Seminars 2009

Title: Probing novel quantum phenomena with high energy resolution scanning tunneling spectroscopy
Speaker:Dr Xi Chen
Date:16 December 2009 


Title: Transport studies of individual crystalline nanowirescontacted by superconducting and normal electrodes
Speaker:Dr Jian Wang
Date:11 December 2009 


Title: Fabrication of nanobowlstructure and its plasmonicproperties
Speaker:Ms Ma Yun
Date:29 September 2009


Title: Cavity Solitons in Vertical Cavity Surface Emitter Lasers (VCSEL)
Speaker:Professor Jorge R. Tredicce
Date:18 September 2009 


Title: Physics and Properties of Localized Structures in Optical Systems
Speaker:Professor Jorge R. Tredicce
Date:11 September 2009


Title: Far-Infrared Spectroscopy of Complex Materials
Speaker:Professor Richard D. Averitt
Date:31 August 2009 


Title: Self-directed assembly of nano-objects in surfactant bilayers transferred on solid surfaces
Speaker:Dr Jean-Jacques Benattar
Date:13 July 2009


Title: Interface effects in heterostructures with high Tc cuprates
Speaker:Professor Adrian Mihai Gozar
Date:7 July 2009


Title: Carbon based spintronic material (Fe,Co)x-C1-x /Si nanostructure
Speaker:Professor Zhang Xiaozhong
Date:6 July 2009 


Title: Stabilization of Multifunctional Artificial Superlattices by Laser Ablation
Speaker:Dr Wilfrid Prellier
Date:3 July 2009


Title: Frequency Standards Research on the West Coast of Australia
Speaker:Professor Andre Luiten
Date:19  June 2009
Time: 2.15pm - 3.15pm 
Venue: Hilbert Space (PAP‐02‐02)
Host:Nanyang Assistant Professor Dr Rainer Dumke
Abstract: Clocks and oscillators are key enabling technologies for precision measurements in industrial and academic environments. I will commence this talk with an overview of our research in the areas of compact optical clocks using hollow‐core optical fibres as well as tests of physics based on precision measurement.  For the majority of the talk, however, I will concentrate on two particular examples of time and frequency technology that we have been working on in the last year:

(1) A compact thermal beam clock.
We have constructed an optical frequency standard based on a thermal beam of Calcium atoms combined with diodes for both laser interrogation (red) and a shelved detection system (blue). The standard has the potential for both portability and even substantial improvement beyond its current performance in the 10‐14 fractional frequency regime. I will describe the approach we have taken as well as the limitations to date.

(2) Absolute Thermometry based on Laser Spectroscopy.
The second application I want to discuss is the use of high‐resolution spectroscopy to ascertain, with high accuracy, the Doppler width of a spectral line of an atomic vapour.  If the measurement process can be sufficiently well understood, and the vapour is in sufficiently good thermal contact with a bath at well‐defined thermodynamic temperature, then this technique potentially offers an independent method to measure the Boltzmann constant with high accuracy as well as a means to define temperature in terms of the fundamental constants. I will discuss the status of the current experiment with room temperature alkali vapours, the substantial (but very interesting) challenges of the experiment, as well as where we are heading in the near future.


Title: Field Emission Studies of Singled 1D Nanostructure Field‐Emitter
Speaker:Dr Yeong Kuan Song
Date:19 June 2009
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP‐02‐02)
Host:Nanyang Asst Prof Xiong Qihua
Abstract: Field emitters are conventionally based on micrometer‐sized cathodes, albeit with very sharp tips. Studies have suggested that a further reduction in emission area would change the field emission properties significantly. This work studies the field‐emission properties of 1‐D nanostructures as individual cold field‐ emitters. The project involves the setting up of a field emission characterization system, synthesis and characterization of 1D nanostructures, fabrication of single field emitter cathodes, and finally a detailed of field‐emission characteristics. The cathodes studied include tungsten nanowires and carbon nanotips synthesized by the field‐emission‐induced growth method, multiwalled carbon nanotube, and zinc oxide nanowires. Compared to conventional tungsten cold field emitters, the 1D nanostructures studied showed unusual characteristics and phenomena, such as deviation from the Fowler Nordheim equation, good emission current stability, and structural changes during emission. These observations not only help to further elucidate physical mechanisms that affect field emission, but also provide directions for the development of novel electron sources.


Title: Physics of ultrafast laser induced high current electron emission from metal surface
Speaker:Associate Professor L. K. (Ricky) Ang
Date:9 April 2009
Time: 3.00pm - 4.00pm 
Venue: Hilbert Space (PAP-02-02)
Host:Professor Shen Zexiang

In this talk, we will present a model to explain the dynamic of electron emission from a dc-biased metal surface under the ultrafast laser excitation [1]. While the model has made some assumptions, it is able to explain and confirm the three recent experimental results from other groups in USA and Europe [2,3,4]. In solving the couple-Boltzmann equations, the non-equilibrium electronic state of the metal under the laser excitation is first calculated, and it is used to calculate the time-resolved electron emission current density. It is found the both field emission and multiphoton emission are important. The effects of space charge effects at ultrafast time scale and quantum regime will be discussed [5,6]. The application of such ultrafast electron pulse and the some interesting unsolved problems will be discussed.

1. W. Lin and L. K. Ang, Phys. Rev. B 78, 224112 (2008).
2. P. Hommelhoff, C. Kealhofer, and M. A. Kasevich, Phys. Rev. Lett. 97, 247402 (2006).
3. C. Ropers, D. R. Solli, C. P. Schulz, C. Lienau, and T. Elsaesser, Phys. Rev. Lett. 98, 043907 (2007).
4. B. Barwick, C. Corder, J. Strohaber, N. Chandler-Smith, C. Uiterwaal, and H. Batelaan, New J. Phys. 9, 142 (2007).
5. L. K. Ang, and P. Zhang, Phys. Rev. Lett. 98, 164802 (2007).
6. L. K. Ang, T. J. T. Kwan and Y. Y. Lau, Phys. Rev. Lett. 91, 208303 (2003)


Title: Modeling Complex Systems: Catalsis, Clusters, DNA
Speaker:Professor Noter Roesch
Date:30 March 2009


Title: Micro/Nano-fluidic Systems for Cell Signaling Studies
Speaker:Dr Zhizhong Yin
Date:30 March 2009


Title: Australian Participation in the International SKA Project
Speaker:Professor Peter Quinn
Date:20 March 2009 


Title: Quantum Dots: Results & Unknowns
Speaker:Professor Rudi Marcus
Date:6 March 2009


Title: Thermal transport in graphene nano-ribbon
Speaker:Dr Lan Jinghua
Date:5 March 2009
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP-02-02)
Host:Asst Prof Kuo Jer-Lai
Abstract: Graphene has attracted considerable attention in recent years due to its versatile electronic properties which are important for future nanoelectronics. It is desirable to understand the size effect on the thermal transport properties in order to miniaturize the electronic devices. Since geometric effects are important at nanoscale, we unveiled thermal properties related to atomic details in GNRs explicitly with the phonon nonequilibrium Green's function NEGF method. We first consider the natural edge effect on thermal transport of GNRs. We find that natural edge will reduce thermal conductance which agrees well with experimental results. Then we study the thermal transport in GNRs with different geometries. Interesting results are found, such as wide phonon band gap in sandwiched model and reduction of thermal conductance by two orders of magnitude due to holes and so on.


Title: Illustration of Chemical Bonding and Its Guidance to Rational Materials Design
Speaker:Dr Yim Wai-Leung
Date:5 March 2009
Time: 10.00am – 11.00am
Venue: Hilbert Space (PAP-02-02)
Host:Assistant Professor Kuo Jer-Lai
Abstract: For newly developed chemical systems, the investigation of its underlying chemical bonding mechanism is particularly important. However, the use of classical chemical concepts on novel systems is surprisingly rare. One of the reasons might be the limited availability of chemical analysis methods for condensed phase calculations, especially for those using plane-wave basis sets. For condensed phase systems, several analysis methods can be utilized, such as electron localization function, partial density of states and charge density difference plots. Recently, charge topology analysis according to Bader’s scheme has been made feasible by Henkelman et al. In this talk, another implementation for characterizing the bond critical point will be described. Such an implementation allows us to analyze three dimensional charge density grids which can be generated by Gaussian package and VASP. By using this implementation, we have successfully explored the role of electrostatic effect on engineering reaction barriers for: 1) oxygen reduction reaction (ORR) on noble metals; and 2) CO activation process on cobalt surfaces.


Title: Quantum Valley Hall Effect in Graphene
Speaker:Dr Ivar Martin
Date:3 March 2009


Title: Is 25% the upper limit of internal efficiency for fluorescent OLEDs?
Speaker:Dr Chen Zhikuan 
Date:13 February 2009


Title: Spintronics: from Spins to Devices
Speaker:Dr Jiang XIAO
Date:3 February 2009 
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP‐02‐02)
Host:Professor Alfred Huan
Abstract: About two decades ago, spintronics appeared on horizon marked by the discovery of giant‐ magnetoresistance (GMR), where the current flow is affected by the magnetization configuration. Just over one decade ago, the frontier of spintronics was pushed further by the prediction of spin‐transfer effect, where the magnetization configuration is affected by the current flow. The current‐induced spin‐transfer torque can excite magnetization dynamics and even magnetization reversal in magnetic heterostructures. Inversely, we also found that a magnetization dynamics can induced a current flow due to the spin and charge pumping effect. When at thermal equilibrium without bias voltage, the electric noise in a magnetic heterostructure is found to be fundamentally different from that in a normal conductor. In normal conductors, there is only one noise source: thermal agitation of charge carriers, which causes the white Johnson‐Nyquist noise. However, in magnetic heterostructures, there is another independent noise source: thermal agitation of the magnetization, which also contributes to the electric noise by spin and charge pumping effect. The noise power spectrum from the latter consists of two absorption lines at zero frequency and at the ferromagnetic resonance frequency on top of a white noise background. The relative intensities depend on the magnetization configuration.


Title: Graphene: from bench‐top particle‐physics Laboratory to Revolutionary Micro‐electronics
Speaker:Professor Antonio H. Castro Neto
Date:23 January 2009 
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP‐02‐02)
Host:Professor Alfred Huan
Abstract: The isolation of graphene in 2004, a one atom thick form of carbon, completes a saga that started with the invention of the pencil from graphite in 1564, and continued through the synthesis of one‐dimensional carbon nanotubes, and then of buckyballs. The electrons in graphene behave as relativistic particles, albeit with a velocity of propagation 300 times smaller than the speed of light, allowing the use of graphene as a testbed for many strange effects predicted in the theory of quantum relativity. Because of its robust structural and electrical properties, graphene can be considered the natural evolution of the silicon‐based technology that permeates the modern world. It is believed that graphene may replace silicon in electronic devices because of its amazing potential for miniaturization and extraordinary electric properties.


Title: A combined NMR and SAXS study of a picornaviral replication complex
Speaker:Dr Steven M. Pascal
Date:16 January 2009 


Title: Bound excitons in Sr2CuO3
Speaker:Dr Kyungwan Kim 
Date:16 January 2009


Title: Raman Epitaxial Metal-oxide Films - from Single Phase to Nanocomposite
Speaker:Dr Hao Yang
Date:13 January 2009


Title: Characterization and control of electron dynamics in ultracold plasmas
Speaker:Professor Micheal Lim
Date:13 January 2009


Title: Statistics of Single Molecule Measurements
Speaker:Dr Jianshu Cao
Date:9 January 2009


Title: Raman Scattering from Optical Phonons in Semiconductor Nanowires
Speaker:Dr Qihua Xiong
Date:7 January 2009
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP‐02‐02)
Host:Professor Shen Ze Xiang
Abstract: Semiconductor nanowires (SNWs) show great promises as building blocks for nanoelectronics, optoelectronics and biological or chemical sensors. Due to their quasi‐one‐dimensional nature, research into the fundamental physical properties of nanowires has focused on quantum size effects, e.g., transverse confinement for electrons or phonons. However, the effects of the shape of nanowires on the physical properties of SNWs have not yet been systematically studied. In this presentation, Raman scattering from either an ensemble of or individual nanowires shows that the properties of optical phonons are dependent on the shape of the nanowire. The term “shape” is taken to refer not only to the cross section geometric form (e.g., circle, hexagon, square, etc.) but also to the aspect ratio of the nanowire. The modulation of the cross sectional area activates surface optical (SO) phonon Raman scattering in nanowires. The modulation is identified with a growth instability. The SO phonon dispersion is shown strongly dependent on the cross sectional shape. Furthermore, we report the first observation of a nano‐antenna effect from individual nanowires where the incident laser produces Raman scattering as if the individual nanowire is a dipole antenna. The polarized Raman scattering intensity is a complicated interplay between the symmetry of the phonon scattering and the dipolar nature of the local fields. From our experiment and theory based on Discrete Dipole Approximation, we show that the antenna effects dominate for small diameter nanowires (d<60 nm), but isolated higher order resonances at much larger nanowire diameters are also possible. Future work will be briefly discussed.


Title: Molecules on metals: A STM Approach
Speaker:Dr Shih‐Hsin Chang
Date:6 January 2009
Time: 11.00am - 12.00pm 
Venue: Hilbert Space (PAP‐02‐02)
Host:Professor Alfred Huan
Abstract: The study of organic molecules has received remarkable attention during the last decades for the development of thin film transistors. Following the trend of scaling down of IC chips sooner or later the fabrication dimension will fall within the lower nanometer scale. How to well control molecules on an atomic level becomes a central challenge in current nanotechnology. The first step is to understand the adsorption behavior of isolated molecules and their interaction with the supporting substrate and neighboring molecules. Scanning tunneling microscopy (STM) with a high special resolution is a proper technique to achieve this goal.

In this talk I will focus on two kinds of molecules adsorbed on metals to show how they behave on metals by means of STM; of the metal phthalocyanines (MPcs) and tetra‐phenyl‐porphyrins (TPPs). We investigated the temperature dependent adsorption behavior of 4‐fold symmetric MPcs on metals with commensurate and incommensurate symmetries. On the 4‐fold symmetric Cu(100) surface, planar and 4‐fold molecular structures in two equivalent orientations were found for MPcs when prepared at room temperature. In addition, two metastable orientations were identified when prepared at low temperature which can be depopulated upon annealing. MPcs adsorbed on the 6‐fold symmetric Cu(111) surface showed a disturbed molecular appearance. The symmetry of molecular structures changed from 4‐fold to 2‐fold which is discussed in terms of molecule‐substrate interaction. At coverages of up to ~1 ML, well‐order molecular structures are formed, and instead of isolated molecules found at low coverages self‐assembled domains start to appear after the completion of the first layer. The growth behavior on metals is also compared with that on insulating layers, i.e. NaCl.

TPP molecules behave differently to Pcs. Self‐assembled domains are formed on metals at lower coverages. By combination of STM observations and numerical modeling, deformations of the molecular structure are identified reflecting the interaction of the phenyl periphery with the sub‐strate. Moreover, the molecule‐substrate interaction can be manipulated by ligands attached to the molecule. More details will be presented in this talk.


Title: Chartered’s Research Collaboration Program with NTU
Speaker:Dr Ng Chee Mang
Date:5 January 2009
Time: 11am 
Venue: SPMS-LT4
Host:Professor Shen Zexiang
Abstract: In his presentation, Dr Ng will share some research projects that Chartered are interested to collaborate with SPMS faculties under the Chartered University Research Program. Faculties who are interested to co-supervise students under this program are strongly encouraged to attend and interact with Dr Ng.