蒙特卡洛法研究硅纳米线热导率
首发时间:2009-01-06
摘要:由于声子在纳米尺度下的输运需要考虑量子效应与边界效应, 通过解析方法获得其传输特性比较困难,本文采用蒙特卡洛方法(Monte Carlo, MC)构建了声子在体态硅与硅纳米线结构中的输运模型, 简化了边界散射的选择机制与处理方法. 在15K至1000K的温度范围内, 对体态硅的热导率进行了模拟, 验证了MC模型对本征散射处理方法的正确性, 进而模拟了等效直径为22nm、37nm与56nm的硅纳米线在15K至315K温度范围内的热导率, 其中等效直径为37nm和56nm的硅纳米线热导率与实验值符合较好, 等效直径为22nm的硅纳米线热导率比实验值偏大. 分析认为随着等效半径的减小, 声子色散曲线发生改变, 导致迟豫时间减小, 声子发生边界散射的频率增加, 热阻增大. 基于以上分析, 通过对边界散射迟豫时间的修正, 获得了与实验值较为一致的结果.
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Monte Carlo study on the thermal conductivity of Si nanowire
Abstract:For the quantum and boundary effects, it is hard to obtain the properties of phonon transport in a low dimensional structure by means of analytical solutions. In this paper, a dedicated Monte Carlo model was built by simplifying the phonon scattering processes to study the thermal properties for bulk silicon and silicon nanowire. Phonon transport in bulk silicon was simulated at temperature ranging from 15K to 1000K , which proved the correctness of the MC model and then silicon nanowires with equivalent diameter of 22nm, 37nm and 56nm over a temperature of 15-315K were simulated. Though the results for 37nm and 56nm nanowires agreed well with experimental data, the 22nm one deviated significantly. The results indicate with the decrease of diameter of nanowire, the phonon disperse relations deviate from that for bulk material greatly, which leads to the reduction of boundary relaxation time and increase of the frequency of boundary scattering. By modifying the relaxation time scale, reasonable simulation results are obtained in our model.
Keywords: Monte Carlon nanowire thermal conductivity phonon
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