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6 Apr 1998

Volume 72, Issue 14, pp. 1667-1789

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How good is the polarization selection rule for intersubband transitions?

H. C. Liu, M. Buchanan, and Z. R. Wasilewski

Appl. Phys. Lett. 72, 1682 (1998); http://dx.doi.org/10.1063/1.121151 (3 pages) | Cited 45 times

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Using GaAs based quantum well infrared photodetectors (QWIPs) with either GaAs or InGaAs wells, we experimentally investigate the accuracy of the polarization selection rule for conduction band intersubband transitions. We employ a device structure and a light coupling geometry where the parasitic light scattering is negligible. The experiments imply that the selection rule is followed to an accuracy of 0.2% for a 8.1 μm QWIP with GaAs wells; this degrades to 3% for a 4.6 μm QWIP with In0.1Ga0.9As wells. © 1998 American Institute of Physics.
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85.60.Gz Photodetectors (including infrared and CCD detectors)
85.35.Be Quantum well devices (quantum dots, quantum wires, etc.)
73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems

Effect of external electric field on the growth of nanotubules

Anchal Srivastava, A. K. Srivastava, and O. N. Srivastava

Appl. Phys. Lett. 72, 1685 (1998); http://dx.doi.org/10.1063/1.121152 (3 pages) | Cited 4 times

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In the present investigation, we have studied the effect of electric field on the growth of carbon nanotubules. Different electric fields corresponding to 3, 6, 9, 15, and 21 V have been applied during the growth of the tubules. The estimate of the electric field corresponding to these voltages cannot be precisely evaluated in view of only approximately defined electrode dimensions. It has been observed that the application of electric field leads to the agglomerates (bundles) of nanotubules. The size, length, and alignment of these bundles varies with the strength of the applied electric field. The best results have been obtained with electric field corresponding to 6 V where the as-formed tubules are in parallel alignment and exist as bundles. As the electric field is increased, the alignment of tubules in the bundle becomes randomly oriented. The degree of randomness increases with increase of electric field after its optimum value corresponding to 6 V. The parallel alignment of the graphitic tubules is thought to result due to orientation of the tubule axis along the direction of the applied electric field corresponding to an optimum value (which for the present case is 6 V) of the impressed voltage. © 1998 American Institute of Physics.
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61.46.-w Structure of nanoscale materials
81.07.-b Nanoscale materials and structures: fabrication and characterization

Localized excitonic transitions in a ZnSe-Zn0.75Cd0.25Se double-superlattice grown by molecular beam epitaxy

Z. P. Guan, G. K. Kuang, E. Griebl, M. Kastner, and W. Gebhardt

Appl. Phys. Lett. 72, 1688 (1998); http://dx.doi.org/10.1063/1.121153 (3 pages) | Cited 2 times

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A group of well-defined exciton transitions from the localized states were observed in ZnSe-Zn0.75Cd0.25Se double-superlattice structure. The photoluminescence and photoreflectance have been employed to study the subband transitions at low temperatures. At 1.4 K, except the two ground states and two higher subbands of n = 1 light-hole and n = 2 heavy-hole excitonic transitions, other four peaks (A, B, C, and D) also were observed in wider-well superlattice. Those peaks were attributed to the excitonic transitions from n = 2 heavy-hole subband due to the fluctuation of well-barrier interface. Another localized excitonic transition from narrower-well superlattice appeared as increasing the modulated intensity in photoreflectance spectra. © 1998 American Institute of Physics.
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73.21.-b Electron states and collective excitations in multilayers, quantum wells, mesoscopic, and nanoscale systems
73.20.Fz Weak or Anderson localization
71.35.-y Excitons and related phenomena
78.66.Hf II-VI semiconductors
72.80.Ey III-V and II-VI semiconductors
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
73.61.Ga II-VI semiconductors
78.55.Et II-VI semiconductors
78.20.-e Optical properties of bulk materials and thin films

Equation of state of wurtzitic boron nitride to 66 GPa

Vladimir L. Solozhenko, Daniel Häusermann, Mohamed Mezouar, and Martin Kunz

Appl. Phys. Lett. 72, 1691 (1998); http://dx.doi.org/10.1063/1.121186 (3 pages) | Cited 20 times

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The compressibility of wurtzitic boron nitride (wBN) taken in mixture with cubic BN has been measured at room temperature up to 66 GPa, using a diamond anvil cell and powder diffraction of synchrotron radiation. From the obtained pressure-volume relation for wBN the isothermal bulk modulus of B0 = 375±9 GPa and its first pressure derivative of dB0/dp = 4.9±0.7 have been calculated indicating that this phase has nearly the same compressibility as cBN (B0 = 377±4 GPa and dB0/dp = 4.1±0.2). Thermodynamic calculations using our findings on wBN equation of state have shown that wurtzitic boron nitride is metastable over the whole ranges of pressures and temperatures. © 1998 American Institute of Physics.
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64.30.-t Equations of state of specific substances
81.40.Lm Deformation, plasticity, and creep
62.20.F- Deformation and plasticity
62.20.D- Elasticity
81.40.Jj Elasticity and anelasticity, stress-strain relations

Arsenic incorporation in HgCdTe grown by molecular beam epitaxy

P. S. Wijewarnasuriya and S. Sivananthan

Appl. Phys. Lett. 72, 1694 (1998); http://dx.doi.org/10.1063/1.121154 (3 pages) | Cited 22 times

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We report the results of in situ arsenic doping in HgCdTe layers grown by molecular beam epitaxy (MBE). Arsenic incorporation was carried out by two mechanisms called conventional doping and planar doping. The obtained results indicate that for both mechanisms, after Hg anneal, arsenic was successfully incorporated as an acceptor during the MBE growth. Secondary ion mass spectrometry and Hall-effect measurements before and after Hg annealing were used to characterize arsenic activity in the grown layers. Close to 100% acceptor doping efficiency with arsenic has been obtained on these MBE grown layers up to total arsenic concentrations of approximately 2×1018 cm−3, which is more than sufficient for a wide range of infrared devices. At much higher total arsenic concentrations, electrical activity falls off drastically as the doping level saturates. © 1998 American Institute of Physics.
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81.05.Dz II-VI semiconductors
68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.uj III-V and II-VI semiconductors
71.55.Gs II-VI semiconductors
81.15.Hi Molecular, atomic, ion, and chemical beam epitaxy
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
82.80.Ms Mass spectrometry (including SIMS, multiphoton ionization and resonance ionization mass spectrometry, MALDI)
73.50.Jt Galvanomagnetic and other magnetotransport effects (including thermomagnetic effects)
72.20.My Galvanomagnetic and other magnetotransport effects
61.72.Cc Kinetics of defect formation and annealing

Local determination of the stacking sequence of layered materials

J. Fompeyrine, R. Berger, H. P. Lang, J. Perret, E. Mächler, Ch. Gerber, and J.-P. Locquet

Appl. Phys. Lett. 72, 1697 (1998); http://dx.doi.org/10.1063/1.121155 (3 pages) | Cited 21 times

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The ability to modify the stacking sequence of ultrathin films offers a unique way to change either the interaction strength or the doping, but demands a careful control of each atomic monolayer. Progress is hampered by the lack of a direct method that allows differentiation on a local scale between the various terminating layers of a crystal. Here, the combination of a vacuum annealing process and friction force microscopy reveals this local distinction on a SrTiO3 surface. Using the friction contrast, we find how the terminating layer of a single crystal profoundly influences the terrace edge structure. © 1998 American Institute of Physics.
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68.35.B- Structure of clean surfaces (and surface reconstruction)
61.72.Cc Kinetics of defect formation and annealing
81.40.Gh Other heat and thermomechanical treatments
07.79.Lh Atomic force microscopes

Optical and electrical properties of aluminum oxide films deposited by spray pyrolysis

M. Aguilar-Frutis, M. Garcia, and C. Falcony

Appl. Phys. Lett. 72, 1700 (1998); http://dx.doi.org/10.1063/1.121156 (3 pages) | Cited 34 times

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The optical and electrical characteristics of spray pyrolysis deposited aluminum oxide films are reported. The films were deposited from a spraying solution of aluminum acetylacetonate in N,N-dimethylformamide using an ultrasonic mist generator on (100) Si substrates. The addition of water mist during the spraying deposition process resulted in an overall improvement of the films characteristics. The substrate temperature during deposition was in the 450–650 °C range. Deposition rates up to 90 Å/s were obtained depending on the spraying solution concentration and substrate temperature with an activation energy of the order of 31 kJ/mol. The optical energy band gap for these films was 5.63 eV and the refractive index at 630 nm up to 1.66 was measured by ellipsometry. The electrical characteristics of the films were determined from the capacitance and current versus voltage measurements of metal–oxide–semiconductor (MOS) structures incorporating them. A dielectric constant of 7.9, interface states density of the order of 1011×1/eV cm2 as well as breakdown fields higher than 5 MV/cm were determined in this way. © 1998 American Institute of Physics.
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78.66.Nk Insulators
77.55.-g Dielectric thin films
81.15.Rs Spray coating techniques
78.20.Ci Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity)
77.22.Ch Permittivity (dielectric function)
73.20.At Surface states, band structure, electron density of states

Hydrogen-decorated lattice defects in proton implanted GaN

Marcie G. Weinstein, C. Y. Song, Michael Stavola, S. J. Pearton, R. G. Wilson, R. J. Shul, K. P. Killeen, and M. J. Ludowise

Appl. Phys. Lett. 72, 1703 (1998); http://dx.doi.org/10.1063/1.121157 (3 pages) | Cited 22 times

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Several vibrational bands were observed near 3100 cm−1 in GaN that had been implanted with hydrogen at room temperature and subsequently annealed. Our results indicate that these bands are due to nitrogen-dangling-bond defects created by the implantation that are decorated by hydrogen. The frequencies are close to those predicted recently for VGa–Hn complexes, leading us to tentatively assign the new lines to VGa defects decorated with different numbers of H atoms. © 1998 American Institute of Physics.
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61.72.uj III-V and II-VI semiconductors
61.80.Jh Ion radiation effects
61.82.Fk Semiconductors
85.40.Ry Impurity doping, diffusion and ion implantation technology

A model of bonding and band-forming for oxides and nitrides

Chang Q. Sun

Appl. Phys. Lett. 72, 1706 (1998); http://dx.doi.org/10.1063/1.121158 (3 pages) | Cited 24 times

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Correlation between chemical bonds, energy bands, and the corresponding properties of oxides and nitrides is established. It is proposed that an oxygen or nitrogen atom can hybridize and form a tetrahedron with its four neighbors through bonding orbitals and nonbonding lone pairs. As a result, the energy states of the host material are modified with four additional features, namely, sp3-hybrid bonding, nonbonding (lone pair), antibonding (dipole), and hole states. Therefore, oxygen and nitrogen possess the special ability of not only enlarging the band gap by hole production but also adding an antibonding subband above the Fermi level. © 1998 American Institute of Physics.
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61.50.Lt Crystal binding; cohesive energy
71.20.Nr Semiconductor compounds
71.20.Ps Other inorganic compounds
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