We demonstrate a facile and safe anisotropic gas etching technique for β-Ga2O3 under atmospheric pressure using forming gas, a H2/N2 gas mixture containing 3.96 vol% H2. This etching gas, being ...neither explosive nor toxic, can be safely exhausted into the atmosphere, simplifying the etching system setup. Thermodynamic calculations confirm the viability of gas-phase etching above 676°C without the formation of Ga droplets. Experimental verification was achieved by etching ( 1 - 02) β-Ga2O3 substrates within a temperature range of 700-950°C. Moreover, selective-area etching using this method yielded trenches and fins with vertical and flat sidewalls, defined by (100) facets with the lowest surface energy density, demonstrating significant anisotropic etching capability.We demonstrate a facile and safe anisotropic gas etching technique for β-Ga2O3 under atmospheric pressure using forming gas, a H2/N2 gas mixture containing 3.96 vol% H2. This etching gas, being neither explosive nor toxic, can be safely exhausted into the atmosphere, simplifying the etching system setup. Thermodynamic calculations confirm the viability of gas-phase etching above 676°C without the formation of Ga droplets. Experimental verification was achieved by etching ( 1 - 02) β-Ga2O3 substrates within a temperature range of 700-950°C. Moreover, selective-area etching using this method yielded trenches and fins with vertical and flat sidewalls, defined by (100) facets with the lowest surface energy density, demonstrating significant anisotropic etching capability.
Abstract GaN mesas were fabricated by sequential dry and wet etching of a + c -oriented GaN layer onto a lattice-matched AlInN layer for future applications of positive beveled edge termination, ...which is desirable for preventing premature breakdown of power devices. The dry etching produced hexagonal AlInN/GaN mesas surrounded by m -plane sidewalls with six protrusions at the vertices. The subsequent hot phosphoric acid etching selectively etched the AlInN layer to expose and etch the chemically unstable − c surface of the GaN layer, which formed reverse-tapered { 10 1 ¯ 2 ¯ } facets. The protrusions were sacrificed during the wet etching to prevent undesirable positive tapering at the vertices.
Sensitization of a wide-gap oxide semiconductor with a visible-light-absorbing dye has been studied for decades as a means of producing H2 from water. However, efficient overall water splitting using ...a dye-sensitized oxide photocatalyst has remained an unmet challenge. Here we demonstrate visible-light-driven overall water splitting into H2 and O2 using HCa2Nb3O10 nanosheets sensitized by a Ru(II) tris-diimine type photosensitizer, in combination with a WO3-based water oxidation photocatalyst and a triiodide/iodide redox couple. With the use of Pt-intercalated HCa2Nb3O10 nanosheets further modified with amorphous Al2O3 clusters as the H2 evolution component, the dye-based turnover number and frequency for H2 evolution reached 4580 and 1960 h–1, respectively. The apparent quantum yield for overall water splitting using 420 nm light was 2.4%, by far the highest among dye-sensitized overall water splitting systems reported to date. The present work clearly shows that a carefully designed dye/oxide hybrid has great potential for photocatalytic H2 production, and represents a significant leap forward in the development of solar-driven water splitting systems.
We report the characterization and application of mist-CVD-grown rutile-structured Ge _x Sn _1− _x O _2 ( x = ∼ 0.53) films lattice-matched to isostructural TiO _2 (001) substrates. The grown surface ...was flat throughout the growth owing to the lattice-matching epitaxy. Additionally, the film was single-crystalline without misoriented domains and TEM-detectable threading dislocations due to the coherent heterointerface. Using the Ge _0.49 Sn _0.51 O _2 film with a carrier density of 7.8 × 10 ^18 cm ^−3 and a mobility of 24 cm ^2 V ^−1 s ^−1 , lateral Schottky barrier diodes were fabricated with Pt anodes and Ti/Au cathodes. The diodes exhibited rectifying properties with a rectification ratio of 8.2 × 10 ^4 at ±5 V, showing the potential of Ge _x Sn _1- _x O _2 as a practical semiconductor.
The effects of thermal annealing on stacking faults and dislocations in single-crystal diamonds with a low defect density were investigated by synchrotron X-ray topography. We compared the X-ray ...topography images before and after annealing under various diffraction conditions. We found that the stacking faults disappeared after annealing, and new dislocations appeared at the edges of disappeared stacking faults. These results indicate that the stacking faults were Shockley type, and they were sandwiched between two Shockley partial dislocations. Therefore, we concluded that the Shockley stacking faults disappeared as a result of the movement of the Shockley partial dislocations. Before annealing, the perfect dislocations were straight along the 21¯1 direction; annealing caused these dislocations to bend along the 11¯0 and 101 directions. We identified two dislocation shapes; upper bending and lower bending dislocations. An analysis based on contrast extinction criterion; indicated that the bending direction depends on the Burgers vector, for example, a dislocation with b=a/2101 moved along the 011¯ direction, and a dislocation with b=a/211¯0 moved along the 011 direction.
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•The annealing effects of diamond single crystal were investigated by synchrotron X-ray topography.•Shockley stacking faults were disappeared due to the movement of Shockley partial dislocations.•Dislocations with b=a/2〈110〉 were bent along the 〈110〉 direction.
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