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In the present study, thermal stability of α-Ga2O3 under vacuum and ambient pressure conditions was investigated in situ by x-ray diffraction and transmission electron microscopy (TEM). It was observed that the thermal stability of α-Ga2O3 increased by 200 °C when pressure was lowered from an atmospheric to a vacuum level. This finding can be explained by oxygen diffusion under different oxygen partial pressures. In addition, in situ TEM imaging revealed that, once past the decomposition temperature, the onset of phase change propagates from the top crystal surface and accumulates strain, eventually resulting in a fractural film. The mechanism of α-Ga2O3 to β-Ga2O3 transition is evaluated through experiments and is discussed in this manuscript.

In the search for chemically stable two-dimensional (2D) materials with high in-plane mobility, proper bandgap, and compatibility with vapor-based fabrication, van der Waals semiconductor SiP has become a potential candidate as a robust variation of black phosphorous. While bulk SiP crystals were synthesized in the 1970s, the vapor-based synthesis of SiP nanostructures or thin films is still absent. We here report the first chemical vapor growth of SiP nanostructures on SiO2/Si substrate. SiP islands with lateral size up to 20 µm and showing well-defined Raman signals were grown on SiO2/Si substrate or on SiP-containing concentric rings. The presence of SiP phase is confirmed by XRD. The formation of rings and islands is explained by a multiple coffee ring growth model where a dynamic fluctuation of droplet growth front induces the topography of concentric ring surfaces. This new growth method might shed light on the controlled growth of group IV-III high-mobility 2D semiconductors.

There is increasing interest in α-polytype Ga2O3 for power device applications, but there are few published reports on dielectrics for this material. Finding a dielectric with large band offsets for both valence and conduction bands is especially challenging given its large bandgap of 5.1 eV. One option is HfSiO4 deposited by atomic layer deposition (ALD), which provides conformal, low damage deposition and has a bandgap of 7 eV. The valence band offset of the HfSiO4/Ga2O3 heterointerface was measured using x-ray photoelectron spectroscopy. The single-crystal α-Ga2O3 was grown by halide vapor phase epitaxy on sapphire substrates. The valence band offset was 0.82 ± 0.20 eV (staggered gap, type-II alignment) for ALD HfSiO4 on α-Ga0.2O3. The corresponding conduction band offset was −2.72 ± 0.45 eV, providing no barrier to electrons moving into Ga2O3.

Obtaining uniform silicon concentration, especially with low concentrations (ranging from 1 × 1016 to 1 × 1018 cm−3) by molecular beam epitaxy, has been challenging due to oxidation of a silicon solid source in the oxide environment. In this work, Si doping of β-Ga2O3 (010) films by diluted disilane as the Si source is investigated using hybrid plasma-assisted molecular beam epitaxy. The impact of growth temperature, disilane source concentration, and disilane flow rate on Si incorporation was studied by secondary ion mass spectrometry. Uniform Si concentrations ranging from 3 × 1016 to 2 × 1019 cm−3 are demonstrated. Si-doped β-Ga2O3 films with different silicon concentrations were grown on Fe-doped β-Ga2O3 (010) substrates. The electron concentration and mobility were determined using van de Pauw Hall measurements. A high mobility of 135 cm2/V s was measured for an electron concentration of 3.4 × 1017 cm−3 at room temperature.

低温电输运特性是非晶态材料理论研究中的关键问题. 通过在Ti-Zr-Hf-Cu-Ni高熵非晶合金薄膜材料中掺入氧, 可以诱导其在低温下显示出异常的电输运行为. 低于8 K时, 掺氧高熵非晶合金薄膜的电阻率分别与温度和外加磁场强度的1/2次方（即 T 1/2和 H 1/2）呈线性关系. 研究表明, 氧的掺入增强了高熵非晶合金薄膜中电子-电子间的库伦作用和电子自旋之间的交互作用, 从而导致含氧高熵非晶合金薄膜的低温异常磁电输运行为. 因此，我们可通过对高熵非晶合金材料掺氧实现对该材料低温导电性能的调控.