Nanoindentation pop-in effects of Bi2Te3 thermoelectric thin films

•Bi2Te3 films are deposited on c-plane sapphire substrates using PLD.•The mechanical properties of Bi2Te3 films are measured by nanoindentation.•The dislocation loops in Bi2Te3 films is estimated by classical dislocation theory.

The structural, surface morphological and nanomechanical characteristics of Bi2Te3 thin films are investigated by means of X-ray diffraction (XRD), atomic force microscopy (AFM) and nanoindentation techniques. The Bi2Te3 thin films are deposited on c-plane sapphire substrates using pulsed laser deposition (PLD). The XRD result showed that Bi2Te3 thin film had a c-axis preferred orientation and a smoother surface feature from AFM observation. Nanoindentation results exhibit the discontinuities (so-called multiple “pop-ins” event) in the loading segments of the load–displacement curves, indicative of the deformation behavior in the hexagonal-structured Bi2Te3 thin film is the nucleation and propagation of dislocations. Based on this scenario, an energetic estimation of nanoindentation-induced dislocation resulted from pop-in effects is made. Furthermore, the hardness and Young’s modulus of Bi2Te3 thin films were measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) mode. The obtained values of the hardness and Young’s modulus are 5.7 ± 0.8 GPa and 158.6 ± 6.2 GPa, respectively.