Search

Truly bulk ZnGa2O4 single crystals were obtained directly from the melt. High melting point of 1900 ± 20 °C and highly incongruent evaporation of the Zn- and Ga-containing species impose restrictions on growth conditions. The obtained crystals are characterized by a stoichiometric or near-stoichiometric composition with a normal spinel structure at room temperature and by a narrow full width at half maximum of the rocking curve of the 400 peak of (100)-oriented samples of 23 arcsec. ZnGa2O4 is a single crystalline spinel phase with the Ga/Zn atomic ratio up to about 2.17. Melt-grown ZnGa2O4 single crystals are thermally stable up to 1100 and 700 °C when subjected to annealing for 10 h in oxidizing and reducing atmospheres, respectively. The obtained ZnGa2O4 single crystals were either electrical insulators or n-type semiconductors/degenerate semiconductors depending on growth conditions and starting material composition. The as-grown semiconducting crystals had the resistivity, free electron concentration, and maximum Hall mobility of 0.002–0.1 Ωcm, 3 × 1018–9 × 1019 cm−3, and 107 cm2 V−1 s−1, respectively. The semiconducting crystals could be switched into the electrically insulating state by annealing in the presence of oxygen at temperatures ≥700 °C for at least several hours. The optical absorption edge is steep and originates at 275 nm, followed by full transparency in the visible and near infrared spectral regions. The optical bandgap gathered from the absorption coefficient is direct with a value of about 4.6 eV, close to that of β-Ga2O3. Additionally, with a lattice constant of a = 8.3336 Å, ZnGa2O4 may serve as a good lattice-matched substrate for magnetic Fe-based spinel films. [ABSTRACT FROM AUTHOR]

Sn-doped β-GaO epitaxial layers have been grown on (100) β-GaO substrates by metal organic vapour-phase epitaxy. Triethylgallium (TEGa), molecular oxygen (O) and tetraethyltin (TESn) were used as Ga, O and Sn precursors, respectively. Layers grown at optimized temperature and chamber pressure, i.e. 850 °C and 5 mbar, had flat surfaces with a rms roughness of about 600 pm. Structural analysis by transmission electron microscopy revealed that the main defects in the layers were stacking faults and twin lamella. The incoherent boundaries of these defects are supposed to act as compensation and scattering centres, limiting the carrier mobility. Sn was homogeneously incorporated with a flat profile throughout the whole layer at concentration levels ranging from 2 × 10 to 3 × 10 cm proportionally to the used TESn flux. All layers were electrically conductive. However, an unambiguous Hall effect was measurable only for Sn concentrations higher than 1 × 10 cm, resulting in electron concentrations from 5 × 10 to 2 × 10 cm at room temperature. For increasing free carrier concentrations, the electron mobility showed the tendency to increase from 10 to 30 cm/Vs. The maximum mobility of 41 cm/Vs, measured in a sample with free carrier concentration of 1 × 10 cm, represents the highest value reported for β-GaO layers grown by MOVPE so far. [ABSTRACT FROM AUTHOR]

The title compounds are synthesized by physical vapor deposition of subnanometer elemental layers followed by annealing under a nitrogen atmosphere leading to self-assembly of the precursors into the desired [(SnSe)1.15]m(VSe2) (m = 1, 2, 3, and 4) intergrowth products. [ABSTRACT FROM AUTHOR]