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Author

Youdou Zheng

Other affiliations: Xiamen University
Bio: Youdou Zheng is an academic researcher from Nanjing University. The author has contributed to research in topics: Chemical vapor deposition & Materials science. The author has an hindex of 31, co-authored 493 publications receiving 5015 citations. Previous affiliations of Youdou Zheng include Xiamen University.


Papers
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Journal ArticleDOI
Lijia Pan1, Lin Pu1, Yi Shi1, Shiyan Song1, Zhou Xu1, Rong Zhang1, Youdou Zheng1 
TL;DR: In this article, Wan and coworkers have synthesized a hollow octahedral structure of PAni using crystal-reductive Cu and showed that the template-removal step can result in the disorder or destruction of the mesostructures oraffect the chemical structure.
Abstract: These templates are not involved in the reactionand must be selectively removed from the final products insome applications. However, the template-removing step canresult in the disorder or destruction of the mesostructures oraffect the chemical structure of PAni. Recently, Wan andcoworkers have synthesized a hollow octahedral structure ofPAni using crystal-reductive Cu

200 citations

Journal ArticleDOI
TL;DR: Single crystalline α-Ga2O3 epilayers are achieved on nonpolar ZnO (112̅0) substrates for the first time and a high performance Au/α-Ga3/ZnO isotype heterostructure-based Schottky barrier avalanche diode is demonstrated, holding promise for developing high performance solar-blind photodetectors.
Abstract: The metastable α-phase Ga2O3 is an emerging material for developing solar-blind photodetectors and power electronic devices toward civil and military applications. Despite its superior physical properties, the high quality epitaxy of metastable phase α-Ga2O3 remains challenging. To this end, single crystalline α-Ga2O3 epilayers are achieved on nonpolar ZnO (1120) substrates for the first time and a high performance Au/α-Ga2O3/ZnO isotype heterostructure-based Schottky barrier avalanche diode is demonstrated. The device exhibits self-powered functions with a dark current lower than 1 pA, a UV/visible rejection ratio of 103 and a detectivity of 9.66 × 1012 cm Hz1/2 W–1. Dual responsivity bands with cutoff wavelengths at 255 and 375 nm are observed with their peak responsivities of 0.50 and 0.071 A W–1 at −5 V, respectively. High photoconductive gain at low bias is governed by a barrier lowing effect at the Au/Ga2O3 and Ga2O3/ZnO heterointerfaces. The device also allows avalanche multiplication processes in...

141 citations

Journal ArticleDOI
Jiandong Ye1, Shulin Gu1, S.N. Zhu1, Tong Chen1, Liqun Hu1, Feng Qin1, Rong Zhang1, Yi Shi1, Youdou Zheng1 
TL;DR: The effect of doping and annealing on the optical and structural properties of single-crystal ZnO films has been investigated by means of X-ray diffraction (XRD), photoluminescence (PL) spectrum and atomic force microscopy (AFM) as mentioned in this paper.

135 citations

Journal ArticleDOI
TL;DR: In this paper, the fabrication of 2D molecular single-crystal semiconductors with precise layer definition by using a floating-coffee-ring-driven assembly is presented, where bilayer molecular films exhibit singlecrystalline features with atomic smoothness and high film uniformity over a large area; field effect transistors yield average and maximum carrier mobilities of 4.8 and 13.0 cm2 V−1 s−1, respectively.
Abstract: 2D organic materials with in-plane van der Waals forces among molecules have unique characteristics that ensure a brilliant future for multifunctional applications. Soluble organic semiconductors can be used to achieve low-cost and high-throughput manufacturing of electronic devices. However, achieving solution-processed 2D single-crystalline semiconductors with uniform morphology remains a substantial challenge. Here, the fabrication of 2D molecular single-crystal semiconductors with precise layer definition by using a floating-coffee-ring-driven assembly is presented. In particular, bilayer molecular films exhibit single-crystalline features with atomic smoothness and high film uniformity over a large area; field-effect transistors yield average and maximum carrier mobilities of 4.8 and 13.0 cm2 V−1 s−1, respectively. This work demonstrates the strong potential of 2D molecular crystals for low-cost, large-area, and high-performance electronics.

129 citations

Journal ArticleDOI
TL;DR: In this article, the polarization effect within the AlGaN barrier was incorporated into calculation of the near-surface electrical field ES underneath the Schottky contact metal, which determined the field-dependent characteristics of reverse gate leakage current of high-frequency capacitance-voltage measurement combined with electrostatic analysis is used to estimate ES as a function of reverse bias voltage.
Abstract: In this work, we include the polarization effect within the AlGaN barrier into calculation of the near-surface electrical field ES underneath the Schottky contact metal which determines the field-dependent characteristics of reverse gate leakage current of AlGaN/GaN high electron mobility transistors High-frequency capacitance-voltage measurement combined with electrostatic analysis is used to estimate ES as a function of reverse bias voltage The resultant log(I/ES) versus ES curves over a temperature range from 293 to 453 K agree well with the predicted model of Frenkel–Poole (FP) emission of electrons up to the conductive states of threading dislocations Around zero bias, the reverse polarization-field-induced FP emission current is balanced by a forward defect-assisted tunneling current, both of which follow the same temperature dependent characteristics

125 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Journal ArticleDOI
TL;DR: A large amount of work world wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si as mentioned in this paper, and the key importance of crystalline Si nanostructures in determining the behaviour of porous si is highlighted.
Abstract: A large amount of work world-wide has been directed towards obtaining an understanding of the fundamental characteristics of porous Si. Much progress has been made following the demonstration in 1990 that highly porous material could emit very efficient visible photoluminescence at room temperature. Since that time, all features of the structural, optical and electronic properties of the material have been subjected to in-depth scrutiny. It is the purpose of the present review to survey the work which has been carried out and to detail the level of understanding which has been attained. The key importance of crystalline Si nanostructures in determining the behaviour of porous Si is highlighted. The fabrication of solid-state electroluminescent devices is a prominent goal of many studies and the impressive progress in this area is described.

2,371 citations

Journal ArticleDOI
TL;DR: The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed in this article, along with the influence of process-induced or grown-in defects and impurities on the device physics.
Abstract: The role of extended and point defects, and key impurities such as C, O, and H, on the electrical and optical properties of GaN is reviewed. Recent progress in the development of high reliability contacts, thermal processing, dry and wet etching techniques, implantation doping and isolation, and gate insulator technology is detailed. Finally, the performance of GaN-based electronic and photonic devices such as field effect transistors, UV detectors, laser diodes, and light-emitting diodes is covered, along with the influence of process-induced or grown-in defects and impurities on the device physics.

1,693 citations

Posted Content
TL;DR: The two-step solution-phase reactions to form hybrid materials of Mn(3)O(4) nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications should offer a new technique for the design and synthesis of battery electrodes based on highly insulating materials.
Abstract: We developed two-step solution-phase reactions to form hybrid materials of Mn3O4 nanoparticles on reduced graphene oxide (RGO) sheets for lithium ion battery applications. Mn3O4 nanoparticles grown selectively on RGO sheets over free particle growth in solution allowed for the electrically insulating Mn3O4 nanoparticles wired up to a current collector through the underlying conducting graphene network. The Mn3O4 nanoparticles formed on RGO show a high specific capacity up to ~900mAh/g near its theoretical capacity with good rate capability and cycling stability, owing to the intimate interactions between the graphene substrates and the Mn3O4 nanoparticles grown atop. The Mn3O4/RGO hybrid could be a promising candidate material for high-capacity, low-cost, and environmentally friendly anode for lithium ion batteries. Our growth-on-graphene approach should offer a new technique for design and synthesis of battery electrodes based on highly insulating materials.

1,587 citations

Journal ArticleDOI
TL;DR: In this paper, a general review of the advances in widebandgap semiconductor photodetectors is presented, including SiC, diamond, III-nitrides and ZnS.
Abstract: Industries such as the automotive, aerospace or military, as well as environmental and biological research have promoted the development of ultraviolet (UV) photodetectors capable of operating at high temperatures and in hostile environments. UV-enhanced Si photodiodes are hence giving way to a new generation of UV detectors fabricated from wide-bandgap semiconductors, such as SiC, diamond, III-nitrides, ZnS, ZnO, or ZnSe. This paper provides a general review of latest progresses in wide-bandgap semiconductor photodetectors.

1,194 citations