jap banner
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue Next Issue

1 Aug 2010

Volume 108, Issue 3, Articles (03xxxx)

Return to All Sections
back to top
RSS Feeds
back to top Nanoscale Science and Design

Strain effects on the performance of zero-Schottky-barrier double-walled carbon nanotube transistors

Md. Abdul Wahab and Quazi D. M. Khosru

J. Appl. Phys. 108, 034301 (2010); http://dx.doi.org/10.1063/1.3465083 (8 pages) | Cited 1 time

Online Publication Date: 3 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Schrodinger’s equation is solved using recursive Green’s function algorithm self-consistently with Poisson’s equation to study the transport physics of uniaxial and torsional strained double-walled (DW) carbon nanotube (CNT) field-effect transistors (FETs) and to analyze their performance. The characteristics and performance of proposed DW CNTFET are compared with existing single-walled (SW) CNTFET. The strain has great impact on the I-V characteristics of both SW and DW CNT devices. Tensile and torsional strains improve greatly the off-state current and on/off current ratio of both devices. Compressive strain improves on-state current, but this improvement is comparatively small. The effect of strain on off-state current, on-state current, and on/off current ratio is higher in SW CNTFET. The inverse subthreshold slope of DW CNTFET is better than SW CNTFET. But the variation in inverse subthreshold slope with strain is smaller in DW CNTFET. Unlike SW CNTFET the on-state transconductance of DW CNTFET improves with tensile and torsional strains, and degrades with compressive strain. The on-state cut-off frequency of DW CNTFET also shows opposite behavior to SW CNTFET with strain following on-state transconductance. Concrete Physical description is provided to explain all above changes with strain.
Show PACS
85.35.Kt Nanotube devices

Damaged carbon nanotubes get healed by ion irradiation

Kiran Jeet, V. K. Jindal, L. M. Bharadwaj, D. K. Avasthi, and Keya Dharamvir

J. Appl. Phys. 108, 034302 (2010); http://dx.doi.org/10.1063/1.3466774 (6 pages) | Cited 6 times

Online Publication Date: 4 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Carbon nanotubes (CNTs) are being used for varied applications. It is therefore important to study their stability under extreme conditions of temperature and irradiation. In this work, we report the stability of CNTs [both single-wall CNTs (SWCNTs) and multiwalled CNTs (MWCNTs)] under irradiation of a carbon ion beam of energy 55 MeV. The irradiated samples were analyzed using Raman spectroscopy. The Raman results indicate the interesting phenomenon of healing or annealing of CNTs under ion beam irradiation. The annealing process appears to begin at the lowest value of fluences and persists for quite a good range of fluence values. As the irradiation dose increases ( ≈ 1×1014 ions/cm2) the MWCNTs begin to amorphize whereas the SWCNTs system continues to heal.
Show PACS
61.80.Jh Ion radiation effects
61.82.Rx Nanocrystalline materials
61.46.Fg Nanotubes
61.72.Cc Kinetics of defect formation and annealing

Excitation-induced germanium quantum dot formation on Si(100)-(2×1)

Ali Oguz Er and Hani E. Elsayed-Ali

J. Appl. Phys. 108, 034303 (2010); http://dx.doi.org/10.1063/1.3462436 (10 pages) | Cited 4 times

Online Publication Date: 4 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effect of nanosecond pulsed laser excitation on the self-assembly of Ge quantum dots grown by pulsed laser deposition on Si(100)-(2×1) was studied. In situ reflection high-energy electron diffraction and ex situ atomic force microscopy were used to probe the quantum dot structure and morphology. At room temperature, applying the excitation laser decreased the surface roughness of the grown Ge film. With surface electronic excitation, crystalline Ge quantum dots were formed at 250 °C, a temperature too low for their formation without excitation. At a substrate temperature of 390 °C, electronic excitation during growth was found to improve the quantum dot crystalline quality, change their morphology, and decrease their size distribution almost by half. A purely electronic mechanism of enhanced surface hopping of the Ge adatoms is proposed.
Show PACS
81.07.Ta Quantum dots
81.05.Cy Elemental semiconductors
81.15.Fg Pulsed laser ablation deposition
68.55.ag Semiconductors
73.63.Kv Quantum dots
78.67.Hc Quantum dots

Formation of core/shell structured cobalt/carbon nanoparticles by pulsed laser ablation in toluene

H. Y. Kwong, M. H. Wong, C. W. Leung, Y. W. Wong, and K. H. Wong

J. Appl. Phys. 108, 034304 (2010); http://dx.doi.org/10.1063/1.3457216 (5 pages) | Cited 10 times

Online Publication Date: 4 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Magnetic cobalt nanoparticles encapsulated in shells of layered structure have been produced by the technique of pulsed laser ablation in toluene. The morphology, microstructure, and magnetic properties of the prepared nanoparticles were characterized by electron microscopy, micro-Raman spectroscopy, and superconducting quantum interference device magnetometry, respectively. The results indicated that the cobalt nanoparticles fabricated are noncrystalline but coated with the graphitic carbon layers. It is believed that the formation of these carbon layers well-protect the cobalt nanoparticles to be oxidized thus maintaining the superparamagnetic property. This is an important feature that makes the cobalt nanoparticles a useful material for medical and many other magnetic based applications.
Show PACS
81.07.Bc Nanocrystalline materials
81.15.Fg Pulsed laser ablation deposition
75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
78.30.Hv Other nonmetallic inorganics

Silver/silicon nanostructure for surface-enhanced fluorescence of Ln3+ (LnNd, Ho, and Er)

Shu-Juan Zhuo, Ming-Wang Shao, Liang Cheng, Rong-Hui Que, Dorthy Duo Duo Ma, and Shuit-Tong Lee

J. Appl. Phys. 108, 034305 (2010); http://dx.doi.org/10.1063/1.3457218 (4 pages) | Cited 4 times

Online Publication Date: 4 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The surface-enhanced fluorescence of lanthanide ions (neodymium ions Nd3+, holmium ions Ho3+, and erbium ions Er3+) owing to resonant plasmons oscillation on the surface of Ag/Si nanostructure was described. In the presence of Ag/Si nanomaterials, the fluorescence peaks were significantly enhanced, which resulted in a typical 185-fold enhancement at 592 nm for Nd3+, 82-fold at 550 nm for Ho3+, and 80-fold at 533 nm for Er3+ at the concentration of 0.05 M. This Ag/Si nanostructure had larger enhancement factor than that caused by unsupported Ag nanoparticles, which might be attributed to the local field overlap originated from the closed and fixed Ag nanoparticles on silicon nanowires.
Show PACS
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
78.55.Ap Elemental semiconductors
78.66.Db Elemental semiconductors and insulators

Giant electrorheological effect in Fe2O3 nanofluids under low dc electric fields

Vijay S. Raykar, S. K. Sahoo, and Ashok K. Singh

J. Appl. Phys. 108, 034306 (2010); http://dx.doi.org/10.1063/1.3462445 (5 pages) | Cited 1 time

Online Publication Date: 4 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this paper, we report the electrorheological (ER) properties of low concentration Fe2O3 nanofluids prepared in ethylene glycol (EG). Spherical Fe2O3 nanoparticles (NPs) were obtained by emulsion method in powder form. The obtained NPs were stabilized in time by acetylacetone in EG. The prepared Fe2O3 NPs were characterized using X-ray diffraction and transmission electron microscopy. Fe2O3 nanofluids were tested for ER behavior at low dc electric fields. Giant ER (GER) effect was observed in Fe2O3 nanofluid of higher concentration at electric field of 10 V/mm. The current passing through suspensions and electrohydrodynamic (EHD) convection was reflected in ring like structure formation of Fe2O3 NPs. Relation between suspension viscosity and Mason number revealed that the analysis has to be revised for GER fluids.
Show PACS
47.65.Gx Electrorheological fluids
83.80.Gv Electro- and magnetorheological fluids
82.70.Kj Emulsions and suspensions
47.57.Bc Foams and emulsions
75.50.Mm Magnetic liquids
47.65.Cb Magnetic fluids and ferrofluids

Spin glasslike behavior and magnetic enhancement in nanosized Ni–Zn ferrite system

B. Ghosh, S. Kumar, A. Poddar, C. Mazumdar, S. Banerjee, V. R. Reddy, and A. Gupta

J. Appl. Phys. 108, 034307 (2010); http://dx.doi.org/10.1063/1.3456174 (8 pages) | Cited 4 times

Online Publication Date: 5 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The effects of particle size, structure, microstrain, and cation distribution on magnetic property of nanosized Ni0.35Zn0.65Fe2O4 prepared through high-energy ball milling have been explored by a wide variety of experimental technique namely, x-ray diffraction, high-resolution transmission electron microscopy, dc magnetization measurement, and Mössbauer spectroscopy. The sample exhibits mixed magnetic behavior with a collective magnetic state between 300 and 60 K while spin glasslike freezing of magnetic moments has taken place below 60 K. The sample has displayed enhancement in magnetization, magnetic hyperfine field, coercivity, and anisotropy energy. The inherent superparamagnetic relaxation of ferrite nanoparticles has significantly reduced and it shows evidence of magnetic hysterisis at room temperature. These properties could be profitably used to overcome the inherent instability of magnetic nanoparticles. The intersublattice interaction (JAB) in the sample has strengthened due to migration of Fe3+ ions from octahedral (B) site to tetrahedral (A) site and this accounts for the genesis of counterintuitive magnetic enhancement in the sample.
Show PACS
75.75.-c Magnetic properties of nanostructures
75.50.Tt Fine-particle systems; nanocrystalline materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Vv High coercivity materials

Defect engineering of the electrochemical characteristics of carbon nanotube varieties

Mark A. Hoefer and Prabhakar R. Bandaru

J. Appl. Phys. 108, 034308 (2010); http://dx.doi.org/10.1063/1.3457227 (6 pages) | Cited 2 times

Online Publication Date: 5 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The electrochemical behavior of carbon nanotubes (CNTs) containing both intrinsic and extrinsically introduced defects has been investigated through the study of bamboo and hollow multiwalled CNT morphologies. The controlled addition of argon ions was used for varying the charge and type of extrinsic defects. It was indicated from Raman spectroscopy and voltammetry that the electrocatalytic response of hollow type CNTs could be tailored more significantly, compared to bamboo type CNTs which have innately high reactive site densities and are less amenable to modification. An in-plane correlation length parameter was used to understand the variation of the defect density as a function of argon ion irradiation. The work has implications in the design of nanotube based chemical sensors, facilitated through the introduction of suitable reactive sites.
Show PACS
81.07.De Nanotubes
82.45.Yz Nanostructured materials in electrochemistry
61.80.Jh Ion radiation effects
61.72.-y Defects and impurities in crystals; microstructure
78.30.-j Infrared and Raman spectra
82.80.Fk Electrochemical methods

Fundamental study of mechanical energy harvesting using piezoelectric nanostructures

Chengliang Sun, Jian Shi, and Xudong Wang

J. Appl. Phys. 108, 034309 (2010); http://dx.doi.org/10.1063/1.3462468 (11 pages) | Cited 20 times

Online Publication Date: 5 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
This paper numerically estimates the potential, the output power and the energy conversion efficiency of piezoelectric nanostructures, including rectangular nanowires (NWs), hexagonal NWs, and two-dimensional vertical thin films (the nanofins). Static analysis studies the maximum piezoelectric potential that can be produced by a BaTiO3 NW, a ZnO NW, and a ZnO nanofin when they are subjected to a constant external force. Dynamic analysis is performed to study the power generation ability via the vibration of these nanostructures agitated by ambient vibration energy. ZnO NW and nanofin are selected as two representative nanogenerator elements. Their dynamic responses are modeled using a single-degree of freedom system with a series of damping ratios. Combining the transfer functions of mechanical vibration and piezoelectric charge generation, we define the output power and efficiencies as functions of the vibration frequency and the sizes. The optimal size for constructing a high efficiency and high-power nanogenerator is suggested. The material dependence of a dynamic system is also studied based on different piezoelectric and ferroelectric material systems, including ZnO, BaTiO3, and (1−x)Pb(Mg1/3Nb2/3)O3−xPbTiO3. This research reveals a comprehensive relationship between the mechanical energy harvesting ability and the nanomaterials’ morphologies, dimensions, and properties. It provides a guideline for the design of high-power nanogenerators and the development of piezoelectric nanodevices in general.
Show PACS
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
68.65.La Quantum wires (patterned in quantum wells)
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
77.84.Cg PZT ceramics and other titanates
77.80.-e Ferroelectricity and antiferroelectricity
77.65.-j Piezoelectricity and electromechanical effects

Effective thermal conductivity of polycrystalline materials with randomly oriented superlattice grains

Fan Yang, Teruyuki Ikeda, G. Jeffrey Snyder, and Chris Dames

J. Appl. Phys. 108, 034310 (2010); http://dx.doi.org/10.1063/1.3457334 (12 pages) | Cited 8 times

Online Publication Date: 5 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A model has been established for the effective thermal conductivity of a bulk polycrystal made of randomly oriented superlattice grains with anisotropic thermal conductivity. The in-plane and cross-plane thermal conductivities of each superlattice grain are combined using an analytical averaging rule that is verified using finite element methods. The superlattice conductivities are calculated using frequency dependent solutions of the Boltzmann transport equation, which capture greater thermal conductivity reductions as compared to the simpler gray medium approximation. The model is applied to a PbTe/Sb2Te3 nanobulk material to investigate the effects of period, specularity, and temperature. The calculations show that the effective thermal conductivity of the polycrystal is most sensitive to the in-plane conductivity of each superlattice grain, which is generally four to five times larger than the cross-plane conductivity of a grain. The model is compared to experimental measurements of the same system for periods ranging from 287 to 1590 nm and temperatures from 300 to 500 K. The comparison suggests that the effective specularity increases with increasing annealing temperature and shows that these samples are in a mixed regime where both Umklapp and boundary scattering are important.
Show PACS
72.15.Eb Electrical and thermal conduction in crystalline metals and alloys
81.40.Gh Other heat and thermomechanical treatments
63.22.Kn Clusters and nanocrystals
63.22.Np Layered systems

Contact mechanisms and design principles for (Schottky and Ohmic) metal contacts to semiconductor nanowires

S. Noor Mohammad

J. Appl. Phys. 108, 034311 (2010); http://dx.doi.org/10.1063/1.3446845 (23 pages) | Cited 4 times

Online Publication Date: 6 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Contact mechanisms and design principles for (Ohmic and Schottky) metal (M) contacts to semiconductor nanowires (NWs) have been studied. The NWs have been assumed to be cylindrical. A unified model has been developed for the contacts. The model takes into consideration the amorphicity of the M/NW interface structure, the diameter dependence of the energy band gap, the barrier height modulation, and the fluctuations in both the barrier height and the applied bias. While the fluctuations in the barrier height are assumed to involve band tails, the fluctuations in applied bias are assumed to involve tiny Gaussian peaks. Several different features of the Ohmic and the Schottky contacts have been addressed. These include temperature and dimension dependencies of the current-voltage characteristics, the influence of the M/NW interface on the contact characteristics, the relationship between the barrier height and the ideality factor, and the barrier height reduction as a function of temperature. The model appears to be very general. It seems to explain all experimental results available to date in the literature. The calculated results are almost always in good correspondence with the experimental results. The study seemingly demonstrates an alternative to the doping dependence of the Ohmic contacts. It elucidates the fundamental physics underlying M/NW contacts. It highlights means to yield low-resistivity Ohmic contacts by thermionic emission. It describes design criteria for both Ohmic and Schottky contacts. The design criteria for Ohmic contacts tend to address the long-term reliability concerns for devices. They explain also the behavior of both good and bad Ohmic contacts. All these may be the most striking attributes of the study. These attributes explain why Schottky contacts to NWs, with proper gate modulation, may act also as Schottky barrier transistors.
Show PACS
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
84.32.Dd Connectors, relays, and switches
68.35.Ct Interface structure and roughness

Coverage dependence of magnetic domain structure and magnetic anisotropy in supported Fe nanoparticles on Al2O3/NiAl(100)

Wen-Chin Lin, C. B. Wu, P. J. Hsu, H. Y. Yen, Zheng Gai, Lan Gao, Jian Shen, and Minn-Tsong Lin

J. Appl. Phys. 108, 034312 (2010); http://dx.doi.org/10.1063/1.3457794 (6 pages) | Cited 1 time

Online Publication Date: 6 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Studies of magnetic domain and magnetic anisotropy in collected nanoparticles are crucial for both understanding interparticle interaction and engineering in applications. In order to characterize the microscopic surface morphology and the nanoscale magnetic domain structure of Fe nanoparticles, a scanning tunneling microscope and a scanning electron microscope with polarization analysis (SEMPA) were used in our experiment. For the coverage of 9–13 monolayers (MLs) Fe deposited on Al2O3/NiAl(100), circular and well-separated nanoparticles were grown. As the coverage increased up to 23–33 ML, these Fe nanoparticles started to coalesce and form elongated islands. Therefore a transition from isotropic to anisotropic in-plane magnetism was observed. Our proposed uniaxial magnetic anisotropy models effectively explain the azimuthal angle dependent two-step hysteresis loops. Moreover, the in situ measured SEMPA images clearly show the coverage dependent evolution of magnetic domain structure. Variations in interparticle interaction and magnetic correlation length with increasing Fe coverage are also reported.
Show PACS
75.75.Fk Domain structures in nanoparticles
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
75.60.Ch Domain walls and domain structure
75.30.Gw Magnetic anisotropy
75.75.Cd Fabrication of magnetic nanostructures
81.16.-c Methods of micro- and nanofabrication and processing

Linear plasmon ruler with tunable measurement range and sensitivity

Shao-Ding Liu and Mu-Tian Cheng

J. Appl. Phys. 108, 034313 (2010); http://dx.doi.org/10.1063/1.3463415 (9 pages) | Cited 5 times

Online Publication Date: 6 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The multiple localized surface plasmon resonances of nanorod dimers are theoretically investigated. The dark plasmon resonance of nanorod dimer aligned side-by-side is highly distance dependent. Based on this property, nanospheres are used to modify surface plasmon coupling between the two nanorods. The resonant wavelength shift increases approximately linearly with the increasing of nanospheres interparticle separations. This property makes such structure useful as plasmon ruler with homogeneous measurement sensitivity. The measurement range is increased to more than 100 nm, the resonant frequency is extended to the near-infrared region, and one can modify the structure size and nanorod aspect ratio freely to get the desired measurement range and sensitivity.
Show PACS
73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)

Effect of surface hydrophilicity on the nanofretting behavior of Si(100) in atmosphere and vacuum

Jiaxin Yu, Linmao Qian, Bingjun Yu, and Zhongrong Zhou

J. Appl. Phys. 108, 034314 (2010); http://dx.doi.org/10.1063/1.3463306 (10 pages) | Cited 9 times

Online Publication Date: 9 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
With an atomic force microscopy, the effect of surface hydrophilicity on the nanofretting behavior of Si(100) against SiO2 microsphere was investigated under vacuum and atmosphere conditions, respectively. The surface hydrophilicity revealed a strong effect on the motion behavior, adhesion force, friction force, and nanofretting damage of Si(100)/SiO2 pairs. The increase in the hydrophilicity of Si(100) surface could expand the stick regime of Si(100)/SiO2 pairs into a higher value of displacement amplitude. While the nanofretting ran in atmosphere, both adhesion and friction forces in the initial cycle would be larger when the Si(100) surface was more hydrophilic. However, because of the in situ chemical modification of SiO2 tip in nanofretting, they might reveal a decrease with increasing nanofretting cycles. Either in vacuum or in atmosphere, the nanofretting damage was weaker when the Si(100) surface was more hydrophobic. Because of the lack of oxygen and vapor in vacuum, the nanofretting damage on the Si(100) surface was dominated by mechanical interaction. The damage was characterized as the depression of 0.1–0.2 nm in depth on hydrophilic Si and the hillocks of 0.8–0.9 nm in height on hydrophobic Si and original Si. However, the nanofretting damage in atmosphere was much more serious, which was identified as the grooves of 8–11 nm in depth on Si(100) surfaces. Analysis indicated that even if the nanofretting damage in atmosphere was the coupled results of mechanical interaction and tribochemical reaction, the tribochemical reaction played a dominated role. These results will help us to understand the effect of surface properties on nanofretting of silicon and optimize the surface treatment technology to minimize the potential nanofretting failure of microdevices in microelectromechanical system (MEMS).
Show PACS
81.05.Cy Elemental semiconductors
68.47.Fg Semiconductor surfaces
68.08.Bc Wetting
81.65.Ps Polishing, grinding, surface finishing
68.37.Ps Atomic force microscopy (AFM)
81.40.Pq Friction, lubrication, and wear

Visible light emission from self-catalyzed GaInP/GaP core-shell double heterostructure nanowires on silicon

J. Tatebayashi, A. Lin, P. S. Wong, R. F. Hick, and D. L. Huffaker

J. Appl. Phys. 108, 034315 (2010); http://dx.doi.org/10.1063/1.3457355 (5 pages) | Cited 3 times

Online Publication Date: 9 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The authors report on the formation, structural analyses, and optical properties of GaInP/GaP self-catalyzed core-shell double heterostructure nanowires (NWs) grown on Si(111) substrates. The NW growth is initiated with the formation of Ga droplets as catalysts, followed by the growth of GaP core and GaInP double heterostructure shells. Structural analyses elucidate the existence of interfaces among GaP core and GaInP double heterostructure shells. Light emissions at 640 and 800 nm are observed at 77 K from GaInP core-shell double heterostructure NWs and surface states of GaInP layers, respectively. The signal from the surface state can be mitigated via surface passivation with ammonium sulfide solution. These results will enable the realization of novel NW-based light-emitting diodes or nanolasers grown on Si substrates utilizing mature Si technologies.
Show PACS
78.67.Uh Nanowires

Linear and nonlinear optical properties of a two-subband system in a symmetric semiconductor quantum well

Spyridon G. Kosionis, Andreas F. Terzis, Constantinos Simserides, and Emmanuel Paspalakis

J. Appl. Phys. 108, 034316 (2010); http://dx.doi.org/10.1063/1.3457855 (5 pages) | Cited 6 times

Online Publication Date: 9 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We study the linear and nonlinear optical response of intersubband transitions in a semiconductor quantum well. We describe the coupling of the quantum well structure with the electromagnetic field by using the nonlinear density matrix equations, in the two-subband approximation. We provide proper approximate analytical solutions to these equations that are used for the closed-form determination of the optical susceptibilities χ(1), χ(3), and χ(5). We also explore the dependence of χ(1), χ(3), and χ(5) on the electron sheet density for a specific double GaAs/AlGaAs quantum well.
Show PACS
78.67.De Quantum wells
42.65.An Optical susceptibility, hyperpolarizability
73.20.At Surface states, band structure, electron density of states
71.20.Nr Semiconductor compounds

Metal–dielectric interface toughening by molecular nanolayer decomposition

Saurabh Garg, Ashutosh Jain, C. Karthik, Binay Singh, Ranganath Teki, V. S. Smentkowski, Michael W. Lane, and Ganpati Ramanath

J. Appl. Phys. 108, 034317 (2010); http://dx.doi.org/10.1063/1.3437648 (4 pages) | Cited 1 time

Online Publication Date: 9 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Recent work has shown that copper–silica interfaces can be toughened several fold by combining interface functionalization with an organosilane molecular nanolayer (MNL) and thermal annealing. In order to understand the role of annealing-induced MNL instabilities on interface toughness, we studied the effects of interface chemical changes on the fracture toughness of copper–silica interfaces tailored with organosilane or organogermane MNLs. Our results indicate that MNL decomposition into its inorganic constituents and consequent intermixing can provide an interface toughening mechanism. Organogermane–tailored interfaces exhibit higher toughness values due to Ge-diffusion induced copper silicate formation, not observed at organosilane tailored interfaces. These findings show that organic nanolayer decomposition at a buried interface could be exploited to tailor interfacial properties through appropriate choice of MNL chemistry and processing treatments.
Show PACS
82.45.Mp Thin layers, films, monolayers, membranes
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing

Transverse resonant properties of strained gold nanowires

Pär A. T. Olsson

J. Appl. Phys. 108, 034318 (2010); http://dx.doi.org/10.1063/1.3460127 (10 pages) | Cited 4 times

Online Publication Date: 10 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
In this work, resonant and elastic properties of single crystal gold nanowires have been studied through classical molecular dynamics simulations. The considered nanowires have perfect square cross sections and are oriented with the [100] direction along the wire axis and with {100} side surfaces. Three different sizes were simulated; 4.08×4.08 nm2, 5.71×5.71 nm2, and 7.34×7.34 nm2 cross sectional dimensions, with the respective unrelaxed lengths 49.0 nm, 68.5 nm, and 88.1 nm and the simulations were performed at two different temperatures, 4.2 K and 300 K. Tensile simulations reveal, that the stiffness decreases with decreasing size, and that the size dependence for nanowires at 4.2 K can be accurately described using the concept of surface energy. Comparing results from the resonant simulations reveals that the fundamental eigenfrequency is in good agreement with predictions from Bernoulli–Euler continuum beam theory when the size dependence of the stiffness is taken into account. The eigenfrequencies of the first and second excited modes turn out to be low in comparison with analytical Bernoulli–Euler continuum calculations.
Show PACS
62.23.Hj Nanowires
62.25.Jk Mechanical modes of vibration
65.40.gp Surface energy
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.dq Other elastic constants

Groove-gratings to optimize the electric field enhancement in a plasmonic nanoslit-cavity

Chang Chen (陈昌), Niels Verellen, Kristof Lodewijks, Liesbet Lagae, Guido Maes, Gustaaf Borghs, and Pol Van Dorpe

J. Appl. Phys. 108, 034319 (2010); http://dx.doi.org/10.1063/1.3457017 (8 pages) | Cited 1 time

Online Publication Date: 10 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We study the spectral properties of a triangular plasmonic nanoslit-cavity with periodic triangular grooves to optimize the field enhancement inside the nanoslit. This work is mainly based on numerical calculations and also partly supported by experimental evidence. In the nanoslit-cavity, we can distinguish following three main contributions to the field enhancement: electrostatic interaction in the nanoslit, surface plasmon polariton standing waves in the cavity and excitation, and reflection of surface plasmon polaritons by the grating. The importance of phase matching between surface plasmons generated at the nanoslit and the gratings is also investigated in order to optimize the local field intensity in the nanoslit.
Show PACS
73.22.Lp Collective excitations
42.79.Dj Gratings
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)

Microcantilever dynamics in liquid environment dynamic atomic force microscopy when using higher-order cantilever eigenmodes

Daniel Kiracofe and Arvind Raman

J. Appl. Phys. 108, 034320 (2010); http://dx.doi.org/10.1063/1.3457143 (4 pages) | Cited 4 times

Online Publication Date: 10 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Dynamic atomic force microscopy is currently evolving from a single to a multifrequency instrument for nanoscale imaging often employing higher-order microcantilever eigenmodes for improved resolution and force spectroscopy. In this work the authors study the fundamentals of cantilever dynamics and energy dissipation when soft cantilevers are driven at their second flexural eigenmode and interact with samples in liquid environments. Contrary to the conventional first eigenmode operation, second eigenmode operation in liquids is often dominated by a subharmonic response (e.g., one tap every four drive cycles) and there is an energy transfer to the first eigenmode creating a new channel of energy dissipation and compositional contrast.
Show PACS
07.79.Lh Atomic force microscopes
07.10.Cm Micromechanical devices and systems

InAs quantum wire induced composition modulation in an In0.53Ga0.37Al0.10As barrier layer grown on an InP substrate

K. Cui, B. J. Robinson, D. A. Thompson, and G. A. Botton

J. Appl. Phys. 108, 034321 (2010); http://dx.doi.org/10.1063/1.3460643 (8 pages) | Cited 3 times

Online Publication Date: 11 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Composition modulations are observed by transmission electron microscopy in In0.53Ga0.37Al0.10As barrier layers that overgrow both single- and multilayer InAs quantum wire structures grown on an InP substrate. Indium-rich (gallium-deficient) regions were observed in the region of the barrier layer lying directly above individual quantum wires, while indium-deficient (gallium-rich) regions were detected in the barrier above the gaps between adjacent underlying quantum wires. The magnitude of such modulation was typically 7% (atomic percent) for both indium and gallium as estimated from the energy dispersive x-ray analysis. The origin of such composition modulations was determined by modeling the chemical potential distribution for indium and gallium on the growth front of the barrier layer at the initial capping stage of the quantum wires with finite element simulations. It is found that the number and positions of the indium-rich regions are determined by the combined effects of strain and surface energy distributions on the barrier material capping the quantum wires. Moreover the estimated magnitudes of the composition modulation for both indium and gallium from the finite element models are in good agreement with the experimental observations. This method provides a simple way to understand the origin of, and to estimate the magnitude of the quantum wire-induced composition modulation in the barrier layer.
Show PACS
81.07.Vb Quantum wires
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
65.40.gp Surface energy
68.65.Ac Multilayers

Influence of pressure on the Pt nanoparticle growth modes during pulsed laser ablation

Daria Riabinina, Eric Irissou, Boris Le Drogoff, Mohamed Chaker, and Daniel Guay

J. Appl. Phys. 108, 034322 (2010); http://dx.doi.org/10.1063/1.3463204 (6 pages) | Cited 9 times

Online Publication Date: 12 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Pulsed laser deposition of a platinum target was performed in solution and in a He background gas atmosphere at pressures ranging from 10−5 to 11 Torr. The influence of the plasma dynamics on the structural properties of the nanostructured Pt films was investigated by time-of-flight and space-resolved emission spectroscopy (velocity measurements). It is shown that two different growth modes exist. In the first, formation of nanoparticle is occurring in the surrounding media (gas or solution), while in the second one, diffusion and reorganization of atomic species at the substrate surface is favored. In a gaseous environment, the transition between both modes is occurring at He pressure of ∼ 0.5 Torr, which corresponds to a velocity of ∼ 5.8×103 m s−1.
Show PACS
81.07.Wx Nanopowders
81.15.Fg Pulsed laser ablation deposition
81.16.Mk Laser-assisted deposition

Magnetic properties of Fe2O3 nanoparticles embedded in hollows of periodic nanoporous silica

A. Zeleňáková, J. Kováč, and V. Zeleňák

J. Appl. Phys. 108, 034323 (2010); http://dx.doi.org/10.1063/1.3466748 (5 pages) | Cited 6 times

Online Publication Date: 13 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The magnetic properties of the nanocomposite consisting of hematite (α-Fe2O3) nanoparticles embedded in the hollows of the periodic nanoporous silica matrix were investigated. The magnetic measurements showed on the superparamagnetic behavior of the nanoparticles. This behavior was evidenced by the irreversibility of magnetization curves measured in zero-field-cooled and field cooled regimes, by the presence of a maximum in zero-field-cooled magnetization curve related to blocking temperature TB ∼ 37 K and also by revealing of the coercivity HC below TB. The value of the magnetic moment mP ∼ 300 μB of each iron-oxide particle was estimated. The interparticle interactions were investigated from dynamic properties using ac susceptibility. The susceptibility study shows, that the in-phase ac susceptibility χ′ is frequency dependent and the peak position increases with the increase in the frequency. The quantitative analysis of χ′ using theoretical models shows on the existence of weak dipolar interactions between particles. It was shown from correlation of experimental data with Arrhenius and Vogel–Fulcher laws that the incorporation of the nanoparticles into porous SiO2 matrix provides the effective method for the reducing of dipolar interactions between magnetic nanoparticles with the size below 10 nm.
Show PACS
75.75.-c Magnetic properties of nanostructures
75.20.-g Diamagnetism, paramagnetism, and superparamagnetism
75.30.Cr Saturation moments and magnetic susceptibilities
75.50.Tt Fine-particle systems; nanocrystalline materials
75.78.Cd Micromagnetic simulations
75.40.Mg Numerical simulation studies

Lattice thermal conductivity of freestanding gallium nitride nanowires

Jie Zou

J. Appl. Phys. 108, 034324 (2010); http://dx.doi.org/10.1063/1.3463358 (7 pages) | Cited 4 times

Online Publication Date: 13 August 2010

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We report detailed calculations of the lattice thermal conductivity of freestanding gallium nitride (GaN) nanowires with diameters ranging from 20 to 140 nm. Results are compared with experimental data on GaN nanowires grown by thermal chemical vapor deposition (CVD). Calculations are based on the Boltzmann transport equation and take into account the change in the nonequilibrium phonon distribution in the case of diffuse scattering at the surfaces. Phonon dispersion relation is obtained in the elastic continuum approximation for each given nanowire. For valid comparisons with the experimental data, simulations are performed with a dopant concentration and impurity profile characteristic of thermal CVD GaN nanowires. Our results show that the room-temperature thermal conductivity of the nanowires has very low values, ranging from 6.74 W/m K at 20 nm to 16.4 W/m K at 140 nm. The obtained results are in excellent agreement with the experimental data. We have also demonstrated that in addition to impurity scattering, boundary scattering, and phonon confinement, the change in the nonequilibrium phonon distribution leads to a further reduction in the thermal conductivity of the nanowires and has to be taken into account in the calculations. Our conclusion is different from that of an earlier study which attributed the very low thermal conductivity to the unusually large mass-difference scattering in the nanowires.
Show PACS
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
61.72.U- Doping and impurity implantation
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
71.55.Eq III-V semiconductors
61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
Return to All Sections
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close