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Epitaxial κ -(Al x Ga1− x )2O3 thin films and heterostructures grown by tin-assisted VCCS-PLD

2019; American Institute of Physics; Volume: 7; Issue: 11 Linguagem: Inglês

10.1063/1.5124231

2166-532X

Philipp Storm, Max Kneiß, Anna Hassa, Thorsten Schultz, Daniel Splith, Holger von Wenckstern, Norbert Koch, Michael Lorenz, Marius Grundmann,

Advanced Photocatalysis Techniques

The structural, surface, and optical properties of phase-pure κ-(AlxGa1−x)2O3 thin films on c-sapphire and STO(111):Nb substrates as well as on MgO(111) and κ-Ga2O3 templates are reported as a function of alloy composition for x < 0.4. The thin films were grown by tin-assisted pulsed laser deposition (PLD). For the variation of the Al-content, we utilized radially segmented PLD targets that enable the deposition of a thin film material library by discrete composition screening. Growth on κ-Ga2O3 (001) thin film templates enhanced the phase pure growth window remarkably up to x = 0.65. The crystallization of the κ-phase was verified by X-ray diffraction 2θ-ω-scans for all samples. Both in- and out-of-plane lattice constants in dependence on the Al-content follow a linear relationship according to Vegard’s law over the complete composition range. Atomic force microscope measurements confirm smooth surfaces (Rq ≈ 1.4 nm) for all investigated Al-contents. Furthermore, bandgap tuning from 4.9 eV to 5.8 eV is demonstrated and a linear increase in the bandgap with increasing Al-content was observed.