Cross-sectional observation on the indentation of [001] silicon
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Cross-sectional observation on the indentation of [001] silicon Y. Q. Wu State Key Laboratory for Fatigue and Fracture of Materials, Institute of Metal Research, The Chinese Academy of Sciences, Shenyang, 110015, People’s Republic of China and Laboratory of Atomic Imaging of Solids, Institute of Metal Research, The Chinese Academy of Sciences, Shenyang, 110015, People’s Republic of China
G. Y. Shi Department of Electronic Science and Engineering, University of Liaoning, Shenyang, 110036, People’s Republic of China
Y. B. Xu State Key Laboratory for Fatigue and Fracture of Materials, Institute of Metal Research, The Chinese Academy of Sciences, Shenyang, 110015, People’s Republic of China and Laboratory of Atomic Imaging of Solids, Institute of Metal Research, The Chinese Academy of Sciences, Shenyang, 110015, People’s Republic of China (Received 27 February 1998; accepted 27 July 1998)
A transmission electron microscope (TEM) micrograph of cross-sectionally viewed Vickers indentation made on the surface of (001) silicon at ambient temperature was obtained. The picture clearly reveals a triangle area, pointing downward and having nondiffraction-contrast, left after unloading, which further confirms the amorphized range induced by indentation in silicon. Analysis of the picture directly manifests a significant recovery of indentation depth. Surface shape and range of the amorphous silicon region do not coincide with that of the indenter and the corresponding distribution pattern of hydrostatic stress beneath indentation predicted by elastoplastic theory, respectively. It seems that the amorphization could not be attributed to the result of hydrostatic stress alone.
I. INTRODUCTION
Many investigators studied amorphization induced by indentation using various methods in covalent bond crystals such as single crystal silicon.1–7 It is generally agreed that the formation of the amorphous silicon can be explained using a mechanism of phase transformation under high pressure. In addition, a significant depth recovery of indentation is found during unloading of the indenter.4,6 But the evidence is only the measured curves of load against indentation depth, from which the information obtained is not direct. Atomic force microscopy (AFM) is also helpful to study the indentation region,8 including measurement of the indentation depth, but it is still limited. It should be noted that all the samples used to directly confirm the amorphization induced by indentation in the above papers are plan-view. The information from this kind of observation is surely limited on studying the actual affected region of indentation on the material from surface to inside. In order to get a better understanding of the phenomenon occurring during indentation, the directly cross-sectional study is not substitutive. Lack of this kind of information is mainly because of the difficulty in preparing a suitable cross-section sample for observing in a transmission electron microscope (TEM). J. Mater. Res., V
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