Is Silicon a Glass? Measurements of the Mechanical Properties of Boron-Doped and Single-Crystal Silicon

Abstract

The low-temperature mechanical properties of single-crystal silicon have been studied by Kleiman et al. [1] (KAB). A high-purity (110) wafer, with ρ = 20K Ω-cm and a few ppm non-electronic impurities was used to fabricate the oscillator. They observed a temperature independent dissipation to 100mK, decreasing linearly for T < 100mK. The frequency shift shows softening below 60mK, with a log T dependence near the frequency maximum. Such a mechanical response is qualitatively similar to that of glasses [2]. KAB propose that glassy defects are intrinsic to silicon, and estimate a defect concentration ~1% of that found in vitreous silica. Other explanations have been offered for the mechanical response. [3,4] Keyes proposed that electronic states, split by a small energy, would fit the frequency shift data at a much smaller concentration.KeywordsDefect ConcentrationEnergy SplittingVitreous SilicaPeriod ShiftResonant PeriodThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.