Nanoindentation of Bi₂Se₃ Thin Films.

Hong-Da Lai,Jenh-Yih Juang,Phuoc Le,Le Tuyen,Sheng-Rui Jian,Chih-Wei Luo

doi:10.3390/mi9100518

Abstract

The nanomechanical properties and nanoindentation responses of bismuth selenide (Bi2Se3) thin films are investigated in this study. The Bi2Se3 thin films are deposited on c-plane sapphire substrates using pulsed laser deposition. The microstructural properties of Bi2Se3 thin films are analyzed by means of X-ray diffraction (XRD). The XRD results indicated that Bi2Se3 thin films are exhibited the hexagonal crystal structure with a c-axis preferred growth orientation. Nanoindentation results showed the multiple “pop-ins” displayed in the loading segments of the load-displacement curves, suggesting that the deformation mechanisms in the hexagonal-structured Bi2Se3 films might have been governed by the nucleation and propagation of dislocations. Further, an energetic estimation of nanoindentation-induced dislocation associated with the observed pop-in effects was made using the classical dislocation theory.

Highlights

Topological insulators (TIs) have attracted enormous research attention owing to their intriguing fundamental physical properties, such as their conduction mechanisms [1,2], as well as their potential applications in the emergent fields of spintronics [3], optoelectronics [4] and quantum computation [5]
The Bi2Se3 films prepared by metal organic chemical vapor deposition and thermal evaporation exhibited polycrystalline morphologies and c-axis preferred oriented structures [21,22]
The indenter was loaded for the fourth and final time at a strain rate of 0.05 s−1, with a 5 s holding period inserted at the peak load in order to avoid the influence of creep on unloading characteristics, which were used to compute the mechanical properties of Bi2Se3 thin films

Summary

Introduction

Topological insulators (TIs) have attracted enormous research attention owing to their intriguing fundamental physical properties, such as their conduction mechanisms [1,2], as well as their potential applications in the emergent fields of spintronics [3], optoelectronics [4] and quantum computation [5]. PLD has become one of the most widely used deposition techniques for growing thin films containing multi-elements. Both epitaxial and polycrystalline Bi2Se3 thin films have been successfully prepared by PLD [9,17,18,19,20]. We report the nanomechanical properties of Bi2Se3 thin films deposited on c-plane sapphire substrates by PLD using nanoindentation with the aid of the continuous contact stiffness (CSM) mode. In addition to obtaining the characteristic nanomechanical properties of Bi2Se3 thin films, we performed detailed analyses on the first pop-in event displayed on the load-displacement curves of nanoindentation to elucidate the underlying plastic deformation mechanisms and the associated dislocation physics [34,35,36,37]

Materials and Methods

Findings

Conclusions