Preparation And Performance Analysis And Device Design Of Bismuth-based Thermoelectric Thin Films

As early as 1823 the thermoelectric effect was found.Thermoelectric material is the basic of to convert thermal energy to electronic energy.With the social development,people urgently need refrigeration equipment which has quality with environment friendly and high energy efficiency.Therefore,no pollution,small volume of the refrigerator which based on Bi2Te3 thermoelectric materials has been noticed by people.Compared with other thermoelectric materials,Bi2Te3 has higher energy conversion efficiency.With the development of nanotechnology and nanometer material,People found that two dimensional thermoelectric materials have higher thermal power optimal value than block materials.Two-dimensional material can increase the thermal phonon scattering,thus reducing thermal conductivity,improve the Seebeck coefficient.The purpose of this paper is that to research the performance of the two dimensional thermoelectric materials by means of sputtering Bi/Te multilayer thin film and annealing film by rapid thermal processing(RTP).Firstly,this paper start form thermal electric optimal value(Z7)equation,to research factors of influencing thermal electric optimal value.In order to increase ZT value,proposed improvement scheme of material structure,to decrease thermal conductivity ? and increasing Seebeck coefficient,conductivity ?.Alternately sputtering Bi and Te target material on the substrate by using magnetron sputtering,supplemented by rapid thermal processing,Bi and Te generated Bi2Te3 compounds,and to reduce the defects in Bi2Te3 and improve the Seebeck coefficient.In reaction to generate Bi2Te3 materials,Bi and Te elemental can form grain boundary in the middle of layer,so as to improve the phonon scattering,reduces the thermal conductivity.Secondly,quantum size effect of two-dimensional thermoelectric materials has studied.With the extension of annealing time,thermoelectric parameters of thin films produced obvious oscillation phenomenon.Some time,the oscillation phenomenon makes Seebeck coefficient and power factor is much higher than bulk materials.By controlling the annealing temperature(room temperature?400?)and annealing time(0min?26min)to study thermoelectric parameters,Found Seebeck coefficient has obtain maximum value 190.41 ?VK-1 at 400 ?,the power factor has obtain maximum value 30.96?W·K-2·m-1 at same temperature.Oscillation trend of various thermal parameters under different annealing temperature has studied too.Found that the higher annealing temperature,the amplitude of thermal parameters(Including the Seebeck coefficient,carrier concentration,conductivity,power factor,mobility,etc)will increase too.The relationship between the thermal parameters were studied,found that the carrier concentration and Seebeck coefficient is inversely proportional relationship,carrier concentration and electrical conductivity is proportional relationship.Using XRD equipment to measure element construction of samples which under different annealing temperature.Finally,Using software to build the model structure of thermoelectric devices and designed for horizontal and vertical structure.To import optimal thermoelectric parameters which given by experiment into ANSYS,changing the current of through the thermocouple and dimensions of thermocouple respectively,to find out the parameter settings of optimal thermoelectric conversion efficiency,and studied the relationship between the dimensions,current and thermoelectric conversion efficiency.Subsequently,making practice for thermoelectric device manufacturing process.