ICT2014 Abstracts

To enhance the thermoelectric property, strained materials are widely studied, and the strain effects are known to enhance the thermoelectric performance. There are several methods to induce the strain in the material such as using substrate with lattice mismatch, putting pressure and pulling samples. Although these methods have exhibited to improve the thermoelectric properties, it is challenging to control both the magnitude and direction of the stress at the same time. Then, a bending-stress induced thin film on flexible substrate is one of the methods to compensate the lack of above mentioned methods. This method is able to control various compressive and tensile stresses while changing the bending radius of the flexible films systematically. Organic thin film transistors have examined to use this method, and found to change their electrical properties. However, there are few reports to investigate thermoelectric properties of bending-stress induced thin films.

Then, in this study, we induced various compressive and tensile stresses by changing the bending radius of the flexible substrate deposited on bismuth-telluride based thin films by sputtering method. It was found that the Seebeck coefficient of the thin films increased at the condition of compressive stress, and then it decreased at the condition of tensile strain, while the electrical conductivity was not largely changed by inducing both directions of stress. In the conference, we present the structural and thermoelectric properties of strained thin films, and then discuss the relationship between the induced stresses and thermoelectric properties in detail.