Lattice-distortion-induced amorphization in indented [110] silicon
- PDF / 396,230 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 46 Downloads / 280 Views
MATERIALS RESEARCH
Welcome
Comments
Help
Lattice-distortion-induced amorphization in indented [110] silicon Y. Q. Wu and Y. B. Xu State Key Laboratory For Fatigue and Fracture of Materials and Laboratory of Atomic Imaging of Solids, Institute of Metal Research, The Chinese Academy of Sciences, Shenyang, 110015, People’s Republic of China (Received 20 October 1997; accepted 30 July 1998)
High-resolution transmission electron microscopy (HRTEM) is used to reveal fine structures of amorphous silicon induced by Vickers indentation and its interface with unindented silicon matrix. Deformation microtwins at the interface and continuous transition from lattice structure of crystal into amorphous structure at the interface are observed. Within the amorphous silicon near the periphery of the indented region, there are many clusters characterized by distorted silicon lattice. A possible mechanism of lattice-distortion-induced amorphization at the periphery of indented silicon is suggested. All the indentations are performed at ambient temperature.
I. INTRODUCTION 1
Since Clarke et al. reported a transformation of silicon from the crystal to the amorphous phase induced by indentation using transmission electron microscopy (TEM) in 1988, Callahan and Morris in 1992,2 Page et al. in 1992,3 Suzuki and Ohmura in 1996,4 etc., confirmed this phenomenon in succession. According to indentation microhardness, for example, 12 GPa reported by Suzuki and Ohmura4 and 120 kbar mentioned by Gerk and Tabor,5 which is comparable with the pressure of phase transformation of silicon under high pressure, e.g., 16 GPa reported by Jamieson6 and more precise, 11.3–12.5 GPa reported by Hu et al.,7 as well as a change of conductivity under the indentation impression,1 the authors indicated that the formation of amorphous silicon (a-Si) can be explained using a mechanism of phase transformation under high pressure. That is, the crystal silicon (c-Si) transforms to the ductile metallic b –Sn structure Si(II) during indentation loading, and then transforms to metastable amorphous phase Si(I0 ) upon unloading because of the insufficient thermal energy to all rearrangement back to the diamond cubic form. Using this mechanism, Gerk and Tabor5 explained the formation of permanent indentation in germanium and silicon, and also Shen et al.8 explained the formation of amorphous silicon produced by ball milling (these authors also suggested a model of crystalline-refinement induced amorphization). Because the confirmation of the a-Si in the above references is based on methods of electron diffraction and diffraction contrast, Suzuki and Ohmura4 pointed out that “It should be noted that the term amorphous here is on a diffraction scale; it can possibly be a polycrystal of very fine grain or a nanocrystal.” 682
http://journals.cambridge.org
J. Mater. Res., Vol. 14, No. 3, Mar 1999
Downloaded: 02 Apr 2015
Although it can explain many experimental facts, the mechanism of phase transformation under high pressure is still not enough. The mechanism of phase
Data Loading...
