Theory of interface states at Si/transition-metal-silicide interfaces

Abstract

The Si/NiSi2 (lll) interface is of both fundamental and technological interest: From the fundamental point of view, it is the best characterized of all semiconductor/metal interfaces, with two well-determined geometries (A and B) involving nearly perfect bonding. (This is because Si and NiSi2 have nearly the same lattice spacing.) Consequently, a theoretical treatment of this system makes sense-- as it would not for messier systems-- and one can have some confidence that the theoretical predictions are relevant to experimental observations. From the technological point of view, Si/NiSi2 is representative of the class of semiconductor/metal interfaces that are currently of greatest interest in regard to electronic devices-Si/transition-metal-silicide interfaces. The calculations of this dissertation are for the intrinsic interface states of Si/NiSi2 -A geometry. These calculations also provide a foundation for later studies of defects at this interface, and for studies of other related systems, such as CoSi2 . The calculations employ empirical tight-binding Hamiltonians for both Si and NiSi2 (with the parameters fitted to prior calculations of the bulk band structures, which appear to be in agreement with the available experimental data on bulk Si and NiSi2). We also employ Green's function techniques-- in particular, the subspace Hamiltonian technique. Our principal results are the following...