Nitronium tetranitratogallate [NO2][Ga(NO3)4] , referred also as anhydrous gallium nitrate, was studied by single-crystal X-ray diffraction. It was found that nitronium tetranitratogallate undergoes reversible, first-order phase transition from a room temperature polymorph indexed to a tetragonal cell (space group I4¯.) to a rotationally-twinned, low-temperature monoclinic polymorph (space group I2) without any apparent damage to the crystal at ~250 K. The room-temperature, noncentrosymmetric, body-centered tetragonal (I) polymorph (a = 9.2774(3) Å, c = 6.1149(2) Å, Z = 2) consists of well-separated nitronium and tetranitratogallate [Ga(NO3)4]- ions having a slightly squashed tetrahedral geometry in which all of the ligands are monodentate. Below approximately 250 K, distortions lower the symmetry to the chiral, body-centered monoclinic nonstandard space group I2. Both components (2a: a = 9.5857(2) Å, b = 5.9399(1) Å, c = 8.9759(2) Å, β = 90.409(1)°, Z = 2. 2b: a = 9.5898(2) Å, b = 5.9376(1) Å, c = 8.9784(1) Å, β = 90.420(1)°, Z = 2) of the twinned structure were independently refined and found to be enantiomeric with nearly identical distance and angle parameters. The most notable change is that 2 of 4 nitrato ligands in the [Ga(NO3)4]- ions that have become bidendate, casing molecular structure to distort towards octahedral geometry. [411]
Nitronium tetranitratogallate [NO2][Ga(NO3)4], referred also as anhydrous gallium nitrate, has been applied for of amorphous Ga2O3 layers by CVD. [412]
“Anhydrous gallium nitrate” [NO2][Ga(NO3)4] has been applied for the growth of GaN layers by ALD, using NH3 as co-reactant. Growth rate of 0.5Å per cycle was achieved, producing 100nm thickness films. [413]