A special reactor coupled with a high‐temperature mass spectrometer for the investigation of the vaporization and cracking of organometallic compounds

Abstract

A special reactor coupled to a high-temperature mass spectrometer was specifically designed for the study of vaporization and thermal cracking of organometallic precursors. This reactor has two kinds of settings. One is a single Knudsen effusion cell which enables the analysis of the composition of saturated vapors and the determination of the partial pressure of each gaseous molecule in equilibrium with its condensed phase. This cell is an evaporation/sublimation cell (operating from 243 to 473 K), which can be tightly closed--like a vacuum chamber--in order to protect organometallic compounds against moisture and atmospheric components. This cell can be independently weighed usefully to evaluate the equilibrium vapor pressures of the sample using the mass-loss method. During experiments, the effusion aperture is externally opened for direct mass spectrometric measurements. The other setting dedicated to the study of thermal decomposition of gaseous molecules consists of a set of tandem cells: the previously described Knudsen cell and a cracking cell (operating from 293 to 973 K).

Cracking study of pentakis(dimethylamino)tantalum vapors by Knudsen cell mass spectrometry

“…A special effusion reactor with two effusion cells (tandem cells) had been designed and built in our laboratory as described previously13 in order to analyze the composition and cracking of organometallic compounds. The evaporation cell and the cracking cell are placed vertically one above the other and they are linked by a transfer tube 13.…”

“…A special effusion reactor with two effusion cells (tandem cells) had been designed and built in our laboratory as described previously13 in order to analyze the composition and cracking of organometallic compounds. The evaporation cell and the cracking cell are placed vertically one above the other and they are linked by a transfer tube 13. The reactor can work either as a conventional Knudsen evaporation cell – where the organometallic sample is evaporated using the only lower (or first) Knudsen cell and the mass spectrometric analysis is thus performed on saturated vapors – or as tandem cells (the evaporation cell is linked to the cracking cell) in order to analyze the non‐saturated gas‐phase materials produced from the thermal decomposition.…”

“…with the temperature of the cracking cell as close as possible to that of the evaporation cell. This calibration method was previously described and tested with mercury 13. Therefore, from Eqn.…”

“…In previous work,12 we analyzed the saturated gaseous phase produced by the vaporization of a PDMAT sample using a special effusion reactor13 coupled with a mass spectrometer. This showed that this organometallic vapor phase is composed of three molecules: mainly Ta(NC 2 H 6 ) 4 (g) (i.e.…”

Thermodynamics Simulations Applied to Gas-Solid Materials Fabrication Processes

“…Indeed, thermodynamics predicted total cracking of both Ta [N(CH3)2]5(g) and amine molecules in the whole investigated temperature ranges, while in mass spectrometric experiments, Ta [N(CH3)2]5(g) and NC2H7 (g) amine have been observed only in the low temperature below 623 K [26,29]. The deviation vs. equilibrium could be analyzed experimentally by the use of various sizes of cracking cell as well as the deliberate and controlled introduction of H2(g).…”