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α-Ga2O3has the corundum structure analogous to that of α-Al2O3. The bandgap energy of α-Ga2O3is 5.3 eV and is greater than that of β-Ga2O3, making the α-phase attractive for devices that benefit from its wider bandgap. The O–H and O–D centers produced by the implantation of H+and D+into α-Ga2O3have been studied by infrared spectroscopy and complementary theory. An O–H line at 3269 cm−1is assigned to H complexed with a Ga vacancy (VGa), similar to the case of H trapped by an Al vacancy (VAl) in α-Al2O3. The isolated VGaand VAldefects in α-Ga2O3and α-Al2O3are found by theory to have a “shifted” vacancy-interstitial-vacancy equilibrium configuration, similar to VGain β-Ga2O3, which also has shifted structures. However, the addition of H causes the complex with H trapped at an unshifted vacancy to have the lowest energy in both α-Ga2O3and α-Al2O3.
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A general photocatalytic hydrodefluorination and defluoroalkylation of electronically-variable ArCF 3 by changing commercially-available arenethiolates
The selection of electronically-different thiolate-based photosensitizers is employed to achieve a precise and specific C–F bond defluorination of a broad range of trifluoromethylarenes, enabling the synthesis of 88 α,α-difluoromethyl compounds.
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- Award ID(s):
- 1955284
- PAR ID:
- 10532394
- Publisher / Repository:
- Royal Society of Chemistry
- Date Published:
- Journal Name:
- Green Chemistry
- Volume:
- 26
- Issue:
- 8
- ISSN:
- 1463-9262
- Page Range / eLocation ID:
- 4518 to 4527
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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We report on growth and electrical properties of α-Ga2O3films prepared by halide vapor phase epitaxy (HVPE) at 500 °C on α-Cr2O3buffers predeposited on sapphire by magnetron sputtering. The α-Cr2O3buffers showed a wide microcathodoluminescence (MCL) peak near 350 nm corresponding to the α-Cr2O3bandgap and a sharp MCL line near 700 nm due to the Cr+intracenter transition. Ohmic contacts to Cr2O3were made with both Ti/Au or Ni, producing linear current–voltage ( I– V) characteristics over a wide temperature range with an activation energy of conductivity of ∼75 meV. The sign of thermoelectric power indicated p-type conductivity of the buffers. Sn-doped, 2- μm-thick α-Ga2O3films prepared on this buffer by HVPE showed donor ionization energies of 0.2–0.25 eV, while undoped films were resistive with the Fermi level pinned at ECof 0.3 eV. The I– V and capacitance–voltage ( C– V) characteristics of Ni Schottky diodes on Sn-doped samples using a Cr2O3buffer indicated the presence of two face-to-face junctions, one between n-Ga2O3and p-Cr2O3, the other due to the Ni Schottky diode with n-Ga2O3. The spectral dependence of the photocurrent measured on the structure showed the presence of three major deep traps with optical ionization thresholds near 1.3, 2, and 2.8 eV. Photoinduced current transient spectroscopy spectra of the structures were dominated by deep traps with an ionization energy of 0.95 eV. These experiments suggest another pathway to obtain p–n heterojunctions in the α-Ga2O3system.more » « less
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Abstract Phosphane, PH3—a highly pyrophoric and toxic gas—is frequently contaminated with H2and P2H4, which makes its handling even more dangerous. The inexpensive metal–organic framework (MOF) magnesium formate, α‐[Mg(O2CH)2], can adsorb up to 10 wt % of PH3. The PH3‐loaded MOF, PH3@α‐[Mg(O2CH)2], is a non‐pyrophoric, recoverable material that even allows brief handling in air, thereby minimizing the hazards associated with the handling and transport of phosphane. α‐[Mg(O2CH)2] further plays a critical role in purifying PH3from H2and P2H4: at 25 °C, H2passes through the MOF channels without adsorption, whereas PH3adsorbs readily and only slowly desorbs under a flow of inert gas (complete desorption time≈6 h). Diphosphane, P2H4, is strongly adsorbed and trapped within the MOF for at least 4 months. P2H4@α‐[Mg(O2CH)2] itself is not pyrophoric and is air‐ and light‐stable at room temperature.more » « less
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We determine the composition dependence of the transverse and longitudinal optical infrared-active phonon modes in rhombohedral α-(AlxGa1−x)2O3alloys by far-infrared and infrared generalized spectroscopic ellipsometry. Single-crystalline high quality undoped thin-films grown on m-plane oriented α-Al2O3substrates with x = 0.18, 0.37, and 0.54 were investigated. A single mode behavior is observed for all phonon modes, i.e., their frequencies shift gradually between the equivalent phonon modes of the isostructural binary parent compounds. We also provide physical model line shape functions for the anisotropic dielectric functions. We use the anisotropic high-frequency dielectric constants for polarizations parallel and perpendicular to the lattice c axis measured recently by Hilfiker et al. [Appl. Phys. Lett. 119, 092103 (2021)], and we determine the anisotropic static dielectric constants using the Lyddane–Sachs–Teller relation. The static dielectric constants can be approximated by linear relationships between those of α-Ga2O3and α-Al2O3. The optical phonon modes and static dielectric constants will become useful for device design and free charge carrier characterization using optical techniques.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d3gc05041f
