Abstract
We present a study of a-Si X C 1− X :H films. The films were deposited on Si by an ion beam deposition method using a C 6H 14 vapour mixture with a hydrogen and silicon source. After deposition the a-Si X C 1− X :H layers were irradiated by Ar + (20–4000 eV) beams. Current densities were 0.1–1.5 mA/cm 2 and energy densities of the ion beam were 10–400 J/cm 2. The properties of the films were investigated by Raman spectroscopy (RS), ellipsometry, X-ray photoelectron spectroscopy (XPS), Rutherford backscattering spectrometry (RBS), and measurements of electrical resistivity. The RBS showed that a-Si X C 1− X :H films have carbon (∼73%), oxygen (∼10%), silicon (∼17%), and less than 0.5% metal contamination. XPS indicated that the oxygen concentration increases in the surface layer after low energy (50–500 eV) ion irradiation and the position of the C1s peak shifts to higher energy. This means that the graphite component (peak at 284.3 eV) and C–Si (peak at 283.3 eV) decrease and the diamond or C–H (peak at 285.1 eV) increases and these changes were bigger at higher ion energy or current density. The optical measurements also showed that ion irradiation improves the diamond-like properties of a-Si X C 1− X :H films: the optical band gap increases from 1.53 to 2.27 eV in ellipsometric measurements; the position of the G-band shifts to lower wave number from 1515 to 1505 cm −1; the width (FWHM) of the G-band increases from 153 to 180 cm −1 in Raman spectra. These changes were bigger when the energy density of the ion beam was more than 100 J/cm 2. RS data suggests that a critical energy density exists (∼100 J/cm 2) and, after that, the processes were intensified. The electrical measurements confirmed the XPS, RS, and ellipsometry data. We observed an increase in resistivity of a-Si X C 1− X :H films, especially, at higher ion energy (3000–4000 eV).
Published Version
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