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24 Sep 2001

Volume 79, Issue 13, pp. 1933-2115

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Temperature-dependent conduction of W-containing composite diamond films

M. L. Terranova, V. Sessa, S. Piccirillo, S. Orlanducci, D. Manno, G. Micocci, A. Serra, A. Tepore, and M. Rossi

Appl. Phys. Lett. 79, 2007 (2001); http://dx.doi.org/10.1063/1.1403335 (3 pages) | Cited 2 times

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We report on the synthesis and electrical characterizations of composite W-containing diamond films. These layers have been produced by a hybrid chemical-vapor-deposition/powder flowing technique that allows control of the dispersion of the foreign W phase inside a diamond matrix. The electrical behavior of such material in the 25–500 K temperature range is found characterized by a nonlinear response, typical of metal/insulator composite materials, with conductivity reaching the maximum value of 95 Ω−1 cm−1 at 148 K. Structural and morphological investigations performed by reflection high-energy electron diffraction, scanning electron microscopy, and dispersive x-ray spectrometry indicate that the presence of a percolating network of metallic grains did not perturb the quality of the diamond lattice. © 2001 American Institute of Physics.
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73.61.-r Electrical properties of specific thin films
82.80.Ej X-ray, Mössbauer, and other γ-ray spectroscopic analysis methods
68.55.-a Thin film structure and morphology

Real-time evolution of trapped charge in a SiO2 layer: An electrostatic force microscopy study

G. H. Buh, H. J. Chung, and Y. Kuk

Appl. Phys. Lett. 79, 2010 (2001); http://dx.doi.org/10.1063/1.1404404 (3 pages) | Cited 30 times

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Time-dependent motion of localized electrons and holes trapped in a SiO2 layer is visualized with electrostatic force microscopy. Both negative and positive charges of up to ∼ 1010 e/cm2 are trapped at a SiO2–Si interface in ∼ 500-nm-diam area with a voltage stress between the tip and the sample. There is a higher probability for trapped charges to spread out in the plane direction than to de-trap toward the Si substrate. The dynamics is explained with diffusion and drift of the charges induced by Coulombic interaction. © 2001 American Institute of Physics.
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73.61.Ng Insulators
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
68.37.Ps Atomic force microscopy (AFM)
73.50.Gr Charge carriers: generation, recombination, lifetime, trapping, mean free paths
73.40.Cg Contact resistance, contact potential

Tunneling carrier escape from InAs self-assembled quantum dots

J. Ibáñez, R. Leon, D. T. Vu, S. Chaparro, S. R. Johnson, C. Navarro, and Y. H. Zhang

Appl. Phys. Lett. 79, 2013 (2001); http://dx.doi.org/10.1063/1.1402642 (3 pages) | Cited 9 times

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Deep-level transient spectroscopy measurements in InAs quantum dots (QDs) grown in both n-GaAs and p-GaAs show that tunneling is an important mechanism of carrier escape from the dots. The doping level in the barrier strongly affects the tunneling emission rates, enabling or preventing the detection of a transient capacitance signal from a given QD level. The relative intensity of this signal acquired with different rate windows allows the estimation of tunneling emission energies. © 2001 American Institute of Physics.
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73.61.Ey III-V semiconductors
73.63.Kv Quantum dots
71.55.Eq III-V semiconductors
73.20.Hb Impurity and defect levels; energy states of adsorbed species

Solubility limit and precipitate formation in Al-doped 4H-SiC epitaxial material

M. K. Linnarsson, M. S. Janson, U. Zimmermann, B. G. Svensson, P. O. Å. Persson, L. Hultman, J. Wong-Leung, S. Karlsson, A. Schöner, H. Bleichner, and E. Olsson

Appl. Phys. Lett. 79, 2016 (2001); http://dx.doi.org/10.1063/1.1402160 (3 pages) | Cited 18 times

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Heavily Al-doped 4H–SiC structures have been prepared by vapor phase epitaxy. Subsequent anneals have been carried out in an Ar atmosphere in a rf-heated furnace between 1500 °C and 2000 °C for 0.5 to 3 h. Secondary ion mass spectrometry has been utilized to obtain Al concentration versus depth as well as lateral distributions (ion images). Transmission electron microscopy (TEM) has been employed to study the crystallinity and determine phase composition after heat treatment. A solubility limit of ∼ 2×1020 Al/cm3 (1900 °C) is extracted. Three-dimensional ion images show that the Al distribution does not remain homogeneous in layers heat treated at 1700 °C or above when the Al concentration exceeds 2×1020 cm−3. Al-containing precipitates are identified by energy-filtered TEM. © 2001 American Institute of Physics.
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68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.
61.72.Cc Kinetics of defect formation and annealing
79.20.Rf Atomic, molecular, and ion beam impact and interactions with surfaces
61.72.S- Impurities in crystals
81.30.Mh Solid-phase precipitation
64.75.-g Phase equilibria

Ultraviolet and visible resonance-enhanced Raman scattering in epitaxial Al1−xInxN thin films

V. M. Naik, W. H. Weber, D. Uy, D. Haddad, R. Naik, Y. V. Danylyuk, M. J. Lukitsch, G. W. Auner, and L. Rimai

Appl. Phys. Lett. 79, 2019 (2001); http://dx.doi.org/10.1063/1.1404402 (3 pages) | Cited 16 times

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We report the observation of ultraviolet and visible near-resonance enhanced Raman scattering in epitaxial wurtzite Al1−xInxN (0001) (0 ⩽ x<0.7) thin films. The films (thickness ∼ 150 nm) were grown by plasma source molecular beam epitaxy on sapphire (0001) substrates. A substantial spectral enhancement is seen for Al-rich samples using 244 nm (5.01 eV) radiation due to the closeness of their band gap energy to the excitation energy. On the other hand, samples with x ∼ 0.6 (energy band gap ∼ 2.5 eV) show significant enhancement with 514.5 nm (2.41 eV) excitation. The A1(LO) and E2 zone center phonons have been observed for all the samples. The A1(LO) phonon frequency shows the expected decrease with increasing x. The E2 mode shows a two-mode behavior supporting the recent theoretical predictions. Due to increased resonance enhancement, strong second- and third-order spectra are seen in some films. © 2001 American Institute of Physics.
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78.66.Fd III-V semiconductors
78.30.Fs III-V and II-VI semiconductors
63.20.D- Phonon states and bands, normal modes, and phonon dispersion
71.20.Nr Semiconductor compounds

Metalorganic vapor-phase epitaxial growth and photoluminescent properties of Zn1−xMgxO(0 ⩽ x ⩽ 0.49) thin films

W. I. Park, Gyu-Chul Yi, and H. M. Jang

Appl. Phys. Lett. 79, 2022 (2001); http://dx.doi.org/10.1063/1.1405811 (3 pages) | Cited 165 times

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High-quality Zn1−xMgxO(0.00 ⩽ x ⩽ 0.49) thin films were epitaxially grown at 500–650 °C on Al2O3(00⋅1) substrates using metalorganic vapor-phase epitaxy. By increasing the Mg content in the films up to 49 at. %, the c-axis constant of the films decreased from 5.21 to 5.14 Å and no significant phase separation was observed as determined by x-ray diffraction measurements. Furthermore, the near-band-edge emission peak position showed blueshifts of 100, 440, and 685 meV at Mg content levels of 9, 29, and 49 at. %, respectively. Photoluminescent properties of the alloy films are also discussed. © 2001 American Institute of Physics.
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81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
68.55.A- Nucleation and growth
81.15.Kk Vapor phase epitaxy; growth from vapor phase
78.55.Hx Other solid inorganic materials
78.66.Li Other semiconductors

Transport spectroscopy of the ultrasmall silicon quantum dot in a single-electron transistor

Masumi Saitoh, Toshiki Saito, Takashi Inukai, and Toshiro Hiramoto

Appl. Phys. Lett. 79, 2025 (2001); http://dx.doi.org/10.1063/1.1405805 (3 pages) | Cited 25 times

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We investigate electron transport through the ultrasmall silicon quantum dot in a single-electron transistor. The device is fabricated in the form of a silicon point-contact channel metal–oxide–semiconductor field-effect transistor. The size of the formed dot is estimated to be as small as 5.3 nm. Negative differential conductance is clearly observed up to 25 K. It turns out that this is caused by discreteness of quantum levels in the silicon dot and variation of the tunneling rates to each level. The fine structure of conductance persists up to 77 K. Modeling of the electron transport through the silicon dot is carried out. Good agreement between experiment and calculation is obtained, which confirms the validity of our model. © 2001 American Institute of Physics.
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73.63.Kv Quantum dots
72.80.Cw Elemental semiconductors
85.35.Gv Single electron devices
85.30.Tv Field effect devices

Anisotropic electrical conductivity of delafossite-type CuAlO2 laminar crystal

M. S. Lee, T. Y. Kim, and D. Kim

Appl. Phys. Lett. 79, 2028 (2001); http://dx.doi.org/10.1063/1.1405809 (3 pages) | Cited 34 times

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Delafossite-type CuAlO2 laminar crystals (Rmathm) were prepared through melt by a cooling method from 1423 K. The layer-by-layer structure of the crystal was observed. Because of the structural anisotropy of the crystal, electrical conductivity along the ab plane (σab) was higher than that along the c axis (σc), σab≳25σc. The anisotropy unveiled that the main conduction path of the crystal is closed-packed Cu+ layers. The values of the activation energies which were estimated from the Arrhenius plot were ∼0.20 and ∼0.13 eV for σc and σab, respectively. The linearity in the log σ vs (1/T)1/4 plot and the positive thermoelectric power (>+300 μV/K) of the crystal suggested p-type variable-range hopping conduction. © 2001 American Institute of Physics.
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72.20.Pa Thermoelectric and thermomagnetic effects
72.20.Ee Mobility edges; hopping transport
72.80.Ga Transition-metal compounds
72.80.Sk Insulators

Si/SiGe modulation-doped heterostructures grown on silicon-on-insulator substrates for high-mobility two-dimensional electron gases

L. Di Gaspare, K. Alfaramawi, F. Evangelisti, E. Palange, G. Barucca, and G. Majni

Appl. Phys. Lett. 79, 2031 (2001); http://dx.doi.org/10.1063/1.1400769 (3 pages) | Cited 7 times

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The growth of high-mobility modulation-doped Si/SiGe heterostructures on silicon-on-insulator substrates is demonstrated. The structural and electrical properties of the samples are reported to be comparable with those of similar samples grown on standard Si substrates. Electron mobilities as high as 2900 cm2/Vs at room temperature and 8.2×104 cm2/Vs at 4.2 K were obtained. © 2001 American Institute of Physics.
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73.40.Lq Other semiconductor-to-semiconductor contacts, p-n junctions, and heterojunctions
72.20.Ee Mobility edges; hopping transport
72.20.Fr Low-field transport and mobility; piezoresistance
68.35.Ct Interface structure and roughness
73.20.At Surface states, band structure, electron density of states
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