Autocatalytic Behavior of Trimethylindium during Thermal Decomposition

Abstract

Pyrolysis of trimethylindium (TMIn) in a hot-wall flow-tube reactor has been investigated at temperatures between 573 and 723 K using a modulated molecular-beam mass-sampling technique and detailed numerical modeling. The TMIn was exposed to various mixtures of carrier gases: He, H 2 , D 2 , and C 2 H 4 , in an effort to elucidate the behavior exhibited by this compound in different chemical environments. The decomposition of TMIn is a heterogeneous, autocatalytic process with an induction period that is carrier-gas dependent and lasts on the order of minutes. After activation of the tube wall, the thermolysis exhibits a steadystate behavior that is surface mediated. This result is contrary to prior literature reports, which state that decomposition occurs in the gas phase via successive loss of the CH 3 ligands. This finding also suggests that the bond dissociation energy for the (CH 3 ) 2 In-CH 3 bond derived from flow-tube investigations is erroneous and should be reevaluated.

Nature of the parasitic chemistry during AlGaInN OMVPE

“…However, removing NH 3 did not reduce the amount of CH 4 formed, so it is likely that these conditions simply represent the beginning of homogeneous and/or heterogeneous TMIn decomposition in H 2 . In fact, our CH 4 production rate is consistent with literature values for TMIn decomposition [20]. Experiments using N 2 as the carrier gas (with or w/o NH 3 ) produced no measurable CH 4 production at otherwise identical conditions.…”

“…path-B in Fig. 1, is responsible for InN and GaN particle nucleation, then we would expect this temperature difference because TMIn pyrolysis occurs at a much lower temperature than TMGa pyrolysis [17][18][19][20]. Trends with temperature, total pressure, and residence time observed for GaN and AlN have the same direction (though the magnitudes may be different).…”

“…Since path-B involves radical reactions, it is more likely that the carrier gas might directly influence the chemistry. For instance, the pyrolysis rate of both TMGa and TMIn are accelerated in H 2 relative to the rate in inert gases [19,20].…”

Materials Chemistry of Group 13 Nitrides

“…Recent high-level G2 calculations by Allendorf et al gave a bond enthalpy of ∆H 298 = 321 kJ/mol [90]. A reinvestigation of the similar pyrolysis of InMe 3 , for which the same discrepancy between the experimental and theoretical values was observed, has been performed by McDaniel et al, again using the "toluene carrier" method [91]. They found a substantial surface effect, and could prove that the measured activation energies are lower due to an autocatalytic surface mechanism, that most probably also comes into play for GaMe 3 .…”

Soluble InP and GaP Nanowires: Self‐Seeded, Solution–Liquid–Solid Synthesis and Electrical Properties

“…The decomposition temperature of these metal-organic precursors is close to 300 8C, [28][29][30] enabling seed-generation from their decomposition prior to NW formation. The temperatures of 290 8C for InP and 300 8C for GaP, applied to the typical syntheses, have been determined to be the optimized seed-generation conditions.…”