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11 Aug 2003

Volume 83, Issue 6, pp. 1063-1275

Issue Cover Spotlight Figure

Appl. Phys. Lett. 83, 1163 (2003); http://dx.doi.org/10.1063/1.1599972 (3 pages)

M. C. Rogge, C. Fühner, U. F. Keyser, R. J. Haug, M. Bichler, G. Abstreiter, and W. Wegscheider
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Specific heat capacity and hemispherical total emissivity of liquid Si measured in electrostatic levitation

Y. S. Sung, H. Takeya, K. Hirata, and K. Togano

Appl. Phys. Lett. 83, 1122 (2003); http://dx.doi.org/10.1063/1.1599623 (3 pages) | Cited 11 times

Online Publication Date: 5 August 2003

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Containerless solidification of Si was carried out via electrostatic levitation. Typical undercooling up to 370 K, which is 0.22 of its melting temperature, was obtained. A t(T) function in a time–temperature profile was analytically determined from radiative cooling curves measured during containerless solidification. With the analytical t(T) function, the ratio of constant pressure specific heat capacity to hemispherical total emissivity cP(T)/εT(T) was estimated. cP(T) and εT(T) were further derived to describe the temperature-dependent cooling behavior of liquid Si during containerless solidification in electrostatic levitation, which can be expressed as cPdrv(T) = 3R+4.8×10−4⋅T+4.157×105⋅T−2−1.002×10−7⋅T2 (J/mol K) and εTdrv(T) = 0.267−5.615×10−5⋅T+9.133×10−9⋅T2, respectively. © 2003 American Institute of Physics.
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65.20.-w Thermal properties of liquids
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
81.05.Cy Elemental semiconductors
64.70.D- Solid-liquid transitions

Recombination-enhanced formation of the metastable boron–oxygen complex in crystalline silicon

Karsten Bothe, Rudolf Hezel, and Jan Schmidt

Appl. Phys. Lett. 83, 1125 (2003); http://dx.doi.org/10.1063/1.1600837 (3 pages) | Cited 17 times

Online Publication Date: 5 August 2003

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The formation process of the boron- and oxygen-related defect complex in crystalline silicon, responsible for the performance degradation of solar cells made on boron-doped Czochralski silicon (Cz–Si), is investigated on Cz–Si solar cells as a function of the applied voltage in the dark at temperatures ranging from 298 to 373 K. We show that the defect formation is not only a consequence of illumination or the application of a forward bias voltage but also occurs under equilibrium conditions at elevated temperatures in the dark. It can be partly suppressed by applying a reverse voltage. Our findings provide clear experimental evidence that a recombination-enhanced mechanism correlated with the total recombination rate is the driving force of the formation of the metastable defect. © 2003 American Institute of Physics.
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61.72.Yx Interaction between different crystal defects; gettering effect
84.60.Jt Photoelectric conversion
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Transport properties of phosphorus-doped ZnO thin films

Y. W. Heo, S. J. Park, K. Ip, S. J. Pearton, and D. P. Norton

Appl. Phys. Lett. 83, 1128 (2003); http://dx.doi.org/10.1063/1.1594835 (3 pages) | Cited 93 times

Online Publication Date: 5 August 2003

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The doping behavior of phosphorus in ZnO thin films grown by pulsed laser deposition is examined. The transport properties of epitaxial ZnO films doped with 1–5 at. % P were characterized via room temperature Hall measurements. As-deposited films doped with phosphorus are highly conductive and n type. The origin of the shallow donor level appears to be either substitution of P on the Zn site or formation of a donor complex. Annealing these phosphorus-doped films significantly reduces the carrier density, transforming the transport from highly conducting to semi-insulating. These results indicate that the phosphorus-related donor defect is relatively unstable, and suggests the formation of a deep level upon annealing. The latter is consistent with phosphorus substitution on the O site yielding a deep level in the gap. © 2003 American Institute of Physics.
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73.61.Ga II-VI semiconductors
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping
72.20.My Galvanomagnetic and other magnetotransport effects
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
71.55.Gs II-VI semiconductors
72.80.Ey III-V and II-VI semiconductors
81.05.Dz II-VI semiconductors
61.72.uj III-V and II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
81.15.Fg Pulsed laser ablation deposition
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.40.Gh Other heat and thermomechanical treatments
61.72.Cc Kinetics of defect formation and annealing
81.40.Rs Electrical and magnetic properties related to treatment conditions

Synthesis of iron-based bulk metallic glasses as nonferromagnetic amorphous steel alloys

V. Ponnambalam, S. Joseph Poon, Gary J. Shiflet, Veerle M. Keppens, R. Taylor, and G. Petculescu

Appl. Phys. Lett. 83, 1131 (2003); http://dx.doi.org/10.1063/1.1599636 (3 pages) | Cited 91 times

Online Publication Date: 5 August 2003

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Iron-based amorphous metals are investigated as nonferromagnetic amorphous steel alloys with magnetic transition temperatures well below ambient temperatures. Rod-shaped amorphous samples with diameters reaching 4 mm are obtained using injection casting. Amorphous steel alloys are designed by considering atomistic factors that enhance the stability of the amorphous phase, coupled with the realization of low-lying liquidus temperatures. The present alloys are found to exhibit superior mechanical strengths. In particular, the elastic moduli are comparable to those reported for super austenitic steels. © 2003 American Institute of Physics.
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81.05.Bx Metals, semimetals, and alloys
75.50.Kj Amorphous and quasicrystalline magnetic materials
62.20.D- Elasticity

Hydrogenation of Zr60Ti2Cu20Al10Ni8 bulk metallic glass

Norbert Mattern and Annett Gebert

Appl. Phys. Lett. 83, 1134 (2003); http://dx.doi.org/10.1063/1.1600836 (2 pages) | Cited 8 times

Online Publication Date: 5 August 2003

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The influence of hydrogen on the short-range order of Zr60Ti2Cu20Al10Ni8 bulk metallic glass has been investigated. Interstitial solution of hydrogen up to a hydrogen-to-metal ratio of H/M = 0.43 was reached in 1 mm thick bulk samples by slow electrochemical charging. Preferred occupation of interstitial sites of polyhedra formed by Zr atoms is observed. The atomic distances of higher coordination shells expand with hydrogen analogously to the macroscopic volume expansion. © 2003 American Institute of Physics.
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61.43.Fs Glasses

Growth of a-plane InN on r-plane sapphire with a GaN buffer by molecular-beam epitaxy

Hai Lu, William J. Schaff, Lester F. Eastman, J. Wu, Wladek Walukiewicz, Volker Cimalla, and Oliver Ambacher

Appl. Phys. Lett. 83, 1136 (2003); http://dx.doi.org/10.1063/1.1599634 (3 pages) | Cited 45 times

Online Publication Date: 5 August 2003

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We report heteroepitaxial growth of InN on r-plane sapphire substrates with an AlN nucleation layer and GaN buffer using plasma-assisted molecular-beam epitaxy. The InN film was identified to be nonpolar (11math0) a-plane which follows the a-plane GaN buffer. Optical absorption and photoluminescence measurements of this material show that InN has a fundamental band gap of about 0.7 eV, which is also seen for growth on c-plane sapphire. The room-temperature Hall mobility of undoped a-plane InN is around 250 cm2/V s with a carrier concentration around 6×1018 cm−3. We also studied the electrical properties of the a-plane InN as a function of film thickness. In contrast to c-plane InN grown on c-plane sapphire, we did not observe apparent improvement of electrical properties of a-plane InN by growing thicker films. © 2003 American Institute of Physics.
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68.55.-a Thin film structure and morphology
78.66.Fd III-V semiconductors
73.61.Ey III-V semiconductors
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
78.55.Cr III-V semiconductors

Defects in m-face GaN films grown by halide vapor phase epitaxy on LiAlO2

R. R. Vanfleet, J. A. Simmons, H. P. Maruska, D. W. Hill, M. M. C. Chou, and B. H. Chai

Appl. Phys. Lett. 83, 1139 (2003); http://dx.doi.org/10.1063/1.1599962 (3 pages) | Cited 9 times

Online Publication Date: 5 August 2003

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Free-standing wafers (50 mm diameter) of GaN were grown by halide vapor phase epitaxy on lattice-matched γ-LiAlO2. We report a transmission electron microscopy study of defects and defect densities in these wafers. The growth direction is [10math0]. Stacking faults in the basal plane are seen when viewing the specimen in the [1math10] direction with an average spacing of less than 100 nm. Convergent beam electron diffraction measurements show no switch in the polarity and thus the faults are proposed to be ABABACAC changes in the stacking. Threading dislocations are found to have a correlated arrangement with a density of 3×108 cm−2 when viewing the [1math10] direction and widely varying (depending upon location) when viewing in the [0001] direction. These dislocations act as “seeds” for postgrowth surface features that directly exhibit the correlated nature of these threading dislocations. © 2003 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Nn Stacking faults and other planar or extended defects
61.72.Lk Linear defects: dislocations, disclinations
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)
68.37.Lp Transmission electron microscopy (TEM)
68.37.Hk Scanning electron microscopy (SEM) (including EBIC)
68.35.B- Structure of clean surfaces (and surface reconstruction)

Electronic structure of Li(Co0.7−xAl0.3)MgxO2 studied by electron energy-loss spectroscopy

G. Chen, C. Li, X. Xu, J. Li, and U. Kolb

Appl. Phys. Lett. 83, 1142 (2003); http://dx.doi.org/10.1063/1.1599969 (3 pages) | Cited 1 time

Online Publication Date: 5 August 2003

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Electronic structure of Li(Co0.7−xAl0.3)MgxO2 (x = 0.01, 0.03, and 0.05) is studied via electron energy-loss spectroscopy. Oxygen K edge and Co L2,3 edge were used to investigate the effect of Mg substitution on both the valence state of Co ion and the density of unoccupied states of O ion. A change in the ratio of the white lines of Co ion, L3/L2, is used to identify the change in the valence state in Co ion, which reveals that Mg substitution gives rise to an increase of the average valence of Co ion. This is a mixed valence state of Co3+ and Co4+ in Mg substitution materials. Relative lowering of the integrated intensity of prepeak in oxygen K edge with the Mg concentration connects with a lower covalency of the Co–O bond, which indicates a significant electron feeding back from Co 3d to O 2p. This makes the oxygen ions closer to the feature of closed shell, which helps electron hopping between Co3+ and Co4+ based on the double-exchange process. © 2003 American Institute of Physics.
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71.20.Ps Other inorganic compounds
79.20.Uv Electron energy loss spectroscopy
68.49.Jk Electron scattering from surfaces

Dynamic formation of ring-shaped patterns of colloidal particles in microfluidic systems

David S. W. Lim, J. Patrick Shelby, Jason S. Kuo, and Daniel T. Chiu

Appl. Phys. Lett. 83, 1145 (2003); http://dx.doi.org/10.1063/1.1600532 (3 pages) | Cited 9 times

Online Publication Date: 5 August 2003

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This letter reports the formation of patterns of micrometer-sized beads within the steady-state recirculation flow of a microvortex generated in a microfluidic system. The mechanism by which these patterns form relies on a delicate balance between the centrifugal and displacement forces experienced by the recirculating particles with a lift force exerted on the particles near the solid boundary of the microcavity. Our observation was made possible by the small dimensions of the microchannels we used and by the presence of steep velocity gradients unique to microfluidic devices. © 2003 American Institute of Physics.
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47.54.-r Pattern selection; pattern formation
85.85.+j Micro- and nano-electromechanical systems (MEMS/NEMS) and devices
47.55.Kf Particle-laden flows
47.32.C- Vortex dynamics
47.85.Np Fluidics
82.70.Dd Colloids
47.60.-i Flow phenomena in quasi-one-dimensional systems
83.50.Ha Flow in channels

Epitaxial growth and large band-gap bowing of ZnSeO alloy

Y. Nabetani, T. Mukawa, Y. Ito, T. Kato, and T. Matsumoto

Appl. Phys. Lett. 83, 1148 (2003); http://dx.doi.org/10.1063/1.1600510 (3 pages) | Cited 19 times

Online Publication Date: 5 August 2003

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ZnSeO alloy was grown by molecular-beam epitaxy up to 1.3% O composition on GaAs substrate using rf plasma. The crystal structure of epitaxial ZnSeO alloy was zinc-blende. O composition was estimated by a strain-free lattice constant. No phase separation was observed by in situ reflection high-energy electron diffraction and x-ray diffraction. Photoluminescence intensity was larger than that of ZnSe. The peak energy shifted toward lower energies with increasing O composition. The band-gap energy determined by photoluminescence excitation spectra decreased with increasing O composition. A bowing parameter as high as 8 eV was obtained. This large band-gap bowing widens the controllable energy-gap range of II-VI semiconductor. © 2003 American Institute of Physics.
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81.05.Dz II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
78.66.Hf II-VI semiconductors
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
78.55.Et II-VI semiconductors
61.66.Fn Inorganic compounds

Quantum mechanical predictions of nonscalar equations of state and nonmonotonic elastic stress-strain relations

Damian C. Swift and Graeme J. Ackland

Appl. Phys. Lett. 83, 1151 (2003); http://dx.doi.org/10.1063/1.1599043 (3 pages) | Cited 5 times

Online Publication Date: 5 August 2003

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In continuum mechanics, the isotropic part of the stress deviator (mean pressure) is routinely assumed to depend on the isotropic part of the strain deviator (compression). This assumption was tested using ab initio quantum mechanical calculations of elastic stress as a function of elastic strain and compression. Except for face-centered-cubic elements, the mean pressure varied significantly with shear strain as well as compression. In general, the shear stress did not increase monotonically with elastic shear strain. These phenomena may be important when comparing experimental data obtained on different time scales, particularly when interpreting dynamic response data from short-pulse laser experiments. © 2003 American Institute of Physics.
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46.05.+b General theory of continuum mechanics of solids
46.35.+z Viscoelasticity, plasticity, viscoplasticity
62.20.F- Deformation and plasticity
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