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25 Feb 2008

Volume 92, Issue 8, Articles (08xxxx)

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Appl. Phys. Lett. 92, 081101 (2008); http://dx.doi.org/10.1063/1.2883874 (3 pages)

Marcel W. Pruessner, Todd H. Stievater, and William S. Rabinovich
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Electron dephasing in nanocrystalline silicon thin films

K. Zhang and W. Z. Shen

Appl. Phys. Lett. 92, 083101 (2008); http://dx.doi.org/10.1063/1.2840179 (3 pages) | Cited 3 times

Online Publication Date: 25 February 2008

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In combination with dephasing and weak localization theories, we have presented a detailed magnetotransport investigation for the electron dephasing characteristics in hydrogenated nanocrystalline silicon thin films. It is found that the experimental magnetoconductivity can be well fitted by an integration of diffusive Fermi surface and scaling models, taking into account both the two-dimensional quasielastic small energy transfer via scattering of localized electrons on potential barriers of several different dots (Nyquist mechanism) and three-dimensional inelastic phonon scattering contribution. The dephasing time and length have also been extracted with a temperature exponent p ≈ 1.2 for the natural semiconductor quantum dot system.
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73.61.Cw Elemental semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
73.20.Fz Weak or Anderson localization
73.21.La Quantum dots
73.63.Kv Quantum dots
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials

Resonance frequency analysis for surface-coupled atomic force microscopy cantilever in ambient and liquid environments

Boris Mirman and Sergei V. Kalinin

Appl. Phys. Lett. 92, 083102 (2008); http://dx.doi.org/10.1063/1.2801524 (3 pages) | Cited 6 times

Online Publication Date: 25 February 2008

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Shifts in the resonance frequencies of surface-coupled atomic force microscope (AFM) probes are used as the basis for the detection mechanisms in a number of scanning probe microscopy techniques including atomic force acoustic microscopy (AFAM), force modulation microscopy, and resonance enhanced piezoresponse force microscopy (PFM). Here, we analyze resonance characteristics for AFM cantilever coupled to surface in liquid environment, and derive approximate expressions for resonant frequencies as a function of vertical and lateral spring constant of the tip-surface junction. This analysis provides a simplified framework for the interpretation of AFAM and PFM data in ambient, liquid, and vacuum environments.
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43.20.Ks Standing waves, resonance, normal modes
68.37.Ps Atomic force microscopy (AFM)

Influence of an ultrathin GaAs interlayer on the structural properties of InAs/InGaAsP/InP (001) quantum dots investigated by cross-sectional scanning tunneling microscopy

J. M. Ulloa, S. Anantathanasarn, P. J. van Veldhoven, P. M. Koenraad, and R. Nötzel

Appl. Phys. Lett. 92, 083103 (2008); http://dx.doi.org/10.1063/1.2884692 (3 pages) | Cited 6 times

Online Publication Date: 25 February 2008

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Cross-sectional scanning tunneling microscopy is used to study at the atomic scale how the structural properties of InAs/InGaAsP/InP quantum dots (QDs) are modified when an ultrathin (0–1.5 ML) GaAs interlayer is inserted underneath the QDs. Deposition of the GaAs interlayer suppresses the influence of the As/P exchange reaction on QD formation and leads to a planarized QD growth surface. A shape transition from quantum dashes, which are strongly dissolved during capping, to well defined QDs takes place when increasing the GaAs interlayer thickness between 0 and 1.0 ML. Moreover, the GaAs interlayer allows the control of the As/P exchange reaction, reducing the QD height for increased GaAs thicknesses above 1.0 ML, and decreases the QD composition intermixing, producing almost pure InAs QDs.
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68.65.Hb Quantum dots (patterned in quantum wells)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation

Effect of a metallic gate on the energy levels of a shallow donor

A. F. Slachmuylders, B. Partoens, F. M. Peeters, and W. Magnus

Appl. Phys. Lett. 92, 083104 (2008); http://dx.doi.org/10.1063/1.2888742 (3 pages) | Cited 8 times

Online Publication Date: 26 February 2008

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We have investigated the effect of a metallic gate on the bound states of a shallow donor located near the gate. We calculate the energy spectrum as a function of the distance between the metallic gate and the donor and find an anticrossing behavior in the energy levels for certain distances. We show how a transverse electric field can tune the average position of the electron with respect to the metallic gate and the impurity.
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71.55.-i Impurity and defect levels
32.80.Xx Level crossing and optical pumping

How long can single-walled carbon nanotube ropes last under static or dynamic fatigue?

Gang Ma, Yu Ren, Jun Guo, Tan Xiao, Feng Li, Huiming Cheng, Zongrong Zhou, and Kin Liao

Appl. Phys. Lett. 92, 083105 (2008); http://dx.doi.org/10.1063/1.2883940 (3 pages) | Cited 4 times

Online Publication Date: 26 February 2008

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We report a study on the static and dynamic fatigue behavior of unidirectional, aligned single-walled carbon nanotube (SWCNT) ropes. By bench marking against the behavior of graphite fiber, it is found that the static fatigue strength of SWCNT ropes is at least twice that of graphite fiber within 104 s and is similar to that of graphite fiber at longer times, while the dynamic fatigue strength is twice that of the graphite fiber to up to 107 cycles. Fatigue limit seems to exist for SWCNT ropes within the time scale of the investigation at 4–5 GPa. Based on experimental data and results of a molecular life prediction scheme, it is suggested that the fatigue behavior of SWCNT ropes may be controlled by preexisting defects.
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62.25.-g Mechanical properties of nanoscale systems
62.20.me Fatigue
81.40.Np Fatigue, corrosion fatigue, embrittlement, cracking, fracture, and failure

Epitaxial assembly and ordering of two-dimensional colloidal crystals

Rongguo Xie and Xiang-Yang Liu

Appl. Phys. Lett. 92, 083106 (2008); http://dx.doi.org/10.1063/1.2841850 (3 pages) | Cited 8 times

Online Publication Date: 26 February 2008

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An epitaxial assembly method is described to direct the crystallization of two-dimensional colloidal crystals under an alternating electric field (AEF). By using a colloidal line as an epitaxial template, the colloidal crystals with a predefined orientation have been assembled at specified position of an electrode. The epitaxial correlation between the colloidal crystals and the template can be tuned by varying the frequency of the AEF. By control of the template and the frequency, well-defined linear defects have been incorporated into the colloidal crystals, whereas the unwanted defects can be in situ eliminated through a template-guided annealing process.
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82.70.Dd Colloids
61.43.-j Disordered solids
64.70.dg Crystallization of specific substances
81.40.Gh Other heat and thermomechanical treatments

Metal-semiconductor junction of graphene nanoribbons

Seokmin Hong, Youngki Yoon, and Jing Guo

Appl. Phys. Lett. 92, 083107 (2008); http://dx.doi.org/10.1063/1.2885095 (3 pages) | Cited 25 times

Online Publication Date: 26 February 2008

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Patterned all-graphene circuits, in which semiconducting graphene nanoribbon (GNR) device channels are connected by metallic GNR interconnects, raise possibilities for carbon-based electronics. The properties of GNR metal-semiconductor junctions, which are the key elements in all-graphene circuits, are studied by atomistic simulations. The junction conductance strongly depends on the atomistic features of the access geometry from the metallic GNR to the semiconducting GNR. Highly localized states exist at the junction edges, which can result in sharp metal-induced gap states. A defect of a single lattice vacancy can significantly increase rather than decrease the junction conductance for certain junction geometries.
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73.40.Ns Metal-nonmetal contacts
73.22.-f Electronic structure of nanoscale materials and related systems
85.40.Ls Metallization, contacts, interconnects; device isolation

Adsorption and dissociation of hydrogen molecules on a Pt atom on defective carbon nanotubes

Yongjin Park, Gunn Kim, and Young Hee Lee

Appl. Phys. Lett. 92, 083108 (2008); http://dx.doi.org/10.1063/1.2838732 (3 pages) | Cited 12 times

Online Publication Date: 28 February 2008

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Using density functional calculations, we investigate the catalytic effect of a Pt atom on a defective carbon nanotube. The Pt atom binds more strongly to the vacancy site than to the Stone-Wales defect and to the pure surface of the nanotube. The binding energy of the H2 molecule on the vacancy is significantly reduced to 0.68 eV from 1.26 eV of the pure (5,5) nanotube but still sufficient enough to maintain minimum bond strength on the Pt atom. Moreover, the H–H distance is separated to 2.16 Å. The feasibility to the fuel cell is further discussed.
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68.43.Mn Adsorption kinetics
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
61.72.jd Vacancies
82.47.-a Applied electrochemistry

A generic approach to nanocables via nanochannel-confined sequential electrodeposition

Dachi Yang, Guowen Meng, Qiaoling Xu, Xianglong Zhao, Jianxiong Liu, Mingguang Kong, Zhaoqin Chu, Xiaoguang Zhu, and Lide Zhang

Appl. Phys. Lett. 92, 083109 (2008); http://dx.doi.org/10.1063/1.2839434 (3 pages) | Cited 3 times

Online Publication Date: 28 February 2008

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We have exploited a generic method for nanocables, consisting of two materials that can be obtained via electrodeposition, by first electrodepositing the cable “shells” on the interior walls of nanochannels inside anodic aluminum oxide template with one planar surface side coated with a thin meshlike Au layer and then filling the cavities inside the shells by electrodeposition again to achieve the cable “cores.” The method has been demonstrated for the nanocables of Cu-Bi (Cu shell and Bi core) and Bi-Cu (Bi shell and Cu core). Nanocables of other two materials with tunable shell thickness and inner core diameter can be achieved by modulating the Au-layer thickness, and might have potential in the future nanotechnology.
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61.46.-w Structure of nanoscale materials
82.45.Qr Electrodeposition and electrodissolution

Surface plasmon polariton modes in a single-crystal Au nanoresonator fabricated using focused-ion-beam milling

E. J. R. Vesseur, R. de Waele, H. J. Lezec, H. A. Atwater, F. J. García de Abajo, and A. Polman

Appl. Phys. Lett. 92, 083110 (2008); http://dx.doi.org/10.1063/1.2885344 (3 pages) | Cited 22 times

Online Publication Date: 28 February 2008

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We use focused-ion-beam milling of a single-crystal Au surface to fabricate a 590-nm-long linear ridge that acts as a surface plasmon nanoresonator. Cathodoluminescence imaging spectroscopy is then used to excite and image surface plasmons on the ridge. Principal component analysis reveals distinct plasmonic modes, which proves confinement of surface plasmon oscillations to the ridge. Boundary-element-method calculations confirm that a linear ridge is able to support highly localized surface plasmon modes (mode diameter <100 nm). The results demonstrate that focused-ion-beam milling can be used in rapid prototyping of nanoscale single-crystal plasmonic components.
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73.20.Mf Collective excitations (including excitons, polarons, plasmons and other charge-density excitations)
81.20.Wk Machining, milling
71.36.+c Polaritons (including photon-phonon and photon-magnon interactions)
63.20.Pw Localized modes
78.60.Hk Cathodoluminescence, ionoluminescence

Optical properties of InAs quantum dots grown on patterned Si with a thin GaAs buffer layer

Zuoming Zhao, Zhibiao Hao, Kameshwar Yadavalli, Kang L. Wang, and Ajey P. Jacob

Appl. Phys. Lett. 92, 083111 (2008); http://dx.doi.org/10.1063/1.2833700 (3 pages) | Cited 8 times

Online Publication Date: 29 February 2008

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InAs quantum dots (QDs) were grown on patterned Si substrates with a thin GaAs buffer using SiO2 as a mask by molecular beam epitaxy. GaAs was firstly selectively grown on the exposed Si surface with feature size around 250 nm. The InAs QDs were selectively grown on top of the GaAs. Low temperature photoluminescence (PL) measurements show strong optical activity in the wavelength range from 900 to 1050 nm. The temperature dependent measurement of the PL response indicates that, for temperatures over 110 K, the carrier escape from quantum dots leads to quenching of the signal. The PL results demonstrate that using nanostructures, it is possible to integrate high quality direct gap III-V materials on Si with high optical activity, leading to potentially new optoelectronic applications on Si and other convenient substrates which are lattice mismatched to InAs and other III-V materials.
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78.67.Hc Quantum dots
78.55.Cr III-V semiconductors
81.07.Ta Quantum dots
81.05.Ea III-V semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Influence of capping layer and atomic interdiffusion on the strain distribution in single and double self-assembled InAs/GaAs quantum dots

Mou Yang, S. J. Xu, and Jian Wang

Appl. Phys. Lett. 92, 083112 (2008); http://dx.doi.org/10.1063/1.2841065 (3 pages) | Cited 6 times

Online Publication Date: 29 February 2008

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The strain distribution in single and double self-assembled InAs/GaAs quantum dots is theoretically investigated by using a valence-force-field model. The results show strong influence of the capping conditions on the strain distribution in individual and stacked dots with wetting layers. In particular, the intermixing of atoms is incorporated into the strain calculations, leading to a conclusion that the atomic intermixing can notably modify the strain profiles near the interfaces of the stacked dot system.
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66.30.Ny Chemical interdiffusion; diffusion barriers
68.35.Fx Diffusion; interface formation
68.65.Hb Quantum dots (patterned in quantum wells)
62.23.Eg Nanodots
66.30.Pa Diffusion in nanoscale solids
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