ORCID Profile
0000-0002-3776-3648
Current Organisation
Nanyang Technological University
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Publisher: Springer Science and Business Media LLC
Date: 27-01-2009
DOI: 10.1140/EPJE/I2008-10430-4
Abstract: We report dewetting of thermodynamically stable, thick (approximately 100 nm) polystyrene films by titanium ion implantation. The dynamic dewetting patterns in time evolution are recorded. The dewetting mechanism is determined to be heterogeneous nucleation, where the defects and Ti nanoparticles formed by ion implantation serve as the nuclei. In addition, we observe abundant rims with regular polygonal shapes in dewetting patterns. This is attributed to fingering instability, which results from the balance between the driving force arisen from thermally induced surface tension gradient and the resistive forces from the combination of friction force, Laplace pressure and long-range van der Waals interactions. Finally, a model based on mass conservation is used to qualitatively describe the transition from circular to polygonal shaped rims at a critical diameter for holes.
Publisher: IEEE
Date: 2008
Publisher: AIP Publishing
Date: 13-08-2007
DOI: 10.1063/1.2772668
Abstract: Surface modification of ZnO nanocombs was performed through a Ti plasma immersion ion implantation (PIII) with low bias voltages ranging from 0to5kV to quench surface-originated exciton emission. The ion energy dependent surface modification on ZnO was investigated using transmission electron microscopy and temperature-dependent photoluminescence (PL). The surface exciton (SX) was clearly identified for the as-grown s le at 4.5K, and complete quenching was observed for s le treated with 5kV PIII due to surface state passivation. The SX related surface states were located within 5nm in depth from the surface corresponding to the implantation depth of 5kV PIII. Room-temperature PL enhancement of these surface-modified ZnO nanocombs was observed and discussed. The results show that PIII can become a viable technique for nanostructure surface passivation.
Publisher: World Scientific Pub Co Pte Lt
Date: 20-01-2002
DOI: 10.1142/S0217979202009470
Abstract: It has been elegantly accepted that oxygen adsorption onto the Cu (110) surface induces an expansion of the first layer-spacing and a contraction of the second in addition to the alternative Cu [001] row that is either missing or forming the O-Cu-O row of high protrusions. However, it needs yet to clarify the vertical position of the oxygen and the hard-sphere models of added-, missing- and buckled-row. Here we justify that all the structures determined and all the models developed so far are correct in the sense of numerical solutions and phenomenological descriptions. A tetrahedral bond configuration of sp-orbital hybridization developed recently, however, may serve as a criterion to identify the physical solution that could account consistently for the observations using scanning tunneling microscopy/spectroscopy (STM/S), X-ray diffraction (XRD), and ultraviolet photoelectron spectroscopy (UPS).
Publisher: Elsevier BV
Date: 04-2011
Publisher: Elsevier BV
Date: 04-2007
Publisher: IOP Publishing
Date: 22-08-2002
Publisher: Wiley
Date: 28-11-2007
DOI: 10.1002/APP.27414
Publisher: American Vacuum Society
Date: 27-06-2002
DOI: 10.1116/1.1486227
Abstract: Nanocomposite amorphous carbon films such as a-C:Al, a-C:Ti, and a-C:Si have been prepared using a filtered cathodic vacuum arc technique. The films were characterized using x-ray photoelectron spectroscopy (XPS), atomic force microscopy, surface profilometry, a nanoindenter, and Raman spectrometry. It was found that metal contents in the films deviate from the target depending on the constituent element, which is attributed to the effect of dynamic balance deposition. XPS results revealed the presence of a carbide phase in a-C:Ti and a-C:Si but not in a-C:Al nanocomposite carbon films. Incorporating metal into amorphous carbon films significantly reduces the compressive stress but maintains the relative high hardness and Young’s modulus.
Publisher: Elsevier BV
Date: 07-2009
Publisher: IOP Publishing
Date: 30-07-2003
Publisher: AIP Publishing
Date: 16-02-2009
DOI: 10.1063/1.3086874
Publisher: IEEE
Date: 2008
Publisher: Elsevier BV
Date: 03-2011
Publisher: Elsevier BV
Date: 05-2005
Publisher: American Physical Society (APS)
Date: 09-06-2004
Publisher: AIP Publishing
Date: 26-01-2009
DOI: 10.1063/1.3077605
Abstract: This paper deals with the experimental observation of time-dependent electrical double layer (EDL) in electrolyte. A potential-distance diagram is used to fully understand different stages in the formation of EDL. The influence of the thickness of the blocking layer and the ionic strength to the formation of EDL is discussed based on the equivalent circuit. With this simple method, it is found that in addition to Debye screening length, the frequency has to be considered if an alternating electric field is used to control the movement of charged biomolecules inside EDL.
Publisher: Wiley
Date: 03-04-2017
Abstract: Due to the intriguing optical and electronic properties, 2D materials have attracted a lot of interest for the electronic and optoelectronic applications. Identifying new promising 2D materials will be rewarding toward the development of next generation 2D electronics. Here, palladium diselenide (PdSe
Publisher: American Chemical Society (ACS)
Date: 21-09-2002
DOI: 10.1021/JP025868L
Publisher: IOP Publishing
Date: 16-11-2004
Publisher: OSA
Date: 2017
Publisher: SPIE
Date: 23-02-2005
DOI: 10.1117/12.582855
Publisher: Elsevier BV
Date: 12-2003
Publisher: Elsevier BV
Date: 08-2005
Publisher: IOP Publishing
Date: 29-05-2002
Publisher: AIP Publishing
Date: 26-07-2004
DOI: 10.1063/1.1766086
Abstract: CF 4 plasma-passivation enhanced size dependence of the blueshift in photoemission and photoabsorption, E2p-level shift, and band-gap expansion of porous silicon has been measured and analyzed numerically based on the recent “bond order-length-strength” correlation [C. Q. Sun, Phys. Rev. B 69, 045105 (2004)]. Matching predictions to the measurements conducted before and after fluorination reveals that fluorination further enhances both the crystal binding intensity that determines the band gap and core level shift and the electron-phonon coupling that contributes to the energies of photoemission and photoabsorption. This approach enables us to discriminate the effect of surface-bond contraction from the effect of surface-bond nature alteration on the unusual behavior of photons, phonons, and electrons in nanosolid Si.
Publisher: Elsevier BV
Date: 02-2009
Publisher: Elsevier BV
Date: 10-2003
Publisher: Elsevier BV
Date: 08-2005
Publisher: AIP Publishing
Date: 12-05-2003
DOI: 10.1063/1.1576890
Publisher: American Chemical Society (ACS)
Date: 16-09-2009
DOI: 10.1021/NN900846P
Abstract: The possibility of effective control of the wetting properties of a nanostructured surface consisting of arrays of amorphous carbon nanoparticles capped on carbon nanotubes using the electrowetting technique is demonstrated. By analyzing the electrowetting curves with an equivalent circuit model of the solid/liquid interface, the long-standing problem of control and monitoring of the transition between the "slippy" Cassie state and the "sticky" Wenzel states is resolved. The unique structural properties of the custom-designed nanocomposites with precisely tailored surface energy without using any commonly utilized low-surface-energy (e.g., polymer) conformal coatings enable easy identification of the occurrence of such transition from the optical contrast on the nanostructured surfaces. This approach to precise control of the wetting mode transitions is generic and has an outstanding potential to enable the stable superhydrophobic capability of nanostructured surfaces for numerous applications, such as low-friction microfluidics and self-cleaning.
Publisher: American Chemical Society (ACS)
Date: 18-12-2003
DOI: 10.1021/JP0372946
Publisher: Elsevier BV
Date: 07-2006
Publisher: AIP Publishing
Date: 31-03-2004
DOI: 10.1063/1.1686905
Abstract: Deep level transient spectroscopy and optical absorption spectroscopy measurement revealed three outstanding features of density-of-states (DOS) appeared above the valence band edge (Ev) of Al oxide thin films. The broad peak located at 0.39 eV above Ev disappears while the other two located at 1.0 and 1.3 eV shift in position and attenuate in intensity upon annealing at 200 °C. The latter two peaks are removed by annealing at temperature up to 400 °C. The observed midgap DOS feature dynamics is in accordance with the oxygen lone pair features as confirmed earlier with Raman spectroscopy in the low-frequency ranges [C. Q. Sun et al., J. Appl. Phys. 90, 2615 (2001)] and thermal desorption measurements of other oxide surfaces.
Publisher: IOP Publishing
Date: 05-12-2001
Publisher: SPIE
Date: 27-12-2007
DOI: 10.1117/12.695666
Publisher: AIP Publishing
Date: 03-2007
DOI: 10.1063/1.2709578
Abstract: Polyimide s les modified by aluminum (Al) ions produced by filtered cathodic vacuum arc (FCVA) with plasma immersion ion implantation (PIII) technique, under ambient argon and oxygen gases (flow rate Ar:O2=2:1) were investigated by x-ray photoelectron spectroscopy (XPS). The working pressure was about 8×10−4 Torr and the plasma density was estimated to be 109 ions∕cm3. The applied bias voltages were varied from 5 to 12.5 kV but with fixed frequency at 900 Hz and duty time of 15μs. For 1 min process time, C 1s and O 1s spectra for modified s les clearly indicated that the carbonyl group (C=O) was largely destroyed by incident Al ions while Al 2p spectra suggested Al atoms remain inside polyimide matrices in the form of C-O-Al complexes. For a 5 min process time, when the ion fluence became large, both C 1s and O 1s spectra suggested a structure of “aluminum oxide-mixed layer-polyimide” and Al 2p spectra confirmed that most Al atoms were bonded to oxygen atoms on the top surface. These XPS results revealed the chemical bonds between implanted and deposited Al ions and polyimide matrix by using the PIII technique. The structural information can also be suggested. Furthermore in this paper, some discussions with the theoretical [the stopping and range of ions in matter (SRIM)] simulation were also mentioned in order to explore the effectiveness of Al ions irradiation on polyimide.
Publisher: AIP Publishing
Date: 29-07-2003
DOI: 10.1063/1.1594822
Abstract: Carbon nitride films have been deposited by rf reactive magnetron sputtered graphite carbon in an N2 discharge. The process parameters, viz., nitrogen partial pressure (PN2), substrate temperature (Ts), and substrate bias (Vb) were varied in order to investigate their influence on the field emission properties. The effective work function for carbon nitride films determined using the Fowler–Nordheim equation is in the range of 0.01–0.1 eV. Insight is presented into the nitrogen-lowered threshold of cold cathode electron emission of carbon from the perspective of nitride tetrahedron bond formation. The involvement of nonbonding (lone pair) and lone-pair-induced antibonding (dipole) states is suggested to be responsible for lowering the work function and hence the electron emission threshold. It is found that the substrate temperature of 200 °C, floating potential at the substrate, and nitrogen partial pressure of 0.3 Pa are favorable to promote the reaction that lowers the work function.
Publisher: IEEE
Date: 2006
Publisher: AIP Publishing
Date: 06-2009
DOI: 10.1063/1.3148667
Abstract: Superhydrophobic amorphous carbon/carbon nanotube nanocomposites are fabricated by plasma immersion ion implantation with carbon nanotube forests as a template. The microstructure of the fabricated nanocomposites shows arrays of carbon nanotubes capped with amorphous carbon nanoparticles. Contact angle measurements show that both advancing and receding angles close to 180° can be achieved on the nanocomposites. The fabrication here does not require patterning of carbon nanotubes or deposition of conformal coatings with low surface energy, which are usually involved in conventional approaches for superhydrophobic surfaces. The relationship between the observed superhydrophobicity and the unique microstructure of the nanocomposites is discussed.
Publisher: American Physical Society (APS)
Date: 08-2004
Publisher: IOP Publishing
Date: 17-07-2001
Publisher: Elsevier BV
Date: 11-2001
Publisher: American Chemical Society (ACS)
Date: 23-10-2002
DOI: 10.1021/JP0266805
Publisher: American Chemical Society (ACS)
Date: 08-05-2003
DOI: 10.1021/JP0272015
Publisher: IEEE
Date: 2013
Publisher: Elsevier BV
Date: 06-2007
DOI: 10.1016/J.BIOS.2007.01.006
Abstract: In this paper, a novel erometric glucose biosensor was constructed by alternative self-assembly of positively charged poly(diallydimethylammonium chloride) (PDDA) and negatively charged glucose oxidase (GOx) onto a 3D Nafion network via electrostatic adsorption. The amount of Nafion in the electrode and the number of the (PDDA/GOx)(n) multilayers were optimized to develop a sensitive and selective glucose biosensor. Under optimal conditions, the glucose biosensor with (PDDA/GOx)(5) multilayers exhibited remarkable electrocatalytic activity, capable of detecting glucose with enhanced sensitivity of 9.55 microA/mM cm(2) and a commendably low detection limit of 20 microM (S/N=3). A linear response range of 0.05-7 mM (a linear correlation coefficient of 0.9984, n=20) was achieved. In addition, the glucose biosensor demonstrated superior selectivity towards glucose over some interferents, such as ascorbic acid (AA) and uric acid (UA), at an optimized detection potential of 0.6 V versus Ag/AgCl reference.
Publisher: American Chemical Society (ACS)
Date: 18-08-2007
DOI: 10.1021/JP0727087
Publisher: American Vacuum Society
Date: 03-2004
DOI: 10.1116/1.1651108
Abstract: The effect of plasma fluorination on the band gap, 2p core-level energy, and the dielectric behavior of porous silicon (PS) prepared under constant conditions has been examined using Fourier transform infrared spectroscopy, x-ray photoelectron spectroscopy, photoluminescence, and reflection. It has been found that with increasing extent of fluorination, the band gap expands, and the 2p level and the dielectric constant drop down substantially compared with those of the as-grown PS, being quite similar to the effect of particle size reduction. These findings could be interpreted as the fluorination-induced crystal field enhancement and the valence charge repopulation of silicon. The surface fluorination may provide an effective method for tuning the optical and dielectric properties of nanometric silicon.
Publisher: Wiley
Date: 08-07-2015
Abstract: Two metal nitrides, TiN porous layers and Fe2 N nanoparticles, are grown uniformly with the assistance of atomic layer deposition on vertically aligned graphene nanosheets and used as the cathode and anode for solid-state supercapacitors, respectively. Full cells are constructed and show good flexibility, high-rate capability, and 98% capacitance retention after 20,000 cycles.
Publisher: AIP Publishing
Date: 30-07-2007
DOI: 10.1063/1.2761233
Abstract: The authors used the plasma immersion ion implantation and deposition technique to modify polyethylene terephthalate (PET) and by using conductive atomic force microscope, the spatial distribution of ∼10nm size titanium nanoclusters embedded in PET matrices were observed. The I-V plots showed typical metal-semiconductor junction conductivity between the conductive tip and the surface. In addition, the authors also measured the temperature dependent conductivity and fitted it well to the Mott law, which implied that the conductance arose from electron hopping process. Such technique to create the surface structure of metal olymer nanocomposites may open an alternative way for plastic nanoelectronics.
Publisher: Elsevier BV
Date: 06-2007
Publisher: Elsevier BV
Date: 08-2007
DOI: 10.1016/J.BIOS.2007.03.014
Abstract: ZnO:Co nanoclusters were synthesized by nanocluster-beam deposition with averaged particle size of 5 nm and porous structure, which were for the first time adopted to construct a novel erometric glucose biosensor. Glucose oxidase was immobilized into the ZnO:Co nanocluster-assembled thin film through Nafion-assisted cross-linking technique. Due to the high specific active sites and high electrocatalytic activity of the ZnO:Co nanoclusters, the constructed glucose biosensor showed a high sensitivity of 13.3 microA/mA cm2. The low detection limit was estimated to be 20 microM (S/N=3) and the apparent Michaelis-Menten constant was found to be 21 mM, indicating the high affinity of the enzyme on ZnO:Co nanoclusters to glucose. The results show that the ZnO:Co nanocluster-assembled thin films with nanoporous structure and nanocrystallites have potential applications as platforms to immobilize enzyme in biosensors.
Publisher: Elsevier BV
Date: 2005
Publisher: Elsevier BV
Date: 2004
Publisher: Springer Science and Business Media LLC
Date: 28-07-2010
Publisher: IOP Publishing
Date: 21-06-2011
DOI: 10.1088/0957-4484/22/29/295712
Abstract: Novel nanostructures such as vertically aligned carbon nanotube (CNT) arrays have received increasing interest as drug delivery carriers. In the present study, two CNT arrays with extreme surface wettabilities are fabricated and their effects on the release of recombinant human bone morphogenetic protein-2 (rhBMP-2) are investigated. It is found that the superhydrophilic arrays retained a larger amount of rhBMP-2 than the superhydrophobic ones. Further use of a poloxamer diffusion layer delayed the initial burst and resulted in a greater total amount of rhBMP-2 released from both surfaces. In addition, rhBMP-2 bound to the superhydrophilic CNT arrays remained bioactive while they denatured on the superhydrophobic surfaces. These results are related to the combined effects of rhBMP-2 molecules interacting with poloxamer and the surface, which could be essential in the development of advanced carriers with tailored surface functionalities.
Publisher: Elsevier BV
Date: 03-2012
Publisher: Oxford University Press (OUP)
Date: 08-2004
DOI: 10.1017/S1431927604886100
Abstract: Extended abstract of a paper presented at Microscopy and Microanalysis 2004 in Savannah, Georgia, USA, August 1–5, 2004.
Publisher: American Physical Society (APS)
Date: 28-04-2008
Publisher: IEEE
Date: 2001
Publisher: AIP Publishing
Date: 15-02-2002
DOI: 10.1063/1.1434546
Abstract: An approach improving diamond–metal adhesion has been developed based on modeling predictions and experimental verifications on the interfacial stresses modified by catalytic reaction. It is found that N-plasma irradiating onto Ti and tungsten-carbide substrates generates tensile surface stresses while C-plasma irradiation creates strongly compressive stress at the surfaces, both of which deteriorate the diamond–metal adhesion. It is also found that surface oxidation prevents diamond nucleation. Therefore, we applied a graded TiCN interlayer with carefully adjusting the ratio of C and N in the gas mixture to neutralize the interfacial stress and, hence, we have improved the diamond–metal adhesion substantially.
Publisher: Elsevier BV
Date: 10-04-2007
Publisher: American Chemical Society (ACS)
Date: 18-12-2002
DOI: 10.1021/JP027027K
Publisher: American Vacuum Society
Date: 07-03-2007
DOI: 10.1116/1.2712196
Abstract: A thin passivation layer of aluminum oxide was deposited on polyimide by using the combined plasma immersion ion implantation and deposition (PIII& D) and cathodic vacuum arc technique. X-ray photoelectron spectroscopy C 1s spectra showed that the carbonyl bond (CO) and ether group (C–O–C and C–N–C) presented in pristine polyimide were damaged by implantation of aluminum ions and deposition of an aluminum oxide passivation layer. O 1s and Al 2p spectra confirmed the formation of a thin aluminum oxide passivation layer. This passivation layer can be implemented in aerospace engineering where polyimide may suffer degradation from fast atomic oxygen in the low-earth-orbit environment. To test the protection of this passivation layer to energetic oxygen ions, a plasma-enhanced chemical vapor deposition system was used to simulate the oxygen-ion irradiation, and the results showed that a higher weight occurred for passivated s les compared to pristine ones. X-ray diffraction showed that Al peaks were presented on the surface region, but no aluminum oxide peak was detected. The authors then concluded that Al clusters were formed in polyimide besides aluminum oxide, which was in an x-ray amorphous state. Furthermore, contact-angle measurements showed a reduced contact angle for passivated polyimide from a pristine value of 78° to 20° by using deionized water. Several discussions have been made on the surface chemical and structural property changes by using the combined PIII& D and cathodic vacuum arc technique.
Publisher: Springer Science and Business Media LLC
Date: 2003
Publisher: Wiley
Date: 27-10-2015
Publisher: AIP Publishing
Date: 09-2001
DOI: 10.1063/1.1390305
Abstract: It is shown that bond contraction and nonbonding lone-pair interaction dominate at nitride surfaces. The maximum elastic recovery of a nitride surface was found to be 100% under a relatively lower nanoindentation load (& .0 mN) and the hardness of the surface was found to be 100% higher than the bulk value. It is interpreted that the spontaneous bond contraction, estimated at 12%–14%, strengthens the binding energy and hence the hardness and Young’s modulus at the surface. The lone-pair weak interaction claims the responsibility for (i) the high elastic recovery, (ii) the lower Raman frequencies of vibration, and (iii) the existence of critical loads for slide friction or lone-pair broken.
Publisher: AIP Publishing
Date: 20-08-2001
DOI: 10.1063/1.1394946
Abstract: A single band of photoluminescence (PL) has been detected at room temperature from the Pb(ZrxTi1−x)O3 (x=0–1.0) surface. The intense and stable PL band covers 475±50 nm (or 2.67±0.25 eV) wavelengths and the corresponding photoexcitation (PE) band is in the range of 305±45 nm. It is found that changing the x value causes a negligible shift of the PL and PE peaks, and the light emission is subject to the Pb presence. The minimal lifetime of the excited photons was found to be 0.03 ms at x=0.5 and the maximum lifetime of 0.60 ms can be achieved by either decreasing or increasing the x values.
Publisher: Wiley
Date: 11-04-2007
DOI: 10.1002/JRS.1683
Publisher: Inderscience Publishers
Date: 2009
Publisher: IEEE
Date: 2008
Publisher: SPIE
Date: 24-10-2000
DOI: 10.1117/12.405426
Publisher: IEEE
Date: 2006
Publisher: American Chemical Society (ACS)
Date: 23-02-2007
DOI: 10.1021/JP0651844
Publisher: Elsevier BV
Date: 12-2003
Publisher: Wiley
Date: 06-05-2016
Publisher: American Chemical Society (ACS)
Date: 16-07-2003
DOI: 10.1021/JP035070H
Publisher: Elsevier BV
Date: 2009
Publisher: AIP Publishing
Date: 10-2008
DOI: 10.1063/1.2981189
Abstract: Single-crystalline, transparent conducting ZnO nanowires were obtained simply by Ti plasma immersion ion implantation (PIII). Electrical transport characterizations demonstrate that the n-type conduction of ZnO nanowire could be tuned by appropriate Ti-PIII. When the energy of PIII is increased, the resistivity of ZnO decreases from 4×102 to 3.3×10−3 Ω cm, indicating a semiconductor-metal transition. The failure-current densities of the metallic ZnO could be up to 2.75×107 A/cm2. Therefore, this facile method may provide an inexpensive alternative to tin doped indium oxide as transparent conducting oxide materials.
Location: Singapore
No related grants have been discovered for Beng Kang Tay.