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β-Ga2O3 is attracting considerable attention for applications in power electronics and deep ultraviolet (DUV) optoelectronics owing to the ultra-wide bandgap of 4.85 eV and amendable n-type conductivity. In this work, we report the achievement of Si-doped β-Ga2O3 (Si:β-Ga2O3) thin films grown on vicinal α-Al2O3 (0001) substrates with high electrical conductivity and DUV transparency of promising potential as transparent electrodes. The use of Al2O3 substrates with miscut angles promotes step-flow growth mode, leading to substantial improvement of crystalline quality and electrical properties of the Si:β-Ga2O3 films. A high conductivity of 37 S·cm−1 and average DUV transparency of 85% have been achieved for 0.5% Si-doped film grown on a 6° miscut substrate. High-resolution x-ray and ultraviolet photoemission spectroscopy were further used to elucidate the surface electronic properties of the grown Si:β-Ga2O3 films. An upward surface band bending was found at the surface region of Si:β-Ga2O3 films. Interestingly, all the Si:β-Ga2O3 films have a very low work function of approximately 3.3 eV, which makes Si:β-Ga2O3 suitable materials for efficient electron injection. The present Si:β-Ga2O3 films with high conductivity, DUV transparency, and low work function would be useful as the DUV transparent electrode to develop advanced DUV optoelectronic devices. [ABSTRACT FROM AUTHOR]

Ga2O3 is a wide bandgap semiconductor suitable for solar‐blind photodetection, but there exist two issues for Ga2O3‐based photodetectors: first, it is difficult to achieve reliable p‐type Ga2O3 and therefore form a homojunction photodetector, and the other is related with the slow response speed of Ga2O3‐based photodetectors. In this work, a self‐powered solar‐blind photodetector with a fast response using a p‐GaN/i‐Ga2O3/n‐Ga2O3 (pin) heterojunction with a fully depleted active region is realized, where i‐Ga2O3 serves as the main light‐absorbing active region. The device exhibits good self‐powered characteristics with a high responsivity of 72 mA W−1, a high photo‐to‐dark current ratio of 18 800, a high specific detectivity of 3.22 × 1012 Jones, and a fast response speed with a rise time/decay time of 7 ms/19 ms, respectively, without an external power supply. A detailed study of the interfacial electronic structure between p‐GaN and i‐Ga2O3 reveals a conduction band offset and valence band offset of 0.16 and 1.37 eV, respectively. Meanwhile, it has a large built‐in potential of 1.03 eV and a wide depletion region width of 235 nm in the i‐Ga2O3 side of heterojunction. It is believed that excellent device performance comes from a suitable energy band structure and wide depletion region. [ABSTRACT FROM AUTHOR]

Water radical cations, (H2O)n+•, have attracted considerable attention owing to their potential practical applications in analytical chemistry, structural chemistry, radiotherapy, and radiochemistry. Recently, atmospheric pressure chemical ionization has emerged as a versatile method for direct mass spectrometric analysis. Usually, H3O+ is the major proton donor during ionization and only the pseudo molecular ion peaks, instead of molecular ions are detected. In this work, (H2O)2+• ions with high oxidizability and reactivity were generated using hydrothermally grown TiO2 nanoneedle arrays in combination with a linear ion trap mass spectrometer under low operating voltage and applied to the direct mass spectrometric analysis of a mixture of volatile aromatic hydrocarbons. (H2O)2+• ions were generated with a high absolute ion current of up to 1.07 × 105 counts/s at atmospheric pressure. Using the generated (H2O)2+• as the primary ion permitted the tandem mass spectrometric analysis of a mixed vapor sample of aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]