By the molecular dynamics method, a computer simulation of a scratch test with a nanometer scale was performed. The specimen was composed of 1008 silicon atoms with a diamond single-crystal structure. The indentor was assumed to be a perfect rigid body, and the Morse potential was utilized as the interaction between the indentor and a silicon atom. Two types of potential, i.e., Stillinger-Weber and Tersoff potentials, were examined as the interaction between silicon atoms. The present simulation clarified that the standard deviation of the friction constant increased with decreasing scratch depth and became maximum when the indentor just began to scratch the specimen surface at critical load. The friction coefficient, indentation hardness and scratch hardness at critical load were estimated to be 1.2-1.6, 80-90 GPa and 8.5-9.4 GPa, respectively.

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Computer experiments on silicon nano indentation were performed. Conical shaped rigid indentor was pushed into silicon single crystal under constant load condition. The motion of silicon atoms was calculated using molecular dynamics method, where Stillinger Weber potential was assumed as interaction between silicon atoms. The dynamic load indentation depth curve was calculated and the universal hardness was evaluated from the maximum indentation depth. The obtained value of hardness was similar to the experimental value of silicon. The changes in the radial distribution function and bond angle distribution during the indentation process were calculated for the atoms in the neighborhood region of the indentor. It is suggested from the change in the radial distribution function and bond angle distribution that the structure of the atoms become meta stable structure similar to liquid rather than amorphous by the indentation.

By using a molecular dynamics method, a computer simulation of a scratch test on bilayer thin films on a nanometer scale has been performed. In the present simulation, the substrate and thin-film material are TiN or SiO 2 and Al or Cu, respectively. The indentor is assumed to be a perfect rigid body, and the Morse potential is utilized as the interaction between the indentor and a specimen atom. The extended Tersoff potential is assumed as the interaction between specimen atoms. Results indicate that the standard deviation of the friction constant becomes maximum when the scratching load is critical to spalling. The critical loads obtained by the present simulation and actual experiments do not match quantitatively. In contrast, the maximum standard deviation reproduces the spalling strength evaluated from actual experiments. On the basis of this finding, a new evaluation technique for adhesion strength using a nanoscratching test is proposed.