A New Cell for In Situ High-Temperature Micro-Raman Experiments: Studying the Dynamics of Oxygen Vacancy Formation in α-MoO₃

A multifunctional cell for in situ Raman spectroscopy, working at high temperatures and in controlled gas pressure conditions, is described in the present work. The developed design enables variable range thermal annealing processes up to ∼1000 °C both in high vacuum (10–4 mbar) as well as in a precise partial pressure of the selected gas. It is shown that in situ Raman data can be collected up to 850 °C. A thin optical window allows Raman signal acquisition of the samples ranging from bulk to low-thickness amorphous films. In this work, we investigate as a case study the effect of temperature and oxygen partial pressure on the structural dynamics of α-MoO3 using in situ Raman spectroscopy. Our results show the modulation of the defect concentration in oxygen-poor environments as a function of the temperature. A model for quantifying the oxygen vacancy concentration in MoO3–x is proposed. Our results highlight a reversible modulation of the O/Mo ratio within the crystalline material between ∼2.965 and ∼2.926. The described setup facilitates accurate in situ investigations of the structural dynamics during thermal treatments.