Correlation of dynamic friction and the dislocation etch pit density surrounding annealed scratches in (1 1 1) p-type silicon

The dynamic friction coefficient between a 90° pyramid diamond and a (1 1 1) p-type silicon single crystal has been measured for linear, unidirectional scratches made in the [1 1 0] direction in laboratory air, deionized water and ethanol. The friction coefficient for grooves formed in air increased from 0,6 to 0.7 as the number of scratches increased, reaching a steady state value after ten scratches. The friction coefficient for grooves formed in deionized water and ethanol decreased from 0.7 to 0.5 and also reached a steady state value after ten scratches. Scanning electron microscopy showed that the groove morphology depended on the fluid in contact with the surface during the scratch test. The grooves formed after ten scratches were annealed to 750° C for 3600 sec and etch pits were measured as a function of distance from the groove wall. The etch pit density and their distance from the groove wall was related to the type of fluid used in the scratch test: the density was highest and the distance from the groove wall largest for the groove formed in air and lowest for the groove formed in ethanol. These results imply that the deformation mode and the magnitude of the residual stresses surrounding the groove depend on the enviromental conditions during the scratch test. The friction coefficient was found to vary linearly with the average etch pit density.