Insulator-metal transitions at microindentations

For all tetrahedrally bonded semiconductors (five group IV plus nine III-V compounds and nine II-VI compounds), it is shown that the critical pressure needed to transform the semiconductor into the metallic state correlates with the microindentation hardness number. The same is done for five alkaline earth oxides. The critical transition pressures have been estimated from Herzfeld's theory—that is, from the compression at which the dielectric constant diverges to infinity. Experimental transition pressures also correlate with hardness numbers, and they correlate with the activation energies for dislocation motion. Since these transitions are electronic they can be influenced by photons, doping (donors enhance while acceptors inhibit them), currents, surface states, etc. Microindentation also provides a simple experimental tool for observing pressure and/or shear induced transformations.