Thermal dissociation of ditertiarybutylselenide and methylallylselenide and its impact on the growth of ZnSe by metalorganic vapour phase epitaxy

Studies of the thermal and photochemical decomposition mechanisms of But2Se in the presence or absence of Me2Zn using deuterium labelled analogues

“…70 The products from codecomposing it with Bu t 2 Se are methane and 2methylpropene with only traces of 2,2-dimethylpropane. We have shown 71 25 This is clear evidence that surface catalysed processes are important for the decompositions carried out in the presence of ZnSe and hence for the codecomposition reactions. If the reaction occurs on the surface, reactions such as ( 12) or ( 13) in Scheme 3 should become thermodynamically accessible since surface bound Se and H are formed rather than the high energy species, Se (g) and H ?…”

“…They were not, however, carried out. 25 In IR studies, we tentatively identi®ed Bu t SeH as a decomposition product of Bu t 2 Se and this together with preliminary theoretical calculations led us to propose that b-H abstraction was important. 26 In view of the somewhat con¯icting data especially on the decomposition pathway for Bu t 2 Se, we have carried out detailed studies of the thermal and photochemical decomposition of Bu t 2 Se in a variety of different ambients (He, H 2 or D 2 ) as well as of d 18 -Bu t 2 Se,{ again in various different ambients, sometimes in the presence of d 0 -Bu t 2 Se and/or Me 2 Zn.…”

“…20 Later studies have generally con®rmed this analysis, 18,21±24 although b-H abstraction has also been proposed. 21,24 For Bu t 2 Se, a marked effect of the nature of the surface over which the reaction is carried out has been noted, 25 perhaps suggesting that surface catalysed reactions may be important, but, despite not having observed Bu t SeH as a product, the b-H abstraction mechanism was proposed. Against this, a possible reaction with H 2 or H ?…”

MOVPE Mechanisms from studies of specially designed and labelled precursors

“…Previous studies had suggested, on rather limited evidence, that b-H elimination might be important. 10,44 We have used both deuterium labelling and designed precursors to study the decomposition of bis-(tertiaryalkyl)selenium compounds and find that a radical mechanism is the only one that explains all of the data. The key observations from the gas phase pyrolysis of Bu t 2 Se in He, H 2 or D 2 in the presence or absence of d 18 The failure to observe 2,2,3,3-tetramethylbutane together with the observation that the 2-methylpropane : 2-methylpropene ratio ≠ 1 might also indicate that the products cannot be formed from reactions of Bu t •.…”