Linear and nonlinear optical properties of silicon micro- and nanocrystallites

Abstract

ABSTRACTSilicon crystallites produced by low temperature plasma-enhanced chemical vapor depositiontechnique have been shown size-dependent photoluminescent and second harmonic generation responses. The crystalline volume fraction was estimated by using Raman spectra. The grain sizes ofcrystallites were measured by using x-ray diffraction. The structural chemical properties of poly-Si films were studied by means of Fourier-transform infrared spectroscopy and transmission spectrophotometry. The size- and shape-dependent second-harmonic generation of poly-Si films is,also, studied. The second-harmonic generation intensity for poly-Si deposited by using SiFLJSiFI/H2gas mixture as function of such deposition conditions as hydrogen flow rate, silicon tetrafluoride flowrate, deposition temperature was studied.Keywords: photoluminescence, second-harmonic generation, poly-Si films, plasma-enhancedchemical vapor deposition, nanocrystallites 1. INTRODUCTION Optical properties of silicon crystallites in polycrystalline silicon (poly-Si) films have received agreat deal of attention recently [1,2]. These properties can be used for designing new optoelectronicdevices. For better understanding of the linear and nonlinear optical properties of poly-Si films withnanocrystallites it is necessary to study its structural properties. The relationship between structuraland linear optical properties of silicon crystallites have been studied intensively in recent years [3,4].Many of these works showed the size-dependent or size-distribution-dependent photoluminescence(P L) due to the quantum confinement in nanocrystals. The optical absorption and PL spectra of suchcomposite materials as poly-Si films must be the sum of the individual properties of crystallites.Accordingly, size and spatial distribution of crystallites, crystalline volume fraction and chemical