Structural information from the Raman spectrum of amorphous silicon.
TL;DR: It is shown that the width of the ``optic peak'' increases roughly linearly with the rms bond-angle distortion of the network, consistent with model-building experience which shows that it is impossible to construct fully bonded amorphous networks with \ensuremath{\Delta}${\ensureMath{\theta}}_{b}$.
Abstract: The Raman scattering from various model structures for amorphous silicon is computed. It is shown that the width of the ``optic peak'' increases roughly linearly with the rms bond-angle distortion \ensuremath{\Delta}${\ensuremath{\theta}}_{b}$ of the network. The experimentally observed linewidths lead to 7.7\ifmmode^\circ\else\textdegree\fi{}\ensuremath{\le}\ensuremath{\Delta}${\ensuremath{\theta}}_{b}$\ensuremath{\le}10.5\ifmmode^\circ\else\textdegree\fi{}. The smaller linewidths (and hence angles) correspond to networks that have been annealed at higher temperatures. These results are consistent with model-building experience which shows that it is impossible to construct fully bonded amorphous networks with \ensuremath{\Delta}${\ensuremath{\theta}}_{b}$\ensuremath{\le}6.6\ifmmode^\circ\else\textdegree\fi{}.
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TL;DR: In this paper, the effect of crystallite sizes L smaller than 100 nm on the integrated Raman cross section Σc of the transverse optical (TO) mode of fcc silicon was studied experimentally in fully nanocrystallized thin films.
Abstract: The effect of crystallite sizes L smaller than 100 nm on the integrated Raman cross section Σc of the transverse optical (TO) mode of fcc silicon was studied experimentally in fully nanocrystallized thin films. The Σc/Σa (amorphous) ratio of this mode is shown to be 1 up to L=30 A, and to decay exponentially down to 0.1 at larger L. A systematic procedure taking into account both this effect and the experimental optical absorption coefficient αexp at the excitation wavelength is then proposed for the determination of the crystalline volume fraction in mixed phase (amorphous/nanocrystalline) silicon systems by Raman measurements.
315 citations
TL;DR: In this paper, the most significant experimental observations related to ion-beam-induced amorphization in Si and the models that have been developed to describe the process are described and analyzed.
Abstract: Ion-beam-induced amorphization in Si has attracted significant interest since the beginning of the use of ion implantation for the fabrication of Si devices. A number of theoretical calculations and experiments were designed to provide a better understanding of the mechanisms behind the crystal-to-amorphous transition in Si. Nowadays, a renewed interest in the modeling of amorphization mechanisms at atomic level has arisen due to the use of preamorphizing implants and high dopant implantation doses for the fabrication of nanometric-scale Si devices. In this paper we will describe the most significant experimental observations related to the ion-beam-induced amorphization in Si and the models that have been developed to describe the process. Amorphous Si formation by ion implantation is the result of a critical balance between the damage generation and its annihilation. Implantation cascades generate different damage configurations going from isolated point defects and point defect clusters in essentially ...
302 citations
TL;DR: In this paper, the structure and physical properties of nanosize crystalline silicon films were studied by means of high-resolution electron microscopy, Raman scattering spectra, x-ray diffraction pattern, IR transmission spectra and ultraviolet ray analysis.
Abstract: Nanosize crystalline silicon films are fabricated by using highly hydrogen‐diluted silane as the reactive gas and activated with rf+dc double‐power sources, in a conventional plasma‐enhanced chemical‐vapor‐deposition system. The structure of the deposited films as studied by means of high‐resolution electron microscopy, Raman scattering spectra, x‐ray‐diffraction pattern, IR transmission spectra, and ultraviolet ray analysis. The results show that there are many novel structural features and new physical properties for these nanosize crystalline silicon films. In particular, it is found that the optical‐absorption coefficient α is higher than that of a‐Si:H and μc‐Si:H films, the room‐temperature conductivity σd has the value of 10−3–10−1 Ω−1 cm−1, and the hydrogen content CH in nc‐Si:H films is higher than 30 at. %. The nc‐Si:H films have their peculiar features which are different from both a‐Si:H and μc‐Si:H films.
271 citations
TL;DR: In this article, a detailed structural characterization by Raman spectroscopy of hydrogenated amorphous silicon and of nanostructured silicon (ns-Si:H) thin films grown in radio-frequency plasma was presented.
Abstract: In this work we present a detailed structural characterization by Raman spectroscopy of hydrogenated amorphous silicon (a-Si:H) and of nanostructured silicon (ns-Si:H) thin films grown in radio-frequency plasma. The ns-Si:H thin films, also called polymorphous Si thin films, consist of a two-phase mixture of amorphous and ordered Si. The Raman spectra were measured at increasing laser intensities. Very low laser power densities (∼1 kW/cm2) were used to thoroughly analyze the structure of as-deposited thin films. Higher Raman laser powers were found to induce the crystallization of the films, which was characterized by the appearance of a sharp peak around 500 cm−1. This was attained faster in the ns-Si:H than in the conventional a-Si:H thin films because the silicon-ordered particles cause a heterogeneous nucleation process in which they act as seeds for crystallization. The laser power densities for film crystallization, crystal size, and surface temperature were determined from this Raman analysis. The ...
238 citations
TL;DR: The surface modification of single-crystalline silicon induced by single 130 femtosecond (fs) Ti:sapphire laser pulses (wavelength 800nm) in air is investigated by means of micro Raman spectroscopy (μ-RS), atomic force microscopy and scanning laser microscopy as mentioned in this paper.
217 citations