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Conductance fluctuations in VHF-PECVD grown hydrogenated microcrystalline silicon thin films
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Coplanar conductance fluctuations or excess noise of undoped hydrogenated microcrystal-line silicon (μc-Si : H) thin films grown by VHF-PECVD from silane-hydrogen mixtures with silane concentrations from 2% to 6% have been studied between room temperature and 470 K. We report that undoped μc-Si : H thin films show similar noise-power spectra to those of undoped a-Si : H films in a coplanar sample geometry. At lower temperatures, the noise with the slope α = 0.60 ± 0.07 and at higher temperatures, the noise with the slope α close to unity dominate the spectrum. The noise magnitude decreases with decreasing silane concentration and becomes strongly temperature dependent with increased crystal unity.