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AlGaN/GaN high-electron-mobility transistors (HEMTs) are widely used in high-frequency and high-power applications owing to the high two-dimensional electron gas (2DEG) concentration. However, the microscopic origin of the 2DEG remains unclear. This hinders the development of device fabrication technologies, such as threshold voltage modulation, current collapse suppression, and 2DEG concentration enhancement technologies, as well as AlGaN/GaN sensors with very high sensitivity to polar liquids. To clarify the 2DEG microscopic origin, we studied the effects of gas molecules on AlGaN/GaN surfaces through various experiments and first-principles calculations. The results indicated that the adsorption of gas molecules on the AlGaN/GaN surface is an important phenomenon, clarifying the microscopic origin of the 2DEG. This study elucidates the properties of AlGaN/GaN heterojunctions and promotes the development of new fabrication technologies for AlGaN/GaN devices.
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http://dx.doi.org/10.3390/nano14141211 | DOI Listing |
Natl Sci Rev
September 2025
Beijing Key Laboratory for Science and Application of Functional Molecular and Crystalline Materials, Department of Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
Covalent organic frameworks (COFs) have great potential as versatile platforms for proton conduction. However, the commonly applied 2D COFs that are easy to design and synthesize have only 1D channels for proton conduction, limiting the formation of continuous hydrogen bonds due to the anisotropy between their crystalline grains. Herein, we report a strategy to construct 3D channels in 2D COFs by using rotaxane structures and eliminate the strong interlayer π-π interactions, facilitating the formation of smooth 3D proton-transfer pathways during guest doping.
View Article and Find Full Text PDFAngew Chem Int Ed Engl
September 2025
Hefei National Research Center for Physical Sciences at the Microscale, School of Chemistry and Materials Science, State Key Laboratory of Precision and Intelligent Chemistry, National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui, 230026, China.
The construction of C─N bonds from simple precursors under ambient conditions is a fundamental challenge in green chemistry, especially when it comes to avoiding energy-intensive protocols. Here, we present a continuous flow photocatalytic platform that enables the efficient coupling of C─N bonds between methanol and ammonia at ambient temperature and pressure. By synergistically engineering a Pd clusters-decorated TiO photocatalyst (1Pd/TiO) and a mass transfer-enhanced gas-liquid-solid Taylor flow reactor, the system achieves a remarkable formamide productivity of 256.
View Article and Find Full Text PDFJ Colloid Interface Sci
September 2025
State Key Laboratory of Hydro Science and Engineering, and Department of Energy and Power Engineering, Tsinghua University, Beijing, 100084, China. Electronic address:
Hypothesis: On highly cleaned planar surfaces submerged in highly cleaned water, flat surface nanobubbles with an angle of attachment of ∼15 are observed - never on engineering surfaces submerged in plain water, though here unidentified cavitation nuclei are always present and cause low tensile strength.
Experiments: In the present study, surface nanobubbles are generated by standard experimental techniques on a polished steel surface, and we find that the shape and the angles of attachment of the bubbles are influenced by the local substrate topography. These observations align with the theory of non-adsorbed liquid zones, which explains a surface nanobubble as a bubble with a skin of contamination molecules, which bond along the bubble rim at a contact angle of ∼14.
J Phys Chem A
September 2025
Department of Basic Science, School of Arts and Sciences, The University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan.
Desorption processes of HO molecules from AlO(HO) ( = 3, 5, 7) and AlO(HO)H ( = 4, 6, 8) clusters were investigated using gas-phase thermal desorption spectrometry to evaluate the HO storage capacity and mechanisms of aluminum oxide clusters. The clusters stored approximately 10 HO molecules at ∼300 K, depending on the size (), and released them upon heating. Even after heating to ∼1000 K, 2-4 HO molecules remained bound.
View Article and Find Full Text PDFPhotoacoustics
October 2025
Hubei Key Laboratory of Intelligent Wireless Communications, Hubei Engineering Research Center of Intelligent IOT technology, College of Electronics and Information Engineering, South-Central Minzu University, Wuhan 430074, China.
A novel gourd-type photoacoustic cell (GTPAC) has been developed, featuring a highly reflective, polished gold film-coated inner wall that minimizes optical loss and maximizes light utilization efficiency. GTPAC integrates two coupled spherical chambers with a radius ratio 2:3, which is close to the golden ratio. Its unique Gaussian curvature distribution enables multi-directional, disordered light beam reflection without complex optical alignment.
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