碲化铋基热电薄膜制备与性能分析及其器件设计

发布时间：2018-05-10 06:35

本文选题：磁控溅射 + Bi/Te多层薄膜　；参考：《天津工业大学》2017年硕士论文

【摘要】：早在1823年热电效应就被人们所发现,该效应是热能和电能之间的相互转换,其产生的原因是热电材料所具有的独特属性所致。随着社会发展,人们对环境友好、能源利用率高的制冷设备的需求更加迫切,因此具有无污染、体积小的基于热电材料微加工制成的高效制冷器受到了人们的关注。相对于其它热电材料,碲化铋(Bi2Te3)具有较高的热电转换效率,并且随着纳米技术及纳米材料的长足发展,人们发现薄膜形式的二维热电材料相对于块体材料有着更高的热电优值,二维材料可增加热声子的散射,从而降低热导率,提高Seebeck系数。因此,本文通过设计Bi/Te基多层薄膜辅以快速退火(RTP)来对Bi/Te基二维热电材料的性能进行研究。为了提高Bi/Te基热电薄膜的热电优值,本文首先从热电优值(ZT)的物理方程出发,通过调节工艺参数来控制热电薄膜的微结构,进而在微结构调整上实现热导率λ减小的同时,使功率因数P(PF=S2σ,用于表征Seebeck系数和电导率的综合效果)增加。其工艺上的实施方法是在微结构中通过磁控溅射的方式在基片上交替生长单质Bi和单质Te,辅以RTP快速退火来使Bi和Te发生反应生成Bi2Te3化合物,并通过退火来减小Bi2Te3中的缺陷从而提高Seebeck系数。在反应生成Bi2Te3材料的同时,Bi和Te单质层中间会形成晶界,从而提高了声子散射,降低了热导率λ。其次,为了进一步提升热电材料的热电优值和降低薄膜的缺陷,对多层二维结构薄膜的样品材料进行快速退火处理,在热处理的过程中,发现随着退火时间的延长,薄膜的热电参数均出现了明显的振荡现象,这些振荡现象使得在退火的某些时刻其Seebeck系数和功率因数远远高于块体材料。并且发现退火温度越高,各个热电参数(包括Seebeck系数,载流子浓度,电导率,功率因数,迁移率等)的振幅也随之升高。经研究发现该现象为二维薄膜材料所特有的量子尺寸效应,通过量子尺寸效应理论,来控制快速退火的温度(室温～400℃)和退火时间(0 min～26 min),并对各个热电参数的振荡关系进一步研究,发现载流子浓度与Seebeck系数成反比关系,载流子浓度与电导率成正比关系。并且在该实验中获得的Seebeck系最大可达到190.41 μV·K-1,功率因数达到30.96 μW·K-2·m-1,这些参数都远高于块体材料,可制备性能更加优良的热电器件。最后为了确定退火后生成物对热电材料性能的影响,对不同温度退火下的样品进行XRD元素测量,分析退火后的元素产物构成及形成原因。最终,为了将研究中所获得的优良特性材料制作成热电器件。本文使用ANSYS Mechanical APDL 17.0软件进行热电器件的结构建模,并设计成横向和纵向结构,然后分析两种结构的优劣。随后将实验中所得到的最优热电参数导入到最优的结构模型当中,分别改变通过热电偶的电流,以及改变热电偶的尺寸参数来找出器件中热电转换效率最优的参数设置,并且研究了通过热电偶的电流,以及器件高度与热电转换效率之间的关系。随后,基于建模后的热电器件尺寸模型,进行了湿法刻蚀的制作工艺流程探索,分析了工艺流程中各个工艺步骤的注意事项并提出了改善方案。
[Abstract]:As early as 1823, the thermoelectric effect was discovered by people. This effect is the mutual conversion between thermal energy and electric energy. The cause is caused by the unique properties of thermoelectric materials. With the development of society, the demand for environment friendly and high energy utilization refrigeration equipment is more urgent, so it has no pollution and small volume based on heat. Compared with other thermoelectric materials, bismuth telluride (Bi2Te3) has a higher efficiency of thermoelectric conversion than other thermoelectric materials. With the rapid development of nanotechnology and nanomaterials, it is found that the two-dimensional thermoelectric material in the form of thin film has a higher thermoelectric value than the block material, two The material can increase the scattering of the heating phonon, thus reducing the thermal conductivity and increasing the Seebeck coefficient. Therefore, this paper studies the performance of the Bi/Te based two-dimensional thermoelectric materials by designing a Bi/Te based multilayer film with rapid annealing (RTP). In order to improve the thermoelectric properties of the Bi/Te based thermoelectric film, the physical equation of the thermoelectric value (ZT) is first obtained. The micro structure of the thermoelectric film is controlled by adjusting the technological parameters, and then the thermal conductivity is reduced by the microstructural adjustment, and the power factor P (PF=S2 Sigma is used to characterize the comprehensive effect of the Seebeck coefficient and the conductivity). The process of implementation is to alternate the substrate on the substrate by magnetron sputtering in the microstructures. The growth of the single substance Bi and the single substance Te, supplemented by RTP rapid annealing, reacts Bi and Te to produce Bi2Te3 compounds, and reduces the defects in Bi2Te3 by annealing to improve the Seebeck coefficient. The grain boundary will be formed in the middle of the Bi and Te monomer layers in the reaction generation of Bi2Te3 materials, thus raising the phonon scattering and reducing the thermal conductivity lambda. Secondly, for the sake of reducing the thermal conductivity lambda. To further enhance the thermoelectric value of the thermoelectric materials and reduce the defects of the film, the sample materials of the multilayer two-dimensional structure film are annealed quickly. In the process of heat treatment, it is found that the thermoelectric parameters of the thin film are obviously oscillating with the prolongation of the annealing time. These oscillations make them at some time in the annealing. The Seebeck coefficient and the power factor are much higher than the bulk material. It is found that the higher the annealing temperature, the amplitude of the thermoelectric parameters, including the Seebeck coefficient, the carrier concentration, the conductivity, the power factor, the mobility and so on, also increases. According to the theory, the temperature (room temperature to 400 C) and annealing time (0 min ~ 26 min) are controlled, and the oscillation relation of each thermoelectric parameter is further studied. It is found that the carrier concentration is inversely proportional to the Seebeck coefficient, and the carrier concentration is proportional to the conductivity. And the maximum of the Seebeck system in this experiment can reach 190.. 41 mu V. K-1, the power factor reaches 30.96 W. K-2. M-1. These parameters are far higher than the bulk material, and can prepare the thermoelectric devices with better performance. Finally, in order to determine the effect of the annealing generation on the properties of the thermoelectric materials, the samples were measured by XRD elements at different temperatures, and the composition and formation of the element products after annealing were analyzed. Finally, in order to make the excellent material obtained in the study into thermoelectric devices. This paper uses ANSYS Mechanical APDL 17 software to model the structure of the thermoelectric device, and designs the transverse and longitudinal structure, and then analyzes the advantages and disadvantages of the two structures. Then, the optimal thermoelectric parameters obtained in the experiment are introduced to the optimal junction. In the structure model, the optimal parameters of thermoelectric conversion efficiency are found by changing the current of the thermocouple and changing the size parameters of the thermocouple, and the relationship between the current through the thermocouple and the relationship between the height of the device and the efficiency of the thermoelectric conversion is studied. The technological process of wet etching was explored, and the matters needing attention in each process step were analyzed, and the improvement plan was put forward.

【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2;TB657

【参考文献】