Deep-level defects induced by implantations of Si and Mg ions into undoped epitaxial GaN.

The properties and concentrations of deep-level defects induced by implantations of Si and Mg ions into unintentionally doped (UID) epitaxial GaN have been revealed by using the Laplace-transform photoinduced transient spectroscopy (LPITS) and molecular dynamics (MD) calculations. The material lattice damage, produced by the Si ions implanted at room temperature in the single process at the energies of 200 and 340 keV, is compared with that produced by the Mg ions implanted in the similar process at the energies of 150, 210, and 270 keV. The LPITS results indicate that the same deep traps with the activation energies of 396, 512, 531, 587, 635, and 736 meV are present in the tail regions of the semi-insulating Si- and Mg-implanted films.

Surface free energy of diamond nanocrystals - a molecular dynamics study of its size dependence.

The dependency of the surface free energy (SFE) of diamond nanocrystals on particle size was studied by means of molecular dynamics (MD) and DFT simulations. It was demonstrated how to avoid the ambiguities in calculating the surface area of very small crystallites by expressing the particle size in terms of the number of atoms which we called the number of atoms convention (NAC) rather than in units of length. The NAC method was applied to a set of models terminated with either (100) or (111) crystal faces.