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Structural, optical and electrical properties of a-Si1-xCx:H films synthesized by DC-magnetron co-sputtering technique
|Amer Brighet 1, Mohamed Kechouane 1, Aissa Keffous 2, Abdelhak Cheriet 2, Youcef Belkacem 2, Hamid Menari 2, Tahar Kerdja 4, Lakhdar Guerbous 3, Assia Boukezzata 2|
1. Laboratoire "Couches Minces et Semiconducteurs" - USTHB - Faculté de Physique -, BP 32 El-Alia - Bab-Ezzouar, Alger 16111, Algeria
In this contribution, SiC layers were fabricated in DC magnetron sputtering system on corning glass and p type Si(100)by co-sputtering of intrinsic silicon as target coated by 10 x 5 mm2 sprigs (32 sprigs) of polycrystalline 6H-SiC in argon and hydrogen plasma mixture. The a-Si1-xCx:H thin films have been characterized by UV-Visible-IR spectrophotometry, Fourier transform infrared spectroscopy (FT-IR), secondary ions mass spectrometry (SIMS), electrical conductivity measurements and photoluminescence (PL).
The band gap energy values of a-SiC:H films, for thicknesses ranging from 0.18 to 2.5 µm, increases until to reach a constant value around 2.70 eV. This behaviour was observed as well in undoped material as in doped a-Si:H, and can be explained by the influence of hydrogen bonding on the valence band edge through the transforming of Si-Si weak bonds to Si-C bonds those correspond to the deep energetic levels in valence band.
FT-IR measurements clearly evidenced the absorption bands at around 660, 769 and 1108 cm-1, which correspond to Si-C transitional phase (Si1-xCx alloys, x < 0.5), SiC transverse optical phonons and Si-O stretching vibration, respectively. The Si-C absorption band is shifted to higher wave number than those for the 6H-SiC phonon mode (located at 780 cm-1). The peak shift was attributed to the size effects of the precipitates.
The effect of a-Si1-xCx:H/pSi film thickness on interface and composition was investigated using dynamic SIMS. The presence of 16O profiles with a high signal at the interface can be ascribed to the possible formation of silicon oxide during deposition; this result confirms the presence of Si-O band in the FT-IR spectra. The film composition is close to a structure as a-Si0.75C0.25:H noticeably identical from all thickness layers.
Photoluminescence spectra of the samples were observed in the visible range at room temperature with two peaks centred at 470 nm and 550 nm. The origin of the PL was discussed.
Presentation: Poster at E-MRS Fall Meeting 2009, Symposium C, by Mohamed Kechouane
See On-line Journal of E-MRS Fall Meeting 2009
Submitted: 2009-05-25 09:28 Revised: 2009-06-07 00:48