Promotion of crystal growth in as-grown Bi2Te3 electrodeposited films without micro-pores using sputtered Bi2Te3 seed layers deposited on a glass substrate

Abstract

Listen

Translate article

To improve the thermoelectric properties of as-grown electrodeposited films, their crystallinity should be increased by promoting crystal growth and suppressing formation of micro-pores. Here, we prepared as-grown bismuth telluride (Bi2Te3) electrodeposited films using sputtered Bi2Te3 seed layers (AES films) on a glass substrate. The seed layers were thermally annealed in advance and the as-grown electrodeposited Bi2Te3 films were formed under galvanostatic conditions in nitric acid-based solution. The in-plane thermoelectric properties of the AES films were measured at approximately 300 K, and the properties of the electrodeposited films alone were calculated from the measured values. The maximum power factor of the as-grown electrodeposited film was 4.2 μW/(cm·K2), which was approximately eight times higher than that of the electrodeposited films grown using a standard method (without the use of the seed layer) mainly because of the significant increase in electrical conductivity. Surface scanning electron microscopy revealed that the AES films consisted of nano-sized crystal grains with densification in the morphology, thus presenting a smooth, homogeneous surface. However, the electrodeposited films obtained using standard methods exhibited dendritic crystals on the top surface, and a large area of micro-pores on the bottom surface of the film after detachment from the substrate. X-ray diffraction analysis clearly showed peaks of the rhombohedral phase of Bi2Te3 in the AES film, indicating that crystal growth also occurred in the electrodeposited film. Therefore, we concluded that the thermoelectric properties of the as-grown electrodeposited Bi2Te3 films increased because of the improved crystallinity and the suppressed micro-pores in the films.