Temperature dependence of Raman and photoluminescence spectra of pure and high-quality MoO3 synthesized by hot wall horizontal thermal evaporation

In this work, a novel system for the hot wall evaporation of MoO3 in a horizontal furnace and at low vacuum atmosphere was settled. Pure MoO3 material was obtained without the presence of other phases and with a strong preferential orientation, as revealed by electron microscopy, micro-Raman spectroscopy and x-ray diffraction. Photoluminescence and Raman spectra were measured as a function of temperature. As a result, the first-order temperature coefficient of the fifteen measured vibrational modes is reported and compared with the scarce literature data available. The relation of these coefficients with the thermal expansion coefficient is discussed in the framework of the Gruneisen model. Moreover, for the first time, the temperature dependence of the different contributions of photoluminescence spectra for MoO3 is reported, and an anomalous increase in PL intensity of all transitions is observed in the range of 40-140 K, followed by a normal quenching at high temperatures. The Shibata model was used to interpret the origin of this anomalous effect.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

In this study, a novel system for hot wall evaporation of MoO3 was developed and characterized in a horizontal furnace under low vacuum atmosphere. Pure MoO3 material with a strong preferential orientation was obtained, and its properties were analyzed using electron microscopy, micro-Raman spectroscopy, and x-ray diffraction. The relationship between photoluminescence and Raman spectra with temperature was investigated. The temperature coefficients of the vibrational modes were reported and compared, and their relation with the thermal expansion coefficient was discussed. Additionally, the temperature dependence of photoluminescent contributions for MoO3 was studied, revealing an anomalous increase in intensity followed by normal quenching at high temperatures. The Shibata model was used to explain this anomalous effect.