Synthesis and characterization of hydrazido- and azido- single precursors for growth of MN (M = Al, Ga) thin films

Abstract

Reaction of $MMe_3$ (M = Al, Ga) with 1 equiv of $NH_2NPh_2$ affords a dimeric complex $[Me_2M-μ-N(H)NPh_2]_2$ [M = Al (1), M = Ga (2)] as a mixture of trans and cis isomers. Purification of 1 and 2 by recrystallization gives only trans isomers 1a and 2a, respectively. Variable-temperature $^1H$ NMR studies reveal that both 1 and 2 in solution undergo trans → cis isomerization with free energy of activation $(ΔG_c^{++})$ values of 15.9 kcal/mol for 1 and 18.3 kcal/mol for 2. The solid state structures of trans isomers 1a and 2a have been determined by single-crystal X-ray diffraction studies. The molecular geometries of 1a and 2a consist of a centrosymmetric and dimeric unit $(M-N)_2$ with two bridging hydrazido groups and two terminal methyl groups bound to each metal atom. The two $N-NPh_2$ groups are trans to each other with respect to the $(M-N)_2$ core plane. The coordination geometry of both metal and nitrogen atoms are distorted tetrahedral. Reaction of trimeric amidogallane, $[Et_2Ga-μ-NH_2]_3$ with 1 equiv of hydrogen azide affords a dialkylazidogallium-ammonia adduct $Et_2(N_3)Ga:NH_3$ (3). Gallium nitride (GaN) film growth has been carried out in a cold wall organometallic chemical vapor deposition (OMCVD) reactor. The crystalline structure, chemical composition, and optical property of the deposited films have been investigated by X-ray diffraction (XRD), pole figure analysis, scanning electron microscopy (SEM), photoluminescence (PL), transmittance electron microscopy (TEM), and Rutherford backscattering spectrometry (RBS). GaN thin films are grown with 3 on Si(111) substrates in the temperature range of 350~450^℃ in the absence of carrier gas by low-pressure chemical vapor deposition. Hexagonal GaN thin films have been obtained on Si (111) substrates at 350℃ and $6.0×10^{-6}$ Torr . The stoichiometry of the resulting film has been determined by RBS. The film structure has been examined by XRD, pole figure analysis, SEM, and TEM. XRD, pole figure, ...