双槽电化学腐蚀法制备介孔硅的热导率

Thermal Conductivity of Meso-Porous Silicon Prepared by the Double-Tank Electrochemical Corrosion Method

提出了一个基于有效介质理论分析介孔硅层传热机理的理论模型,对影响介孔硅有效热导率的因素包括孔隙率、硅的恒容热容和硅的声子平均自由程进行了理论分析,得出用于计算介孔硅有效热导率的计算公式.采用双槽电化学腐蚀法制备孔隙率分别为62%和79%的介孔硅,微喇曼光谱技术测量所制备的介孔硅的热导率为8.315和0.949W/(m·K).SEM分析表明,孔隙率为62%和79%的介孔硅的平均特征尺寸分别为10nm和5nm.应用计算介孔硅有效热导率的公式,得到孔隙率为62%,平均特征尺寸为10nm和孔隙率为79%,平均特征尺寸为5nm的介孔硅层的有效热导率理论值为10.753和1.035W/(m·K).研究分析表明,理论计算与所获得的实验数据一致.介孔硅极低的热导率使其作为一种良好的热绝缘材料有望广泛应用于微传感器和微电子机械系统中.

A theoretical model describing mechanisms of heat transfer in meso-porous silicon （meso-PS） layer based on the effective medium theory is brought forward. The influencing factors of effective thermal conductivity （ETC） of meso-PS,including the porosity of meso-PS,the heat capacity of silicon at constant volume,and the phonon mean free path of silicon, were analyzed theoretically,and a calculation formula of TC of meso-PS was given. The porosities of meso-PS samples prepared by the double-tank electrochemical corrosion method were 62% and 79%,respectively. Their TC values yielded by micro-Raman spectroscopy were 8. 315 and 0. 949W/（m · K）, respectively. Scanning electron microscopy shows that the average characteristic sizes of meso-PS samples with porosities of 62% and 79% are 10 and 5nm,respectively. According to the formula for TC of meso-PS,the theoretical ETC value of a meso-PS layer with a porosity of 62% and an average characteristic size of 10nm is 10. 753 W/（m·K）,and that of meso-PS layer with a porosity of 79% and an average characteristic size of 5nm is 1. 035W/（m·K）. It is shown that the theoretical values are quite in good agreement with experimental data. Meso-PS with low TC is well suited for thermal insulation material, which is attractive for use in microsensors and microelectro-mechanical systems.