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30 Jan 2006

Volume 88, Issue 5, Articles (05xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 88, 051101 (2006); http://dx.doi.org/10.1063/1.2168491 (3 pages)

H. Lohmeyer, K. Sebald, C. Kruse, R. Kröger, J. Gutowski, D. Hommel, J. Wiersig, N. Baer, and F. Jahnke
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Lattice parameter and hole density of (Ga,Mn)As on GaAs(311)A

J. Daeubler, M. Glunk, W. Schoch, W. Limmer, and R. Sauer

Appl. Phys. Lett. 88, 051904 (2006); http://dx.doi.org/10.1063/1.2170408 (3 pages) | Cited 10 times

Online Publication Date: 30 January 2006

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We discuss the structural and electrical properties of (Ga,Mn)As layers with Mn concentrations up to 5%, grown on GaAs(311)A substrates by low-temperature molecular-beam epitaxy. High-resolution x-ray diffraction studies reveal a higher concentration of As antisites and a weaker linear increase of the relaxed lattice constant with Mn content in the (311)A layers compared to (100) reference layers. The hole densities and Curie temperatures, determined from magnetotransport measurements, are drastically reduced in the (311)A layers. The findings are explained by an enhanced incorporation of Mn atoms on nonsubstitutional and noninterstitial sites, probably as Mn–Mn or As–Mn complexes, caused by the larger amount of excess As in the (311)A layers.
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81.05.Ea III-V semiconductors
75.50.Pp Magnetic semiconductors
75.50.Dd Nonmetallic ferromagnetic materials
68.55.A- Nucleation and growth
73.61.Ey III-V semiconductors
68.55.-a Thin film structure and morphology

Local structure around Mn atoms in cubic (Ga,Mn)N thin films probed by fluorescence extended x-ray absorption fine structure

Bo He, Xinyi Zhang, Shiqiang Wei, Hiroyuki Oyanagi, Sergei V. Novikov, Kevin W. Edmonds, C. Thomas Foxon, Gui’en Zhou, and Yunbo Jia

Appl. Phys. Lett. 88, 051905 (2006); http://dx.doi.org/10.1063/1.2168228 (3 pages) | Cited 7 times

Online Publication Date: 31 January 2006

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The local structures of Mn atoms incorporated in zinc-blende (Ga,Mn)N thin films have been investigated by fluorescence extended x-ray absorption fine structure analysis (EXAFS). The EXAFS results provide direct evidence for the substitution of the majority of Mn atoms in Ga sites of GaN at 2.5% doping. On the other hand, the simulation result of 10% doped (Ga,Mn)N shows that secondary phases—Mn clusters—are formed. The long-range-order crystal structures of (Ga,Mn)N are also studied by x-ray diffraction. The broadening of rocking curve of 10% doped (Ga,Mn)N is attributed to the existence of mosaic block, which resulted from the earlier mentioned secondary phases. How Mn dopants affect the properties of GaN films is discussed as well.
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68.55.-a Thin film structure and morphology
75.50.Pp Magnetic semiconductors
78.66.Fd III-V semiconductors
78.70.Dm X-ray absorption spectra
78.55.Cr III-V semiconductors
75.50.Dd Nonmetallic ferromagnetic materials

Ba5SiO4Cl6:Eu2+: An intense blue emission phosphor under vacuum ultraviolet and near-ultraviolet excitation

Qinghua Zeng, Hiroaki Tanno, Kiichirou Egoshi, Nobutsugu Tanamachi, and Shuxiu Zhang

Appl. Phys. Lett. 88, 051906 (2006); http://dx.doi.org/10.1063/1.2168492 (3 pages) | Cited 24 times

Online Publication Date: 31 January 2006

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An intense blue emission of Eu2+-doped Ba5SiO4Cl6 under vacuum ultraviolet and near-ultraviolet excitation was observed. The material exhibits an emission peak at 440 nm with relative intensity 50% under 147 nm, 90% under 254 nm, 120% under 366 nm, and 220% under 405 nm excitation as compared with the commercial blue phosphor BaMgAl10O17:Eu2+. It is a very promising candidate as a blue-emitting phosphor for potential applications in display and light-emitting diode devices.
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78.55.Hx Other solid inorganic materials

Gas diffusion barriers on polymers using Al2O3 atomic layer deposition

M. D. Groner, S. M. George, R. S. McLean, and P. F. Carcia

Appl. Phys. Lett. 88, 051907 (2006); http://dx.doi.org/10.1063/1.2168489 (3 pages) | Cited 80 times

Online Publication Date: 31 January 2006

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Thin films of Al2O3 grown by atomic layer deposition (ALD) were investigated as gas diffusion barriers on flexible polyethylene naphthalate and Kapton® polyimide substrates. Al2O3 ALD films with thicknesses of 1–26 nm were grown at 100–175 °C. For Al2O3 ALD films with thicknesses ≥ 5 nm, oxygen transmission rates were below the MOCON instrument test limit of ∼ 5×10−3 cc/m2/day. Applying a more sensitive radioactive tracer method, H2O-vapor transmission rates of ∼ 1×10−3 g/m2/day were measured for single-sided Al2O3 ALD films with thicknesses of 26 nm on the polymers. Ultrathin gas diffusion barriers grown by Al2O3 ALD may enable organic displays and electronics on permeable, flexible polymer substrates.
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66.30.-h Diffusion in solids
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
68.35.Fx Diffusion; interface formation
81.15.-z Methods of deposition of films and coatings; film growth and epitaxy
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)

Comparative studies of CO and H2O interactions with Pd(111) surface: A theoretical study of poisoning

Dominic R. Alfonso

Appl. Phys. Lett. 88, 051908 (2006); http://dx.doi.org/10.1063/1.2170428 (3 pages) | Cited 5 times

Online Publication Date: 31 January 2006

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Detailed density functional theory calculations were carried out to investigate the adsorption and dissociation of CO and H2O on Pd(111). The bonding of CO on the surface is found to be stronger that H2O. This finding does not support the previous suggestion that the stronger poisoning effect displayed by H2O on a Pd membrane, in comparison to CO, is due its higher binding energy. Instead, our results show that dissociation of H2O is a more facile process compared to CO. The dissociation of H2O gives rise to adsorbed O which is a better poison than CO.
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68.43.Mn Adsorption kinetics
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.39.Wj Ion exchange, dialysis, osmosis, electro-osmosis, membrane processes
61.50.Lt Crystal binding; cohesive energy

Quantum oscillations of the luminescence from a modulation-doped GaAs/InGaAs/GaAlAs quantum well

Adam Babiński, M. Potemski, and H. Shtrikman

Appl. Phys. Lett. 88, 051909 (2006); http://dx.doi.org/10.1063/1.2171487 (3 pages)

Online Publication Date: 31 January 2006

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Magnetospectroscopic studies of a modulation-doped GaAs/InGaAs/GaAlAs quantum well (QW) are presented. Oscillations of the photoluminescence (PL) intensity in magnetic field are investigated. Recombination processes giving rise to the PL are identified and their effect on the PL is established. It is shown how measurements of the oscillations can provide information on the density of the quasi-two-dimensional electron gas confined in the QW.
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78.67.De Quantum wells
78.55.Cr III-V semiconductors
73.21.Fg Quantum wells

Variable liquid crystal pretilt angles by nanostructured surfaces

Fion S. Yeung, Jacob Y. Ho, Y. W. Li, F. C. Xie, Ophelia K. Tsui, P. Sheng, and H. S. Kwok

Appl. Phys. Lett. 88, 051910 (2006); http://dx.doi.org/10.1063/1.2171491 (3 pages) | Cited 87 times

Online Publication Date: 31 January 2006

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Variable liquid crystal pretilt angles of any value from 0 to 90° can be obtained by using a nanostructured alignment layer. This layer is robust and reliable. The pretilt angles obtained are stable against high storage and operating temperatures, and have strong anchoring energies.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
61.46.-w Structure of nanoscale materials

Heterogeneity of a Cu47.5Zr47.5Al5 bulk metallic glass

K. B. Kim, J. Das, F. Baier, M. B. Tang, W. H. Wang, and J. Eckert

Appl. Phys. Lett. 88, 051911 (2006); http://dx.doi.org/10.1063/1.2171472 (3 pages) | Cited 71 times

Online Publication Date: 31 January 2006

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Microstructural investigation of an as-cast Cu47.5Zr47.5Al5 bulk metallic glass (BMG) reveals two amorphous phases formed by liquid phase separation. The morphology of the phase separated amorphous regions is spherical with 10–20 nm in size. These areas are homogeneously distributed throughout the sample. Moreover, a macroscopic heterogeneity also occurs along with the nano-scale liquid phase separation. The macroscopic heterogeneity can be distinguished from the different degree of the chemical fluctuations in the sample, and the existence of nano-scale crystals of less than 5 nm in size. Presumably, both the macroscopic heterogeneity and the nano-scale phase separation enhance branching of the shear bands during deformation in the Cu47.5Zr47.5Al5 BMG.
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81.05.Kf Glasses (including metallic glasses)
61.43.Fs Glasses
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
64.75.-g Phase equilibria

Atomistic simulation of amorphization thermokinetics in lanthanum pyrozirconate

Jean-Paul Crocombette, Alain Chartier, and William J. Weber

Appl. Phys. Lett. 88, 051912 (2006); http://dx.doi.org/10.1063/1.2171651 (3 pages) | Cited 6 times

Online Publication Date: 31 January 2006

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The kinetics of amorphization in La2Zr2O7 pyrochlore is investigated using molecular dynamics simulations. Irradiation damage is simulated by continuous accumulation of cation Frenkel pairs at various temperatures. As observed experimentally, La2Zr2O7 first transitions to the fluorite structure, independent of the temperature, and amorphization occurs at low temperatures. A model fit of the simulated dose-temperature curve reproduces experimental results in the literature, with a low temperature amorphization dose D0 = 1.1 displacement per cation and an activation energy Eact = 0.036 eV. Present simulations indicate that point defect recombination can control the temperature dependence of amorphization driven by point defect accumulation.
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61.43.Bn Structural modeling: serial-addition models, computer simulation
61.72.J- Point defects and defect clusters

Elastic stability and electronic structure of pyrite type PtN2: A hard semiconductor

R. Yu, Q. Zhan, and X. F. Zhang

Appl. Phys. Lett. 88, 051913 (2006); http://dx.doi.org/10.1063/1.2168683 (3 pages) | Cited 52 times

Online Publication Date: 31 January 2006

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The elastic properties and electronic structure of PtN2 with the pyrite structure [PtN2(C2)] were studied with first-principles calculations. The crystal structure is demonstrated to be elastically stable with a lower energy than the metastable fluorite structure proposed before. The calculated shear modulus of 214 GPa suggests that PtN2(C2) is harder than some well-known hard materials such as TiN and SiC. The high elastic moduli are attributed to a stacking of corner-shared PtN6 octahedra bonded by strong N-N covalent bonding. In contrast to the metallic fluorite-type phase, PtN2(C2) is semiconducting with an indirect band gap.
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81.05.Hd Other semiconductors
81.40.Jj Elasticity and anelasticity, stress-strain relations
62.20.D- Elasticity
71.20.Nr Semiconductor compounds
71.15.-m Methods of electronic structure calculations
61.66.Fn Inorganic compounds

Light-emitting filaments composed of nanometer-sized carbon hollow capsules

Koji Asaka, Ryoei Kato, Yoshinari Maezono, Ryozo Yoshizaki, Kun’ichi Miyazawa, and Tokushi Kizuka

Appl. Phys. Lett. 88, 051914 (2006); http://dx.doi.org/10.1063/1.2172013 (3 pages) | Cited 12 times

Online Publication Date: 2 February 2006

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Filaments composed of multilayered carbon hollow capsules less than 10 nm in diameter have been synthesized from crystalline whiskers of fullerene C60 of submicrometer in diameter by preliminary heating at 1373 K and successive impression of current. The structural, electrical and optical properties of the filaments were studied by in situ transmission electron microscopy combined with the functions of scanning probe microscopy. We found that the filaments easily emit visible light at a maximum wavelength of 700-730 nm by the application of a few volts.
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85.60.Jb Light-emitting devices
81.07.Bc Nanocrystalline materials
81.05.ub Fullerenes and related materials
81.40.Gh Other heat and thermomechanical treatments
68.37.Lp Transmission electron microscopy (TEM)

Study of elastic constant ratios in nematic liquid crystals

J. F. Strömer, E. P. Raynes, and C. V. Brown

Appl. Phys. Lett. 88, 051915 (2006); http://dx.doi.org/10.1063/1.2162694 (3 pages) | Cited 12 times

Online Publication Date: 2 February 2006

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A technique has recently been proposed for determining the elastic constant ratio K22/K11 in nematic liquid crystals [ E. P. Raynes, C. V. Brown, and J. F. Strömer, Appl. Phys. Lett. 82, 13 (2003) ]. This technique has been applied to five nematic materials that cover a range of K33/K11 elastic constant ratio values. An unusually high value of K22/K11 is found in one material. High values of the ratio K22/K11 tended to occur in materials that also have high values of the ratio K33/K11. The results are validated with independent measurements of K22 from cholesteric helix unwinding.
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61.30.-v Liquid crystals
42.70.Df Liquid crystals
62.10.+s Mechanical properties of liquids

Thermal donor formation processes in silicon and the catalytic role of hydrogen

L. Tsetseris, Sanwu Wang, and S. T. Pantelides

Appl. Phys. Lett. 88, 051916 (2006); http://dx.doi.org/10.1063/1.2168680 (3 pages) | Cited 13 times

Online Publication Date: 2 February 2006

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We report the results of first-principles calculations on the interactions of hydrogen with oxygen clusters in silicon and other processes that relate to the formation of thermal donors (TD). We find that pre-existing small O clusters transform to thermal donors with a low activation energy of 1.15 eV. Clusters formed due to O–H codiffusion bind H strongly in TD precursor configurations and H release requires high temperatures to overcome a 1.9 eV barrier, a value in agreement with experiments on the dissociation of TD-H complexes. Repeated trapping and release from such clusters establish a catalytic role for H in TD formation.
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61.72.Yx Interaction between different crystal defects; gettering effect
82.65.+r Surface and interface chemistry; heterogeneous catalysis at surfaces
66.30.J- Diffusion of impurities

Nanometer-scale strain measurements in semiconductors: An innovative approach using the plasmon peak in electron energy loss spectra

A. M. Sanchez, R. Beanland, A. J. Papworth, P. J. Goodhew, and M. H. Gass

Appl. Phys. Lett. 88, 051917 (2006); http://dx.doi.org/10.1063/1.2169904 (3 pages) | Cited 3 times

Online Publication Date: 2 February 2006

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We present an innovative technique for quantitative measurement of strain in semiconductor materials with high spatial resolution. The plasmon loss peak, seen in electron energy-loss spectra, has been considered following the Drude-Lorentz model, and we find that plasmon energy is extremely sensitive to lattice parameter. We have tested this model using a heterostructure of In0.2Ga0.8As and AlAs layers in GaAs. The experimental data are in excellent agreement with the model. We estimate that strains smaller than 0.036% can be detected, corresponding to a change of x = 0.005 in InxGa1−xAs, at a spatial resolution better than 2.8 nm.
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68.60.Bs Mechanical and acoustical properties
79.20.Uv Electron energy loss spectroscopy
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons
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Manipulation of g-factor in diluted magnetic semiconductors quantum dots: Optical switching control

V. López-Richard, S. J. Prado, G. E. Marques, C. Trallero-Giner, and A. M. Alcalde

Appl. Phys. Lett. 88, 052101 (2006); http://dx.doi.org/10.1063/1.2168499 (3 pages) | Cited 5 times

Online Publication Date: 30 January 2006

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We propose an optical switch based on a spin tuning mechanism in diluted-magnetic semiconductor quantum dots. At certain critical magnetic field, Bc, the Zeeman spin-splitting energies can cross leading to a zero value of the effective electron g-factor and the Fermi level undergoes a spin-flip transition. Magneto-optical switching is obtained for magnetic fields below and above Bc. Correlations between Bc, confinement shapes, dot sizes, and host material compositions have been established within well-defined temperature and magnetic impurity composition ranges. The generality of the presented theoretical framework allows for its application to magnetic field controlled quantum dot arrays, and spin-injection among others.
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42.65.Pc Optical bistability, multistability, and switching, including local field effects
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
78.20.Ls Magneto-optical effects
72.25.Dc Spin polarized transport in semiconductors
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
75.50.Pp Magnetic semiconductors

A (4×2) reconstruction of CuInSe2 (001) studied by low-energy electron diffraction and soft x-ray photoemission spectroscopy

Th. Deniozou, N. Esser, Th. Schulmeyer, and R. Hunger

Appl. Phys. Lett. 88, 052102 (2006); http://dx.doi.org/10.1063/1.2162677 (3 pages) | Cited 1 time

Online Publication Date: 30 January 2006

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Clean and flat (001) surfaces of CuInSe2/GaAs grown by molecular-beam epitaxy could be prepared by the combination of a Se capping and decapping process and subsequent Ar+ ion sputtering and annealing. The formation of a (4×2) reconstruction was observed with low-energy electron diffraction. Soft x-ray photoemission spectroscopy was performed on the prepared surfaces and revealed surface core-level binding energy shifts in the Cu 2p3/2, Se 3d, and In 4d levels which are associated with surface atoms. The structure model of a combined metal adatom-Se dimer structure is proposed to refer to the (4×2) reconstruction.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
68.47.Fg Semiconductor surfaces
79.60.Bm Clean metal, semiconductor, and insulator surfaces
61.72.Cc Kinetics of defect formation and annealing
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors

Wide-band gap oxide alloy: BeZnO

Y. R. Ryu, T. S. Lee, J. A. Lubguban, A. B. Corman, H. W. White, J. H. Leem, M. S. Han, Y. S. Park, C. J. Youn, and W. J. Kim

Appl. Phys. Lett. 88, 052103 (2006); http://dx.doi.org/10.1063/1.2168040 (2 pages) | Cited 58 times

Online Publication Date: 31 January 2006

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A wide-band gap oxide alloy, BeZnO, is proposed and studied in this letter. The BeZnO films were deposited on sapphire substrates by our hybrid beam deposition growth method. The value of the energy band gap of BeZnO can be efficiently engineered to vary from the ZnO band gap (3.4 eV) to that of BeO (10.6 eV). BeZnO can be used for fabricating films and heterostructures of ZnO-based electronic and photonic devices and for other applications. Changes in the measured energy band gap and lattice constant values with Be content are described for BeZnO alloys.
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81.05.Dz II-VI semiconductors
71.20.Nr Semiconductor compounds
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology

Bimolecular recombination in polymer/fullerene bulk heterojunction solar cells

L. J. A. Koster, V. D. Mihailetchi, and P. W. M. Blom

Appl. Phys. Lett. 88, 052104 (2006); http://dx.doi.org/10.1063/1.2170424 (3 pages) | Cited 131 times

Online Publication Date: 31 January 2006

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Bimolecular recombination in organic semiconductors is known to follow the Langevin expression, i.e., the rate of recombination depends on the sum of the mobilities of both carriers. We show that this does not hold for polymer/fullerene bulk heterojunction solar cells. The voltage dependence of the photocurrent reveals that the recombination rate in these blends is determined by the slowest charge carrier only, as a consequence of the confinement of both types of carriers to two different phases.
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84.60.Jt Photoelectric conversion
85.60.-q Optoelectronic devices
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.50.Pz Photoconduction and photovoltaic effects

Extraordinary optoconductance in metal-semiconductor hybrid structures

K. A. Wieland, Yun Wang, L. R. Ram-Mohan, S. A. Solin, and A. M. Girgis

Appl. Phys. Lett. 88, 052105 (2006); http://dx.doi.org/10.1063/1.2170429 (3 pages) | Cited 7 times

Online Publication Date: 31 January 2006

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We provide the first demonstration of extraordinary optoconductance (EOC) in macroscopic metal-semiconductor hybrid structures fabricated from GaAs and In and the first example of an extraordinary transport (EXX) effect that is based on a perturbation of the relative bulk conductances of the constituents. Four-lead van der Pauw plate structures show a gain of order 500% in the optocondutance when shunted by In relative to unshunted devices. The dependence of the optocondutance on the position of a focussed Ar laser beam has been measured and is in agreement with a Gaussian broadened point charge model that accounts for the Dember effect. We also account quantitatively for the temperature dependence of the EOC.
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72.40.+w Photoconduction and photovoltaic effects

p-type ZnO films with solid-source phosphorus doping by molecular-beam epitaxy

F. X. Xiu, Z. Yang, L. J. Mandalapu, J. L. Liu, and W. P. Beyermann

Appl. Phys. Lett. 88, 052106 (2006); http://dx.doi.org/10.1063/1.2170406 (3 pages) | Cited 64 times

Online Publication Date: 31 January 2006

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Phosphorus-doped p-type ZnO films were grown on r-plane sapphire substrates using molecular-beam epitaxy with a solid-source GaP effusion cell. X-ray diffraction spectra and reflection high-energy electron diffraction patterns indicate that high-quality single crystalline (11math0) ZnO films were obtained. Hall and resistivity measurements show that the phosphorus-doped ZnO films have high hole concentrations and low resistivities at room temperature. Photoluminescence (PL) measurements at 8 K reveal a dominant acceptor-bound exciton emission with an energy of 3.317 eV. The acceptor energy level of the phosphorus dopant is estimated to be 0.18 eV above the valence band from PL spectra, which is also consistent with the temperature dependence of PL measurements.
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81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
68.55.A- Nucleation and growth
68.55.-a Thin film structure and morphology
61.72.uj III-V and II-VI semiconductors
73.61.Ga II-VI semiconductors

Two-dimensional electron gas in InGaAs/InAlAs quantum wells

E. Diez, Y. P. Chen, S. Avesque, M. Hilke, E. Peled, D. Shahar, J. M. Cerveró, D. L. Sivco, and A. Y. Cho

Appl. Phys. Lett. 88, 052107 (2006); http://dx.doi.org/10.1063/1.2168666 (3 pages) | Cited 5 times

Online Publication Date: 31 January 2006

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We designed and performed low-temperature dc transport characterization studies on two-dimensional electron gases confined in lattice-matched In0.53Ga0.47As/In0.52Al0.48As quantum wells grown by molecular beam epitaxy on InP substrates. The nearly constant mobility for samples with the setback distance larger than 50 nm and the similarity between the quantum and transport lifetime suggest that the main scattering mechanism is due to short range scattering, such as alloy scattering, with a scattering rate of 2.2 ps−1. We also obtain the Fermi level at the In0.53Ga0.47As/In0.52Al0.48As surface to be 0.36 eV above the conduction band, when fitting our experimental densities with a Poisson-Schrödinger model.
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73.63.Hs Quantum wells
73.21.Fg Quantum wells

Strain-induced changes in the gate tunneling currents in p-channel metal–oxide–semiconductor field-effect transistors

X. Yang, J. Lim, G. Sun, K. Wu, T. Nishida, and S. E. Thompson

Appl. Phys. Lett. 88, 052108 (2006); http://dx.doi.org/10.1063/1.2168671 (3 pages) | Cited 18 times

Online Publication Date: 31 January 2006

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Changes in the direct gate tunneling current are measured for strained p-channel metal–oxide–semiconductor field-effect transistors (MOSFETs) on (100) wafers for uniaxial and biaxial stress. Decreases/increases in the gate tunneling current for various stresses primarily result from repopulation into a subband with a larger/smaller out-of-plane effective mass. Strain-induced changes in the valence band offset between Si and SiO2 are also important but play a secondary role. Hole tunneling current is found to decrease for biaxial and uniaxial compressive stress and increase for biaxial tensile stress. The hole tunneling data is modeled using k∙p self-consistent solution to Poisson and Schrödinger’s equation, and a transfer matrix method.
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85.30.Tv Field effect devices
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity

Phase formation and work function tuning in fully silicided Co–Ni metal gates with variable Co:Ni ratios

J. Liu and D. L. Kwong

Appl. Phys. Lett. 88, 052109 (2006); http://dx.doi.org/10.1063/1.2167799 (3 pages) | Cited 3 times

Online Publication Date: 31 January 2006

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Dual work function metal gates fabricated by full silicidation of a Co–Ni bilayer with different Co:Ni ratios were investigated by both physical and electrical measurements. Full silicidation, sheet resistance and phase confirmation of CoxNi1−xSi2 were studied by physical characterizations. Complementary metal-oxide-semiconductor work functions were extrapolated by electrical characterization and correlated with dopant accumulation at the gate/oxide interface. The quality of underlying oxide was measured by gate leakage current density and found to be impacted by the Co:Ni ratio in CoxNi1−xSi2.
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85.30.Tv Field effect devices
73.30.+y Surface double layers, Schottky barriers, and work functions

Lifetime-limiting defects in n− 4H-SiC epilayers

P. B. Klein, B. V. Shanabrook, S. W. Huh, A. Y. Polyakov, M. Skowronski, J. J. Sumakeris, and M. J. O’Loughlin

Appl. Phys. Lett. 88, 052110 (2006); http://dx.doi.org/10.1063/1.2170144 (3 pages) | Cited 35 times

Online Publication Date: 1 February 2006

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Low-injection minority carrier lifetimes (MCLs) and deep trap spectra have been investigated in n− 4H-SiC epilayers of varying layer thicknesses, in order to enable the separation of bulk lifetimes from surface recombination effects. From the linear dependence of the inverse bulk MCL on the concentration of Z1/Z2 defects and from the behavior of the deep trap spectra in 4H-SiC p-i-n diodes under forward bias, we conclude that it is Z1/Z2 alone that controls the MCL in this material.
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72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
71.55.Ht Other nonmetals
78.40.Fy Semiconductors
78.66.Li Other semiconductors

Current flow and energy dissipation in low-dimensional semiconductor superlattices

D. Fowler, A. Patané, A. Ignatov, L. Eaves, M. Henini, N. Mori, D. K. Maude, and R. Airey

Appl. Phys. Lett. 88, 052111 (2006); http://dx.doi.org/10.1063/1.2171800 (3 pages) | Cited 5 times

Online Publication Date: 3 February 2006

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By applying high magnetic and electric fields to a semiconductor superlattice (SL) we create quasi-one-dimensional or quasi-zero-dimensional electronic states. This reduced dimensionality restricts the range of inelastic scattering processes available to the conduction electrons, leading to an increase of the inelastic scattering time and a corresponding decrease of the electrical conductance. Our study reveals the fundamental link between current flow and energy dissipation in low-dimensional conductors, which is relevant to the exploitation of artificial nanowires and quantum dot SLs for novel applications, including recently proposed thermoelectric devices.
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73.63.-b Electronic transport in nanoscale materials and structures
73.21.Cd Superlattices
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