本文選題：熱電材料　切入點：多孔硅　出處：《河北師范大學》2015年碩士論文　論文類型：學位論文

【摘要】：Si基材料作為一種新型熱電材料的研究近些年來備受研究者們的廣泛關(guān)注。能成功制備出具有高熱電轉(zhuǎn)換效率的Si基熱電材料,對于解決能源緊缺問題,以及開發(fā)出高性能綠色環(huán)保材料具有重大意義,而且具有廣闊的應(yīng)用前景。具有高孔隙率、有序性高的納米孔尺寸的多孔硅熱電性能較好,而且如果多孔硅的孔徑尺寸在電子平均自由程和聲子平均自由程之間,會發(fā)生強烈的聲子散射,攜帶走大量的熱,使其晶格熱導(dǎo)率降低,同時又不影響載流子的輸運性質(zhì),從而使總熱導(dǎo)率降低,熱電性能提高�；诖�,我們利用沉積單層有序Si O2微球模板法來制備孔均勻且有序性、孔隙率高的多孔硅,從而有效降低熱導(dǎo)率。同時,我們還采用了模板法雙槽電化學腐蝕方法來制備孔深度較深的多孔硅,以盡量減小體硅對其熱電性能的影響,而且通過金屬Nb的注入,使其熱導(dǎo)率進一步降低,同時電阻率也有所下降,更有益于ZT值的提高。本實驗的具體研究內(nèi)容和結(jié)果主要有以下幾部分:(1)我們首先利用了改進的St?ber方法制備出了單分散Si O2微球,目的是通過利用垂直沉積自組裝的方法得到有序的單層Si O2微球模板,將其覆蓋在硅片的表面并退火,進而腐蝕制備出孔隙率高、有序性較高以及腐蝕深度較深的納米孔尺寸的多孔硅來盡量降低其熱導(dǎo)率。而且還通過對比實驗找出了制備的最適合條件,從而得到了大范圍內(nèi)有序的單層Si O2微球模板。(2)將覆有有序的單層Si O2微球模板的硅片進行無電極化學腐蝕,得到了孔較均勻的多孔硅,而且腐蝕速率、孔隙率都要高于直接腐蝕的多孔硅,并對制備出的樣品進行了熱導(dǎo)率測試與分析。(3)為了增加腐蝕深度,避免體硅對其性能的影響,采用了雙槽電化學腐蝕的方法進行研究,發(fā)現(xiàn)在很短的時間內(nèi)就可得到較深的多孔硅層。還利用了Si O2微球模板法進行腐蝕,發(fā)現(xiàn)不僅進一步提高了腐蝕速率,而且還使孔洞更加均勻,孔隙率、有序性有所提高。(4)對制備出的多孔硅進行性能測試,與未腐蝕的體硅相比,其熱導(dǎo)率都明顯降低,Si O2微球模板法電化學腐蝕90min的多孔硅,孔深度大約224μm,300K時熱導(dǎo)率降低至29W/K?m,而且通過Nb的注入使其進一步降低至15 W/K?m,都遠遠比未腐蝕硅片的低。由于樣品表面粗糙度較大、孔隙率高,且具有納米孔尺寸結(jié)構(gòu),發(fā)生強的熱聲子散射,從而熱導(dǎo)率降低,而這對材料的電導(dǎo)率影響很小,而且樣品注入Nb后還使電阻率有所減小,這樣有益于ZT值的增大,提高材料的熱電性能。
[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.
【學位授予單位】：河北師范大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TQ127.2

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