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1. Structural and electronic properties of NbN/GaN junctions grown by molecular beam epitaxy

   https://doi.org/10.1063/5.0083184  

   Wright, John G.; Chang, Celesta S.; Muller, David A.; Xing, Huili G.; Jena, Debdeep (May 2022, APL Materials)

   We report the structural and electronic properties of NbN/GaN junctions grown by plasma-assisted molecular beam epitaxy. High crystal-quality NbN films grown on GaN exhibit superconducting critical temperatures in excess of 10 K for thicknesses as low as 3 nm. We observe that the NbN lattice adopts the stacking sequence of the underlying GaN and that domain boundaries in the NbN thereby occur at the site of atomic steps in the GaN surface. The electronic properties of the NbN/GaN junction are characterized using Schottky barrier diodes. Current–voltage–temperature and capacitance–voltage measurements are used to determine the Schottky barrier height of the NbN/GaN junction, which we conclude is ∼1.3 eV. 

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2. Grain structure and superconducting behavior of electrodeposited ReMo thin films

   https://doi.org/10.1063/5.0271070  

   Liu, Quanhong; Tang, Chunli; Petri, James_L; Kabarowska, Zosia_C; Bi, Wenli; Huang, Qiang (July 2025, Journal of Applied Physics)

   ReMo binary alloy films with a maximum Mo content of 25 at. % are successfully electrodeposited using high concentration acetate solutions in the presence of citric acid. The electrochemical behavior of the ReMo alloy is studied using cyclic voltammetry and anodic stripping methods. Different techniques, including electron microscopy, x-ray diffraction, and four-point probe resistance measurements at cryogenic temperature, are used to characterize the surface morphology, crystal structure, and superconducting critical temperature of alloys, respectively. While all films exhibit a crystalline hcp phase after 700 °C annealing, the film with the highest 25 at. % Mo content shows a second crystalline cubic phase. Mo doping preserves the enhanced superconducting transition temperature (Tc) in electrodeposited amorphous Re films and improves the stability of Tc against thermal annealing at a temperature of 200 °C. This is the first successful demonstration to use a dopant to stabilize the enhanced Tc of electrodeposited films, enabling the fabrication and operation of superconducting connectors above the intrinsic Tc of the materials. 

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3. Molybdenum-Suboxide Thin Films as Anode Layers in Planar Lithium Microbatteries

   https://doi.org/10.3390/electrochem1020012  

   Lakshmi-Narayana, Ambadi; Hussain, Obili M.; Ramana, Chintalapalle V.; Camacho-Lopez, Marco; Abdel-Ghany, Ashraf; Hashem, Ahmed; Mauger, Alain; Julien, Christian M. (June 2020, Electrochem)

   null (Ed.)

   In this paper, we investigate the effects of operational conditions on structural, electronic and electrochemical properties on molybdenum suboxides (MoO3-δ) thin films. The films are prepared using pulsed-laser deposition by varying the deposition temperature (Ts), laser fluence (Φ), the partial oxygen pressure (PO2) and annealing temperature (Ta). We find that three classes of samples are obtained with different degrees of stoichiometric deviation without post-treatment: (i) amorphous MoO3-δ (δ < 0.05) (ii) nearly-stoichiometric samples (δ ≈ 0) and (iii) suboxides MoO3-δ (δ > 0.05). The suboxide films 0.05 ≤ δ ≤ 0.25 deposited on Au/Ti/SiO2/flexible-Si substrates with appropriate processing conditions show high electrochemical performance as an anode layer for lithium planar microbatteries. In the realm of simple synthesis, the MoO3-δ film deposited at 450 °C under oxygen pressure of 13 Pa is a mixture of α-MoO3 and Mo8O23 phases (15:85). The electrochemical test of the 0.15MoO3-0.85Mo8O23 film shows a specific capacity of 484 µAh cm−2 µm−1 after 100 cycles of charge-discharge at a constant current of 0.5 A cm−2 in the potential range 3.0-0.05 V. 

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4. Non-Thermal Annealing of Gamma Irradiated GaN HEMTs with Electron Wind Force

   https://doi.org/10.1149/2162-8777/ac7f5a  

   Rasel, Md Abu; Stepanoff, Sergei; Haque, Aman; Wolfe, Douglas E.; Ren, Fan; Pearton, Stephen (July 2022, ECS Journal of Solid State Science and Technology)

   Radiation damage mitigation in electronics remains a challenge because the only established technique, thermal annealing, does not guarantee a favorable outcome. In this study, a non-thermal annealing technique is presented, where electron momentum from very short duration and high current density pulses is used to target and mobilize the defects. The technique is demonstrated on 60 Co gamma irradiated (5 × 10 6 rad dose and 180 × 10 3 rad h −1 dose rate) GaN high electron mobility transistors. The saturation current and maximum transconductance were fully and the threshold voltage was partially recovered at 30 °C or less. In comparison, thermal annealing at 300 °C mostly worsened the post-irradiation characteristics. Raman spectroscopy showed an increase in defects that reduce the 2-dimensional electron gas (2DEG) concentration and increase the carrier scattering. Since the electron momentum force is not applicable to the polymeric surface passivation, the proposed technique could not recover the gate leakage current, but performed better than thermal annealing. The findings of this study may benefit the mitigation of some forms of radiation damage in electronics that are difficult to achieve with thermal annealing. 

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5. Momentum-resolved electronic structure and band offsets in an epitaxial NbN/GaN superconductor/semiconductor heterojunction

   https://doi.org/10.1126/sciadv.abi5833  

   Yu, Tianlun; Wright, John; Khalsa, Guru; Pamuk, Betül; Chang, Celesta S.; Matveyev, Yury; Wang, Xiaoqiang; Schmitt, Thorsten; Feng, Donglai; Muller, David A.; et al (December 2021, Science Advances)

   The electronic structure of heterointerfaces is a pivotal factor for their device functionality. We use soft x-ray angle-resolved photoelectron spectroscopy to directly measure the momentum-resolved electronic band structures on both sides of the Schottky heterointerface formed by epitaxial films of the superconducting NbN on semiconducting GaN, and determine their momentum-dependent interfacial band offset as well as the band-bending profile. We find, in particular, that the Fermi states in NbN are well separated in energy and momentum from the states in GaN, excluding any notable electronic cross-talk of the superconducting states in NbN to GaN. We support the experimental findings with first-principles calculations for bulk NbN and GaN. The Schottky barrier height obtained from photoemission is corroborated by electronic transport and optical measurements. The momentum-resolved understanding of electronic properties of interfaces elucidated in our work opens up new frontiers for the quantum materials where interfacial states play a defining role. 

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