Study Of The ZnSb Thermoelectric Thin Film Grown By Iron Beam Sputtering And Its Ohmic Contact

Thermoelectric material is a green environmental protection material,which can realize the conversion between thermal energy and electric energy.Thermoelectric devices made of them are widely used in thermoelectric power generation and semiconductor refrigeration.The thin-film of thermoelectric materials not only helps to improve the thermoelectric properties of the materials,but also makes them possible to integrate with other micro-semiconductor devices.Therefore,the research of high-performance thin film thermoelectric materials has important practical value and scientific significance.ZnSb thermoelectric material is safe,non-toxic,low-cost,simple in structure,rich in raw material sources,together with high thermal stability.Therefore,ZnSb thermoelectric material is considered as a promising thermoelectric material.In this paper,ZnSb thermoelectric thin films were prepared by ion beam sputtering.The effects of different preparation conditions on the composition,crystal structure and thermoelectric properties of the films were studied.By optimizing the preparation process,the ZnSb thermoelectric thin films with better performance were prepared.Since the contact resistances between the ZnSb and metal electrodes are of great importance for the performance of nano/micro thermoelectric devices,the ohmic contact-resistivity of the metal electrode and the ZnSb thermoelectric thin film are further studied.The main results obtained in this thesis are as follows:Firstly,ZnSb thermoelectric films were prepared by an ion beam sputtering technique using the alloy compound as the target.The screen pressure,beam current,annealing temperature,and substrate temperature on the properties of the ZnSb films were investigated.It is found that the contents of Zn and Sb in the films can be adjusted within a certain range by changing the ion beam energy and beam current.The annealing process is more effective to improve the crystalline quality and thermoelectric properties of the film than that of the substrate temperature.Results show that the ZnSb thermoelectric film prepared with the ion beam energy of 0.9 keV,the beam current of 15 mA,the deposition time of 3 hours,and the annealing at 420Pa argon atmosphere for 1 hour,has the best thermoelectric performance,and its maximum power factor is 0.69 mWm^-1K^-2.Secondly,a ZnSb thermoelectric film was prepared by using a Zn/Sb conbined target formed by interlacing Zn and Sb strips.The ZnSb films were deposited with various ion beam energies,beam currents,annealing temperatures,and substrate temperatures.The results show that the thermoelectric properties of ZnSb thin films prepared under the condition of 20mA beam current,0.8keV ion beam energy,and375°C annealing temperature is the best.The maximum power factor of it is0.4mWm^-1K^-2.Although the thermoelectric properties of the samples prepared with the conbined target are not improved,the problems of easy damage and slow deposition rate occurred in the alloy target have been successfully solved.Finally,different metal electrodes including Cu,Co,and Mo were sputtered and deposited on the ZnSb thin film by using a mask plate,and the contact resistance between these metals and the ZnSb thin film were measured using the transmission line model.Studies show that Co has the the smallest ohmic contact resistance with the ZnSb thermoelectric film.The contact resistance between the metal electrode and the ZnSb thermoelectric film was futher reduced by etching the ZnSb thermoelectric film with dilute hydrochloric acid and by annealing of the Co electrodes at different temperatures.As a result,the ohmic contact resistivity was significantly reduced from1.49×10^-2 to 4.92×10^-7?·cm².