a b s t r a c tBoron phosphide (BP) is a material of interest for development of a high-efficiency solid-state thermal neutron detector. For a thick film-based device, microstructure evolution is key to the engineering of material synthesis. Here, we report epitaxial BP films grown on silicon carbide with vicinal steps and provide a detailed analysis of the microstructure evolution and strain relief. The BP film is epitaxial in the near-interface region but deviates from epitaxial growth as the film develops. Defects such as coherent and incoherent twin boundaries, dislocation loops, stacking faults concentrate in the near-interface region and segment this region into small domains. The formation of defects in this region do not fully release the strain originated from the lattice mismatch. Large grains emerge above the near-interface region and grain boundaries become the main defects in the upper part of the BP film.

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Pentaneopentyltantalum, Ta(CH(2)Bu(t))(5) (1), was directly observed earlier in the formation of the archetypical alkylidene complex (Bu(t)CH(2))(3)Ta=CHBu(t) (2) from the reaction of either (Bu(t)CH(2))(3)TaCl(2) (3) with 2 equiv of Bu(t)CH(2)Li or (Bu(t)CH(2))(4)TaCl (4) with 1 equiv of Bu(t)CH(2)Li. Ta(CH(2)Bu(t))(5) (1) was, however, short-lived, and its (1)H NMR resonances were mixed with those of (Bu(t)CH(2))(3)Ta=CHBu(t) (2), Bu(t)CH(2)Li, (Bu(t)CH(2))(3)TaCl(2) (3), (Bu(t)CH(2))(4)TaCl (4), and CMe(4) in a fairly narrow region. In the current work, deuterium-labeled Ta(CD(2)Bu(t))(5) (1-d(10)) has been prepared from the reactions of (Bu(t)CD(2))(3)TaCl(2) (3-d(6)) with 2 equiv of Bu(t)CD(2)Li as well as (Bu(t)CD(2))(4)TaCl (4-d(8)) with 1 equiv of Bu(t)CD(2)Li. Due to a kinetic isotope effect, Ta(CD(2)Bu(t))(5) (1-d(10)) has a much longer life than 1. In addition, there are fewer peaks in the (1)H NMR spectra of Ta(CD(2)Bu(t))(5) (1-d(10)). (2)H NMR spectroscopy can also be used to characterize 1-d(10). These properties provide an opportunity to identify and study 1-d(10) in detail. Kinetic studies of the Ta(CD(2)Bu(t))(5) (1-d(10)) --> (Bu(t)CD(2))(3)Ta=CDBu(t) (2-d(7)) and Ta(CH(2)Bu(t))(5) (1) --> (Bu(t)CH(2))(3)Ta=CHBu(t) (2) conversions yield a kinetic isotope effect (KIE) = 14.1(0.8) at 273 K. In addition, kinetic studies of the 1-d(10) --> 2-d(7) conversion at 273-298 K give DeltaH(double dagger)(D) = 21.1(1.5) kcal/mol and DeltaS(double dagger)(D) = -4(6) eu for the alpha-deuterium abstraction reaction.

Ta(NMe(2))(4)[N(SiMe(3))(2)] (1) undergoes the elimination of Me(3)Si-NMe(2) (2), converting the -N(SiMe(3))(2) ligand to the ═NSiMe(3) ligand, to give the imide "Ta(NMe(2))(3)(═NSiMe(3))" (3) observed as its dimer 4. CyN═C═NCy captures 3 to yield guanidinates Ta(NMe(2))(3-n)(═NSiMe(3))[CyNC(NMe(2))NCy](n) [n = 1 (5), 2 (6)]. The kinetic study of α-SiMe(3) abstraction in 1 gives ΔH(‡) = 21.3(1.0) kcal/mol and ΔS(‡) = -17(2) eu.

Boron Phosphide (BP) is a promising material for use as a room temperature semiconductor detector of thermal neutrons. The absorption of a thermal neutron by a 10B nucleus in BP can yield 2.3MeV of energy which in solid state BP can yield ∼0.5 million electron-hole pairs that would be detectable with minimal amplification in a device. BP thin films are grown according to the net reaction below in a cold wall chemical vapor deposition (CVD) reactor: Thin film depositions are performed using diborane and phosphine with a balance of hydrogen gas at near atmospheric pressure with RF induction heating. The resultant BP films are characterized by Raman, XRD, SEM, TEM and TEM-EELS for chemical composition, surface and bulk morphology. BP growths on Si and SiC substrates are compared. SiC provides reduced lattice mismatch for growth of BP and growth of heteroepitaxial BP on SiC will be discussed.