Solid solution strengthening and phase transformation in high-temperature annealed Si80Ge20 alloy

• Published in: Journal of crystal growth Vol. 390; pp. 92 - 95
• Main Authors: Chiang, Tun-Yuan, Wen, Hua-Chiang, Chou, Wu-Ching, Tsai, Chien-Huang
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.03.2014; Elsevier
• Subjects: A1. Characterization; A1. Crystal structure; B2. Semiconducting silicon compounds; Condensed matter: structure, mechanical and thermal properties; Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder; Cross-disciplinary physics: materials science; rheology; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Materials science; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Solubility, segregation, and mixing; phase separation; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; A1. Characterization; B2. Semiconducting silicon compounds; A1. Crystal structure; Temperature dependence; Phase transformations; Segregation; Grazing incidence; Roughness; Mechanical properties; Annealing temperature; XRD; Hardness; Indentation; Silicon compounds; Thin films; Transmission electron microscopy; Solid solutions; Temperature effects; Hafnium; Thermal annealing; Crystal structure
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/j.jcrysgro.2013.12.013

This investigation demonstrates the temperature-dependent mechanical properties of Si80Ge20 alloy films via a nanoindenter in the indentation depth of 100nm. The roughly equal root mean square roughness (Rrms) values and repeatable load–displacement (P–δ) curves for the samples ensure the mechanical performances mainly contributed from the influences of annealing temperatures. The hardness (H) values of samples increase with the temperatures of an initial annealing in the range from RT to 900°C, and, conversely, decrease for annealing temperatures over 900°C. Accordingly, both E/H and hf/hmax values, exhibiting an inverse tendency in the above temperature range, hints that the solid solution strengthening effect and the softening phenomenon occur for the initial-annealing and over-annealing stages, respectively. In addition, grazing incidence X-ray diffraction (GIXRD) analysis demonstrates the lattice expansion and the broadened peak that attribute to the solid solution strengthening of samples and the segregation of Ge, respectively. Through observing the value of the (200) lattice spacing of 5.624Å for a 900°C-annealed sample by transmission electron microscopy (TEM) analysis, it is verified that the segregation of Ge is responsible for the decreased hardness for the 1000°C-annealed sample. •Given the solid solution strengthening, the hardness increases with the lattice constant.•The decreased hardness for 1000°C-annealed sample is caused by the Ge segregation.•In the presence of a (200) lattice spacing of 5.624Å, TEM analysis evidences the Ge segregation for the 900°C-annealed sample.