Stability of SiC and SiN interfaces in titanium carbide and nitride based heterostructures

Abstract

First-principles molecular dynamics simulations of the stability of the NaCl-type (B1) SiC and SiN interfaces in TiX/one multilayer SiY (X,Y=C,N) heterostructures were carried out as functions of temperature. It was previously shown that the SiX interfaces in the heterostructures based on transition metal compounds could be dynamically unstable owing to the elongated interfacial Si-X bonds compared to the Si-X bonds in the B1-SiX phases in equilibrium. However, this criterion is not satisfied for some SiX(111) interfaces. The aim of this work is to study the temperature-induced changes in the structure of the heterostructures under consideration and to clarify a possible origin of instability of the interfaces in them. It is shown that, at finite temperatures, the interfacial layer in the TiN(001)/SiC heterostructure transforms into the zinc blende-type (B3) SiC-like layer, whereas the interfaces in other (001) heterostructures transform into amorphous-like interfacial layers. The TiC(111)/SiC and TiN(111)/SiN heterostructures are stable up to 1400 K. The TiN(111)/B3-like SiC and TiC(111)/B3-like SiN systems form during static relaxation of the initial heterostructures. The phase transformations of the interfaces are explained in terms of dynamical and elastic stability criteria. In contrast to the (111) interfacial layers, all the B1-(001) interfaces are found to be dynamically unstable. The formation of the B3-(111) interfaces occurs due to the elastic instability of the corresponding B1-(111) interface.