As a fundamental science, physics presents major challenges to the human mind and the principles of physics serve as a foundation for engineering and other sciences. The new technologies that physics has spawned are so ingrained in our civilization that their scientific origins are often overlooked. The discoveries of the principles of solid-state transistors, which led to the miniaturization of electronic devices, or atomic hyperfine structure and superconductivity, which made possible nuclear magnetic resonance (NMR) imaging, and of the laser, which underpins present-day information technology are but a few examples: ,-In addition to directly generating technological innovation, physics also indirectly supports progress throughout society by providing tools with which people in other fields create innovations.
Of all areas, optical physics and condensed matter physics (CMP) have the greatest impact on our daily lives. It is thus natural that the Department places emphasis on these fields. Research programs include both experimental and theoretical aspects of linear and non-linear optics, low-dimensional systems, mesoscopic systems, new materials, microstmctured and nanostructured devices, and surfaces and interfaces. A program of regular visiting faculty members and scholars in the other specialties helps ensure a breadth of coverage.
Facilities
A number of central service facilities and interdisciplinary research institutes provide support for the Department's research programs. Particularly relevant are the centers for Materials Characterization and Preparation, Microelectronic Fabrication, Computing Services and Telecommunications, and the research institutes for Information Technology, Advanced Materials, Microsystems, and Scientific Computation. State-of-the-art facilities for large-scale and intensive scientific computation include optical-fibre distributive networks, various workstations, and a massively parallel processing computer. The Department has laboratories for laser physics, photonics, new thin-film materials, surface/interface studies, solid state properties, polymers and liquid crystals, x-ray optics, semiconductor clusters, and non-linear dynamics. The Zheng Ge Ru Thin Film Physics Laboratory, the Joyce M. Kuok Laser and Photonics Laboratory, and the William Mong Semiconductor Clusters Laboratory form a nucleus for HKUST's Advanced Materials Research Institute.
Faculty Profiles
X-ray optics; nanostructured materials;
strong-field QED and coherent processes in aligned crystals; channeling of heavy ions; ion beam analysis; physics education.
Crystal defects; microstructure-properties relationships
Leroy L. CHANG
Semiconductor physics, materials, and devices.
Theoretical high energy physics;
quantum field theory.
Nonlinear optical propagation effects;
two-photon coherent transients;
nonlinear optical studies of surfaces;
state-selective studies of molecule-surface interactions.
Physics of disordered materials;
complex fluids; liquid crystals; wave localisation and multiple scattering;
physics of composites.
Nonlinear and laser optics; nonlinear optical studies of ultra-thin molecular films; electro-optically active glassy polymeric, Langmuir-Blodgett, and complex oxide thin films; MBE growth of semiconductor heterostructures and quantum wells; linear and nonlinear optical spectroscopies of semiconductors.
Quantum many-body theory; low temperature physics; surface physics;
liquid crystals; technology transfer and economic development.
Application of first principles in studying the electronic, structural, and other physical properties of matter;
surface physics; photonic band gaps.
Kwok Kwong FUNG crystal defects by transmission electron diffraction and microscopy;
semiconductor nanostructures, quantum wells, and quantum dots; silicides;
magnetic nanostructures, multilayers, and granular materials; C60 and graphitic nanostructures; diamond thin films; superconducting and perovskite oxides.
Semiconductor physics:
heterostructures, nanostructures, and defects; optical properties.
Mesoscopic physics; non-equilibrium quantum mechanical phenomena; quan-tum spin systems; strongly correlated metals.
Many-body theory; fractals; electronic structure and transport properties in disordered systems; wave propagation and localization in random media;
mesoscopic physics.
Surface physics; epitaxial growth; low energy electron microscopy.
Device fabrication and micromachining technology; semiconductor lasers; semi-conductor heterojunction physics;
integrated optics; micromachines; fiber optic communication technology.
Pak-Wo LEUNG physics; low-dimension quantum spin systems.
Thin film growth by molecular beam epitaxy; II-VI semiconductor quantum structures; visible optoelectronic devices; structural and transport properties of thin films.
Pattern formation in complex systems;
quasi-crystal growth; magnetotransport and f~ustrated spin systems; genetic algorithms and nonlinear forecasting.
Fractals and chaos; dynamics of cellular structures; electrodeposition; directional solidification; complex fluids; digital imaging and machine vision.
Physics of nanoscale objects; growth and characterization of nano-crystals;
optical, electrical, magnetic, and thermal properties of small clusters.
Physics of semiconductor low-dimensional structures; fabrication of semiconductor nanostructures; magneto-transport and optical properties of semiconductor nanostructures; novel device applications.
Growth kinetics and surface microstruc-tures of compound semiconductors; op-tical and electrical properties of semiconductor quantum structures and devices; long wavelength semiconductor lasers; wide gap III-V semiconductor materials.
Statistical physics and condensed matter theory: critical phenomena, fractal physics, and chemical physics.
Kam-Sing WONG
Ultrashort pulse lasers; time-resolved spectroscopy; semiconductor and polymer physics.
Neural networks; complex and dis-ordered systems; optimization;
telecommunication network management; interface growth and corrosion.
Crystal growth; thin film deposition by laser ablation and sputtering;
optoelectronic materials; Monte Carlo simulation.
STM study of surface structure and dynamics; atomic scale study of tribology; surface diffusion; nonlinear optics.
Magnetic inhomogeneity, transport, and magnetic properties of magnetic multi-layers and granular films; soft magnetic materials with potential application in recording heads, field sensors, high-frequency mini-inductors, and magnetic refrigeration devices.
Optical in situ study of thin film growth;
optical and electronic properties and device application of semiconductor nanostructures; properties of other mesoscopic systems; magneto-optical properties of magnetic materials;
properties of polymers and liquid crystals.
Ultrashort pulse laser; ultrafast phenomena; light scattering and imaging in random media; nonlinear optics; x-ray optics and microscopy; laser applications in medicine.
Research Projects
Conference on Surface Science: "Critical Review and Outlook"
Michael S. ALTMAN
Croucher Foundation Project no. CF95/96.SC20 ($100,000) Project completed.
Surface Science: "Critical Review and Outlook" is a conference devoted to assessing the current status of and to identifying important, new directions in the research of surfaces. This conference will benefit local research efforts in surface science and related areas by stimulating communication and the development of scientific collaboration among local and international participants.
Flux Vortex Phase Diagram and Dynamics in High Temperature Superconductors' MichaelS. ALTMAN (PI), Tai Kai NG
RGC Project no. HKUST 623/95P ($60,000)
We will study the phases and dynamics of flux vortices in high temperature superconductors using low energy electron microscopy (LEEM). Direct, real-time imaging of vortices with .LEEM will provide unique information on their motion. Flux vortex motion is of practical importance because it leads to dissipation, which is a limiting factor for superconductivity. Experimental results will be compared directly to computer simulations based upon simple phenomenological flux line and flux point models, as a rigorous test of these models. This work may offer a potential solution to the flux vortex motion problem in high temperature superconductors.
Surface Step Dynamjcs
MichaelS. ALTMAN (PI), Rong-Fu XIAO RGC Project no. HKUST 642/94P ($556,000)
Atomic steps are a common defect at surfaces, and they are known to play an important role in many surface physical and chemical phenomena. The aim of this project is to investigate the dynamics of surface steps during epitaxial growth and upon surface chemical modification. Low energy electron microscopy will be used to assess spatial patterns and temporal evolution of surface steps. This information will allow us to test theoretical predictions of step-related ordering and to explore new avenues for achieving desired step configurations.
Interfaces in Oxide Materials
David J. BARBER (PI), Michael S. ALTMAN, Ian D. WILLIAMS (CHEM) RGC Project no. DAG94/95.SC20 ($162,880)
Oxide ceramic materials are increasingly used in microelectronic and optoelectronic devices which exploit their insulating, dielectric or ferroelectric properties. In multilayer devices the structures and integrity of the various interfaces largely determine the performance. Much less is known about the nature of oxide-oxide interfaces and the interfaces between oxides and other materials than is known about metallic and semiconductors systems. This project uses high resolution electron microscopy and microanalysis techniques to characterise interfaces at the nanoscale in some model oxide systems .. The knowledge gained will show how various preparation techniques and processing conditions affect interface structures and should assist in the choice of materials and procedures for particular applications.
The Influence of Microstructure on Phase Transitions in Non-Metals David J. BARBER
RGC Project no. HKU§Tl19/92E ($627,000) Project completed.
The influence of microstructure and microchemistry on phase transitions in selected non-metals, mainly perovskite-structured compounds, is becoming ever more relevant to device applications. Structural phase transitions in such materials have many potentially valuable effects on physical properties but have not been widely explored. New methods of preparing films of perovskite-structured compounds will allow their microstructures and chemical compositions to be controlled and modified. The behaviour of these films at or
other relevant techniques. The resulting data should enable exploitable physical properties at temperatures close to those of phase transitions to be "tailored" or optimized to match device requirements. En route new fundamental knowledge and expertise will be acquired about the formation and properties of thin-films of this important group of non-metallic materials, the chemical interactions between them and selected substrates, optimal thermal processing, and/or methods of separating films from substrates, etc.
Local Texture and Microstructure Analysis of Naturally Deformed Dolomite David J. BARBER (PI), Bernd LEISS
German Research Fund Project no. Le 948/1-1 ($170,000)
Due to ductile deformation during mountain building, dolomite rocks from the Southern Margin of the Damara Orogen in Namibia show a preferred grain shape fabric and a preferred crystallographic (texture) orientation.
From the geometrical correlation of the quantitative analysis of the grain shape fabric, the texture and the microstructures (dislocations, etc.), information on the deformation mechanisms of dolomite and on the geological deformation history can be deduced. The present study focuses on the investigation of coexisting different grain fabric domains within single samples. For this purpose single grain orientations are measured with the help of crystallographic-related patterns generated by backscattered electrons (EBSP) in the scanning electron microscope. Microstructures are investigated with the transmission electron microscope. A quantitative relation between the single grain orientations (misorientations) and the orientations and the shape and size of the grains will be established and should give a correlation with the type and the orientation of dislocations. This should allow conclusions about the active slip systems and different recrystallisation mechanisms like grain boundary migration or rotation crystallisation.
First Principles Studies of lntermetallic Systems of Industrial Importance Che Ting CHAN
RGC Project no. DAG95/96.SC12 ($100,000)
First principles calculations are used to study the electronic and structural properties of Ti-based martensitic binary alloys. The calculations will provide an understanding at the atomic level ofthe systems concerned. The first principles approach is based on the local density functional formalism which has been very successfully in predicting structural properties of a large class of elements and compounds. These alloys exhibit unusual elastic and mechanical behaviors such as pseudo-elastic and shape memory effects, and has many important industrial applications. The governing mechanism is believed to be a martensitic transformation from the high temperature B2 phase to the low temperature B-19/B-19' phase. With first principles calculations, atomic coordinates, lattice parameters, bulk moduli, elastic constants, cohesive energies, and optical properties of these alloys will be calculated and correlated with the stability of the B2/B 19/B 19' phase and the martensitic transformation temperature. Initial efforts are focused on NiTi, which is by far the best characterized experimentally, and also the most extensively used industrially. Other alloys ofTi will subsequently be studied so that trends can be established and correlated with the electronic properties of the elements. The calculations can give a better understanding at the microscopic level of these systems, and the knowledge accumulated will in the near future be useful for the design and perfection of these materials.
Growth and Properties oflnAS Based 111-V Quantum Heterostructures Leroy L. CHANG (PI), Weikun GE, Jiannong WANG, Yuqi WANG RGC Project no. MFG94/95.SC03 ($673,000)
The aim of this project is to initiate and then establish the capability of conducting research in III-V quantum heterostructures grown by molecular beam epitaxy, with focus on semiconductors centered on InAs and supplemented by GaSh and AlSb. This group of materials is the only group among all the commonly studied ones that consists of three relatively lattice matched semiconductors. Either by their desirable bulk properties or by their unusual interface energies, heterostructures made of this group of semiconductors offer unique opportunities in materials science, condensed matter physics and solid state electronics. In particular, InAs possesses proper surface characteristics ideally suitable for studies in low dimensional electron systems, the frontier in semiconductor physics. It also exhibits a variety of static and dynamic properties, making it the choice material for electronics and optoelectronic devices. This project is an enabling one in nature. Its success will not only provide us with specific observations in physics and innovations in devices but also serve to establish HKUST as a center of expertise in the forefront of semiconductor research.
Agreement between Exxon Research and Engineering Company and the Hong Kong University of Science and Technology
Leroy L.G. CHANG
Exxon Research & Engg Co. Project no. EXX093/94.SC01 (US$240,000) Project terminated
This project was set up as a result of Exxon-HKUST collaboration on Feb 1, 1994. Prof. P. Sheng of the Physics Department, on secondment term from Exxon, was instrumental in setting up two research groups in the Chinese Academy of Sciences, Beijing, and Fudan University, Shanghai, focusing on the three topics of (1) wave inversion, (2) the measurement of the electrokinetic Onsager coefficients of sandstones (samples provided by Exxon), and (3) the lattice-Boltzmann simulation ofmultiphase fluids flow in rock pores. Excellent results have been obtained on all three topics. On (1), a new iterative algorithm has been formulated which is capable of recovering both the accurate structure and materials properties of the Earth's subsurface from wave reflection data. On (2), a new experimental setup was built in Fudan Unviersity which is capable of measuring both the magnitudes and the phases of the electrokinetic coefficients of fluids-saturated rocks. A surprise result -- that the electrokinetic coefficients of oilsaturated and brinesaturated rocks differ by three orders of magnitudes -can have direct implications for the direct detection of subsurface hydrocarbons via seismic means. On (3), a new lattice-Boltzmann formulation, capable ofreproducing the behavior of incompressible fluids flow, has been found and tested, with excellent results. The program has been jointly reviewed by HKUST and Exxon in October 1995. While the research groups in Beijing and Shanghai will continued to be supported by Exxon, the end of Prof. P. Sheng's secondment term on September 30, 1995 altered the original plan of this collaborative project. This project was subsequently terminated retroactively on Sept 30, 1995.
Adsorption and Thin-Film Growth ofFullerenes (Cn) on Metal and Semiconductor Surfaces TingCHEN
RGC Project no. HKUST206/93E ($426,000) Project completed
We propose an systematic investigation of the adsorption and thin-film growth of fullerene molecules on surfaces with different electronic properties (e.g., metal and semiconductor) and different morphological character (noncrystalline and crystalline surfaces.) In particular we concentrate on exploring the nature and strength of the interactions of fullerenes with surfaces and consequences of such interactions on the electronic structure of the adsorbed fullerene molecules and initial-stage growth. Thin films of fullerene molecules, Cn, prepared in situ on metal and semiconductor substrates are studied by scanning tunnelling microscopy and spectroscopy (STM/S) under ultrahigh vacuum conditions. The topographic and spectroscopic (local tunnelling spectroscopy) information are used to characterize the intermolecular interactions among Cn at different growth stages and electronic density-of-states effects due to the adsorption of fullerene molecules on metal and semiconductor substrates.
Research Assistance to Exxon in the Area of Waves and Wave Inversion Nelson CUE (PM)
Exxon Research & Engg Co. Project no. EXX093/94.SC02 (US$150,000)
Research in the area of waves and wave inversion will be conducted in collaboration with personnel from Exxon.
Reactions of C6o with 2H-MoSz(OOOl) Surface Nelson CUE
RGC Project no. HKUST 637/94P ($575,000)
The reactive processes of C6o with the top-most sulphur ofMoS 2 surface and their effects on the initial stage-growth of C6o on MoS2 are being investigated using a state-of-the-art UHV/STM and surface analysis system.
Studies using HOPG, a layered type semimetal, also are being made for comparison purposes. The results obtained using C6o coverage ranging from submoncilayer to multilayers and for a range of temperatures could lead to a novel method ofnanoscale "etching" on compound surfaces.
New x-Ray Sources, Optics and Multidisciplinary Applications
Nelson CUE (PM), Kwong-Mow YOO, Kwok-Kwong FUNG, Paul M.W. CHAN (SEPO) UGC Project no. RI91/92.SC05 ($2,024,206)
A new compact breed of x-ray systems will be developed jointly with the Institute of Roentgen Optical Systems in Moscow (Russia), and prototypes will be installed at HKUST for research and applications in several science and technology areas. The first of such X-Ray Optics Systems (XROS) consists of a compact Plasma Pinch (PP) x-ray source and multi-capillary x-ray lenses, occupies no more than a few square meters in area but yet can provide x-ray intensities comparable to those obtained from a Synchrotron Radiation (SR) source. SR requires a very expensive and very expansive accelerator and associated storage ring. With an XROS, we can undertake in-house research in such topical areas as: 1) materials processing and modification under pulsed, intense VUV and soft x-ray irradiation; 2) x-ray lithography of devices with submicron structure; 3) x-ray microscopy of untreated or unhydrated specimens; and 4) x-ray mammography.
Transmission Electron Diffraction and Microscopy Study of Strains and Misfit Dislocations at Interfaces of Semiconductor Epilayers and Superlattices
Kwok-Kwong FUNG
RGC Project no. HKUST118/92E ($626,000) Project completed.
To study defects in thin layers of semiconductors (a few hundred
A
thick) grown by MBE by transmission electron microscopy. Specifically, we are interested in the elastic strain in the layers and the plastic strain (dislocations) at the interfaces of the layers. The layers studied are II-VI semiconductor epilayers and superlattices grown in the Zheng Ge Ru Thin Film Physics Laboratory at HKUST.High Resolution Electron Microscopy Study of ZnSTe-Based Epilayers and Superlattices Grown by Molecular Beam Epitaxy
Kwok Kwong FUNG
RGC Project no. HKUST 621/95P ($361,000)
It has been shown recently that very thin epilayers and superlattices based on the relatively unexplored II-VI semiconductor ZnSTe grown by molecular beam epitaxy in our department are promising materials for colour display and laser structures covering the whole visible spectrum. All the blue green laser structures based on ZnSe which have been intensely studied in recent years show rapid degradation in operation and have short lifetimes. Transmission electron microscopy (TEM) study on As-grown and defraded laser structures has established that degradation is due to the development and propagation of dislocations from grown-in stacking faults at the ZnSe/GaAs interface. Grown-in stacking faults in elastically strained and dislocations in plastically strained multilayers will be studied by high resolution TEM. The structural results will be correlated with the optical properties and growth conditions.
Developments in the Electron Microscopy of Materials
Kwok Kwong FUNG (PM), David J. BARBER, MichaelS. ALTMAN RGC Project no. MFG94/95.SC02 ($992,592)
Multilayered and nanostructured materials and devices with new and useful properties can now be grown
Multilayered and nanostructured materials and devices with new and useful properties can now be grown