α-Ga2O3 has the corundum structure analogous to that of α-Al2O3. The bandgap energy of α-Ga2O3 is 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-Ga2O3 have been studied by infrared spectroscopy and complementary theory. An O-H line at 3269 cm-1 is 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 VGa and VAl defects in α-Ga2O3 and α-Al2O3 are found by theory to have a “shifted” vacancy-interstitial-vacancy equlibrium configuration, similar to VGa in 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-Ga2O3 and α-Al2O3.
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Electronic properties of bare and functionalized two-dimensional (2D) tellurene structures
Recently, 2D tellurene (Te) structures have been experimentally synthesized. These structures possess high carrier mobility and stability which make them ideal candidates for applications in electronics, optoelectronics and energy devices. We performed density functional theory (DFT) and molecular dynamics (MD) simulations to investigate the stability and electronic structure of 2D α- and β-Te sheets, and hydrogen, oxygen, and fluorine functionalized counterparts, including spin–orbit coupling effects. Our calculations show that bare α and β-Te sheets are stable with band gaps of 0.44 eV and 1.02 eV respectively. When functionalized, α and β monolayers exhibit metallic properties, except for hydrogenated β-Te, which exhibits semiconducting properties with a band gap of 1.37 eV. We see that H, O and F destabilize the structure of α-Te. We also find that F and H cause β-Te layers to separate into functionalized atomic chains and O causes β-Te to transform into a Te 3 O 2 -like structure. We also studied single atom and molecule binding on the Te surface, the effects of adatom coverage, and the effects of functionalized Te on a GaSe substrate. Our results indicate that tellurene monolayers and functionalized counterparts are not only suitable for future optoelectronic devices, but can be used as metallic contacts in nanoscale junctions.
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- Award ID(s):
- 1726213
- PAR ID:
- 10143900
- Date Published:
- Journal Name:
- Physical Chemistry Chemical Physics
- Volume:
- 22
- Issue:
- 12
- ISSN:
- 1463-9076
- Page Range / eLocation ID:
- 6727 to 6737
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Even though transition metal dichalcogenides (TMDCs) are deemed to be novel photonic and optoelectronic 2D materials, the visible band gap being often limited to monolayer, hampers their potential in niche applications due to fabrication challenges. Uncontrollable defects and degraded functionalities at elevated temperature and under extreme environments further restrict their prospects. To address such limitations, the discovery of a new 2D material, α‐PbO is reported. Micromechanical as well as sonochemical exfoliation of 2D atomic sheets of α‐PbO are demonstrated and its optical behavior is investigated. Spectroscopic investigations indicate layer dependent band gaps. In particular, even multilayered PbO sheets exhibit visible band gap > 2 eV (direct) which is rare among semiconducting 2D materials. The emission lifetime of multilayer PbO atomic sheets is 7 ns (dim light) as compared to the monolayer which gives 2.5 ns lifetime and an intense light. Density functional theory calculations of layer dependent band structure of α‐PbO matches well with experimental results. Experimental findings suggest that PbO atomic sheets exhibit hydrophobic nature, thermal robustness, microwave stability, anti‐corrosive behaviour and acid resistance. This new low‐cost, abundant and robust 2D material is expected to find many applications in the fields of electronics, optoelectronics, sensors, photocatalysis and energy storage.
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Inspired by the recent experimental realization of pnictogen–silicon analogues of benzene and great interest in silicene, phosphorene and their heavier counterparts, herein we designed three planar porous 2D nanomaterials, namely porous silaphosphorene (pSiP), silaarsenene (pSiAs) and silaantimonene (pSiSb), and systematically investigated their stability, and electronic and optical properties, as well as their potential as photocatalysts for water splitting. Porous silaphosphorene, silaarsenene and silaantimonene monolayers are all thermodynamically, dynamically and thermally stable, and the aromaticity in each six-membered Si 3 P 3 /Si 3 As 3 /Si 3 Sb 3 ring plays an important role in their enhanced stability. They are all semiconductors with direct band gaps of 1.93, 1.57 and 0.95 eV (HSE06) and have comparable carrier mobility to MoS 2 . Their good stability and exceptional electronic and optical properties make them promising candidates for applications in solar cells and other optoelectronics fields. Moreover, the suitable band edge alignments of pSiP and pSiAs monolayers endow them with potential applications as photocatalysts for water splitting.more » « less
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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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Polarons, quasiparticles from electron-phonon coupling, are crucial for material properties including high-temperature superconductivity and colossal magnetoresistance. However, scarce studies have investigated polaron formation in low-dimensional materials with phonon polarity and electronic structure transitions. In this work, we studied polarons of tellurene, composed of chiral Te chains. The frequency and linewidth of the A1phonon, which becomes increasingly polar for thinner tellurene, change abruptly for thickness below 10 nanometers, where field-effect mobility drops rapidly. These phonon and transport signatures, combined with phonon polarity and band structure, suggest a crossover from large polarons in bulk tellurium to small polarons in few-layer tellurene. Effective field theory considering phonon renormalization in the small-polaron regime semiquantitatively reproduces the phonon hardening and broadening effects. This polaron crossover stems from the quasi–one-dimensional nature of tellurene, where modulation of interchain distance reduces dielectric screening and promotes electron-phonon coupling. Our work provides valuable insights into the influence of polarons on phononic, electronic, and structural properties in low-dimensional materials.
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/D0CP00357C
