Electronic Study of Fracture in Semiconductors

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In this project, excitation of electrons and atoms by deformation and fracture in solids has been investigated theoretically as a fundamental study of the mechanism of electron and atom emission caused by fracture in semiconductors.The following studies have been made : (1) the mechanism of fracture- induced electron emission (2) computer simulations of atomic motions during crack extension ; (3) the electronic response to lattice displacement.The results are summarized as follows(1) The number of emitted electrons and the energy distribution of emitted electrons in fractured metals, and the increase of the electrical conductivity in fractured semiconductors have been calculated in terms of thermoelectronic emission. It has been shown that electrons near fracture surfaces are in the excited states corresponding to about 1,000 K.(2) Computer simulations of atomic motions caused by fracture under tensile strain have been carried out using the two- dimensional model system. It has been shown that there is a critical value of tensile strain above which the number of emitted atoms increases rapidly. This result reproduces fractoemission observed in brittle solids such as semiconductors and insulators.(3) The electronic response to lattice displacement in Pd and Ag has been studied by means of electronic structure calculations. It has been shown that lattice displacement increases the electron energy of Pd relative to that of Ag. An electronic origin of hydrogen embrittlement in Pd has been proposed on the basis of the calculated results.