多孔硅的制备与热电性能研究

发布时间：2018-03-19 12:30

本文选题：热电材料　切入点：多孔硅　出处：《河北师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：Si基材料作为一种新型热电材料的研究近些年来备受研究者们的广泛关注。能成功制备出具有高热电转换效率的Si基热电材料,对于解决能源紧缺问题,以及开发出高性能绿色环保材料具有重大意义,而且具有广阔的应用前景。具有高孔隙率、有序性高的纳米孔尺寸的多孔硅热电性能较好,而且如果多孔硅的孔径尺寸在电子平均自由程和声子平均自由程之间,会发生强烈的声子散射,携带走大量的热,使其晶格热导率降低,同时又不影响载流子的输运性质,从而使总热导率降低,热电性能提高。基于此,我们利用沉积单层有序Si O2微球模板法来制备孔均匀且有序性、孔隙率高的多孔硅,从而有效降低热导率。同时,我们还采用了模板法双槽电化学腐蚀方法来制备孔深度较深的多孔硅,以尽量减小体硅对其热电性能的影响,而且通过金属Nb的注入,使其热导率进一步降低,同时电阻率也有所下降,更有益于ZT值的提高。本实验的具体研究内容和结果主要有以下几部分:(1)我们首先利用了改进的St?ber方法制备出了单分散Si O2微球,目的是通过利用垂直沉积自组装的方法得到有序的单层Si O2微球模板,将其覆盖在硅片的表面并退火,进而腐蚀制备出孔隙率高、有序性较高以及腐蚀深度较深的纳米孔尺寸的多孔硅来尽量降低其热导率。而且还通过对比实验找出了制备的最适合条件,从而得到了大范围内有序的单层Si O2微球模板。(2)将覆有有序的单层Si O2微球模板的硅片进行无电极化学腐蚀,得到了孔较均匀的多孔硅,而且腐蚀速率、孔隙率都要高于直接腐蚀的多孔硅,并对制备出的样品进行了热导率测试与分析。(3)为了增加腐蚀深度,避免体硅对其性能的影响,采用了双槽电化学腐蚀的方法进行研究,发现在很短的时间内就可得到较深的多孔硅层。还利用了Si O2微球模板法进行腐蚀,发现不仅进一步提高了腐蚀速率,而且还使孔洞更加均匀,孔隙率、有序性有所提高。(4)对制备出的多孔硅进行性能测试,与未腐蚀的体硅相比,其热导率都明显降低,Si O2微球模板法电化学腐蚀90min的多孔硅,孔深度大约224μm,300K时热导率降低至29W/K?m,而且通过Nb的注入使其进一步降低至15 W/K?m,都远远比未腐蚀硅片的低。由于样品表面粗糙度较大、孔隙率高,且具有纳米孔尺寸结构,发生强的热声子散射,从而热导率降低,而这对材料的电导率影响很小,而且样品注入Nb后还使电阻率有所减小,这样有益于ZT值的增大,提高材料的热电性能。
[Abstract]:As a new type of thermoelectric material, Si-based materials have attracted much attention in recent years. Si-based thermoelectric materials with high thermoelectric conversion efficiency can be successfully prepared, which can solve the problem of energy shortage. It is of great significance to develop high performance green environmental protection materials, and has a broad application prospect. Porous silicon with high porosity, high order and nanometer pore size has better thermoelectric properties. Moreover, if the pore size of porous silicon is between the electron mean free path and the average phonon free path, strong phonon scattering will occur, and a large amount of heat will be carried away, which will reduce the lattice thermal conductivity without affecting the transport properties of carriers. Therefore, the total thermal conductivity is reduced and the thermoelectric properties are improved. Based on this, we use the template method of deposited monolayer ordered Sio _ 2 microspheres to prepare porous silicon with uniform and ordered pores and high porosity, thus effectively reducing the thermal conductivity. In order to minimize the influence of bulk silicon on the thermoelectric properties of porous silicon with deeper pore depth, the thermal conductivity of porous silicon was further reduced by the implantation of NB. At the same time, the resistivity is also decreased, which is more beneficial to the increase of ZT value. The specific research contents and results of this experiment are as follows: 1) We first used the improved St.? Monodisperse Sio _ 2 microspheres were prepared by ber method. The aim of this paper was to obtain ordered monolayer Sio _ 2 microspheres template by vertical deposition self-assembly method, which was covered on the surface of silicon wafer and annealed, and then corroded to prepare high porosity. Porous silicon with high orderliness and deeper corrosion depth is used to minimize the thermal conductivity of porous silicon. Thus, a monolayer Sio _ 2 microsphere template with a wide range order was obtained. The silicon wafer coated with ordered single-layer Sio _ 2 microsphere template was chemically corroded without electrode, and the porous silicon with uniform pore was obtained, and the corrosion rate was obtained. The porosity of porous silicon is higher than that of directly corroded porous silicon. In order to increase the corrosion depth and avoid the influence of bulk silicon on its performance, the thermal conductivity of the prepared samples is tested and analyzed. It is found that a deeper porous silicon layer can be obtained in a very short time. The Sio 2 microsphere template method is also used for corrosion. It is found that not only the corrosion rate is further increased, but also the porosity of the pore is more uniform. The thermal conductivity of the prepared porous silicon was significantly lower than that of the uncorroded bulk silicon, and the thermal conductivity of the porous silicon was reduced to 29WK / kg at the pore depth of about 224 渭 m ~ 300K by electrochemically etching the porous silicon for 90 min by the O _ 2 / O _ 2 microsphere template method. M, and further reduced to 15 W / K? by injection of NB? Due to the large surface roughness, high porosity and nano-pore size, strong thermal phonon scattering occurs, thus the thermal conductivity decreases, and this has little effect on the conductivity of the material. The resistivity of the sample is decreased after NB implantation, which is beneficial to increase the ZT value and improve the thermoelectric properties of the material.
【学位授予单位】：河北师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ127.2

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