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8 Apr 2002

Volume 80, Issue 14, pp. 2433-2611

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Transport-to-quantum lifetime ratios in AlGaN/GaN heterostructures

L. Hsu and W. Walukiewicz

Appl. Phys. Lett. 80, 2508 (2002); http://dx.doi.org/10.1063/1.1468260 (3 pages) | Cited 21 times

Online Publication Date: 2 April 2002

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We have calculated ratios of the transport-to-quantum lifetimes τt/τq of the two-dimensional electron gas in AlGaN/GaN heterostructures at low temperatures. In contrast to conventional interpretations, we show that large values of this ratio do not necessarily indicate that long-range scattering mechanisms such as Coulomb scattering are the dominant carrier scattering mechanisms and that large ratios (>20) can be obtained even when short-range scattering mechanisms are dominant. © 2002 American Institute of Physics.
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73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.63.Hs Quantum wells
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
68.35.Ct Interface structure and roughness

Cross sectional studies of buried semiconductor interfaces by means of photoemission microscopy

F. Barbo, M. Bertolo, A. Bianco, G. Cautero, S. Fontana, T. K. Johal, S. La Rosa, R. C. Purandare, N. Svetchnikov, A. Franciosi, D. Orani, M. Piccin, S. Rubini, and R. Cimino

Appl. Phys. Lett. 80, 2511 (2002); http://dx.doi.org/10.1063/1.1468264 (3 pages) | Cited 1 time

Online Publication Date: 2 April 2002

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An important application of photoemission spectromicroscopy would be to measure heterostructures and semiconductor devices in cross section to directly determine band offsets and band bending. We present here studies of p-n GaAs homojunctions and Al/GaAs Schottky junctions fabricated by molecular-beam epitaxy. Our results suggest that a minimum experimental uncertainty of about 0.15 eV will effect band offset determination. In general, useful quantitative information on the junction electrostatics can be obtained provided that the experimental data are analyzed to substract the diffuse photon background and take into account the intensity profile of the photon spot. © 2002 American Institute of Physics.
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68.37.Xy Scanning Auger microscopy, photoelectron microscopy
68.35.Ct Interface structure and roughness
73.20.At Surface states, band structure, electron density of states
79.60.Jv Interfaces; heterostructures; nanostructures
73.30.+y Surface double layers, Schottky barriers, and work functions
73.40.Ns Metal-nonmetal contacts
73.40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions

Impact of atomic-layer-deposited TiN on the gate oxide quality of W/TiN/SiO2/Si metal–oxide–semiconductor structures

Dae-Gyu Park, Kwan-Yong Lim, Heung-Jae Cho, Tae-Ho Cha, In-Seok Yeo, Jae-Sung Roh, and Jin Won Park

Appl. Phys. Lett. 80, 2514 (2002); http://dx.doi.org/10.1063/1.1468273 (3 pages) | Cited 24 times

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We demonstrate the impact of atomic-layer-deposited TiN gate on the characteristics of W/TiN/SiO2/p-Si metal–oxide–semiconductor (MOS) systems. Damage-free gate oxide quality was attained with atomic-layer-deposition (ALD)–TiN as manifested by an excellent interface trap density (Dit) as low as ∼ 4×1010 eV−1 cm−2 near the Si midgap. ALD–TiN improved the Dit level of MOS systems on both thin SiO2 and high-permittivity (high-k) gate dielectrics. The leakage current of a MOS capacitor gated with ALD–TiN is remarkably lower than that with sputter-deposited TiN and poly-Si gate at the similar capacitance equivalent thickness (CET). Less chlorine content in ALD–TiN films appears to be pivotal in minimizing the CET increase against postmetal anneal and improving gate oxide reliability, paving a way for the direct metal gate process. © 2002 American Institute of Physics.
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85.40.Ls Metallization, contacts, interconnects; device isolation
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
85.40.Qx Microcircuit quality, noise, performance, and failure analysis
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
85.40.Sz Deposition technology
84.32.Tt Capacitors

N-type organic thin-film transistor with high field-effect mobility based on a N,N′-dialkyl-3,4,9,10-perylene tetracarboxylic diimide derivative

Patrick R. L. Malenfant, Christos D. Dimitrakopoulos, Jeffrey D. Gelorme, Laura L. Kosbar, Teresita O. Graham, Alessandro Curioni, and Wanda Andreoni

Appl. Phys. Lett. 80, 2517 (2002); http://dx.doi.org/10.1063/1.1467706 (3 pages) | Cited 213 times

Online Publication Date: 2 April 2002

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N,N′-dioctyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C8H) thin films have been implemented into organic thin-film field-effect transistors. Mobilities up to 0.6 cm2 V−1 s−1 and current on/off ratios >105 were obtained. Linear regime mobilities were typically half of those measured in the saturation regime. X-ray studies in reflection mode suggest a spacing of ∼20 Å for thin evaporated films of PTCDI-C8H, which is consistent with the value of ∼ 21±2 Å obtained from our simulations when an interdigitated packing structure is assumed. © 2002 American Institute of Physics.
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85.30.Tv Field effect devices

Enhancement of photoluminescence by microdisk formation from Si/Ge/Si single quantum wells

Suk-Ho Choi, Jung Nam Kim, Hea Young Kim, Young-Kyu Hong, Ja-Yong Koo, JangHyeon Seok, and JaeYon Kim

Appl. Phys. Lett. 80, 2520 (2002); http://dx.doi.org/10.1063/1.1468918 (3 pages) | Cited 3 times

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A significant enhancement of photoluminescence (PL) intensity is observed in microdisks of 0.5 and 1 μm diam, which have been fabricated from Si/Ge/Si single quantum wells (SQWs) grown by molecular-beam epitaxy. The three major PL peaks found at 0.972, 0.957, and 0.920 eV are identified as a no-phonon transition of localized exciton, associated transverse-acoustical, and transverse-optical phonon replicas in Si, respectively. It is suggested that the formation of microdisks from the Si/Ge/Si SQWs enhances the intrinsic PL transitions significantly by suppressing the impurity-related ones. © 2002 American Institute of Physics.
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78.55.Ap Elemental semiconductors
78.67.De Quantum wells
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Periodic elastic domains of coexisting phases in epitaxial MnAs films on GaAs

T. Plake, M. Ramsteiner, V. M. Kaganer, B. Jenichen, M. Kästner, L. Däweritz, and K. H. Ploog

Appl. Phys. Lett. 80, 2523 (2002); http://dx.doi.org/10.1063/1.1467699 (3 pages) | Cited 78 times

Online Publication Date: 2 April 2002

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The surface topography of epitaxial MnAs films on GaAs(001) is studied by scanning probe microscopy. We provide direct experimental evidence for temperature-dependent elastic domains of the coexisting ferromagnetic αMnAs and paramagnetic βMnAs phases. The results agree well with a theoretical model for the elastic equilibrium of periodic domains. © 2002 American Institute of Physics.
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75.70.Ak Magnetic properties of monolayers and thin films
75.50.Dd Nonmetallic ferromagnetic materials
75.20.Ck Nonmetals
68.37.Ps Atomic force microscopy (AFM)
68.55.-a Thin film structure and morphology

Polaronic quasiparticle injection in organic copper (II) phthalocyanine/Bi2Sr2CaCu2O8+δ tunnel junctions

Sunmi Kim, Jungyoon E, Kiejin Lee, Takayuki Ishibashi, Katsuaki Sato, and Barry Friedman

Appl. Phys. Lett. 80, 2526 (2002); http://dx.doi.org/10.1063/1.1467703 (3 pages) | Cited 1 time

Online Publication Date: 2 April 2002

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We report the current transport properties of an organic conductor/superconductor tunnel junction as a high-Tc superconducting three terminal device. The organic copper (II) phthalocyanine (Cu–Pc) layer was used for a polaronic quasiparticle (QP) injector. The junction was investigated in the dark and under ultraviolet radiation. The injection of polaronic QP from the Cu–Pc interlayer into a superconductor Bi2Sr2CaCu2O8+δ (BSCCO) thin film generated a substantially larger nonequilibrium effect as compared to the normal QP injection current. The tunneling spectroscopy of a Cu–Pc/BSCCO junction exhibited a zero bias conductance peak, which may be interpreted as Andreev reflection at a Cu–Pc/d-wave superconductor junction. © 2002 American Institute of Physics.
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85.25.Cp Josephson devices
74.78.-w Superconducting films and low-dimensional structures
74.72.-h Cuprate superconductors
71.38.-k Polarons and electron-phonon interactions

Simplified analysis of two-layer antiferromagnetically coupled media

H. J. Richter, Er. Girt, and H. Zhou

Appl. Phys. Lett. 80, 2529 (2002); http://dx.doi.org/10.1063/1.1467977 (3 pages) | Cited 25 times

Online Publication Date: 2 April 2002

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Analytic expressions for the energy barrier at zero applied field and the switching field for a field applied along the easy axis are derived for a pair of antiferromagnetically coupled (AFC) single-domain particles at zero temperature. The energy barriers of the two single-domain particles add in zero field if the antiferromagnetic coupling exceeds a critical value ∣Jc∣ = 2(KV)1(KV)2/[S((KV)1+(KV)2)]. The antiferromagnetic coupling increases both the effective energy barrier as well as the switching field, so that optimized AFC media for recording applications require less than critical coupling ∣Jc∣. © 2002 American Institute of Physics.
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75.50.Tt Fine-particle systems; nanocrystalline materials
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.60.Ch Domain walls and domain structure
75.50.Ss Magnetic recording materials
75.40.Mg Numerical simulation studies
75.30.Gw Magnetic anisotropy
85.70.Kh Magnetic thin film devices: magnetic heads (magnetoresistive, inductive, etc.); domain-motion devices, etc.

Giant magnetoimpedance in FeAg granular alloys

J. M. Soares, J. H. de Araújo, F. A. O. Cabral, T. Dumelow, F. L. A. Machado, and A. E. P. de Araújo

Appl. Phys. Lett. 80, 2532 (2002); http://dx.doi.org/10.1063/1.1468274 (3 pages) | Cited 5 times

Online Publication Date: 2 April 2002

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We have observed giant magnetoimpedance (GMI) in an FeAg granular alloy. Impedance and transverse susceptibility (TS) measurements as a function of the external dc magnetic field were made at room temperature. The variation of the magnetoimpedance ratio with magnetic field has been related to a corresponding TS ratio change as a function of the magnetic field. The peaks in the GMI and TS curves are in the same position and have been associated in both cases to effective anisotropy fields. © 2002 American Institute of Physics.
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75.47.De Giant magnetoresistance
81.05.Rm Porous materials; granular materials
72.15.Gd Galvanomagnetic and other magnetotransport effects
75.30.Cr Saturation moments and magnetic susceptibilities
75.30.Gw Magnetic anisotropy
75.50.Tt Fine-particle systems; nanocrystalline materials

System for fast time-resolved measurements of c-axis quasiparticle conductivity in intrinsic Josephson junctions of Bi2Sr2CaCu2O8+δ

J. C. Fenton, P. J. Thomas, G. Yang, and C. E. Gough

Appl. Phys. Lett. 80, 2535 (2002); http://dx.doi.org/10.1063/1.1470261 (3 pages) | Cited 16 times

Online Publication Date: 2 April 2002

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A wide-band cryogenic amplifier measurement system for time-resolved four-point current-voltage (I-V)-characteristic measurements on Bi2Sr2CaCu2O8+δ mesa structures is described. We present measurements which demonstrate the importance of self-heating on ∼ 50 ns time scales. Such heating is likely to have been very significant in many previously published measurements, where the reported nonlinear I-V characteristics have been used to derive superconducting energy gaps. © 2002 American Institute of Physics.
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74.50.+r Tunneling phenomena; Josephson effects
74.72.-h Cuprate superconductors
74.25.F- Transport properties
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Oxygen-related dielectric relaxation and leakage characteristics of Pt/(Ba,Sr)TiO3/Pt thin-film capacitors

Mingrong Shen, Zhenggao Dong, Zhaoqiang Gan, Shuibing Ge, and Wenwu Cao

Appl. Phys. Lett. 80, 2538 (2002); http://dx.doi.org/10.1063/1.1468259 (3 pages) | Cited 17 times

Online Publication Date: 2 April 2002

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The leakage characteristics and dielectric properties of Pt/(Ba,Sr)TiO3/Pt thin-film capacitors were found to be remarkably sensitive to the postannealing temperature in oxygen and nitrogen atmosphere. High leakage currents and low-frequency dielectric relaxation were found in as-deposited capacitors after they had been postannealed in nitrogen at 550 °C and subsequently annealed in oxygen at 350 °C. Such results are related to the mobile oxygen ions and oxygen vacancies accumulated in the (Ba,Sr)TiO3 films. The chemical process of the formation of charged oxygen ions during postannealing is proposed. © 2002 American Institute of Physics.
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84.32.Tt Capacitors
73.40.Rw Metal-insulator-metal structures
77.22.Gm Dielectric loss and relaxation
81.40.Rs Electrical and magnetic properties related to treatment conditions
81.40.Gh Other heat and thermomechanical treatments
61.72.J- Point defects and defect clusters

Epitaxial Y-stabilized ZrO2 films on silicon: Dynamic growth process and interface structure

S. J. Wang and C. K. Ong

Appl. Phys. Lett. 80, 2541 (2002); http://dx.doi.org/10.1063/1.1467970 (3 pages) | Cited 48 times

Online Publication Date: 2 April 2002

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We have studied the initial stage of the growth of yttria-stabilized zirconia (YSZ) films on natively oxidized (100) Si wafer by pulsed-laser deposition. X-ray photoelectron spectroscopy and high-resolution electron microscopy show that, for the first few monolayers of crystalline YSZ deposited on (100) Si, the dynamic processes appear to be the decomposition of SiO2 to SiO, the formation of ZrO2, and the desorption of SiO. The native amorphous SiO2 layer is removed completely with the continued deposition of YSZ. The atomically sharp and commensurate YSZ/Si interface is suggested to have a sequence of Si–Si–O–Zr–O–. © 2002 American Institute of Physics.
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81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.35.Ct Interface structure and roughness
79.60.Jv Interfaces; heterostructures; nanostructures
68.37.Lp Transmission electron microscopy (TEM)
64.75.-g Phase equilibria
77.55.-g Dielectric thin films
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.

Stable scattering-matrix method for surface acoustic waves in piezoelectric multilayers

Th. Pastureaud, V. Laude, and S. Ballandras

Appl. Phys. Lett. 80, 2544 (2002); http://dx.doi.org/10.1063/1.1467620 (3 pages) | Cited 21 times

Online Publication Date: 2 April 2002

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A scattering matrix approach is proposed to avoid numerical instabilities arising with the classical transfer matrix method when analyzing the propagation of plane surface acoustic waves in piezoelectric multilayers. The method is stable whatever the thickness of the layers, and the frequency or the slowness of the waves. The computation of the Green’s function and of the effective permittivity of the multilayer is outlined. In addition, the method can be easily extended to the case of interface acoustic waves. © 2002 American Institute of Physics.
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77.65.Dq Acoustoelectric effects and surface acoustic waves (SAW) in piezoelectrics
68.35.Iv Acoustical properties
68.65.Ac Multilayers
02.60.Dc Numerical linear algebra
43.35.Pt Surface waves in solids and liquids
77.55.-g Dielectric thin films

Temperature dependence of electrical properties of N2O/O2/N2O-grown oxides on strained SiGe

S. K. Samanta, S. Chatterjee, L. K. Bera, H. D. Banerjee, and C. K. Maiti

Appl. Phys. Lett. 80, 2547 (2002); http://dx.doi.org/10.1063/1.1469221 (3 pages) | Cited 3 times

Online Publication Date: 2 April 2002

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Temperature dependence of electrical properties of split-N2O grown oxides on strained SiGe layers by rapid thermal oxidation is reported. The reliability and thermal stability of ultrathin oxides have been examined by high frequency capacitance–voltage and current density versus electric field measurements. It is observed that at a low (<6 MV/cm) electric field, the shallow trap-assisted conduction mechanism is responsible for the leakage current below 100 °C and the Frenkel–Poole conduction dominates above 100 °C. At a high (>11 MV/cm) electric field, however, the leakage current is mainly governed by the Fowler–Nordheim tunneling. Charge-to-breakdown measurements at a constant current stressing show a higher reliability for the split-N2O grown oxides. © 2002 American Institute of Physics.
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77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
77.55.-g Dielectric thin films
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.50.Fq High-field and nonlinear effects
81.65.Mq Oxidation
68.60.Dv Thermal stability; thermal effects
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Gas-phase thermodynamic models of nitrogen-induced nanocrystallinity in chemical vapor-deposited diamond

Raymond B. Corvin, Joseph G. Harrison, Shane A. Catledge, and Yogesh K. Vohra

Appl. Phys. Lett. 80, 2550 (2002); http://dx.doi.org/10.1063/1.1467618 (3 pages) | Cited 15 times

Online Publication Date: 2 April 2002

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Gas-phase thermodynamic equilibrium calculations involving H2/CH4/N2 mixtures were performed to investigate the chemical interactions leading to nitrogen-induced nanocrystallinity in microwave plasma chemical vapor deposition of diamond films. The strong influence of the CN radical in causing nanocrystallinity is confirmed by the correlation of its modeled composition in the gas phase with the degree of nanocrystallinity as determined experimentally for diamond films grown with different N2 additions. For a given CH4 feedgas concentration, there exists a critical N2 feedgas concentration, above which the change in the CH3/CN ratio is minimal and further induced nanocrystallinity is diminished. This is verified experimentally where it is observed that the same critical N2 feedgas concentration exists, above which a further decrease in diamond crystallinity and surface roughness of the grown diamond films is minimal. © 2002 American Institute of Physics.
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68.55.-a Thin film structure and morphology
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Raman scattering and thermogravimetric analysis of iodine-doped multiwall carbon nanotubes

Weiya Zhou, Sishen Xie, Lianfeng Sun, Dongsheng Tang, Yubao Li, Zuqin Liu, Lijie Ci, Xiaoping Zou, Gang Wang, Pingheng Tan, Xiaoli Dong, Bo Xu, and Boru Zhao

Appl. Phys. Lett. 80, 2553 (2002); http://dx.doi.org/10.1063/1.1468269 (3 pages) | Cited 10 times

Online Publication Date: 2 April 2002

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Iodine-doped multiwall carbon nanotubes (I-MWNTs) were characterized by means of Raman scattering and thermogravimetric analysis. The results show that multiwall carbon nanotubes (MWNTs) can be effectively doped by iodine and exchange electrons with iodine. Iodine atoms form charged polyiodide chains inside tubes of different inner diameter, which is similar to the iodine-doped single-wall carbon nanotubes (I-SWNTs), but can not intercalate into the graphene walls of MWNTs. The Raman scattering behavior of I-MWNTs exhibits some differences from that of I-SWNTs and the low-dimensional conductive hydrocarbon-iodine complex perylene⋅I2.92. © 2002 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
78.67.Ch Nanotubes
65.80.-g Thermal properties of small particles, nanocrystals, nanotubes, and other related systems
78.30.Na Fullerenes and related materials

Local electrostatic potential and process-induced boron redistribution in patterned Si/SiGe/Si heterostructures

A. Orchowski, W.-D. Rau, H. Rücker, B. Heinemann, P. Schwander, B. Tillack, and A. Ourmazd

Appl. Phys. Lett. 80, 2556 (2002); http://dx.doi.org/10.1063/1.1467712 (3 pages) | Cited 3 times

Online Publication Date: 2 April 2002

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We present microscopic maps of the electrostatic potential in Si/SiGe/Si patterned structures of the type used in heterostructure bipolar transistors. By obtaining such maps before and after anneals typically used in device processing, we directly reveal the “vertical” and “lateral” redistribution of boron during device fabrication. Such data can be compared with the results of process simulation to extract the fundamental parameters for dopant diffusion in complex device structures. © 2002 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
61.72.Cc Kinetics of defect formation and annealing
85.30.Pq Bipolar transistors
81.05.Cy Elemental semiconductors
61.72.uf Ge and Si
61.72.up Other materials
85.40.Ry Impurity doping, diffusion and ion implantation technology
61.72.S- Impurities in crystals

Hybridized boron–carbon nitride fibrous nanostructures on Ni substrates

Yoke Khin Yap, Masashi Yoshimura, Yusuke Mori, and Takatomo Sasaki

Appl. Phys. Lett. 80, 2559 (2002); http://dx.doi.org/10.1063/1.1468270 (3 pages) | Cited 13 times

Online Publication Date: 2 April 2002

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Stoichiometric BC2N films can be deposited on Si (100) at 800 °C, however, they are phase separated as pure carbon and BN phases. Likewise, hybridized boron–carbon nitride (BCN) films can be synthesized on Ni substrates. On Ni, the carbon and BN phases are hybridized through carbon nitride and boron carbide bonds. These films appeared as fibrous nanostructures. Evidence indicates that the Ni substrate acts as a sink for the carbon and forces the carbon composites to grow on top of the B and N atoms. However, as these films are grown thicker, phase separation occurs again. These results indicate that hybridized BCN phases should now be regarded as semiconducting or superhard nanostructures. High-temperature deposition on Ni substrates might be a solution to the obstacle of preparing hybridized BCN phases. © 2002 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
68.55.-a Thin film structure and morphology
61.46.-w Structure of nanoscale materials
68.55.Nq Composition and phase identification
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.15.Fg Pulsed laser ablation deposition
81.16.Mk Laser-assisted deposition
52.77.Dq Plasma-based ion implantation and deposition
64.75.-g Phase equilibria
78.30.Hv Other nonmetallic inorganics

Conceptual design of nanostructures for efficient photoinduced phase transitions

Tohru Kawamoto and Shuji Abe

Appl. Phys. Lett. 80, 2562 (2002); http://dx.doi.org/10.1063/1.1468263 (3 pages) | Cited 10 times

Online Publication Date: 2 April 2002

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By means of Monte Carlo simulations on a kinetic model, we demonstrate that the efficiency of a photoinduced phase change can in general be enhanced drastically by using a superstructure of an appropriate combination of two components. This is due to the accelerated nucleation of converted domains in the structural blocks relatively close to local instability. The present mechanism provides a general guideline on the design of photocontrollable materials with potential applications for memory and storage devices. © 2002 American Institute of Physics.
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64.70.Nd Structural transitions in nanoscale materials
64.60.-i General studies of phase transitions
61.80.Ba Ultraviolet, visible, and infrared radiation effects (including laser radiation)

Nanopatterning of alkyl monolayers covalently bound to Si(111) with an atomic force microscope

Masato Ara, Harald Graaf, and Hirokazu Tada

Appl. Phys. Lett. 80, 2565 (2002); http://dx.doi.org/10.1063/1.1467973 (3 pages) | Cited 30 times

Online Publication Date: 2 April 2002

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Alkyl monolayers covalently bound to silicon were prepared through the reaction between 1-alkene molecules and hydrogen-terminated Si. The surfaces were anodized in nanometer scale with a contact-mode atomic force microscope (AFM) by applying positive bias voltage to the surface with respect to a conducting cantilever under ambient conditions. Following the anodization, patterned areas were selectively modified by chemical etching and coating with different molecules. The alkyl monolayers showed high resistance against chemical etching and protected Si surfaces from oxidation. AFM lithography of monolayers on Si was found to be useful for nanofabrication of organic/inorganic interfaces based on the Si–C covalent bond. © 2002 American Institute of Physics.
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81.16.Rf Micro- and nanoscale pattern formation
81.16.Ta Atom manipulation
81.65.Cf Surface cleaning, etching, patterning
81.65.Kn Corrosion protection
68.35.B- Structure of clean surfaces (and surface reconstruction)

Enhanced tunneling across nanometer-scale metal–semiconductor interfaces

G. D. J. Smit, S. Rogge, and T. M. Klapwijk

Appl. Phys. Lett. 80, 2568 (2002); http://dx.doi.org/10.1063/1.1467980 (3 pages) | Cited 50 times

Online Publication Date: 2 April 2002

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We have measured electrical transport across epitaxial, nanometer-sized metal–semiconductor interfaces by contacting CoSi2 islands grown on Si(111) with the tip of a scanning tunneling microscope. The conductance per unit area was found to increase with decreasing diode area. Indeed, the zero-bias conductance was found to be ∼ 104 times larger than expected from downscaling a conventional diode. These observations are explained by a model, which predicts a narrower barrier for small diodes and, therefore, a greatly increased contribution of tunneling to the electrical transport. © 2002 American Institute of Physics.
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73.40.Ns Metal-nonmetal contacts
73.30.+y Surface double layers, Schottky barriers, and work functions
85.30.Kk Junction diodes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)

Quasiregular quantum-dot-like structure formation with postgrowth thermal annealing of InGaN/GaN quantum wells

Yen-Sheng Lin, Kung-Jen Ma, Cheng Hsu, Yi-Yin Chung, Chih-Wen Liu, Shih-Wei Feng, Yung-Chen Cheng, C. C. Yang, Ming-Hua Mao, Hui-Wen Chuang, Cheng-Ta Kuo, Jian-Shihn Tsang, and Thomas E. Weirich

Appl. Phys. Lett. 80, 2571 (2002); http://dx.doi.org/10.1063/1.1467983 (3 pages) | Cited 42 times

Online Publication Date: 2 April 2002

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Postgrowth thermal annealing of an InGaN/GaN quantum-well sample with a medium level of nominal indium content (19%) was conducted. From the analyses of high-resolution transmission electron microscopy and energy filter transmission electron microscopy, it was found that thermal annealing at 900 °C led to a quasiregular quantum-dot-like structure. However, such a structure was destroyed when the annealing temperature was raised to 950 °C. Temperature-dependent photoluminescence (PL) measurements showed quite consistent results. Blueshift of the PL peak position and narrowing of the PL spectral width after thermal annealing were observed. © 2002 American Institute of Physics.
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68.65.Fg Quantum wells
68.65.Hb Quantum dots (patterned in quantum wells)
68.35.Ct Interface structure and roughness
78.55.Cr III-V semiconductors
78.66.Fd III-V semiconductors
81.05.Ea III-V semiconductors
78.67.De Quantum wells
81.07.St Quantum wells
78.67.Hc Quantum dots
81.07.Ta Quantum dots
81.40.Gh Other heat and thermomechanical treatments
68.37.Lp Transmission electron microscopy (TEM)

Controlled placement of an individual carbon nanotube onto a microelectromechanical structure

P. A. Williams, S. J. Papadakis, M. R. Falvo, A. M. Patel, M. Sinclair, A. Seeger, A. Helser, R. M. Taylor, S. Washburn, and R. Superfine

Appl. Phys. Lett. 80, 2574 (2002); http://dx.doi.org/10.1063/1.1467701 (3 pages) | Cited 38 times

Online Publication Date: 2 April 2002

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We report on the precise placement of a single carbon nanotube (CNT) onto a microlectromechanial system (MEMS) structure. Using a hybrid atomic force microscope/scanning electron microscope (AFM/SEM) system, an individual multiwalled CNT was retrieved from a cartridge by the AFM tip, translated to a MEMS device, and then placed across a gap between an actuating and a stationary structure. Progress toward a resistance versus stress/strain measurement on a CNT will be discussed, including SEM images of a MEMS structure we have designed specifically for such a measurement. © 2002 American Institute of Physics.
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81.16.Ta Atom manipulation
81.07.De Nanotubes
85.35.Kt Nanotube devices
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices

Few-electron filling effect in laterally coupled spherical InAs/GaAs quantum-dot system

Zhen-Hong Dai, Li-De Zhang, Jin-Zuo Sun, Zuo-Hong Li, and Shi-Yong Huang

Appl. Phys. Lett. 80, 2577 (2002); http://dx.doi.org/10.1063/1.1468262 (3 pages) | Cited 2 times

Online Publication Date: 2 April 2002

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Artificial molecules, i.e., systems of excess electrons confined in multiple semiconductor InAs/GaAs quantum dots, are studied with the unrestricted Hartree–Fock–Roothaan method. We focus our attention on calculating the chemical potential for two laterally coupled spherical quantum dots. The confinement potential in each quantum dot of the molecule is assumed in a form of three-dimensional spherical finite potential well of radius R and depth V0. The chemical potential is found to depend strongly on the proportionality of the radii of the two quantum dots. This method can be extended to study large quantum-dot arrays. © 2002 American Institute of Physics.
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73.21.La Quantum dots
71.15.Ap Basis sets (LCAO, plane-wave, APW, etc.) and related methodology (scattering methods, ASA, linearized methods, etc.)

Nanoparticle-templated carbon nanotube ring nucleus formation

James R. Hester and Oleg A. Louchev

Appl. Phys. Lett. 80, 2580 (2002); http://dx.doi.org/10.1063/1.1465112 (3 pages) | Cited 7 times

Online Publication Date: 2 April 2002

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A mechanism for nanotube ring nucleus formation via the interaction of a carbon nanosheet with a nanoparticle is proposed based on consideration of both short-range covalent and long-range interactions. In nanosheet–nanoparticle interaction, the potential barrier for nanosheet folding into a nanoring segment caused by covalent bonds distortions can be significantly decreased by long-range interaction with the nanoparticle. This effect, alone or in combination with the kinetic energy of collision, is shown to be able to fold the nanosheet around the nanoparticle and lead to the eventual formation of a nanotube ring nucleus. © 2002 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
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