Dynamic vapour pressure measurements of di-tertiarybutyl sulphide using an ultrasonic monitor

Abstract Di-tertiarybutyl sulphide is an attractive precursor for the growth, using metal-organic vapour-phase epitaxy (MOVPE), of sulphur-based wide band-gap II-VI compounds due to its lower volatility compared to other more commonly used sulphur sources and likely suppression of unwanted gas-phase pre-reactions. The vapour pressure of MOVPE precursors is a key parameter and needs to be precisely known in order to control the concentration of source materials entering the reactor. Only scattered and incomplete vapour pressure data exist for di-tertiarybutyl sulphide. The concentration under dynamic conditions was measured with an Epison concentration monitor and used to predict the saturated vapour pressures. The vapour pressure equation (log 10 p =8.559(±0.082)−(2338(±23)/ T ) was obtained and the measured vapour pressures were found to be consistently smaller than the reported literature values. The saturated vapour pressure for tertiarybutyl thiol under dynamic conditions has also been measured and new data are reported.