高性能Bi_(2)Te_(3-x)Se_(x)热电薄膜的可控生长

Structural control for high performance Bi_(2)Te_(3-x)Se_(x) thermoelectric thin films

碲化铋基材料一直被认为是室温下性能最优异的热电材料之一,也是商用热电器件首选的块体材料.然而面对柔性或高密度设备等应用需求时,薄膜热电材料比块体材料更具优势.因此,提升薄膜材料热电性能及可控制备技术至关重要.与碲化铋基块体材料和P型碲化铋基薄膜相比,N型碲化铋基薄膜的性能相对偏低.本工作利用磁控溅射法制备了一系列N型碲化铋薄膜,研究衬底温度和工作压强对薄膜生长模式的影响规律,从而通过溅射参数精确调控薄膜的形貌、结构和生长取向,在合适的衬底温度和工作压强的共同作用下,制备出(00l)方向层状生长的高质量致密薄膜.由于层状结构薄膜具有超高的面内载流子迁移率,该薄膜实现了大于10^(5) S/m的超高电导率.由于兼具高电导率与高Seebeck系数,该层状薄膜试样在室温下的功率因子高达42.5μW/(cm·K^(2)),克服了N型碲化铋基薄膜材料难以匹配P型碲化铋基薄膜材料的困难.

Bi_(2)Te_(3)-based alloys have been long regarded as the materials chosen for room temperature thermoelectric(TE)applications.With superior TE performances,Bi_(2)Te_(3)-based bulk materials have been commercially used to fabricate TE devices already.However,bulk materials are less suitable for the requirements for applications of flexible or thin film TE devices,and therefore the thin film materials with advanced TE properties are highly demanded.Comparing with bulk materials and P-type Bi_(2)Te_(3)-based thin films,the TE properties of N-type Bi_(2)Te_(3)-based thin films have been relatively poor so far and need further improving for practical applications.In this study,a series of N-type Bi_(2)Te_(3-x)Se_(x)thin films is prepared via magnetron sputtering method,and their structures can be precisely controlled by adjusting the sputtering conditions.Preferential layered growth of the Bi_(2)Te_(3-x)Se_(x)thin films along the(001)direction is achieved by adjusting the substrate temperature and working pressure.Superior electrical conductivity over 105 S/m is achieved by virtue of high in-plane mobility.combining the advanced Seebeck coefficient of Bi_(2)Te_(3)-based material with superior electrical conductivity of highly oriented Bi_(2)Te_(3-x)Se_(x)thin film,a high power factor(PF)of the optimal Bi_(2)Te_(3-x)Se_(x)thin film can be enhanced to 42.5μW/(cm·K^(2))at room temperature,which is comparable to that of P-type Bi_(2)Te_(3)-based thin film and bulk material.