Existence of Equistable Quasi-Microphases in Degenerate Silicon: Revelation through an Atypical Thermal Response of the Fano–Raman Parameter

Abstract

Temperature-induced quasi-phase transition in degenerate crystalline silicon has been studied using temperature-dependent Raman spectroscopy. Atypical temperature dependence of Raman spectral width has been observed, which shows a parabolic nature, making it inconsistent with the existing anharmonic phonon decay theory. This has been analyzed by considering the presence of multiple phonon decay pathways, which depend differently under thermal stimuli. The data have been analyzed to explore the possibility of the existence of quasi-microphases and their reversible temperature-induced phase transition. Thermal hysteresis has been investigated to understand the phase stability and relative activation energy. A theoretical model has been developed to explain the parabolic nature of the Raman width vs temperature curve, showing a good agreement between the two. Temperature-dependent coupling parameters for electron–phonon interactions have been calculated, which confirm the existence of quasi-microscopic temperature-induced phases. The comprehensive analysis of the temperature-dependent variation of Raman parameters and developed theoretical model thereafter may be useful in understanding temperature-dependent electrical properties in electronic-grade doped semiconductors.