Photodegradation and Thermal Effects in Violet Phosphorus

TL;DR

This study investigates the photodegradation and thermal stability of violet phosphorus, revealing how light wavelength, exposure, and temperature affect its properties and potential for optoelectronic use.

Contribution

It provides a comprehensive analysis of VP's degradation mechanisms and thermal effects, including excitation wavelength influence and temperature-dependent optical and vibrational properties.

Findings

Degradation rate increases with above bandgap light exposure.

Exciton and trion intensities depend linearly on excitation power at low temperature.

VP remains stable up to 673K as shown by Raman spectroscopy.

Abstract

Violet phosphorus (VP) has garnered attention for its appealing physical properties and potential applications in optoelectronics. We present a comprehensive investigation of the photo-degradation and thermal effects of exfoliated VP on SiO2 substrate. The degradation rate of VP was found to be strongly influenced by the excitation wavelength and light exposure duration. Light exposure to the above bandgap ({\lambda} > 532 nm) leads to faster degradation, attributed to interactions with reactive oxygen species. Power-dependent photoluminescence (PL) measurements at low temperature (T=4 K) showed neutral exciton (X0) and trion (T) intensities linearly increased with excitation power, while the energy difference between their peak energies decreased, indicating changes in the exciton energy gap due to degradation. At room temperature X0 and T peaks were observed with higher X0 spectral weight, indicating reduced thermal stability of T. As the temperature decreased to 4 K, both X0 and T emissions intensified with blue-shifted peak positions. The T/X0 spectral weight ratio increased from 0.28 at 300 K to 0.69 at 4 K, suggesting enhanced T formation due to reduced phonon scattering. Temperature-dependent Raman spectroscopy revealed the presence of VP up to 673K. By tracking the peak position of 9 Raman modes with temperature the linear first-order temperature coefficient were obtained and found to be linear for all modes up to 673 K. Our results provide a deeper understanding of VP's degradation behavior and implications for optoelectronic applications.