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Hydrogenated amorphous silicon carbide deposition using electron cyclotron resonance chemical vapor deposition under high microwave power and strong hydrogen dilution

2002; American Institute of Physics; Volume: 92; Issue: 5 Linguagem: Inglês

10.1063/1.1500418

1520-8850

Kok Wai Chew, Rusli Rusli, S. F. Yoon, J. Ahn, V. Ligatchev, E. J. Teo, T. Osipowicz, F. Watt,

Silicon Nanostructures and Photoluminescence

We have investigated the growth of a-Si1−xCx:H using the electron cyclotron resonance chemical vapor deposition (ECR-CVD) technique, under the conditions of high microwave power and strong hydrogen (H2) dilution. The microwave power used is 900 W and a gas mixture of CH4 and SiH4 diluted in H2 is varied to give carbon (C) fractions x ranging from 0 to 1. We aim to understand the effects of these deposition conditions on the characteristics of ECR-CVD grown a-Si1−xCx:H films at different x. Their microstructure and optical properties are investigated using infrared absorption, Raman scattering, UV-visible spectrophotometry, and photothermal deflection spectroscopy. Information on the atomic fraction x is obtained with Rutherford backscattering spectrometry. The B parameter in the Tauc relation is found to decrease and the Urbach energy Eu increase with x, which are indicative of a higher degree of disorder with C incorporation. At intermediate x, the presence of Si–C bonds can be clearly seen from the IR absorption and Raman scattering results. The T peak around 1200 cm−1 is observed in the Raman spectra of the C-rich samples, with a redshift noted at increasing x. This suggests an increased presence of sp3 C–C bonds in these films, which is attributed to the high microwave power and strong H2 dilution that enhance C sp3 bonding and indirectly limit the number of C sp2 sites. This accounts for the large E04 gaps of more than 3.2 eV observed in such films, which are nearly saturated at large x, instead of exhibiting a maximum at an intermediate x as are commonly reported. Blue photoluminescence (PL) is observed, and the PL peak energies (EPL) are correlated to the E04 gap. The full width at half maximum of the PL are also correlated to the Urbach energy Eu. These results support that the PL broadening is attributed to the disorder broadening arising from the broad band tails.