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17 Mar 2003

Volume 82, Issue 11, pp. 1649-1799

Issue Cover Spotlight Figure

Appl. Phys. Lett. 82, 1709 (2003); http://dx.doi.org/10.1063/1.1560575 (3 pages)

Ji-Won Oh, Masahiro Yoshita, Hidefumi Akiyama, Loren N. Pfeiffer, and Ken W. West
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Sub-5-nm-spatial resolution in scanning spreading resistance microscopy using full-diamond tips

D. Álvarez, J. Hartwich, M. Fouchier, P. Eyben, and W. Vandervorst

Appl. Phys. Lett. 82, 1724 (2003); http://dx.doi.org/10.1063/1.1559931 (3 pages) | Cited 27 times

Online Publication Date: 10 March 2003

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Scanning spreading resistance microscopy is a two-dimensional carrier profiling technique now widely used for the characterization of silicon (Si) devices as well as other semiconductor materials. Whereas the state-of-the-art spatial resolution for this technique using commercial-diamond-coated silicon probes is limited to 10–20 nm, enhanced resolution is demonstrated through the use of full-diamond tips integrated in Si cantilevers. Sub-5-nm-spatial resolution is obtained on fully depleted silicon on isolator devices, putting the technique closer to the characterization requirements of the forthcoming semiconductor dimensions. Resistance and scanning electron microscope measurements clearly show that this enhanced resolution results from a smaller effective radius for full diamond tips as compared to the diamond-coated Si probes. © 2003 American Institute of Physics.
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73.25.+i Surface conductivity and carrier phenomena
72.80.Cw Elemental semiconductors
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)

Current-induced structural modification of silicon-on-insulator nanocircuits

N. Clement, A. Francinelli, D. Tonneau, Ph. Scotto, F. Jandard, H. Dallaporta, V. Safarov, D. Fraboulet, and J. Gautier

Appl. Phys. Lett. 82, 1727 (2003); http://dx.doi.org/10.1063/1.1561573 (3 pages) | Cited 10 times

Online Publication Date: 10 March 2003

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Silicon-on-insulator (SOI) materials are considered the next form of Si for extending the metal–oxide–silicon technology. Here, we report the electrical study correlated with the topographical modification of nanostructures built on 20-nm-thick SOI. At current densities around 3×106 A cm−2, we noticed an irreversible modification characterized by formation of nanochannels and failures at n+n contacts. The origin of these channels can be attributed either to hydrodynamic diffusion of positive Si ions or to momentum exchange with holes created by impact ionization at high electric field (105 V/cm). We show also that the heating of the circuit plays an important role in the process. © 2003 American Institute of Physics.
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85.35.-p Nanoelectronic devices
85.65.+h Molecular electronic devices
81.07.Lk Nanocontacts
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
73.63.Rt Nanoscale contacts
81.65.-b Surface treatments

Infrared ellipsometry of GaAs epilayers on Si(100)

G. Yu, N. L. Rowell, D. J. Lockwood, and T. Soga

Appl. Phys. Lett. 82, 1730 (2003); http://dx.doi.org/10.1063/1.1561577 (3 pages) | Cited 1 time

Online Publication Date: 10 March 2003

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Infrared spectroscopic ellipsometry is used to characterize the structure of molecular-beam-epitaxial grown GaAs layers on Si(100) before and after thermal cycle (TC) annealing. The dielectric function of the GaAs epilayer has been described by the sum of a factorized form and a classical Drude model in the spectral fitting procedure. The epilayer LO phonon frequency shifts toward lower frequency with increasing TC number while the opposite is seen for TO phonon. The shift of the LO mode indicates that the tensile stress increases with increasing TC number, while the shift of the TO mode is attributed mainly to the self-energy effect in GaAs:Si. Unequal thermal diffusion of SiAs− and SiGa+ is indicated. © 2003 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
63.22.-m Phonons or vibrational states in low-dimensional structures and nanoscale materials
66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves
07.60.Fs Polarimeters and ellipsometers
68.35.Ja Surface and interface dynamics and vibrations

Magnetic study of an amorphous conducting polyaniline

Debangshu Chaudhuri, Ashwani Kumar, D. D. Sarma, M. García-Hernández, Janhavi P. Joshi, and S. V. Bhat

Appl. Phys. Lett. 82, 1733 (2003); http://dx.doi.org/10.1063/1.1561166 (3 pages) | Cited 11 times

Online Publication Date: 10 March 2003

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We show that newly found BF3-doped polyaniline, although highly conducting, remains amorphous. Magnetic studies reveal many unusual properties, while suggesting that the intrinsic conductivity of this system is significantly larger than all other known forms of conducting polyaniline, establishing it as an interesting class of highly conducting amorphous polymer. © 2003 American Institute of Physics.
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72.15.Nj Collective modes (e.g., in one-dimensional conductors)
75.20.Ck Nonmetals
76.30.Lh Other ions and impurities
61.41.+e Polymers, elastomers, and plastics

Surface charge accumulation of InN films grown by molecular-beam epitaxy

Hai Lu, William J. Schaff, Lester F. Eastman, and C. E. Stutz

Appl. Phys. Lett. 82, 1736 (2003); http://dx.doi.org/10.1063/1.1562340 (3 pages) | Cited 163 times

Online Publication Date: 10 March 2003

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A series of thin InN films down to 10 nm in thickness were prepared by molecular-beam epitaxy on either AlN or GaN buffers under optimized growth conditions. By extrapolating the fitted curve of sheet carrier density versus film thickness to zero film thickness, a strong excess sheet charge was derived, which must come from either the surface or the interface between InN and its buffer layer. Since metal contacts, including Ti, Al, Ni, and a Hg probe, can always form an ohmic contact on InN without any annealing, it is determined that at least part of the excess charge is surface charge, which was also confirmed by capacitance–voltage measurements. © 2003 American Institute of Physics.
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73.61.Ey III-V semiconductors
81.05.Ea III-V semiconductors
73.40.Ns Metal-nonmetal contacts
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
72.20.My Galvanomagnetic and other magnetotransport effects
68.47.Fg Semiconductor surfaces

Field-effect transistors on rubrene single crystals with parylene gate insulator

V. Podzorov, V. M. Pudalov, and M. E. Gershenson

Appl. Phys. Lett. 82, 1739 (2003); http://dx.doi.org/10.1063/1.1560869 (3 pages) | Cited 192 times

Online Publication Date: 10 March 2003

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We report on the fabrication and characterization of the organic field-effect transistors (OFETs) on the surface of single crystals of rubrene. The parylene polymer film has been used as the gate insulator. At room temperature, these OFETs exhibit the p-type conductivity with the field-effect mobility 0.1–1 cm2/V s and the on/off ratio ≥ 104. The temperature dependence of the mobility is discussed. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices

High-selectivity etching of polycrystalline 3C-SiC films using HBr-based transformer coupled plasma

Di Gao, Roger T. Howe, and Roya Maboudian

Appl. Phys. Lett. 82, 1742 (2003); http://dx.doi.org/10.1063/1.1560561 (3 pages) | Cited 14 times

Online Publication Date: 10 March 2003

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We report a highly selective reactive ion etching process for 3C-SiC films using HBr-based chemistry in a commercial transformer coupled plasma (TCP) etcher. SiO2 and Si3N4 are employed as etch masks. Etch rates for SiC, SiO2, and Si3N4 are measured as functions of chamber pressure and TCP source power. Etch rate ratios of 20:1 for SiC/SiO2 and 22:1 for SiC/Si3N4 are achieved. In addition, a SiC micromechanical resonator is fabricated to demonstrate integration of the etching process into conventional microfabrication technologies. © 2003 American Institute of Physics.
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81.65.Cf Surface cleaning, etching, patterning
52.77.Bn Etching and cleaning
81.05.Hd Other semiconductors
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
68.55.-a Thin film structure and morphology

Ni-seeding effects on the properties of polycrystalline silicon–germanium grown at low temperature

Jianjun Zhang, Kousaku Shimizu, and Junichi Hanna

Appl. Phys. Lett. 82, 1745 (2003); http://dx.doi.org/10.1063/1.1561574 (3 pages) | Cited 1 time

Online Publication Date: 10 March 2003

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We have investigated the Ni-seeding effects on the low-temperature growth of the polycrystalline silicon–germanium (poly-SixGe1−x) films by reactive thermal chemical vapor deposition with Si2H6 and GeF4. Very thin Ni films (<2 nm) were deposited on the glass substrates by electron beam evaporation in prior to poly-SixGe1−x deposition. The crystallinity and electrical performance of the poly-SixGe1−x films were characterized. p-channel bottom-gate thin-film transistors (TFTs) were also fabricated with these films to evaluate the effect of Ni seeding on device performance. We found that a certain amount of Ni, i.e., less than 0.5 nm, impacts upon the grain size and crystallinity without additional degradation of electrical properties due to the incorporation of Ni in the film. A 0.2 nm equivalent thickness of Ni gives the best crystallinity and the largest grain size (135 nm) and results in the highest mobility (31 cm2/V s) in p-channel TFTs fabricated on SiO2/Si substrates. © 2003 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.-a Thin film structure and morphology
73.61.Le Other inorganic semiconductors
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
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Point-dipole response from a magnetic force microscopy tip with a synthetic antiferromagnetic coating

Yihong Wu, Yatao Shen, Zhiyong Liu, Kebin Li, and Jinjun Qiu

Appl. Phys. Lett. 82, 1748 (2003); http://dx.doi.org/10.1063/1.1560863 (3 pages) | Cited 11 times

Online Publication Date: 10 March 2003

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A point-dipole-like magnetic force microscopy tip has been realized using an antiferromagnetically coupled synthetic structure consisting of two CoCrPt layers separated by an ultrathin Ru layer. This is made possible through magnetizing one of the CoCrPt layers in either upward or downward direction along the tip axis and the other in the opposite direction through antiferromagnetic coupling. The new tip was found to have a superior resolution and a point-dipole-like magnetic response when being used to image magnetic patterns recorded on longitudinal media. © 2003 American Institute of Physics.
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68.37.Rt Magnetic force microscopy (MFM)
75.70.Cn Magnetic properties of interfaces (multilayers, superlattices, heterostructures)
75.25.-j Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.)
75.50.Ss Magnetic recording materials
75.50.Cc Other ferromagnetic metals and alloys
75.50.Ee Antiferromagnetics

Structure and magnetic properties of high coercive NdFeB films with a perpendicular anisotropy

L. K. E. B. Serrona, A. Sugimura, N. Adachi, T. Okuda, H. Ohsato, I. Sakamoto, A. Nakanishi, M. Motokawa, D. H. Ping, and K. Hono

Appl. Phys. Lett. 82, 1751 (2003); http://dx.doi.org/10.1063/1.1561576 (3 pages) | Cited 25 times

Online Publication Date: 10 March 2003

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Relatively good hard magnetic properties obtained from Nd2Fe14B films prepared by the rf sputtering technique were investigated in terms of the microstructural development. Although as-deposited films on Mo substrates deposited at substrate temperatures (Ts) of 365 °C were amorphous with the dispersion of nanocrystalline NdO particles, columnar grains of Nd2Fe14B phase with the c-axis perpendicular to the film plane developed after annealing at 650 °C at an optimized heating rate. Nd2Fe14B grain size was about 400 nm in average and NdO particles of about 10 nm were dispersed within the grains and along the grain boundaries. These films exhibited good perpendicular hard magnetic properties of iHc = 1356 kA/m and (BH)MAX ∼ 216 kJ/m3. © 2003 American Institute of Physics.
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75.50.Ww Permanent magnets
75.70.Ak Magnetic properties of monolayers and thin films
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
75.30.Gw Magnetic anisotropy
81.15.Cd Deposition by sputtering
75.50.Bb Fe and its alloys
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Rs Electrical and magnetic properties related to treatment conditions
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
61.72.Mm Grain and twin boundaries

Microstructure and high critical current of powder-in-tube MgB2

A. Serquis, L. Civale, D. L. Hammon, J. Y. Coulter, X. Z. Liao, Y. T. Zhu, D. E. Peterson, and F. M. Mueller

Appl. Phys. Lett. 82, 1754 (2003); http://dx.doi.org/10.1063/1.1561572 (3 pages) | Cited 31 times

Online Publication Date: 10 March 2003

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We report dc transport and magnetization measurements of the critical current density, Jc, and microstructural analyses of MgB2 wires fabricated by the powder-in-tube method (PIT) using commercial MgB2 powder with 5 at. % Mg powder added as an additional source of magnesium and stainless steel as a sheath material. We identify a weak-link behavior in the as-drawn wire associated with the presence of microcracks. By appropriate heat treatments, we can increase Jc by more than one order of magnitude due to a recrystallization process promoted by the excess Mg, which results in the elimination of most of our microcracks. In contrast, inappropriate annealing conditions result in a deterioration of connectivity due to an inhomogeneous loss of Mg. Grain size and porosity play only a secondary role in determining Jc in PIT MgB2. © 2003 American Institute of Physics.
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74.70.Ad Metals; alloys and binary compounds (including A15, MgB2, etc.)
74.25.Sv Critical currents
74.25.Ha Magnetic properties including vortex structures and related phenomena
81.20.Ev Powder processing: powder metallurgy, compaction, sintering, mechanical alloying, and granulation
81.40.Ef Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization
81.40.Rs Electrical and magnetic properties related to treatment conditions
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High-performance TaN/HfSiON/Si metal-oxide-semiconductor structures prepared by NH3 post-deposition anneal

Mohammad Shahariar Akbar, S. Gopalan, H.-J. Cho, K. Onishi, R. Choi, R. Nieh, C. S. Kang, Y. H. Kim, J. Han, S. Krishnan, and Jack C. Lee

Appl. Phys. Lett. 82, 1757 (2003); http://dx.doi.org/10.1063/1.1544062 (3 pages) | Cited 21 times

Online Publication Date: 10 March 2003

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Electrical and chemical characteristics of metal-oxide semiconductor field-effect transistors (MOSFETs) prepared by low-thermal-budget (∼600 °C) NH3 post-deposition annealing of HfSiON gate dielectric have been investigated. Compared to control Hf-silicate, HfSiON showed excellent thickness scalability, low leakage current density (J), and superior thermal stability. With proper annealing-time optimization, effective oxide thickness as low as 9.2 Å with J<100 mA/cm2 at gate voltage Vg = −1.5 V has been achieved. C–V hysteresis of HfSiON MOSFET was found to be small (<20 mV). Unlike NH3 surface nitridation (NH3 pre-treatment prior to Hf-silicate deposition), no degradation in Gm (transconductance), Id–Vg (drain current–gate voltage), or Id–Vd (drain current–drain voltage) characteristics has been observed. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
77.55.-g Dielectric thin films
68.60.Dv Thermal stability; thermal effects
61.72.Cc Kinetics of defect formation and annealing
73.61.Ng Insulators

Electromechanical properties of Nd-doped Bi4Ti3O12 films: A candidate for lead-free thin-film piezoelectrics

Hiroshi Maiwa, Naoya Iizawa, Daichi Togawa, Takashi Hayashi, Wataru Sakamoto, Mio Yamada, and Shin-ichi Hirano

Appl. Phys. Lett. 82, 1760 (2003); http://dx.doi.org/10.1063/1.1560864 (3 pages) | Cited 84 times

Online Publication Date: 10 March 2003

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Neodymium-doped Bi4Ti3O12 (BNT) films are evaluated for use as lead-free thin-film piezoelectrics in microelectromechanical systems. Bi4Ti3O12, Bi3.25La0.75Ti3O12, and Bi3.25Nd0.75Ti3O12 films were fabricated by chemical solution deposition on Pt/TiOx/SiO2/Si substrates. Nd substitution promoted random orientation with low (00l) diffraction peaks. The 1-μm-thick Bi3.25Nd0.75Ti3O12 film annealed at 750 °C exhibited a remanent polarization of 26 μC/cm2. Typical butterfly field-induced strain loops were obtained in the BNT film capacitors. The electrically induced strain is 8.4×10−4 under the bipolar driving field of 220 kV/cm. These results show that BNT is a promising candidate for use in lead-free thin-film piezoelectrics. © 2003 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
77.65.Ly Strain-induced piezoelectric fields
77.22.Ej Polarization and depolarization
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.22.Ch Permittivity (dielectric function)
77.80.Dj Domain structure; hysteresis
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
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Polarized incandescent light emission from carbon nanotubes

Peng Li, Kaili Jiang, Ming Liu, Qunqing Li, Shoushan Fan, and Jialin Sun

Appl. Phys. Lett. 82, 1763 (2003); http://dx.doi.org/10.1063/1.1558900 (3 pages) | Cited 31 times

Online Publication Date: 10 March 2003

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Polarized light emission from multiwalled carbon nanotube (MWNT) bundles due to current heating is observed. The spectra of the emitted light fit well with the blackbody radiation distribution. And the emitted light is partially polarized with a degree of 0.33 along the axis of MWNT bundle, which is qualitatively explained in terms of one-dimensional structure of carbon nanotubes (CNTs). Negative temperature-dependent resistance is also observed, which is different from normal metal filaments. The MWNT bundles are very stable at high temperature in vacuum during light emitting, indicating that CNTs can be a good candidate as polarized incandescent light sources. © 2003 American Institute of Physics.
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78.67.Ch Nanotubes
61.46.-w Structure of nanoscale materials
73.63.Fg Nanotubes

Highly anisotropic morphologies of GaAs(331) surfaces

V. R. Yazdanpanah, Z. M. Wang, and G. J. Salamo

Appl. Phys. Lett. 82, 1766 (2003); http://dx.doi.org/10.1063/1.1561571 (3 pages) | Cited 18 times

Online Publication Date: 10 March 2003

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The surface morphology of the GaAs(331) surface was investigated by in situ reflection high-energy electron diffraction and scanning tunneling microscopy. It was found, that GaAs(331) A and B surfaces are both faceted on a nanometer scale, containing (110) and (111) facets which are atomically resolved in real space. The resulting highly anisotropic ridge-like surfaces can prove useful in the fabrication of quantum wire structures. © 2003 American Institute of Physics.
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68.47.Fg Semiconductor surfaces
68.35.B- Structure of clean surfaces (and surface reconstruction)
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
61.05.jh Low-energy electron diffraction (LEED) and reflection high-energy electron diffraction (RHEED)
68.65.La Quantum wires (patterned in quantum wells)

Spontaneous growth and luminescence of zinc sulfide nanobelts

Ying-Chun Zhu, Yoshio Bando, and Dong-Feng Xue

Appl. Phys. Lett. 82, 1769 (2003); http://dx.doi.org/10.1063/1.1562339 (3 pages) | Cited 78 times

Online Publication Date: 10 March 2003

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ZnS nanobelts have been synthesized by a simple thermal evaporation method in a N2 atmosphere containing a small amount of CO and H2 gases. The synthesized ZnS nanobelts have a width in the range of 40 to 120 nm, a thickness of 20 nm, and a length of several micrometers. The nanobelts are single crystals with a hexagonal wurtzite structure growing along the [001] direction. A vapor–solid process is proposed for the formation of such nanobelts. The as-prepared nanobelts shows two emission bands, around 450 and 600 nm. © 2003 American Institute of Physics.
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81.07.Bc Nanocrystalline materials
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
78.55.Et II-VI semiconductors
61.46.-w Structure of nanoscale materials
81.10.Bk Growth from vapor

Ordering self-assembled islands without substrate patterning

G. Capellini, M. De Seta, C. Spinella, and F. Evangelisti

Appl. Phys. Lett. 82, 1772 (2003); http://dx.doi.org/10.1063/1.1561163 (3 pages) | Cited 27 times

Online Publication Date: 10 March 2003

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The self-patterning of the strain field that arises in the growth of stacked multilayers of heteroepitaxial islands, together with the capability of tuning the island size by acting on the deposition temperature, are here exploited to obtain self-organization, resulting in well-ordered clusters composed of regularly disposed, nanosized islands. Our results show that the island spatial distribution can be tuned from a random one to a well-ordered square lattice of island clusters, and that the number of islands inside each cluster can be selected. Moreover, due to the dipole repulsive interaction between adjacent islands, the islands themselves arrange in an ordered fashion inside a single cluster along the same [010]-[100] crystalline directions of the long-range cluster ordering. © 2003 American Institute of Physics.
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81.16.Dn Self-assembly
81.05.Cy Elemental semiconductors
68.55.A- Nucleation and growth
68.43.Hn Structure of assemblies of adsorbates (two- and three-dimensional clustering)
68.47.Fg Semiconductor surfaces
68.55.-a Thin film structure and morphology
68.37.Ps Atomic force microscopy (AFM)
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Magnetotransport of p-type GaMnN assisted by highly conductive precipitates

K. H. Kim, K. J. Lee, D. J. Kim, H. J. Kim, Y. E. Ihm, D. Djayaprawira, M. Takahashi, C. S. Kim, C. G. Kim, and S. H. Yoo

Appl. Phys. Lett. 82, 1775 (2003); http://dx.doi.org/10.1063/1.1561580 (3 pages) | Cited 55 times

Online Publication Date: 10 March 2003

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GaMnN growth on GaAs (100) using a GaN single precursor via molecular beam epitaxy was undertaken. The grown layers revealed p-type conduction. It is confirmed that p-GaMnN reveals room temperature ferromagnetism with hysteresis loop having a coercivity of ∼ 100 Oe. The segregated phase showing a transition temperature of ∼ 200 K is assigned to Mn3GaN, and which enhances the conductivity of the surrounding GaMnN region. As a consequence, the GaMnN layer with segregation revealed an anomalous Hall effect at room temperature proving magnetotransport in GaMnN phase. The enhanced conductivity of GaMnN by the highly conductive second phase also revealed the importance of the role of the free carriers in the carrier-mediated ferromagnetism. © 2003 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.70.Ak Magnetic properties of monolayers and thin films
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
64.75.-g Phase equilibria
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy

Fabrication of thiol-capped Pd nanoparticles: An electrochemical method

P. Zhang and T. K. Sham

Appl. Phys. Lett. 82, 1778 (2003); http://dx.doi.org/10.1063/1.1562334 (3 pages) | Cited 8 times

Online Publication Date: 10 March 2003

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A simple electrochemical method is developed to prepare thiol-capped Pd nanoparticles on a Si (100) surface by reducing Pd2+ in solution in the presence of thiol molecules. The structure, bonding, and electronic properties of the electrodeposited Pd nanoparticles (NPs), together with a series of Pd model systems, were studied by electron microscope and x-ray absorption spectroscopy at the S K-edge and the Pd L3,2-edge. The thiol-capped electrodeposits are found to be metallic Pd particles of a few nanometers, with local structures and electronic behavior considerably different from the non-thiol-capped electrodeposits, but rather comparable to colloidal thiol-capped NPs. © 2003 American Institute of Physics.
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81.07.Wx Nanopowders
81.16.Be Chemical synthesis methods
81.15.Pq Electrodeposition, electroplating
61.46.-w Structure of nanoscale materials
78.70.Dm X-ray absorption spectra
82.45.Qr Electrodeposition and electrodissolution
68.37.Vj Field emission and field-ion microscopy
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
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Coherent phonon spectroscopy of GaP Schottky diode

Y.-M. Chang

Appl. Phys. Lett. 82, 1781 (2003); http://dx.doi.org/10.1063/1.1560874 (3 pages) | Cited 7 times

Online Publication Date: 10 March 2003

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Coherent longitudinal optical and acoustic phonons in GaP Schottky diode are impulsively generated and detected with time-resolved second-harmonic generation. A coherent longitudinal optical (LO) phonon is launched in the near-surface depletion region of GaP. The dephasing time of this coherent LO phonon is ∼10 ps and mainly due to the anharmonic decay into two zone-edge half-energy longitudinal acoustic (LA) phonons. Simultaneously, a coherent LA wave packet is created in the metal–semiconductor interface via transient thermal absorption in the metal thin layer. This acoustic wave packet propagates into the bulk with the sound velocity ∼ 5.8×105 cm/s of a GaP LA phonon. © 2003 American Institute of Physics.
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63.20.D- Phonon states and bands, normal modes, and phonon dispersion
85.30.Kk Junction diodes
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation
78.47.-p Spectroscopy of solid state dynamics
63.20.Ry Anharmonic lattice modes

Efficient CsF/Yb/Ag cathodes for organic light-emitting devices

M. Y. Chan, S. L. Lai, M. K. Fung, S. W. Tong, C. S. Lee, and S. T. Lee

Appl. Phys. Lett. 82, 1784 (2003); http://dx.doi.org/10.1063/1.1561579 (3 pages) | Cited 39 times

Online Publication Date: 10 March 2003

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A high-performance cathode consisting of an ultrathin CsF layer and a rare-earth ytterbium (Yb) metal is reported for application in organic electroluminescent devices. Standard tris-(8-hydroxyquinoline) aluminum/α-napthylphenylbiphenyl diamine devices with this bilayer cathode showed dramatically reduced operating voltage and a low turn-on voltage of 2.42 V as compared to 3.75 and 2.95 V in devices using, respectively, the Mg:Ag and single-layer Yb cathodes. At a current density of 200 mA/cm2, devices with the CsF/Yb cathode exhibited high luminance efficiency of 3.45 cd/A and power efficiency of 1.27 lm/W. Analysis by x-ray photoemission spectroscopy suggested that the performance improvement is related to the substantial reduction of electron injection barrier at the cathode/organic interface. It was found that upon Yb deposition, CsF dissociates to liberate low work function Cs metal atoms resulting in a cathode with a lower electron injection barrier and thus a better balance of carriers in the device. Thermodynamically, this exothermic chemical reaction is expected to take place independent of the type of substrates and organic medium, indicating that this bilayer cathode system may be applicable in a wide range of organic electronic/optoelectronic devices. © 2003 American Institute of Physics.
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85.60.Jb Light-emitting devices
73.30.+y Surface double layers, Schottky barriers, and work functions
73.50.Dn Low-field transport and mobility; piezoresistance

Large memory window and long charge-retention time in ultranarrow-channel silicon floating-dot memory

Masumi Saitoh, Eiji Nagata, and Toshiro Hiramoto

Appl. Phys. Lett. 82, 1787 (2003); http://dx.doi.org/10.1063/1.1562343 (3 pages) | Cited 29 times

Online Publication Date: 10 March 2003

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We propose and demonstrate an ultranarrow-channel silicon floating-dot memory, in which the channel width is scaled to sub-10 nm. In the fabricated ultranarrow-channel memory, a larger threshold voltage shift has been observed than in the wide-channel memory. From numerical calculations, it turns out that this is caused by bottleneck regions that dominate the conductance of the whole channel in the ultranarrow-channel. Moreover, longer charge-retention time has been also obtained in the fabricated ultranarrow-channel memory. This can be explained by the nonlinear dependence of the threshold voltage shift on the number of electrons in the dots due to the classical bottleneck effect and the increase in the ground state energy of the channel due to the quantum confinement. © 2003 American Institute of Physics.
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85.35.Ds Quantum interference devices
85.30.Tv Field effect devices
73.23.Hk Coulomb blockade; single-electron tunneling
73.63.Kv Quantum dots
73.61.Cw Elemental semiconductors

Low-frequency noise overshoot in ultrathin gate oxide silicon-on-insulator metal–oxide–semiconductor field-effect transistors

A. Mercha, E. Simoen, H. van Meer, and C. Claeys

Appl. Phys. Lett. 82, 1790 (2003); http://dx.doi.org/10.1063/1.1561575 (3 pages) | Cited 14 times

Online Publication Date: 10 March 2003

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A noise overshoot phenomenon occurring in the ohmic regime is described in fully depleted and partially depleted silicon-on-insulator metal–oxide–semiconductor field-effect transistors with 2.5 nm nitrided gate oxide. It is characterized by a peak in the current noise spectral density S1 versus the front gate voltage VGS, whereby the peak amplitude can be several orders of magnitude higher than the background 1/f noise. In addition, it is shown that the corresponding spectrum has a Lorentzian shape. Associated with this noise peak is a second maximum in the device transconductance. It is believed that the mechanism of this excess noise is similar as for the kink-related noise overshoot, found in saturation. However, the origin of this floating-body effect is believed to be related to electron valence-band tunneling through the thin dielectric and occurring for a sufficiently large gate voltage. © 2003 American Institute of Physics.
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85.30.Tv Field effect devices
73.40.Gk Tunneling
72.70.+m Noise processes and phenomena
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Morphology and surface reconstructions of GaN(1math00) surfaces

C. D. Lee, R. M. Feenstra, J. E. Northrup, L. Lymperakis, and J. Neugebauer

Appl. Phys. Lett. 82, 1793 (2003); http://dx.doi.org/10.1063/1.1560558 (3 pages) | Cited 20 times

Online Publication Date: 10 March 2003

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GaN is grown by plasma-assisted molecular-beam epitaxy on ZnO(1math00) substrates. Well-oriented (1math00) GaN surfaces are obtained, and (1math01) oriented facets are also observed. On the GaN(1math00) surfaces under Ga-rich conditions, a surface reconstruction with approximate symmetry of 4×5 is found. A model is proposed in which this reconstruction consists of ⩾2 monolayers of Ga terminating the GaN surface. © 2003 American Institute of Physics.
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68.55.A- Nucleation and growth
68.35.B- Structure of clean surfaces (and surface reconstruction)
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
52.77.Dq Plasma-based ion implantation and deposition
68.47.Fg Semiconductor surfaces
81.05.Ea III-V semiconductors
81.15.Jj Ion and electron beam-assisted deposition; ion plating

Experimental investigation for field-induced interaction force of two spheres

Zhiyong Wang, Zheng Peng, Kunquan Lu, and Weijia Wen

Appl. Phys. Lett. 82, 1796 (2003); http://dx.doi.org/10.1063/1.1560556 (3 pages) | Cited 11 times

Online Publication Date: 10 March 2003

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An apparatus is developed to study the interaction forces between two spheres under an external ac electric field. The interaction forces of a pair of spheres as the function of interspherical spacing, electric field strength, and electric field frequency are measured precisely. The results reveal that much stronger interaction can be obtained for metal spheres and high-dielectric spheres compared with the spheres with a very low dielectric constant, such as glass and polymer. The measured forces increase very steeply as the gap of the spheres decreases, and become much larger than those of available theoretical predictions when the two single-crystalline spheres of SrTiO3 are closely spaced. The frequency dependence of the interaction force also shows an anomalous behavior. Our measurements indicate that a more accurate theoretical calculation should be performed to explain the experimental results. © 2003 American Institute of Physics.
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77.65.-j Piezoelectricity and electromechanical effects
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