Investigation On The Preparation And Properties Of Thin Film Thermoelectric Devices Based On N-type Bi₂Te_2.7Se_0.3 Thermoelectric Materials

Thermoelectric technology is a kind of green and environmental protection energy technology,which can realize the mutual conversion of heat energy and electric energy.With the development of semiconductor technology,there are more and more demands for thermoelectric power generation and thermoelectric cooling under complicated conditions,such as chip cooling technology and micro-sensor power supply.The micro and nano thin film thermoelectric device,which is a reliable means to meet the above requirements.In the past two decades,the performance of thin film thermoelectric devices has been improved mainly by changing the type of thermoelectric materials,improving the growth process of thermoelectric materials,changing the type of electrode materials and improving the process of electrode materials.However,the fabrication process of thin film thermoelectric devices is also crucial to the improvement of their performance.Based on that,our work from the perspective of device manufacturing technology,combined with chemical mechanical polishing technology,obtained a super smooth,low lossless sapphire substrate surface,and explored the effect of substrate roughness on the performance of bismuth telluride based thin film thermoelectric device.In our work,Bi₂Te_2.7Se_0.3 and Te targets were co-sputtered to deposite Bi₂Te_2.7Se_0.3 films by magnetron sputtering technology.The optimum process parameters of Bi₂Te_2.7Se_0.3 film growth were obtained by single variable method.Under these conditions,the influence of substrate type and film thickness on thermoelectric performance was investigated by changing substrate type and growth time.The results showed that Bi₂Te_2.7Se_0.3 films grown on sapphire substrate had higher crystallinity,and their thermoelectric properties were about 31%higher than those grown on quartz substrate.In addition,with the increases of film thickness,we concluded that the conductivity increased and the seebeck coefficient decreased gradually,and the power factor reached the maximum value at the film thickness of 600 nm as a result.Secondly,the chemical mechanical polishing technology of substrate is applied to the fabrication process of thin film thermoelectric devices.We designed and fabricated thin film thermoelectric device based on sapphire susbtrate,and the film thermoelectric device testing system was set up to measure the output voltage and output power of the device.The results show that the substrate grinding and polishing process is essential for the fabrication of thin film thermoelectric device.The substrate grinding and polishing process makes the growth of Bi₂Te_2.7Se_0.3 film more regular and the defects reduced significantly,which makes the internal resistance of the device reduced significantly,and the output power up to 1.94?W,which increases by about 35%.These studies will provide an idea for the manufacture of high performance thin film thermoelectric materials and devices.