A novel nanoscratch device compatible with commercial microscope for in situ tests of materials’ mechanics

Introduction

Currently, in view of the rapid development of the material preparation industry, more and more new materials emerge in endlessly. Indentation method has become a powerful lossless testing approach to evaluate the mechanical properties of various materials. And it has extremely wide applications in scientific fields, such as materials engineering, semiconductor, microelectromechanical systems (MEMS)/nanoelectromechanical systems (NEMS), metal alloy, and thin films.^1–12 However, other research methods are needed besides indentation. Up to now, nanoscratch method has been utilized in scientific researches with the materials like superconductor, nanocomposite, and superthin films. Dias et al.¹³ and Jurelo et al.¹⁴ have conducted experiments on lamellar superconductor with the nanoscratch method, and they found that tribological properties were different due to the differences of a(b)c-plane structure. The mechanical and tribological properties of color filter (CF) and thin-film transistor (TFT) glasses were studied by Won et al.¹⁵ Similarly, the mechanical behavior of metal glass and metal alloy was also investigated.^16–19 The mechanical properties of the multilayered and polystyrene materials were studied using the same research technique.^20,21 What is more, scientists investigated films critical performances (physicochemical behavior, structural behavior, friction coefficient, and adherent behavior) due to different materials (Ti/TiN and SiC/Si) and under various conditions (wet/dry and thin/super-thin).^22–28 Besides, the works using nanoscratch method are also executed in other fields.^29,30 In addition, due to the fine output performance of the displacement, the piezoelectric actuator is usually utilized to realize the precise feed motion.^31,32 In this article, the piezoceramic is adopted according to the preceding works.

Some experimental phenomena appear during the tests and disappear after the tests. So, in situ nanoscratch device is urgently needed to make those phenomena clear, like how the cuttings pile up along the scar, how the indenter gets in touch with the specimen, and so on. But, the previous studies did not capture the images real timely during the tests.^13–19,22 The reason is that the indenter and the lens are coaxial, which leads the indenter blocking the optical path. So, the real-time images during the test cannot be captured. In this article, the in situ observation is accomplished because the optical path and the axis of indenter are vertical. The benefit of the in situ...