Radical Species Formed by the Catalytic Decomposition of NH₃on Heated W Surfaces

Abstract

The catalytic decomposition processes of NH 3 on heated W surfaces were examined by employing laser spectroscopic techniques. H atoms and NH 2 radicals were identified as primary decomposition products on the catalyzer surfaces. The effective enthalpies for the production of these species were both determined to be 150 kJ/mol. NH radicals were also identified, but the production of this species is ascribed to secondary processes. N atoms are minor products in both the primary and secondary processes. The absolute density measurements show that the decomposition efficiency of NH 3 is comparable to that of H 2 . The steady-state densities of NH 3 and the stable products, H 2 and N 2 , were also measured by mass spectrometry. When the catalyzer temperature is over 2000 K, the H 2 density is comparable to that of residual NH 3 . H atoms are produced not only by the direct decomposition of NH 3 but also by the decomposition of H 2 .

Formation of aminosilanes in the hot-wire chemical vapor deposition process using SiH4-NH3 gas mixtures

“…The decrease of the SiH 3 + signal intensity with temperature has also been demonstrated by Tange et al 27 Umemoto et al 29 has shown that the NH 2 radical intensity grows with filament temperature, and this is confirmed in our previous work with 50% NH 3 in the HWCVD reactor. An important question to be addressed in studying the gas-phase reaction chemistry of SiH 4 -NH 3 mixtures in HWCVD is whether or not there is any cross-talk between SiH 4 and NH 3 molecules and their respective filament decomposition products during the formation of disilane and trisilane.…”

“…Our examination of the reaction chemistry of NH 3 in the HWCVD process has found that the major gas-phase products correspond to hydrogen and nitrogen. 14,15 The deposition chemistry of ammonia in the HWCVD process has been well characterized by Umemoto et al 29 They have identified H and NH 2 radicals as the primary decomposition products of NH 3 on the hot W filaments. Signals from H 2 and N 2 were also detected using mass spectrometry.…”

Catalytic Decomposition of H2O(D2O) on a Heated Ir Filament to Produce O and OH(OD) Radicals

“…In this technique, radical species are produced from material gases on heated metal surfaces without co-producing ionic or metastable excited species. In order to make clear the decomposition and ejection mechanisms, many studies have been carried out to identify the radical species produced [3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Although it has been rather difficult to produce oxidizing radicals, we have recently shown that atomic oxygen can be produced efficiently by the catalytic decomposition of O 2 , NO, N 2 O, and NO 2 on a heated Ir filament [7,8].…”

Density and production of NH and NH2 in an Ar–NH3 expanding plasma jet

“…[19][20][21] Laser-induced fluorescence has also been used for determining the density of NH and NH 2 produced by NH 3 decomposition on a heated tungsten filament. 22 For depositing systems, few studies of the NH 3 plasma chemistry using mass spectrometry have been reported, for example, for the ammonia-silane chemistry 23,24 and recently also for the ammonia-acetylene chemistry. 25 In both pure NH 3 plasmas and depositing plasmas, the chemistry is very complex and much remains unknown about the NH 3 dissociation and its products.…”