Shuit-Tong Lee

Bio: Shuit-Tong Lee is an academic researcher from Soochow University (Suzhou). The author has contributed to research in topics: Silicon & Nanowire. The author has an hindex of 138, co-authored 1121 publications receiving 77112 citations. Previous affiliations of Shuit-Tong Lee include University of British Columbia & Hong Kong University of Science and Technology.

Core–shell structured photovoltaic devices based on PbS quantum dots and silicon nanopillar arrays

Abstract: We fabricated three-dimensional silicon nanopillar array (SiNP)-based photovoltaic (PV) devices using PbS quantum dots (QDs) as the hole-transporting layers The core–shell structured device, which is based on high aspect ratio SiNPs standing on roughed silicon substrates, displays a higher PV performance with a power conversion efficiency (PCE) of 653% compared with that of the planar device (211%) The enhanced PCE is ascribed to the increased light absorption and the improved charge carrier collections in SiNP-modified silicon surfaces We also show that, for the core–shell structured device, the thickness of the shell layer plays a critical role in enhancing the PV performance and around five monolayers of QDs are preferred for efficient hole-transporting Wafer-scale PV devices with a radial PbS/SiNP heterojunction can be fabricated by solution phase techniques at low temperatures, suggesting a facile route to fabricate unique three-dimensional nanostructured devices

Carrier Dynamics in Si Nanowires Fabricated by Metal-Assisted Chemical Etching

Abstract: Silicon nanowire arrays fabricated by metal-assisted wet chemical etching have emerged as a promising architecture for solar energy harvesting applications. Here we investigate the dynamics and transport properties of photoexcited carriers in nanowires derived from an intrinsic silicon wafer using the terahertz (THz) time-domain spectroscopy. Both the dynamics and the pump fluence dependence of the photoinduced complex conductivity spectra up to several THz were measured. The photoinduced conductivity spectra follow a Lorentz dependence, arising from surface plasmon resonances in nanowires. The carrier lifetime was observed to approach 0.7 ns, which is limited primarily by surface trapping. The intrinsic carrier mobility was found to be ∼1000 cm2/(V·s). Compared to other silicon nanostructures, these relative high values observed for both the carrier lifetime and mobility are the consequences of high crystallinity and surface quality of the nanowires fabricated by the metal-assisted wet chemical etching m...

An effective oxide shell-protected surface-enhanced Raman scattering (SERS) substrate: the easy route to Ag@AgxO-silicon nanowire films via surface doping

Abstract: This paper reported the fabrication of an ultrathin silver oxide shell covered silver nanoparticles embedded in silicon nanowire film (Ag@AgxO-SiNW) by a facile method. The amorphous ultrathin silver oxide layers, which can keep Ag nanoparticles from agglomerating, were confirmed by HRTEM and STEM mapping. The Ag@AgxO-SiNW was employed as a surface-enhanced Raman scattering substrate and exhibited excellent enhancement for the concentration detection (1 × 10−7 M) of rhodamine 6 G and crystal violet with the relative standard deviation of the main Raman vibration modes less than 20%. This core@shell structure may be explained by the surface doping of silicon nanowires.

Enhanced Raman scattering from vertical silicon nanowires array

Abstract: We fabricated ordered hexagonal-packed vertical silicon nanowire (SiNW) arrays with varying diameters of 450–900 nm and varying lengths of 0.54–7.3 μm, and studied their Raman enhancement properties. We found the Raman enhancement per unit volume (REV) increased with decreasing wire diameters and oscillated with wire length, and the REV of seven 450-nm-diameter, 3-μm-long SiNWs was about twice that of a single SiNW having the same size. The differences were attributed to the vertical finite-length cylinder structures of the SiNW array, as supported by finite-difference-time-domain simulation results based on the helical resonant surface wave model.

A roadmap for graphene

Abstract: Recent years have witnessed many breakthroughs in research on graphene (the first two-dimensional atomic crystal) as well as a significant advance in the mass production of this material. This one-atom-thick fabric of carbon uniquely combines extreme mechanical strength, exceptionally high electronic and thermal conductivities, impermeability to gases, as well as many other supreme properties, all of which make it highly attractive for numerous applications. Here we review recent progress in graphene research and in the development of production methods, and critically analyse the feasibility of various graphene applications.

High-performance lithium battery anodes using silicon nanowires

Abstract: There is great interest in developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices. Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh g(-1); ref. 2). Although this is more than ten times higher than existing graphite anodes and much larger than various nitride and oxide materials, silicon anodes have limited applications because silicon's volume changes by 400% upon insertion and extraction of lithium which results in pulverization and capacity fading. Here, we show that silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. We achieved the theoretical charge capacity for silicon anodes and maintained a discharge capacity close to 75% of this maximum, with little fading during cycling.

Nanobelts of Semiconducting Oxides

Abstract: Ultralong beltlike (or ribbonlike) nanostructures (so-called nanobelts) were successfully synthesized for semiconducting oxides of zinc, tin, indium, cadmium, and gallium by simply evaporating the desired commercial metal oxide powders at high temperatures. The as-synthesized oxide nanobelts are pure, structurally uniform, and single crystalline, and most of them are free from defects and dislocations. They have a rectanglelike cross section with typical widths of 30 to 300 nanometers, width-to-thickness ratios of 5 to 10, and lengths of up to a few millimeters. The beltlike morphology appears to be a distinctive and common structural characteristic for the family of semiconducting oxides with cations of different valence states and materials of distinct crystallographic structures. The nanobelts could be an ideal system for fully understanding dimensionally confined transport phenomena in functional oxides and building functional devices along individual nanobelts.

Raman spectroscopy as a versatile tool for studying the properties of graphene

Abstract: Raman spectroscopy is an integral part of graphene research. It is used to determine the number and orientation of layers, the quality and types of edge, and the effects of perturbations, such as electric and magnetic fields, strain, doping, disorder and functional groups. This, in turn, provides insight into all sp(2)-bonded carbon allotropes, because graphene is their fundamental building block. Here we review the state of the art, future directions and open questions in Raman spectroscopy of graphene. We describe essential physical processes whose importance has only recently been recognized, such as the various types of resonance at play, and the role of quantum interference. We update all basic concepts and notations, and propose a terminology that is able to describe any result in literature. We finally highlight the potential of Raman spectroscopy for layered materials other than graphene.

Aggregation-Induced Emission: Together We Shine, United We Soar!

Abstract: Ju Mei,†,‡,∥ Nelson L. C. Leung,†,‡,∥ Ryan T. K. Kwok,†,‡ Jacky W. Y. Lam,†,‡ and Ben Zhong Tang*,†,‡,§ †HKUST-Shenzhen Research Institute, Hi-Tech Park, Nanshan, Shenzhen 518057, China ‡Department of Chemistry, HKUST Jockey Club Institute for Advanced Study, Institute of Molecular Functional Materials, Division of Biomedical Engineering, State Key Laboratory of Molecular Neuroscience, Division of Life Science, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China Guangdong Innovative Research Team, SCUT-HKUST Joint Research Laboratory, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China