高阻值纳米薄膜材料的热电特性测量

Measurement of thermoelectric characteristics of high resistance nano films

为了实现高阻值纳米薄膜材料的热电系数测量,搭建了一套塞贝克系数测量系统。研究了该系统的温控精度和温差生成机制并测量了高阻值条件下微弱电压。首先,建立了高真空度和带有多重电磁屏蔽的真空测试环境;然后,设计了高稳定度温差控制平台,以便为测试样品提供可控温差;同时根据高阻条件下的微弱电压的检测要求,消除了检测通道的漏电流和分布电容的影响。最后,提出了一种循环温差的测量方法,用于有效去除分布电容引起的塞贝克电压长期漂移。采用该方法对高阻值的有机半导体材料进行了塞贝克系数的测定,结果显示:阻值高达7×1012Ω的有机薄膜材料的塞贝克系数的测量精密度<2%,温度控制精度为±0.001K。得到的结果表明,该系统能够实现对样品阻值高达1012Ω的纳米薄膜材料的塞贝克系数的测量。

To measure the thermoelectric characteristics of a high resistance nano film,a Seebeck coefficient measurement apparatus was designed and built.The temperature control accuracy and temperature difference generation mechanism were investigated and the weak voltage signals under a high resistance condition were measured.Firstly,a vacuum environment with an ultra-high vacuum degree and an electric-magnetic shield was setup.Then,a temperature difference control stage was installed inside the vacuum chamber to generate the accurate temperature difference between the two ends of the test sample.Meanwhile,according to the weak voltage detection requirements under the condition of high resistance,the influences of channel leakage current and distributed capacitance were eliminated.Finally,a cyclic temperature gradient generation technique and a corresponding algorithm were proposed to eliminate the negative effects of the long term drift of Seebeck voltage and the Seebeck coefficients of high resistance organic semiconductor materials were measured.Experimental results on a high resistance nano film with resistance over 7×1012Ω indicate that the measuringaccuracy of the measurement apparatus is less than 2%,and temperature control accuracy is about ±0.001K.It means that the apparatus can measure the Seebeck coefficient of nano material with a resistance over 1012Ω.