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25 May 2009

Volume 94, Issue 21, Articles (21xxxx)

Issue Cover Spotlight Figure

Appl. Phys. Lett. 94, 213101 (2009); http://dx.doi.org/10.1063/1.3139865 (3 pages)

Chul-Ho Lee, Jinkyoung Yoo, Young Joon Hong, Jeonghui Cho, Yong-Jin Kim, Seong-Ran Jeon, Jong Hyeob Baek, and Gyu-Chul Yi
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The impact of intermediate reflectors on light absorption in tandem solar cells with randomly textured surfaces

C. Rockstuhl, F. Lederer, K. Bittkau, T. Beckers, and R. Carius

Appl. Phys. Lett. 94, 211101 (2009); http://dx.doi.org/10.1063/1.3142421 (3 pages) | Cited 11 times

Online Publication Date: 26 May 2009

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The impact of dielectric intermediate reflectors on the light absorption in the top cell of an a-Si:H/μc-Si:H tandem solar cell comprising randomly textured surfaces was investigated by rigorous diffraction theory. Despite the strong light scattering, we found Fabry–Pérot oscillations for the absorption with a decreasing modulation for an increasing thickness of the intermediate layer, a larger oscillation period when compared to thin films and a homogenization of the absorption profile. Optimized intermediate reflectors generate an absorption enhancement in the a-Si:H film, which varies between a factor of 2 and more than 3 for wavelengths of strong and weak absorption, respectively.
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84.60.Jt Photoelectric conversion
42.25.Bs Wave propagation, transmission and absorption

Direct measurements of the nonlinear index of refraction of water at 815 and 407 nm using single-shot supercontinuum spectral interferometry

Z. W. Wilkes, S. Varma, Y.-H. Chen, H. M. Milchberg, T. G. Jones, and A. Ting

Appl. Phys. Lett. 94, 211102 (2009); http://dx.doi.org/10.1063/1.3142384 (3 pages) | Cited 3 times

Online Publication Date: 27 May 2009

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Single-shot supercontinuum spectral interferometry was used to measure the nonlinear index of refraction due to the optical Kerr effect in water at both 815 and 407 nm, with pump pulse lengths of ∼ 90 and ∼ 250 fs, respectively. Knowledge of the nonlinear index at 407 nm allows pulse tailoring to achieve remote underwater pulse compression and self-focusing.
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42.65.Jx Beam trapping, self-focusing and defocusing; self-phase modulation
92.10.-c Physical oceanography
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

Donor-related cathodoluminescence of p-AlGaN electron blocking layer embedded in ultraviolet laser diode structure

Rui Li, Jingming Zhang, Li Chen, Huabo Zhao, Ziwen Yang, Tao Yu, Ding Li, Zhicheng Liu, Weihua Chen, Zhijian Yang, Guoyi Zhang, Zizhao Gan, Xiaodong Hu, Qiyuan Wei, Ti Li, et al.

Appl. Phys. Lett. 94, 211103 (2009); http://dx.doi.org/10.1063/1.3143606 (3 pages)

Online Publication Date: 27 May 2009

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Donor-related cathodoluminescence of p-Al0.11Ga0.89N electron blocking layer (EBL) embedded in a laser structure was investigated by low-energy e-beam scanning along the ridge of a vertical taper both at 82 and 300 K. When e-beam probed the close vicinity of multiquantum well from p-side, an emission at 3.313 eV only appeared at 82 K and represented a prominent increase in intensity with a blueshift up to 23 meV. Besides, its intensity exhibited a linear dependence on quantum well (QW) emission intensity at low QW excitation and a sublinear dependence at high QW excitation. Combined with the annealing behaviors of the emission at elevated temperatures, these results were ascribed to the EBL capture of the holes tunneling from neighboring QW under built-in junction field and the subsequent donor-acceptor pairs transition involving a donor level of 116 meV below conduction band, which was presumably related to nitrogen vacancy (VN).
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78.67.De Quantum wells
78.60.Hk Cathodoluminescence, ionoluminescence
68.65.Fg Quantum wells
61.72.Cc Kinetics of defect formation and annealing
61.72.jd Vacancies
73.21.Fg Quantum wells

A large aperture electro-optic deflector

A. Bosco, S. T. Boogert, G. E. Boorman, and G. A. Blair

Appl. Phys. Lett. 94, 211104 (2009); http://dx.doi.org/10.1063/1.3144274 (3 pages)

Online Publication Date: 28 May 2009

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An electro-optic laser beam deflector with a clear optical aperture of 8.6 mm has been designed, realized, and tested. The electro-optic material used to implement the device was a MgO:LiNbO3 crystal. The exceptionally large aperture makes the device suitable for applications where fast scanning of high power laser beams is needed. The measured deflection angle was 120 μrad/kV for a total length of electro-optic material of 90 mm. A mode quality analysis of the laser beam revealed that the M2 of the laser is affected by less than 4% during scan operation when maximum driving voltage is applied.
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42.79.Fm Reflectors, beam splitters, and deflectors
42.79.Ag Apertures, collimators
42.70.-a Optical materials
42.15.Eq Optical system design
42.60.Jf Beam characteristics: profile, intensity, and power; spatial pattern formation

Integrated quantum cascade laser-modulator using vertically coupled cavities

J. Teissier, S. Laurent, C. Sirtori, H. Debrégeas-Sillard, F. Lelarge, F. Brillouet, and R. Colombelli

Appl. Phys. Lett. 94, 211105 (2009); http://dx.doi.org/10.1063/1.3138779 (3 pages) | Cited 1 time

Online Publication Date: 28 May 2009

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We demonstrated an integrated three terminal device able to modulate the cavity losses of quantum cascade lasers. By growing asymmetric doped quantum wells coupled to the laser’s mode an absorption peak can be electrically shifted in and out the laser transition. The use of three terminals allows one to drive the laser independently from the wells and therefore to modulate the laser’s amplitude with an electrical power of only a few milliwatts. This is far less than the power needed for a direct modulation of the laser light.
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42.60.Fc Modulation, tuning, and mode locking
42.55.Px Semiconductor lasers; laser diodes

Polarization sensitive terahertz time-domain spectroscopy for birefringent materials

LiangLiang Zhang, Hua Zhong, Chao Deng, CunLin Zhang, and YueJin Zhao

Appl. Phys. Lett. 94, 211106 (2009); http://dx.doi.org/10.1063/1.3143613 (3 pages) | Cited 9 times

Online Publication Date: 28 May 2009

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We present a polarization sensitive terahertz detection method which is able to measure both orthogonal components of the terahertz electric field. It allows for the study of polarization dependent properties of materials. Azimuthal angle dependent transmittance in 0.2–2.6 THz frequency region for crystalline quartz is measured. Polarized terahertz transmission spectroscopy shows that birefringence can result in transmission minima. This work suggests that polarization sensitive detection is effective for removing fake absorption features caused by material birefringence.
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07.57.Pt Submillimeter wave, microwave and radiowave spectrometers; magnetic resonance spectrometers, auxiliary equipment, and techniques
78.20.Fm Birefringence

Electric field dependent radiative decay kinetics of polar InGaN/GaN quantum heterostructures at low fields

Emre Sari, Sedat Nizamoglu, In-Hwan Lee, Jong-Hyeob Baek, and Hilmi Volkan Demir

Appl. Phys. Lett. 94, 211107 (2009); http://dx.doi.org/10.1063/1.3142386 (3 pages) | Cited 4 times

Online Publication Date: 29 May 2009

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Electric field dependent photoluminescence decay kinetics and its radiative component are studied in polar InGaN/GaN quantum heterostructures at low fields. Under externally applied electric field lower than polarization fields, spectrally and time resolved photoluminescence measurements are taken to retrieve internal quantum efficiencies and carrier lifetimes as a function of the applied field. Subsequently, relative behavior of radiative recombination lifetimes is obtained in response to the applied field. In these characterizations of polar InGaN/GaN structures, we observe that both the carrier lifetime and the radiative recombination lifetime decrease with increasing external electric field, with the radiative component exhibiting weaker field dependence.
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78.55.Cr III-V semiconductors
78.47.jd Time resolved luminescence
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Analytical rates determinations and simulations on diffusion and reaction processes in holographic photopolymerization

Dejin Yin, Haihui Pu, Bin Gao, Hongyue Gao, Haitao Dai, and Jianhua Liu

Appl. Phys. Lett. 94, 211108 (2009); http://dx.doi.org/10.1063/1.3133863 (3 pages) | Cited 4 times

Online Publication Date: 29 May 2009

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An analytical method is proposed to determine the initial diffusion and reaction coefficients for monomer molecules in holographic photopolymerization processes. Those parameters can be obtained directly from the measured first order diffraction efficiency at the onset stage in the formation of volume Bragg gratings. Simulations, according to these parameters, on the evolution of the diffraction efficiency, based on one-dimensional reaction-diffusion model, were well consistent with experimental data in our trimethylolpropane triacrylate based monomer and liquid crystal composite material. It is shown that diffusion and reaction both play important roles in postcuring process.
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82.35.-x Polymers: properties; reactions; polymerization
81.05.Lg Polymers and plastics; rubber; synthetic and natural fibers; organometallic and organic materials
66.30.-h Diffusion in solids
61.30.-v Liquid crystals
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Electrostatic probe disruption of drift waves in magnetized microdischarges

T. Ito and M. A. Cappelli

Appl. Phys. Lett. 94, 211501 (2009); http://dx.doi.org/10.1063/1.3132587 (3 pages) | Cited 5 times

Online Publication Date: 27 May 2009

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Ultrahigh speed images of E×B discharges are collected during electrostatic probing of magnetized microdischarges. Two azimuthally separated floating micro-Langmuir probes inserted into an axisymmetric microscale magnetically confined plasma are used to characterize azimuthal drift waves. The images reveal features associated with probe intrusion, showing how the electrostatic probes may disrupt the otherwise coherent azimuthal waves. The resulting wave dispersion calculated from the probe signals is consistent with the disruptions seen in the images. These images demonstrate how probe measurements of fluctuations and turbulence, even when probe dimensions are much smaller than characteristic discharge scales, must be interpreted with caution.
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52.70.Ds Electric and magnetic measurements
52.80.Pi High-frequency and RF discharges
52.25.Xz Magnetized plasmas
52.35.Kt Drift waves
52.55.-s Magnetic confinement and equilibrium
52.35.Ra Plasma turbulence
52.35.Fp Electrostatic waves and oscillations (e.g., ion-acoustic waves)

Control of morphology and nucleation density of iron oxide nanostructures by electric conditions on iron surfaces exposed to reactive oxygen plasmas

U. Cvelbar, K. Ostrikov, I. Levchenko, M. Mozetic, and M. K. Sunkara

Appl. Phys. Lett. 94, 211502 (2009); http://dx.doi.org/10.1063/1.3147193 (3 pages) | Cited 18 times

Online Publication Date: 29 May 2009

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The possibility to control the morphology and nucleation density of quasi-one-dimensional, single-crystalline α-Fe2O3 nanostructures by varying the electric potential of iron surfaces exposed to reactive oxygen plasmas is demonstrated experimentally. A systematic increase in the oxygen ion flux through rf biasing of otherwise floating substrates and then an additional increase of the ion/neutral density resulted in remarkable structural transformations of straight nanoneedles into nanowires with controlled tapering/aspect ratio and also in larger nucleation densities. Multiscale numerical simulations relate the microscopic ion flux topographies to the nanostructure nucleation and morphological evolution. This approach is applicable to other metal-oxide nanostructures.
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61.46.Km Structure of nanowires and nanorods (long, free or loosely attached, quantum wires and quantum rods, but not gate-isolated embedded quantum wires)
64.70.Nd Structural transitions in nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization
64.70.K- Solid-solid transitions
81.30.Hd Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder

Reconstruction of ion energy distribution function in a capacitive rf discharge

W. C. Chen, X. M. Zhu, S. Zhang, and Y. K. Pu

Appl. Phys. Lett. 94, 211503 (2009); http://dx.doi.org/10.1063/1.3147216 (3 pages) | Cited 7 times

Online Publication Date: 29 May 2009

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A simple one-dimensional ion dynamic model with charge exchange collisions as the predominant ion-neutral reactions in the sheath is used to obtain the ion energy distribution function (IEDF) in a single-frequency collisional capacitive argon discharge. The shape of IEDF strongly depends on the electron density in this model. IEDFs predicted by this model can be in good agreement with those measured by adjusting the electron density at the ion sheath boundary. The electron densities obtained in this way are in good agreement with those from optical emission spectroscopy measurement, which also indicates the validity of the model.
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52.80.-s Electric discharges
52.40.Kh Plasma sheaths
52.20.Hv Atomic, molecular, ion, and heavy-particle collisions
52.25.-b Plasma properties
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Electromechanical stability of dielectric elastomer

Jinsong Leng, Liwu Liu, Yanju Liu, Kai Yu, and Shouhua Sun

Appl. Phys. Lett. 94, 211901 (2009); http://dx.doi.org/10.1063/1.3138153 (3 pages) | Cited 24 times

Online Publication Date: 26 May 2009

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Electromechanical instability may occur in dielectric elastomer films due to the coupling between mechanical forces and electric fields. According to Zhao and Suo [Appl. Phys. Lett. 91, 061921 (2007) ], free-energy in any form, which consists of elastic strain energy and electric energy, can be used to analyze the electromechanical stability of dielectric elastomer. By taking the permittivity as a variable depending on the deformation in a free energy function, a relationship is established among critical nominal electric field, critical real electric field, nominal stress, and principal stretch ratios. The accurate expressions of these parameters are presented for a special equal biaxial stretch case. All the results obtained by utilizing the single material constant neo-Hookean elastic strain energy model coincide with the conclusions by Zhao and Suo.
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81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
65.60.+a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.
77.22.Ch Permittivity (dielectric function)
77.55.-g Dielectric thin films
77.84.Jd Polymers; organic compounds

Metamaterial with polarization and direction insensitive resonant transmission response mimicking electromagnetically induced transparency

N. Papasimakis, Y. H. Fu, V. A. Fedotov, S. L. Prosvirnin, D. P. Tsai, and N. I. Zheludev

Appl. Phys. Lett. 94, 211902 (2009); http://dx.doi.org/10.1063/1.3138868 (3 pages) | Cited 47 times

Online Publication Date: 26 May 2009

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We report on a planar metamaterial, the resonant transmission frequency of which does not depend on the polarization and angle of incidence of electromagnetic waves. The resonance results from the excitation of high-Q antisymmetric trapped current mode and shows sharp phase dispersion characteristic to Fano-type resonances of the electromagnetically induced transparency phenomenon.
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42.65.-k Nonlinear optics
42.70.Nq Other nonlinear optical materials; photorefractive and semiconductor materials
78.66.Bz Metals and metallic alloys

Time-resolved photoluminescence spectroscopy of the initial oxidation stage of small silicon nanocrystals

K. Dohnalová, K. Kůsová, and I. Pelant

Appl. Phys. Lett. 94, 211903 (2009); http://dx.doi.org/10.1063/1.3141481 (3 pages) | Cited 11 times

Online Publication Date: 27 May 2009

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In this paper we study the influence of progressing oxidation on the photoluminescence spectra of small silicon nanocrystals (SiNCs). H-terminated SiNCs exhibit only a fast approximately nanosecond photoluminescence component at ∼ 525 nm, quenched and redshifted to ∼ 550 nm by progressing oxidation. At the same time a new approximately microsecond photoluminescence component appears, intensity of which progressively increases and its peak position redshifts continuously from 575 up to 660 nm. We interpret our observations in terms of the quasidirect core electron-hole pair recombination quenched by the ultrafast trapping into the oxygen-related surface/interface states, forming within the band gap due to oxidation.
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78.47.jd Time resolved luminescence
61.46.Df Structure of nanocrystals and nanoparticles ("colloidal" quantum dots but not gate-isolated embedded quantum dots)
78.55.Ap Elemental semiconductors
81.05.Cy Elemental semiconductors
78.67.Bf Nanocrystals, nanoparticles, and nanoclusters
81.07.Bc Nanocrystalline materials
73.63.Bd Nanocrystalline materials
72.20.Jv Charge carriers: generation, recombination, lifetime, and trapping

Reversible thermal interfaces based on microscale dielectric liquid layers

Gilhwan Cha and Y. Sungtaek Ju

Appl. Phys. Lett. 94, 211904 (2009); http://dx.doi.org/10.1063/1.3142866 (3 pages) | Cited 8 times

Online Publication Date: 27 May 2009

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We present a reversible thermal interface that can circumvent limitations of direct solid-solid contacts. A thin continuous layer of a dielectric liquid is formed between two solid substrates to provide a low-resistance heat conduction path. The liquid is initially confined in an array of discrete microchannels and undergoes reversible morphological transition into a continuous film as the loading pressure is increased. We theoretically and experimentally determine the relationship between loading pressure and liquid morphology. The interfaces can achieve thermal resistance comparable to that of solid-solid contacts but at loading pressures orders of magnitude smaller.
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66.25.+g Thermal conduction in nonmetallic liquids
44.10.+i Heat conduction
68.15.+e Liquid thin films

Dynamics of strain relaxation studied by in situ x-ray diffraction immediately after layer heteroepitaxy

M. Horbaschk, A. Benkert, C. Schumacher, K. Brunner, and R. B. Neder

Appl. Phys. Lett. 94, 211905 (2009); http://dx.doi.org/10.1063/1.3143630 (3 pages) | Cited 2 times

Online Publication Date: 27 May 2009

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The temporal development of strain relaxation is monitored during and immediately after heteroepitaxy by x-ray diffraction with high resolution in strain and time. ZnSe layers on (001)GaAs with thicknesses just a little above the onset of plastic relaxation reveal inhomogeneous, partial relaxation which continues with a time constant of 50 s immediately after the stop of layer growth. A model of generation, glide, and blocking of dislocations well explains the observation that the degree of relaxation finally reached after growth stop is determined by the density of dislocations rapidly generated prior to it.
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68.60.Bs Mechanical and acoustical properties
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Hh Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, EPR, NMR, etc.)
68.55.ag Semiconductors
62.40.+i Anelasticity, internal friction, stress relaxation, and mechanical resonances

Band alignment of InAs1−xSbx (0.05<x<0.13)/InAs0.67P0.23Sb0.10 heterostructures

Chen-Jun Wu, Gene Tsai, and Hao-Hsiung Lin

Appl. Phys. Lett. 94, 211906 (2009); http://dx.doi.org/10.1063/1.3144271 (3 pages) | Cited 1 time

Online Publication Date: 28 May 2009

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We determined the unstrained conduction-band and valence-band edge energies of InAs1−xSbx (0.05<x<0.13) by fitting the photoluminescence peak energy of InAsSb/InAs0.67P0.23Sb0.10 quantum wells (QWs) that was measured in the temperature range 10–300 K. The results reveal that the QWs exhibit type-I band alignment. Furthermore, the valence band accounts for 65% of the energy-gap bowing of InAsSb. We propose a valence-band anticrossing (VBAC) model to explain the bowing of the valence band in InAsSb. Moreover, the spin-orbit splitting energy of InAsSb calculated by our VBAC model fits well with the experimental results reported in previous studies.
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73.21.Fg Quantum wells
68.65.Fg Quantum wells
71.70.Ej Spin-orbit coupling, Zeeman and Stark splitting, Jahn-Teller effect
78.67.De Quantum wells
78.55.Cr III-V semiconductors
71.20.Nr Semiconductor compounds

Structural heterogeneity and homogeneous nucleation of 1BaO-2SiO2 glass

Yoshihiro Takahashi, Minoru Osada, Hirokazu Masai, and Takumi Fujiwara

Appl. Phys. Lett. 94, 211907 (2009); http://dx.doi.org/10.1063/1.3142394 (3 pages) | Cited 8 times

Online Publication Date: 29 May 2009

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Structural relaxation was examined by in situ Boson peak observation in 1BaO-2SiO2 glass with homogeneous nucleation tendency, in order to clarify the structural heterogeneity. The relation between the glass structure in the medium-range scale and nucleation feature is also discussed. From the results, it is predicted that a sheet-like structure with a network modifier in the resulting crystal is an essential condition for homogeneous nucleation.
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61.43.Fs Glasses
64.70.kj Glasses
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Spray deposited molybdenum doped indium oxide thin films with high near infrared transparency and carrier mobility

S. Parthiban, K. Ramamurthi, E. Elangovan, R. Martins, and E. Fortunato

Appl. Phys. Lett. 94, 212101 (2009); http://dx.doi.org/10.1063/1.3142424 (3 pages) | Cited 9 times

Online Publication Date: 27 May 2009

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Molybdenum doped (0–1 at. %) indium oxide thin films with high near infrared (NIR) transparency and carrier mobility were deposited on Corning-1737 glass substrates at 400 °C by spray pyrolysis experimental technique. Films with mobility as high as ∼ 149 cm2/V s were obtained when annealed in vacuum at 550 °C, which also possess carrier concentration of ∼ 1×1020 cm−3 and resistivity as low as ∼ 4.0×10−4 Ω cm. Further, both the average visible transmittance (500–800 nm) and the average NIR transmittance are >83%. This clearly shows that the transmittance is extended well into the NIR region.
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78.66.Li Other semiconductors
73.61.Le Other inorganic semiconductors
78.30.Hv Other nonmetallic inorganics
72.20.Fr Low-field transport and mobility; piezoresistance

Resistance switching at the Al/SrTiO3−xNy anode interface

A. Shkabko, M. H. Aguirre, I. Marozau, T. Lippert, and A. Weidenkaff

Appl. Phys. Lett. 94, 212102 (2009); http://dx.doi.org/10.1063/1.3139761 (3 pages) | Cited 6 times

Online Publication Date: 27 May 2009

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The electroformation and resistance switching behavior of Al/SrTiO3−xNy/Al have been investigated. The resistance of Al/SrTiO3−xNy/Al irreversibly increases when voltages higher than a certain threshold voltage are applied. A bistable resistance switching develops at one of the Al electrodes that performs as the anode. The formation of stacking faults in SrTiO3−xNy during preparation by microwave plasma treatment is a prerequisite for the occurrence of switching as confirmed by site-specific high resolution transmission electron microscopy at the electrode interfaces. The resistance switching effect is discussed by considering the role of stacking fault defects in the oxygen/nitrogen diffusion at the anode metal-oxynitride interface.
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73.40.Ns Metal-nonmetal contacts
52.77.-j Plasma applications
61.72.Ff Direct observation of dislocations and other defects (etch pits, decoration, electron microscopy, x-ray topography, etc.)

First-principles calculations of electron mobilities in silicon: Phonon and Coulomb scattering

O. D. Restrepo, K. Varga, and S. T. Pantelides

Appl. Phys. Lett. 94, 212103 (2009); http://dx.doi.org/10.1063/1.3147189 (3 pages) | Cited 6 times

Online Publication Date: 28 May 2009

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Electron mobilities limited by phonon and ionized impurity scattering have traditionally been modeled by suppressing atomic-scale detail, relying on empirical deformation potentials and either effective-mass theory or bulk energy bands to describe electron velocities. Parameter fitting to experimental data is needed. As modern technologies require modeling of transport at the nanoscale and unprecedented materials are introduced, predictive parameter-free mobility modeling becomes necessary. Here we report the development of first-principles quantum-mechanical methods to calculate scattering rates and electronic mobilities limited by phonon and ionized-impurity scattering. We report results for n-doped silicon that are in good agreement with experiment.
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72.20.Fr Low-field transport and mobility; piezoresistance
72.10.Fk Scattering by point defects, dislocations, surfaces, and other imperfections (including Kondo effect)
71.18.+y Fermi surface: calculations and measurements; effective mass, g factor
72.80.Cw Elemental semiconductors
71.20.Mq Elemental semiconductors
71.15.-m Methods of electronic structure calculations

Metal-oxide-semiconductor field-effect transistors on GaAs (111)A surface with atomic-layer-deposited Al2O3 as gate dielectrics

M. Xu, Y. Q. Wu, O. Koybasi, T. Shen, and P. D. Ye

Appl. Phys. Lett. 94, 212104 (2009); http://dx.doi.org/10.1063/1.3147218 (3 pages) | Cited 19 times

Online Publication Date: 28 May 2009

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GaAs inversion-mode metal-oxide-semiconductor field-effect transistors (MOSFETs) with atomic-layer-deposited Al2O3 as gate dielectrics are fabricated on (111)A and (100) surfaces. With the same channel length of 0.75 μm, the maximum drain current of 15 mA/mm on n-channel MOSFET is obtained on (111)A surface, in great contrast to only 1 μA/mm on (100) surface. For p-channel MOSFETs, maximum drain currents of 0.17 mA/mm and 0.8 mA/mm are obtained on (111)A and (100) surfaces, respectively. An empirical model is proposed to correlate the experimental observation with the existing III-V MOS theories.
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85.30.Tv Field effect devices
85.30.De Semiconductor-device characterization, design, and modeling
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.)

Guided modes in graphene waveguides

Fan-Ming Zhang, Ying He, and Xi Chen

Appl. Phys. Lett. 94, 212105 (2009); http://dx.doi.org/10.1063/1.3143614 (3 pages) | Cited 15 times

Online Publication Date: 28 May 2009

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By analogy of optical waveguides, we investigate the guided modes in graphene waveguides, which is made of symmetric quantum well. The unique properties of the graphene waveguide are discussed based on the two different dispersion relations, which correspond to classical motion and Klein tunneling, respectively. It is shown that the third-order mode is absent in the classical motion, while the fundamental mode is absent in the Klein tunneling case. We hope these phenomena can lead to the potential applications in graphene-based quantum devices.
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78.67.De Quantum wells
81.05.U- Carbon/carbon-based materials
81.07.St Quantum wells
61.48.De Structure of carbon nanotubes, boron nanotubes, and other related systems
42.82.Et Waveguides, couplers, and arrays

Gate-controlled magnetic properties of the magnetic semiconductor (Zn,Co)O

H.-J. Lee, E. Helgren, and F. Hellman

Appl. Phys. Lett. 94, 212106 (2009); http://dx.doi.org/10.1063/1.3147856 (3 pages) | Cited 5 times

Online Publication Date: 29 May 2009

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Electric field-controlled ferromagnetism of (Zn,Co)O is demonstrated via anomalous Hall effect measurements. The electron carrier concentration in this material is 1.65×1020 cm−3 as measured via ordinary Hall effect at 4 K, and an anomalous Hall effect is observed up to 6 K, but with no hysteresis at any temperature. With positive electric gate field, the carrier concentration is increased by approximately 2%, resulting in a clear magnetic hysteresis at 4 K. The ability to reversibly induce/eliminate ferromagnetism by applied gate field alone, measured via the effect on the carriers, is a clear sign of carrier-induced ferromagnetism in this system.
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73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
75.50.Pp Magnetic semiconductors
73.61.Ga II-VI semiconductors
75.70.Ak Magnetic properties of monolayers and thin films
75.60.Ej Magnetization curves, hysteresis, Barkhausen and related effects
75.50.Dd Nonmetallic ferromagnetic materials

Spin polarized tunneling magnetoresistance in the self-doped manganite La0.9MnO3

M. Patra, A. Roy, K. De, S. Majumdar, and S. Giri

Appl. Phys. Lett. 94, 212107 (2009); http://dx.doi.org/10.1063/1.3147873 (3 pages) | Cited 2 times

Online Publication Date: 29 May 2009

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We observe the tunneling magnetoresistance (TMR) at low temperature (T) and low field attributed to the self-doping in polycrystalline La0.9MnO3. The occurrence of TMR is suggested due to the tunneling through the grain boundary (GB) region. Tunneling component of the magnetoresistance ascribed to the disordered magnetic GB region follows the Curie–Weiss-like T dependence. The nonlinear current-voltage curves at low T indicate that the inelastic tunneling via localized states involved with the GB effect is dominant where at low temperature the number of inelastic channels and the fraction of charge carriers entering in each inelastic channel change with temperature.
Show PACS
75.47.Lx Magnetic oxides
61.72.Mm Grain and twin boundaries
72.25.-b Spin polarized transport
61.72.up Other materials
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