Publications by authors named "Titao Li"

4 Publications

  • Page 1 of 1

High-Pressure O Annealing Enhances the Crystallinity of Ultrawide-Band-Gap Sesquioxides Combined with Graphene for Vacuum-Ultraviolet Photovoltaic Detection.

ACS Appl Mater Interfaces 2021 Apr 31;13(14):16660-16668. Epub 2021 Mar 31.

School of Materials, Sun Yat-sen University, Guangzhou, Guangdong 510275, China.

(AlGa)O is emerging as a promising wide-band-gap sesquioxide for vacuum-ultraviolet (VUV, 10-200 nm) photodetectors and high-power field-effect transistors. However, how the key parameters such as the band gap and crystalline phase of the (AlGa)O-based device vary with stoichiometry has not been explicitly defined, which is due to the unclear underlying mechanism of the Al local coordination environment. In this work, a high-pressure O (20 atm) annealing (HPOA) strategy that can significantly improve the crystallinity of β-(AlGa)O and achieve a tunable optical band gap was proposed, facilitating the revelation of the local structure of Al varying with Al content and the kinetic mechanism of Al diffusion. By combining the as-HPOA-treated single-crystalline β-(AlGa)O films with p-type graphene (p-Gr), which serves as a transparent conductor, a VUV photovoltaic detector is fabricated, showing an improved photovoltage (0.80 V) and fast temporal response (2.1 μs). All of these findings provide a rewarding and important strategy for enhancing the band-gap tunability of sesquioxides, as well as the flexibility of zero-power-consumption photodetectors.
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http://dx.doi.org/10.1021/acsami.1c00429DOI Listing
April 2021

Experimental Evidence on Stability of N Substitution for O in ZnO Lattice.

J Phys Chem Lett 2020 Oct 6;11(20):8901-8907. Epub 2020 Oct 6.

School of Materials, Sun Yat-sen University, Guangzhou, Guangdong 510275, China.

Although the dispute remains, the N substitution for the lattice O (N) in zinc oxide (ZnO) demonstrates the promising future in achieving the p-type ZnO-based semiconductor. In this context, a highly crystallized N-doped ZnO (ZnO:N) film is fabricated with ultralow defect density. Based on the synchrotron radiation X-ray absorption near-edge structure (XANES) and low-temperature photoluminescence (PL) spectra combined with first-principles calculations, the results demonstrate that the majority of N ions locate stably at the lattice O site to succeeding the N substitution for lattice O as the N defects. A prototype LED device is built based on the homojunction of ZnO:N film and ZnO:Ga wafer with good electroluminescence performance. These important findings provide a rewarding avenue to the p-type ZnO semiconductor design and device fabrication, and demonstrate a prevailing guidance on the materials design and development as well.
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http://dx.doi.org/10.1021/acs.jpclett.0c02698DOI Listing
October 2020

Rocksalt-Zincblende-Wurtzite Mixed-Phase ZnO Crystals With High Activity as Photocatalysts for Visible-Light-Driven Water Splitting.

Front Chem 2020 29;8:351. Epub 2020 Apr 29.

School of Materials, Sun Yat-sen University, Guangzhou, China.

Finding out the factors that dominate photocatalytic activity is always an essential topic toward the development of highly active photocatalysts. The increased photoactivity of ZnO:Ga (L) may be attributed to the existence of homojunctions and resultant oxygen vacancies in triphasic ZnO:Ga (L), which can reduce the recombination of photogenerated carriers and provide them higher doping efficiency and higher optical gain. Then, the photocatalytic behaviors of as-prepared N doped crystals have been studied and rationalized to understand the role of each of species played in light absorption and photo activation. The N-doped ZnO:Ga (L) sample which showed higher activity than N-doped ZnO:Ga (B) and ZnO:Ga (L), the high activity could be explained by increase of visible light absorption and presence of empty impurity levels introduced by N doping.
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http://dx.doi.org/10.3389/fchem.2020.00351DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7201987PMC
April 2020

Hydrogen Impurities in ZnO: Shallow Donors in ZnO Semiconductors and Active Sites for Hydrogenation of Carbon Species.

J Phys Chem Lett 2020 Apr 12;11(7):2402-2407. Epub 2020 Mar 12.

State Key Laboratory of Optoelectronic Materials and Technologies, School of Materials, Sun Yat-sen University, Guangzhou, Guangdong 510275, China.

ZnO, as a low-cost yet significant semiconductor, has been widely used in solar energy conversion and optoelectronic devices. In addition, Cu/ZnO-based catalysts can convert syngas (H, CO, and CO) into methanol. However, the main concern about the intrinsic connection between the physical and chemical properties and the structure of ZnO still remains. In this work, efforts are made to decipher the physical and chemical information encoded into the structure. Through using NMR-IR techniques, we, for the first time, report a new ZnO model with three H cations incorporated into one Zn vacancy. H magic-angle spinning NMR and IR spectra demonstrate that Ga cations are introduced into the Zn vacancies of the ZnO lattice, which replace the H cation, and thus further confirm the feasibility of our proposed model. The exchange between the H cation in Zn vacancies and the D gas phase shows that ZnO can activate H because of the quantized three H cations in the defect site.
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http://dx.doi.org/10.1021/acs.jpclett.0c00509DOI Listing
April 2020