrogen and oxygen related IR modes in the samples which can be used to explain the PL effect.

High Temperature Anatase TiO2 Stabilization in TiO2/Si Multilayer Structures

ABSTRACTIn this work TiO2/Si multilayer structures have been grown by sputtering. After rapid thermal annealing in pure inert gas or inert gas with oxygen atmosphere the multilayers have been investigated by high resolution transmission electron microscopy, μ-Raman and dynamic secondary ion mass spectrometry for their structure and anatase/rutile phase composition. It has been found that the photocatalytically more active anatase TiO2 is stabilized and that interdiffusion and chemical reaction processes were strongly hindered up to 1100°C annealing temperature in oxygen containing atmosphere. These findings are of particular importance since only at this high temperature simultaneous formation of embedded Si nanocrystallites can be achieved.

Nanostructural, Chemical, and Mechanical Features of nc-Si:H Films Prepared by PECVD

This study examined the effects of film thickness on the nanostructural, chemical, and mechanical features of nc-Si:H films deposited by plasma-enhanced chemical vapor deposition. SiH4and H2were used as the source gases, and the deposition time was varied from 10 to 360 min. The mean nanocrystallites size in the Si films increased from~6 to~8 nm with increasing film thickness from 85 to 4150 nm. Moreover, the nanocrystallite concentration and elastic modulus increased from~7.5 to~45% and from 135 to 147 Gpa, respectively. In the 4150 nm thick film, the relative volume fraction of Si nanocrystallites and relative fraction of Si–H bonds in the films were approximately~45% and~74.5%, respectively.