The micro-indentation test of silicon single crystal was performed under the temperature between 20°C and 1000°C. The plastically deformed zone around the indentation mark has been measured by means of oblique section using electron microscope and optical microscope. Furthermore, using Hill's spherical shell model, the yield points under various temperatures are able to be reasonably estimated from experimentally obtained data. Concerned with the condition of the crack initiation or the plastically deformed zone, the calculated values based on the spherical shell model are compared with experimental values.
The main results obtained are as follows:
(1) The plastically deformed zone is nearly bell shape, but has the neck part at the depth of several microns below the surface. The total depth of deformed zone is 20-30% deeper than the values obtained from spherical shell model. The extent of the zone is extremely affected with temperature.
(2) The cracks of several microns in length are often observed in the vicinity of indentation mark even at the temperatue over 500°C in spite of the estimation deduced from the spherical shell theory that, at these temperature, the crack should not initiate in. Therefore, the initiation of these cracks may be considered to depend on other causes, for example, internal stress originated from cooling.
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