碲化铋热电薄膜的制备及性能研究
发布时间：2018-07-23 16:40
【摘要】：热电材料是一种可以实现热能和电能直接相互转换的功能材料,在温差发电和热电制冷等领域有广泛的应用前景。碲化铋(Bi_2Te_3)基化合物作为室温附近性能最好的热电材料,近年来备受关注。但是经过几十年的研究,室温下块体Bi_2Te_3材料的热电优值仍然在1左右,导致能量转换效率较低,无法与传统发电和制冷系统相媲美。随着纳米科技在热电材料中的应用,热电材料低维化可通过量子禁闭效应提高材料的功率因子,通过界面的声子散射效应降低材料的热导率,从而提高热电优值;因此,低维材料具有更大的空间提高热电性能。本文通过磁控溅射方法在不同条件下制备Bi_2Te_3薄膜,系统研究了薄膜的结构、形貌及热电性能。首先在石英玻璃衬底上制备Bi_2Te_3薄膜,并探索了沉积温度、薄膜成分及Ar流量对薄膜结构和热电性能的影响。研究表明,随沉积温度升高,薄膜表面形貌和晶粒取向发生变化,Seebeck系数不断增大,当沉积温度为400℃时,薄膜的Seebeck系数取得最大值83.96μV/K,此时电导率为11.89×10~4 S/m,同时功率因子具有最佳值6.79μW/cmK~2。当通过Te靶与Bi_2Te_3合金靶共溅射制备Bi_2Te_3薄膜时,发现薄膜中的过量的Te有利于提高Seebeck系数和功率因子;在相同的沉积温度下通过共溅射制备的薄膜的Seebeck系数比单靶溅射制备的薄膜的Seebeck系数高,400℃时,Seebeck系数最大值为92.42μV/K。为了确定最佳的Ar流量,通入不同流量的Ar,同时通过限流阀控制工作气压恒定,制备Bi_2Te_3薄膜;结果发现,工作气压一定时,Ar流量对薄膜的结构和形貌的影响并不明显;但是过高或过低的Ar流量会影响镀膜效率。其次本文探讨了择优取向结构及Te靶功率对Bi_2Te_3薄膜结构和性能的影响,以单晶MgO作为衬底,在400℃下通过Te靶与Bi_2Te_3合金靶共溅射制备了具有高度(00l)取向的Bi_2Te_3薄膜,此时薄膜的Seebeck系数最大值为103.6μV/K,比相同条件下在石英玻璃衬底上制备的薄膜的Seebeck系数高。由于薄膜中的Te含量对热电性能有很大的影响,因此确定最佳的Te含量至关重要。本文中通过调控Te靶的溅射功率,制备了具有不同Te含量的Bi_2Te_3薄膜,并分析了薄膜中的Te含量对Bi_2Te_3薄膜结构及热电性能的影响。结果表明,随着Te靶功率的增加,薄膜的Seebeck系数和电导率先增加后减少,当Te靶溅射功率为8 W时,薄膜具有最高的Seebeck系数和电导率,分别为157.7μV/K及9.68×10~4 S/m,此时功率因子为24.6μW/cmK~2;而Te靶溅射功率为5 W及12 W时,功率因子仅有3.95μW/cmK~2及5.24μW/cmK~2。最后,在优化的工艺参数的基础上,制备了具有高度择优取向及高功率因子的Bi_2Te_3薄膜,其Seebeck为145.6μV/K,电导率为9.68×104 S/m,功率因子高达39.1μW/cm K~2。
[Abstract]:Thermoelectric material is a kind of functional material which can realize the direct conversion between heat energy and electric energy. It has a wide application prospect in thermoelectric power generation and thermoelectric refrigeration. Bismuth telluride (Bi_2Te_3)-based compounds, as the best thermoelectric materials near room temperature, have attracted much attention in recent years. However, after decades of research, the thermoelectric excellence of bulk Bi_2Te_3 at room temperature is still about 1, which leads to low energy conversion efficiency and can not be compared with the traditional generation and refrigeration systems. With the application of nanotechnology in thermoelectric materials, the low-dimensional thermoelectric materials can increase the power factor of the materials by quantum confinement, and reduce the thermal conductivity of the materials by phonon scattering effect at the interface, thus improving the thermoelectric excellence. Low dimensional materials have more space to improve thermoelectric properties. In this paper, Bi_2Te_3 thin films were prepared by magnetron sputtering under different conditions. The structure, morphology and thermoelectric properties of the films were systematically studied. Firstly, Bi_2Te_3 thin films were prepared on quartz glass substrates. The effects of deposition temperature, composition and ar flow rate on the structure and thermoelectric properties of the films were investigated. The results show that the surface morphology and grain orientation of the films increase with the increase of deposition temperature, and the Seebeck coefficient increases continuously when the deposition temperature is 400 鈩，
本文编号：2140006
[Abstract]:Thermoelectric material is a kind of functional material which can realize the direct conversion between heat energy and electric energy. It has a wide application prospect in thermoelectric power generation and thermoelectric refrigeration. Bismuth telluride (Bi_2Te_3)-based compounds, as the best thermoelectric materials near room temperature, have attracted much attention in recent years. However, after decades of research, the thermoelectric excellence of bulk Bi_2Te_3 at room temperature is still about 1, which leads to low energy conversion efficiency and can not be compared with the traditional generation and refrigeration systems. With the application of nanotechnology in thermoelectric materials, the low-dimensional thermoelectric materials can increase the power factor of the materials by quantum confinement, and reduce the thermal conductivity of the materials by phonon scattering effect at the interface, thus improving the thermoelectric excellence. Low dimensional materials have more space to improve thermoelectric properties. In this paper, Bi_2Te_3 thin films were prepared by magnetron sputtering under different conditions. The structure, morphology and thermoelectric properties of the films were systematically studied. Firstly, Bi_2Te_3 thin films were prepared on quartz glass substrates. The effects of deposition temperature, composition and ar flow rate on the structure and thermoelectric properties of the films were investigated. The results show that the surface morphology and grain orientation of the films increase with the increase of deposition temperature, and the Seebeck coefficient increases continuously when the deposition temperature is 400 鈩，
本文编号：2140006
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