Raman scattering and first-principles analysis of Ge nanostructure, h-BN and KIO3

Abstract

High-pressure Raman scattering investigations show a large pressure coefficient for the Ge-Ge mode in the Ge/SiO2 system and the delaminating of SiO2 film from the Si substrate at ~23 kbar in the Ge/SiO2/Si nanosystem, which are explained by the nonhomogeneous distribution of the elastic field within the nanosystems. DFT-LDA studies on h-BN modifications suggest that real h-BN crystals may have mixed stacking sequences and intrinsic stacking faults. The diverse band gap values of h-BN observed experimentally can be ascribed to the variation of its band structure with stacking sequence and the existence of a metastable structure. The calculated phonon dispersion suggests a transient INC phase which exists in phase I of KIO3 near the phase transition. With the appearance of INC phase in phase I, the improper ferroelectric characteristics of phase transition I-II of KIO3 observed by the dielectric constant investigations can be understood easily.