Jing Zhang

Jing Zhang


Postgraduate Research Student

Academic and research departments

Advanced Technology Institute.

My publications

Publications

K Michelakis, S Despotopoulos, V Gaspari, A Vilches, K Fobelets, C Papavassiliou, C Toumazou, J Zhang (2004)SiGe virtual substrate HMOS transistor for analogue applications, In: Applied Surface Science224(1-4)pp. 386-389

Silicon-germanium (SiGe) heterojunction metal-oxide-semiconductor field-effect transistors (SiGe HMOSFETs) have been successfully fabricated on Si substrate. The semiconductor heterostructure, which was grown by gas-source molecular beam epitaxy (GS-MBE), was initiated by the deposition of a Si Ge "virtual substrate". The n-type transistors were fabricated using a standard MOS process. The channel is a thin, undoped layer of strained Si and is buried below an arsenic-doped Si Ge layer, which provides the carriers. The devices exhibited excellent current-voltage (I-V) characteristics in terms of transconductance and drain current, with no breakdown or leakage. A level-1 model was extracted, for use in circuit design. The results suggest that the realisation of buried-channel SiGe n-HMOSFETs is feasible in MOS processes. These devices are of particular importance in analogue applications. © 2003 Elsevier B.V. All rights reserved.

Jing Zhang, Wei Zhang, Huiming Cheng, Ravi Silva (2020)Critical Review of Recent Progress of Flexible Perovskite Solar Cells, In: Materials Today Elsevier

Perovskite solar cells (PSCs) have emerged as a ‘rising star’ in recent years due to their high-power conversion efficiency (PCE), extremely low cost and facile fabrication techniques. To date, PSCs have achieved a certified PCE of 25.2% on rigid conductive substrates, and 19.5% on flexible substrates. The significant advancement of PSCs has been realized through various routes, including perovskite composition engineering, interface modification, surface passivation, fabrication process optimization, and exploitation of new charge transport materials. However, compared with rigid counterparts, the efficiency record of flexible perovskite solar cells (FPSCs) is advancing slowly, and therefore it is of great significance to scrutinize recent work and expedite the innovation in this field. In this article, we comprehensively review the recent progress of FPSCs. After a brief introduction, the major features of FPSCs are compared with other types of flexible solar cells in a broad context including silicon, CdTe, dye-sensitized, organic, quantum dot and hybrid solar cells. In particular, we highlight the major breakthroughs of FPSCs made in 2019/2020 for both laboratory and large-scale devices. The constituents of making a FPSC including flexible substrates, perovskite absorbers, charge transport materials, as well as device fabrication and encapsulation methods have been critically assessed. The existing challenges of making high performance and long-term stable FPSCs are discussed. Finally, we offer our perspectives on the future opportunities of FPSCs in the field of photovoltaics.

K Fobelets, R Ferguson, V Gaspari, E Velazquez, K Michelakis, S Despotopoulos, J Zhang, C Papavassiliou (2002)Experimental study of depletion mode Si/SiGe MOSFETs for low-temperature operation, In: European Solid-State Device Research Conferencepp. 555-558

N-channel enhancement mode Si/SiGe MOSFETs are characterised and studied over a wide temperature range of 10K

Jing Zhang, Anthony T. S. Ho (2005)Efficient Robust Watermarking of Compressed 2-D Grayscale Patterns for H.264/AVC, In: IEEE 7th Workshop on Multimedia Signal Processingpp. 1-4 Institute of Electrical and Electronics Engineers

An efficient and robust video watermarking algorithm for the state-of-the-art video coding standard H.264/AVC is proposed for copyright protection. Grayscale 2-D watermark patterns such as detailed trademarks or logos can be highly compressed by a proposed grayscale watermark pre-processing, and inserted into the low bit-rate H.264/AVC videos in the compressed domain. The marked video sequences maintain good visual quality and the same overall consuming bit-rate. The proposed algorithm can robustly survive transcoding process and common signal processing, such as bit-rate reduction, Gaussian filtering and contrast enhancement.

Stephen A. Lynch, Douglas J. Paul, Paul Townsend, Guy Matmon, Zhang Suet, Robert W. Kelsall, Zoran Ikonic, Paul Harrison, Jing Zhang, David J. Norris, Anthony G. Cullis, Carl R. Pidgeon, Pawel Murzyn, Ben Murdin, Mike Bain, Harry S. Gamble, Ming Zhao, Wei-Xin Ni (2006)Toward Silicon-Based Lasers for Terahertz Sources, In: IEEE Journal of Selected Topics in Quantum Electronics12(6)pp. 1570-1578

Producing an electrically pumped silicon-based laser at terahertz frequencies is gaining increased attention these days. This paper reviews the recent advances in the search for a silicon-based terahertz laser. Topics covered include resonant tunneling in p-type Si/SiGe, terahertz intersubband electroluminescence from quantum cascade structures, intersubband lifetime measurements in Si/SiGe quantum wells, enhanced optical guiding using buried silicide layers, and the potential for exploiting common impurity dopants in silicon such as boron and phosphorus to realize a terahertz laser

JING ZHANG, Xiangang Hu, HUI LI, Kangyu Ji, BOWEI LI, XUEPING LIU, YUREN XIANG, Pengxiang Hou, Chang Liu, Zhiheng Wu, Yonglong Shen, Samuel D. Stranks, S RAVI PRADIP SILVA, HUIMING CHENG, WEI ZHANG (2021)High-performance ITO-free perovskite solar cells enabled by single-walled carbon nanotube films, In: Advanced Functional Materials2104396 Wiley

The unprecedented advancement in power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) has rendered them a promising game-changer in photovoltaics. However, unsatisfactory environmental stability and high manufacturing cost of window electrodes are bottlenecks impeding their commercialization. Here, a strategy is introduced to address these bottlenecks by replacing the costly indium tin oxide (ITO) window electrodes via a simple transfer technique with single-walled carbon nanotubes (SWCNTs) films, which are made of earth-abundant elements with superior chemical and environmental stability. The resultant devices exhibit PCEs of ≈19% on rigid substrates, which is the highest value reported to date for ITO-free PSCs. The facile approach for SWCNTs also enables application in flexible PSCs (f-PSCs), delivering a PCE of ≈18% with superior mechanical robustness over their ITO-based counterparts due to the excellent mechanical properties of SWCNTs. The SWCNT-based PSCs also deliver satisfactory performances on large-area (1 cm2 active area in this work). Furthermore, these SWCNT-based PSCs can retain over 80% of original PCEs after exposure to air over 700 h while ITO-based devices only sustain ≈60% of initial PCEs. This work paves a promising way to accelerate the commercialization of ITO-free PSCs with reduced material cost and prolonged lifetimes.

H A El Mubarek, J M Bonar, G D Dilliway, P Ashburn, M Karunaratne, A F Willoughby, Y Wang, P L Hemment, R Price, J Zhang, P Ward (2004)Effect of Fluorine Implantation Dose on Boron Thermal Diffusion in Silicon, In: Journal of Applied Physics96(8)

This paper investigates how the thermal diffusion of boron in silicon is influenced by a high energy fluorine implant with a dose in the range 5x10(14)-2.3x10(15) cm(-2). Secondary Ion Mass Spectroscopy (SIMS) profiles of boron marker layers are presented for different fluorine doses and compared with fluorine profiles to establish the conditions under which thermal boron diffusion is suppressed. The (SIMS) profiles show significantly reduced boron thermal diffusion above a critical F+ dose of 0.9-1.4x10(15) cm(-2). Fitting of the measured boron profiles gives suppressions of the boron thermal diffusion coefficient by factors of 1.9 and 3.7 for F+ implantation doses of 1.4x10(15) and 2.3x10(15) cm(-2), respectively. The suppression of boron thermal diffusion above the critical fluorine dose correlates with the appearance of a shallow fluorine peak on the (SIMS) profile in the vicinity of the boron marker layer. This shallow fluorine peak is present in samples with and without boron marker layers, and hence it is not due to a chemical interaction between the boron and the fluorine. Analysis of the (SIMS) profiles and cross-section Transmission Electron Microscope micrographs suggests that it is due to the trapping of fluorine at vacancy-fluorine clusters, and that the suppression of the boron thermal diffusion is due to the effect of the clusters in suppressing the interstitial concentration in the vicinity of the boron profile

Jing Zhang, Su Hu, Zilong Liu, Pei Wang, Pei Xiao, Yuan Gao (2019)Real-Valued Orthogonal Sequences for Iterative Channel Estimation in MIMO-FBMC Systems, In: IEEE Access4pp. 1-10 Institute of Electrical and Electronics Engineers (IEEE)

In this paper, we present a novel sequence design for efficient channel estimation in multiple input multiple output filterbank multicarrier (MIMO-FBMC) system with offset QAM modulation. Our proposed sequences, transmitted over one FBMC/OQAM symbol, are real-valued in the frequency domain and display zero-correlation zone properties in the time-domain. The latter property enables optimal channel estimation for a least-square estimator in frequency-selective fading channels. To further improve the system performance, we mitigate the data interference by an iterative feedback loop between channel estimation and FBMC demodulation. Simulation results validate that our proposed real-valued orthogonal sequences and the iterative channel estimation and demodulation scheme provide a practical solution for enhanced performance in preamble-based MIMO-FBMC systems.

Wen Jianqing, J. Evans-Freeman, A. R. Peaker, J. P. Zhang, Peter L. F. Hemment, C. D. Marsh, G. R. Booker (2000)Role of oxygen on the implantation related residual defects in silicon, In: IEEE Proceedings of Electron Devices Meeting, Hong Kong, 2000.pp. 112-115

The role of oxygen concentration on the formation/evolution of residual defects in implanted and rapid thermal annealed silicon was studied in samples with various oxygen concentrations. Photoluminescence (PL) study showed a strong correlation between the D-line intensity and the oxygen concentration. Transmission electron microscopy (TEM) measurements also suggested the extended defects were more favored in the high oxygen sample. High frequency capacitance-voltage (C-V) measurements revealed excess acceptors that were further investigated by deep level transient spectroscopy (DLTS). A hole trap with activation energy of 450 meV was detected and was suggested to relate to agglomerations of point defects associated with more than one type of 3D-metal related deep levels.

Marco Califano, N. Q. Vinh, P. J. Phillips, Z. Ikonić, R. W. Kelsall, P. Harrison, C. R. Pidgeon, B. N. Murdin, D. J. Paul, P. Townsend, J. Zhang, I. M. Ross, A.G. Cullis (2007)Interwell relaxation times in p-Si/SiGe asymmetric quantum well structures: Role of interface roughness, In: Physical Review B75(045338)

We report the direct determination of nonradiative lifetimes in Si/SiGe asymmetric quantum well structures designed to access spatially indirect (diagonal) interwell transitions between heavy-hole ground states, at photon energies below the optical phonon energy. We show both experimentally and theoretically, using a six-band k·p model and a time-domain rate equation scheme, that, for the interface quality currently achievable experimentally (with an average step height 1 greater than or equal to Å), interface roughness will dominate all other scattering processes up to about 200 K. By comparing our results obtained for two different structures we deduce that in this regime both barrier and well widths play an important role in the determination of the carrier lifetime. Comparison with recently published experimental and theoretical data obtained for mid-infrared GaAs/AlxGa1−xAs multiple quantum well systems leads us to the conclusion that the dominant role of interface roughness scattering at low temperature is a general feature of a wide range of semiconductor heterostructures not limited to IV-IV materials.