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.

3.24 – Cubic Boron Nitride Films: Properties and Applications

Abstract: Cubic boron nitride (cBN) is structurally analogous to diamond, with similar or even superior properties for certain applications. Studies on the low-pressure synthesis of cBN films started around 1980. So far a variety of ion-assisted physical vapor deposition and chemical vapor deposition methods to deposit cBN films on various substrates have been developed. This chapter discusses the major issues hindering cBN films for practical applications, and reviews recent progress in the synthesis and characterization of cBN films, in particular, to increase film thickness, improving crystallinity, reducing residual stress, and enhancing adhesion to the substrates. The merits and demerits of different deposition techniques are discussed. Common features and differences in the structures and properties of cBN films deposited by different approaches are described. This chapter also summarizes up-to-date studies on the mechanical, electronic, optoelectronic, and optical properties of cBN films, and presents example applications of cBN films in cutting tools, deep-ultraviolet detectors, and chemical and biological sensors.

Highly efficient nondoped green organic light-emitting devices based on a substituted triphenylpyridine derivative

Abstract: Highly efficient nondoped green organic light-emitting devices based on a triphenylpyridine derivative, 4-[4-(dimethylamino)phenyl]-2,6-diphenylnicotinonitrile (NPDPN), were fabricated and characterized. The double-organic-layer device with a structure of ITO/α-napthylphenylbiphenyl diamine /NPDPN/LiF/Al, in which NPDPN was used as both the emitter and the electron transporter, exhibits a green emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.23,0.52) and a power efficiency of 5.5 lm/W. The result is much better than that of similarly structured device based on tris(8-hydroxyquinoline)aluminum. Furthermore, a high current efficiency of 8.4 cd/A was achieved with an optimized device configuration.

Core/Sheath organic nanocable constructed with a master-slave molecular pair for optically switched memories.

Abstract: Here, we propose a new approach to solve this problem by distributing the above functions to two optoelectronically coupled molecules. Briefl y, a molecule with good photochromic switching properties is used as a “master” molecule. Via optoelectronic coupling, the master molecule will control a “slave” molecule that has no photochromic properties but has good electrical and/or optical properties. The essential optoelectronic coupling is achieved here with a core/sheath nanocable structure, which provides intimate contact between the “master” and the “slave” molecules. Through this design, molecules with more specialized functions can be developed individually, thus meeting the need for developing all-round materials. Here, we demonstrate the above concept with a core/sheath nanocable constructed with two small molecular materials with matched energy levels to enable optoelectronic coupling. The photochromic master molecule used here is a diarylethene derivative, 1-[2-methyl-5-phenyl-3-thienyl]-2-[2-methyl-5-( p -(methyl)phenyl)3-thienyl]-hexaflne ( MPT–MMPT–HFCP ), which has been widely studied for its excellent photochromic properties. [ 1–7 , 14 ] Coronene is used as the slave molecule for the following reasons: 1) it has a large aromatic system and is a good holetransporting semiconductor, with electrical properties that have potential tunability upon combined use with MPT-MMPT-HFCP ; 2) its photoluminescence (PL) spectrum has extensive overlap with the absorption spectrum of MPT-MMPT-HFCP , which may induce effi cient intermolecular energy transfer for the emission modulation; and 3) the π – π interaction between polycyclic aromatic molecules would provide driving force for self-assembling

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