Formation of a Tetrameric, Cyclooctane-like, Azidochlorogallane, [HClGaN3]4, and Related Azidogallanes. Exothermic Single-Source Precursors to GaN Nanostructures

The synthesis of a novel tetrameric gallane, [HClGaN 3 ] 4 ( 1 ),with a heterocyclic cyclooactane-like structure has been demonstrated. A single-crystal X-ray study reveals that the molecule consists of eight-membered Ga 4 N 4 rings with Ga atoms bridged by the α-nitrogens of the azide groups. [HClGaN 3 ] 4 crystallizes in the tetragonal space group space group P 4 2 bc, with a = 17.920(3) Å, c = 10.782(3) Å, V = 3462(2) Å 3, and Z = 8. On the basis of the mass spectrum, the vapor of the compound consists of the trimer [HClGaN 3 ] 3, which is a low-temperature molecular source for growth of GaN layers on sapphire and Si substrates at 500 °C. Solid 1 decomposes exothermically at 70 °C to yield bulk nanocrystalline wurtzite and zinc blende GaN. The reaction between H 2 GaCl and LiN 3 yields the analogous and extremely simple azidogallane (H 2 GaN 3 ) n ( 2 ), which is used to deposit crystalline GaN films at 450 °C. Compound 2 is considerably more reactive than 1, and its decomposition, often initiated at room temperature, yields pure and crystalline nitride material of unusual morphology and microstructure.