Publications (18)46.45 Total impact
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ABSTRACT: The lowenergy electronic states and energy gaps of carbon nanocones in an electric field are studied using a singlepband tightbinding model. The analysis considers five perfect carbon nanocones with disclination angles of 60°, 120°, 180°, 240° and 300°, respectively. The numerical results reveal that the lowenergy electronic states and energy gaps of a carbon nanocones are highly sensitive to its geometric shape (i.e. the disclination angle and height), and to the direction and magnitude of an electric field. The electric field causes a strong modulation of the state energies and energy gaps of the nanocones, changes their Fermi levels, and induces zerogap transitions. The energygap modulation effect becomes particularly pronounced at higher strength of the applied electric field, and is strongly related to the geometric structure of the nanocone.  [Show abstract] [Hide abstract]
ABSTRACT: Influences of temperature and SnCu droplet's composition on reactive wettings of Cu(100), Cu(110), and Cu(111) surfaces were analyzed, by using molecular dynamics (MD) calculations. As a result, the spreading on Cu(110)(Cu(100)) has the fastest (slowest) wetting kinetics. A higher temperature or a diluter Cu content in the SnCu alloy droplet results in a higher wettability. Moreover, this work has addressed a theory for positioning the interface separating the liquidus and solidus alloys in the spreading film to confirm the hypothesis that the reactive wetting will come to the end when the interface saturates with the temperaturedependent solidus weight fraction of Cu.  [Show abstract] [Hide abstract]
ABSTRACT: The mechanical behavior of multiwalled carbon nanotubes (MWNTs), being fixed at both ends under uniaxial tensile loading, is investigated via the molecular dynamics (MD) simulation with the Tersoff interatomic potential. It is found that Young's modulus of the MWNTs is in the range between 0.85 and 1.16 TPa via the curvature method based on strain energy density calculations. Anharmonicity in the energy curves is observed, and it may be responsible for the timedependent properties of the nanotubes. Moreover, the number of atomic layers that is fixed at the boundaries of the MWNTs will affect the critical strain for jumps in strain energy density vs. strain curves. In addition, the boundary conditions may affect “yielding” strength in tension. The van der Waals interaction of the doublewalled carbon nanotube (DWNT) is studied to quantify its effects in terms of the chosen potential.  [Show abstract] [Hide abstract]
ABSTRACT: Motivated by recent experimental works on the modifications of endomorphin2 (EM2, HTyrProPhePheNH2) to develop better painkiller, we performed structureactivityrelationship (SAR) studies to investigate modified Cterminal ligands by using molecular dynamics (MD) simulations. Specifically, instead of the CONH2 for the unmodified EM2's Cterminus, the analogue 2 with its Cterminus being CONHNH2 and analogue 3 with its Cterminus being COOMe are studied. First, a systematic conformer search was performed via the quantum chemical AM1 calculations. The cis/trans isomers of the lowest energy were hence selected as MD initial structures. We further showed that EM2s in water exhibited similar dihedral angles to those in DMSO, obtained from the NMR experiment. This similarity indicates the reliability of our MD simulations, and enables us to discuss related bioactivity. Our results showed that the interactions of the Tyr(1)Phe(3) pair for cis/transEM2s played a considerable role for structural stability. Furthermore, we utilized the chi(1) rotamers of individual aromatic side chains to examine the structural bioactivity. It is shown that this criterion to determine the conformational bioactivity toward muopioid receptor (MOR) is insufficient. Thus, we have further employed rotamercombination approaches to examine the characteristics of SAR for cis/transEM2s. Our results suggested that the bioactive chi(1) rotamers for Tyr(1)Phe(3) pair remained to favor the [transtrans] status for MOR selectivity. Therefore, based on the analysis of the chi(1) rotamers, it is suggested that the analogue 2 exhibit greater structural bioactivity for MOR than the analogue 3, and both of them be greater than unmodified EM2 for trans isomers.  [Show abstract] [Hide abstract]
ABSTRACT: Abstract. Deep nanoindentation of a copper substrate by singlewalled carbon nanotubes (SWCNTs) has been analyzed using molecular dynamics simulations. Three categories of SWCNTs and their relationship with temperature and nanotube length have been extensively investigated. The results of this comprehensive quantitative analysis for deep indentation demonstrate that only SWCNTs with relatively short lengths can indent into a substrate up to a desired depth without buckling. Most notably, a permanent hollow hole with a high aspect ratio will be produced on the copper substrate, while copper atoms in close proximity to the hole are only slightly disordered.  [Show abstract] [Hide abstract]
ABSTRACT: The lowenergy electronic properties of a few graphite layers with AA and ABC stacking under application of the electric field (F), perpendicular to the layers, are explored through the tightbinding model. They strongly depend on the interlayer interactions, the stacking sequences, the layer numbers, and the field strength. In the absence or presence of F, the AAstacked Nlayer graphites (N=3 and 4) exhibit the linear bands near the Fermi energy. The interlayer interactions and electric field chiefly shift the Fermi momenta and the state energies. The ABCstacked Nlayer graphites are characterized by the complicated lowenergy bands due to the stacking effect, on which F has a great influence—the change of the state energies and the subband spacing, the opening of a band gap, the production of the oscillating bands, and the increase of the bandedge states. As a result, the two kinds of special structure, whose positions and heights are modulated by F, are found in the density of states (DOS) in contrast to the featureless DOS of the AA systems. The comparison with the ABstacked fewlayer graphites is also made.  [Show abstract] [Hide abstract]
ABSTRACT: Electronic states of carbon tori in electric and magnetic fields are studied by the tightbinding model with the curvature effect. Electronic properties, such as electronic states, energy gaps, and density of states, are very sensitive to the changes in the direction and the magnitude of the external fields. The electric field can widen the � electron energy width; furthermore, there are more low and extreme energy states. Energy gaps are drastically modulated by E. The zerogap transition (Eg 6¼ 0 ! Eg ¼ 0) happens more frequently when E deviates from the symmetric axis, or its magnitude is sufficiently large. The electric field could change the state degeneracy. Moreover, the modulation of electronic states is enhanced by the magnetic field.  [Show abstract] [Hide abstract]
ABSTRACT: The πelectronic excitations are studied for the AA and ABstacked bilayer graphites within the linear selfconsistentfield approach. They are strongly affected by the stacking sequence, the interlayer atomic interactions, the interlayer Coulomb interactions, and the magnitude of the transferred momentum. However, they hardly depend on the direction of the transferred momentum and the temperature. There are three lowfrequency plasmon modes in the AAstacked system but not the ABstacked system. The AA and ABstacked plasmons exhibit the similar π plasmons. The first lowfrequency plasmon behaves as an acoustic plasmon, and the others belong to optical plasmons. The bilayer graphites quite differ from the monolayer graphite and the ABstacked bulk graphite, such as the lowfrequency plasmons and the smallmomentum π plasmons.  [Show abstract] [Hide abstract]
ABSTRACT: In the presence of a perpendicular electric field, the lowenergy electronic properties of the ABstacked Nlayer graphites with layer number N = 2, 3, and 4, respectively, are examined through the tightbinding model. The interlayer interactions, the number of layers, and the field strength are closely related to them. The interlayer interactions can significantly change the energy dispersions and produce new bandedge states. Bilayer and fourlayer graphites are twodimensional semimetals due to a tiny overlap between the valence and conduction bands, while trilayer graphite is a narrowgap semiconductor. The electric field affects the lowenergy electronic properties: the production of oscillating bands, the cause of subband (anti)crossing, the change in subband spacing, and the increase in bandedge states. Most importantly, the aforementioned effects are revealed completely in the density of states, e.g. the generation of special structures, the shift in peak position, the change in peak height, and the alteration of the band gap.  [Show abstract] [Hide abstract]
ABSTRACT: This paper uses a Tersoff potential molecular dynamics simulation to investigate the interaction between C60 molecules and a diamond substrate. The influence of the C60 molecule incident energy upon the bonding preference, i.e. sp3, sp2, sp or s is investigated. The current results reveal that the coating ratio actually increases rather than decreases as the incident energy of the C60 molecules is increased from 80 to 100 eV. Investigation of the transient structural variation of the C60 molecules shows that the additional increase in the bonding probability noted at an incident energy of 100 eV arises mainly from the changing of the structure from an s structure into an sp2 structure. The steady structure statistical analysis results show that the original sp2 structure of the C60 molecules gradually transforms to an sp structure as the incident energy is increased from 1 to 40 eV. Furthermore, the existence of an s structure is identified at incident energies greater than 30 eV. Finally, it is observed that the impact of C60 molecules on the diamond substrate seldom results in the formation of an sp3 structure.  [Show abstract] [Hide abstract]
ABSTRACT: This article employs a molecular dynamics (MD) simulation approach to investigate the influence of beveled angles on the filling mechanisms of a dual damascene process. The objective of the present study is to propose a method that overcomes the problem of incomplete via filling associated with the traditional dual damascene process. The simulation incorporates three separate MD models, namely the dual via model, the deposition model, and the potential model. Furthermore, the simulation adopts the thermal control layer marching algorithm to increase the accuracy of the solution and to reduce the computational time. The present results indicate that the introduction of beveled angles at the upper via corners has a detrimental impact upon the filling of the lower via at moderately low viaradius ratios (1.75, 2.0). At a viaradius ratio of 1.75, the filling morphology changes from oneof complete filling to one with trapped voids within the via when beveled angles are introduced, while at the slightly larger viaradius ratios of 2.0 and 2.5, the voids in the lower via are observed to grow in size. It is noted that the influence of beveled angles at the upper via corners on the lower via filling becomes less significant as the viaradius ratio increases (2.5, 3.0). In general, it is found that the introduction of beveled angles at the lower via corners is beneficial to the filling coverage of the lower via, but has no impact upon the filling of the upper via. (C) 2003 American Vacuum Society. 
Article: Molecular dynamics simulation of thin film growth on giant magnetoresistance corrugated structures
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ABSTRACT: This paper presents the use of molecular dynamics (MD) in simulating thinfilm growth on giant magnetoresistance corrugated structures. The simulation model mainly concerns the deposition of Co atoms on a Vshape Cu substrate. The manybody, tightbinding potential model is utilized in the MD simulation to represent the interatomic force that exists between the atoms. The interface width is used to quantify the variation of surface roughness at the transient and steady states. The paper investigates the influence of incident energy on the deposited film surface property and on the growing mechanism, for both vertical and oblique deposition. The results demonstrate how the growing characteristics are influenced by different incident energies and by different deposition directions. It is found that at relatively low incident energies the film growth tends to be in a threedimensional cluster mode and that a void track is formed, whose growing direction is almost equal to the surface normal to the two inclined surfaces. The uneven thickness found along the base of the V shape is mainly due to the deposited atoms that accumulate at the bottom of the V groove when the incident energy is at a relatively high level. It is found that there exists an optimal incident energy that produces the, best film surface property. The film surface property can be improved by changing the incident direction relative to the two inclined directions of ±45°. Smaller deviation angles yield better film surface properties for low incident energy. Conversely, higher levels of incident energy result in worse film surface properties. 
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ABSTRACT: The entry flow induced by an applied electrical potential through microchannels between two parallel plates is analyzed in this work. A nonlinear, twodimensional Poisson equation governing the applied electrical potential and the zeta potential of the solid–liquid boundary and the Nernst–Planck equation governing the ionic concentration distribution are numerically solved using a finitedifference method. The applied electrical potential and zeta potential are unified in the Poisson equation without using linear superposition. A body force caused by the interaction between the charge density and the applied electrical potential field is included in the full Navier–Stokes equations. The effects of the entrance region on the fluid velocity distribution, charge density boundary layer, entrance length, and shear stress are discussed. The entrance length of the electroosmotic flow is longer than that of classical pressuredriven flow. The thickness of the electrical double layer (EDL) in the entry region is thinner than that in the fully developed region. The change of velocity profile is apparent in the entrance region, and the axial velocity profile is no longer flat across the channel height when the Reynolds number is large.  [Show abstract] [Hide abstract]
ABSTRACT: The effects of soluble surfactant on the dynamic rupture of thin liquid films are investigated. A nonlinear coupling evolution equation is used to simulate the motion of thin liquid films on free surfaces. A generalized Frumkin model is adopted to simulate the adsorption/desorption kinetics of the soluble surfactant between the surface and the bulk phases. Numerical simulation results show that the liquid film system with soluble surfactant is more unstable than that with insoluble surfactant. Moreover, a generalized Frumkin model is substituted for the Langmuir model to predict the instability of liquid film with soluble surfactant. A numerical calculation using the generalized Frumkin model shows that the surfactant solubility increases as the values of parameters of absorption/desorption rate constant (J), activation energy desorption (nu(d)), and bulk diffusion constant (D(1)) increase, which consequently causes the film system to become unstable. The surfactant solubility decreases as the rate of equilibrium (lambda) and interaction among molecules (K) are increased, which therefore stabilizes the film system. On the other hand, an increase of relative surface concentration (the index of a power law), beta(n), will initially result in a decrease of corresponding shear drag force as beta and n increase from 0 to 0.3 and 0.85, respectively. This will enhance the Marangoni effect. However, a further increase of beta and n to greater than 0.3 and 0.85, respectively, will conversely result in an increase of the corresponding shear drag force. This will weaken the Marangoni effect and thus result in a reduction of interfacial stability. Copyright 2000 Academic Press. 
Article: The Effect of Electromagnetic Retardation on the Rupture Process of a Very Thin Liquid Film
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ABSTRACT: Effects of electromagnetic retardation on the rupture process of a very thin liquid film coated on a flat plate are studied. The analysis results indicate that the electromagnetic retardation effect (D) for the case A > 0 (attraction) is a stabilization factor, which prolongs the rupture time. The wavenumber of the most unstable mode is decreasing as D increases. It is also found that the linear solution of rupture time T(LM) is larger than the nonlinear rupture time T(NM), but the gradient of T(LM) to D is comparable to that of T(NM). Copyright 1999 Academic Press.  [Show abstract] [Hide abstract]
ABSTRACT: Moleculardynamics simulations were used to investigate the spreading of nonvolatile liquid drops in a solid corner formed by two planar substrates. To understand the effect of the corner on the spreading, liquid drops in a corner with angles of 45 degrees, 90 degrees, and 135 degrees as well as on a flat substrate were examined. Both the solid substrate and the liquid drop were modeled using the LennardJones interaction potential in the present study. Simulation results show that the mass center of the liquid molecules migrated towards the corner as time evolved and the spreading rate increased as the corner angle decreased. It is found that the variation of the mean spreading area with time can be described by a general relation of A(t) approximately t, which is in agreement with results obtained by other investigators. The distribution of liquid atoms per unit normalized corner degree shows a similar trend for different corner angles.  [Show abstract] [Hide abstract]
ABSTRACT: A process of nonlinear threedimensional rupture of thin liquid films is numerically analyzed for the first time. With the rupture time being successfully calculated, it has been possible to develop a more complete rupture theory for thin liquid films. In contrast to the linear analysis indicating the shortest rupture time of thin liquid films to be the same for both two and threedimensional rupture, the nonlinear analysis reveals that the latter proceeds faster than the former. In particular, among all threedimensional disturbance modes, the symmetric one makes the thin liquid films rupture fastest. It is concluded that the rupture process develops at a point rather than along a line on thin liquid films.
Publication Stats
336  Citations  
46.45  Total Impact Points  
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Institutions

19992010

National Cheng Kung University
 • Department of Engineering Science
 • Department of Electrical Engineering
Tainan, Taiwan, Taiwan
