Knudsen cell mass spectrometry applied to the investigation of organometallic precursors vapours

The volatility of pentakis(dimethylamido) tantalum (PDMAT) has been studied in the temperature range from − 15 to 60 °C. A special Knudsen cell reactor coupled to a high temperature mass spectrometer, was specifically designed for the study of organometallic precursors. It is composed of an evaporation/sublimation chamber (− 30 to 200 °C), which can be tight closed – like a vacuum chamber – in order to protect the precursors which are likely to be very unstable vs. moisture and atmospheric components. This chamber can be independently weighted for calibration purpose of the mass spectrometric experiments. During experiments, the effusion orifice is externally opened for direct mass spectrometric measurements of saturated vapour pressures. The device has been tested using the well-known mercury vapour pressure. First results obtained for the vaporization of PDMAT are presented.