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  • 1
    Electronic Resource
    Electronic Resource
    Temperature dependence of the properties of heteroepitaxial Y2O3 films grown on Si by ion assisted evaporation (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 198-204 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Heteroepitaxial Y2O3 films were grown on an Si(111) substrate by ion assisted evaporation in an ultrahigh vacuum, and their properties such as crystallinity, film stress, and morphological change were investigated using the various measurement methods. The crystallinity was assessed by x-ray diffraction (XRD) and reflection high-energy electron diffraction. Interface crystallinity was also examined by Rutherford backscattering spectroscopy (RBS) channeling and transmission electron microscopy. The strain of the films was measured by RBS channeling and XRD. Surface and interface morphological characteristics were observed by atomic force microscopy and x-ray scattering method. By comparing the interface with the surface characteristics, we can conclude that many defects at the interface region were generated by interface interaction between the yttrium metal and Si substrate. Moreover, the film quality dominantly depended on the deposition temperature. The crystallinity was greatly improved and the surface roughness was drastically decreased in the temperature range 500–600 °C. On the other hand, in the temperature range 600–700 °C, the compressive stress and film density were further increased, and the island size decreased. Also, the shape of the surface islands was transformed from elliptical to triangular. The film stress was found primarily at the interface area because of the interaction between yttrium and Si substrate. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370717
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic properties of very high permeability, low coercivity, and high electrical resistivity in Fe87Zr7B5Ag1 amorphous alloy (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5298-5302 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetic properties of an Fe87Zr7B5Ag1 (at. %) amorphous alloy, which contains an additional insoluble element (Ag) in a small amount, have been investigated as a function of annealing temperatures in order to know its potential applicability as a core material used at high-frequency. As a result, a new excellent soft magnetic material with very high resistivity was developed. The amorphous alloy annealed at a relatively low temperature of Ta=300 °C exhibited a very high initial permeability μi of 146 000 at 1 kHz and 2 mOe, resistivity ρRT of 4.5 μΩ m, and very low coercivity Hc of 20 mOe, respectively. The values obtained are the best ones among various kinds of Fe-based soft amorphous materials reported up to now. Furthermore, the amorphous ribbon heat treated at Ta=300 °C still retained good ductility enough to endure 180° bending, which is very important from the viewpoint of processing for mass production. The phenomenon of good soft magnetic properties presumably arises from the homogenous formation of very fine α-Fe clusters in an amorphous matrix, which can be deduced from the increase of resistivity, and the reduction of magnetostriction caused by the dissolution of Zr and B into the α-Fe cluster. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359284
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  • 3
    Electronic Resource
    Electronic Resource
    Dependence of damage and strain on the temperature of Si irradiation in epitaxial Ge0.10Si0.90 films on Si(100) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2329-2338 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Damage and strain produced in a 370-nm-thick strained epitaxial Ge0.10Si0.90 film on Si(100) by irradiation with 320 keV 28Si+ ions at fixed temperatures ranging from 40 to 150 °C and for doses from 1 to 30×1014/cm2 have been measured by MeV 4He channeling spectrometry, transmission electron microscopy, and high-resolution x-ray diffractometry. The ion energy was chosen so that the maximum damage created by irradiation occurs very near the GeSi-Si interface. For all temperatures, the retained damage and the perpendicular strain induced by the irradiation are significantly greater in the GeSi epilayer than in the Si substrate. For all doses the retained damage and the induced perpendicular strain become small above 100 °C. Both rise nonlinearly with increasing ion dose. They are related to each other differently in GeSi than in bulk Si or Ge irradiated at room temperature. Postirradiation furnace annealing can remove a large portion of the induced damage and strain for nonamorphized samples. Amorphized samples regrow by solid-phase epitaxy after annealing at 550 °C for 30 min; the regrown GeSi is, however, highly defective and elastically relaxed. A consequence of this defectiveness is that irradiation-induced amorphization in metastable GeSi is undesirable for applications where good crystalline quality is required. Ion implantation above room temperature can prevent amorphization. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.358755
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  • 4
    Electronic Resource
    Electronic Resource
    Solid-phase epitaxial regrowth and dopant activation of P-implanted metastable pseudomorphic Ge0.12Si0.88 on Si(100) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 5160-5166 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Several 265-nm-thick metastable pseudomorphic Ge0.12Si0.88 films grown on a Si(100) substrate by molecular-beam epitaxy were implanted at room temperature with 100 keV phosphorus ions to a dose of 1.5×1015/cm2. The implantation amorphizes the top portion (∼190 nm) of the GeSi layer and leaves the rest of the film single crystalline. Implanted and nonimplanted samples were subsequently annealed simultaneously in vacuum for 30 min from 400 to 800 °C. The implanted samples undergo layer-by-layer solid-phase-epitaxial regrowth during annealing at or above 500 °C. The regrown GeSi layer is relaxed with a high density of threading dislocations (∼1010–1011/cm2). The nonamorphized portion of the layer remains fully strained when annealed between 400 and 600 °C. At or above 700 °C misfit dislocations are observed at the Si/Ge0.12Si0.88 interface. After 800 °C annealing the strain in the whole epilayer is fully relaxed. The strain relaxation is facilitated by the implantation. The presence of phosphorus in GeSi raises its regrowth velocity by about an order of magnitude over that of Ge0.12Si0.88 amorphized by irradiation of Si. The implanted phosphorus reaches ∼100% activation after the completion of solid-phase-epitaxial regrowth. The room-temperature sheet electron mobility in GeSi is ∼20% below that of a Si sample implanted and annealed under the same conditions. It is concluded that metastable Ge0.12Si0.88 on Si(100) amorphized at room temperature by P implantation and recrystallized by solid-phase epitaxy can- not recover its crystalline perfection and its pseudomorphic strain upon steady-state furnace annealing. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359261
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  • 5
    Electronic Resource
    Electronic Resource
    Optical properties of wurtzite GaN grown by low-pressure metalorganic chemical-vapor deposition (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3691-3696 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of optical studies on the properties of GaN grown by low-pressure metalorganic chemical-vapor deposition, with emphasis on the issues vital to device applications such as stimulated emission and laser action as well as carrier relaxation dynamics. By optical pumping, stimulated emission and lasing were investigated over a wide temperature range up to 420 K. Using a picosecond streak camera, the free and bound exciton emission decay times were examined. In addition, the effects of temperature and pressure on the optical interband transitions and the transitions associated with impurity/defect states were studied using a variety of spectroscopic methods, including photoluminescence and photoreflectance. The fundamental band gap of GaN was mapped out as a function of temperature using the empirical Varshni relation. The pressure coefficient of the gap was determined using diamond-anvil pressure-cell technique. The hydrostatic deformation potential for the direct Γ band gap was also derived from the experimental results. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361200
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  • 6
    Electronic Resource
    Electronic Resource
    Excitation energy-dependent optical characteristics of InGaN/GaN multiple quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3181-3183 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have systematically studied the optical properties of InGaN/GaN multiple quantum wells (MQWs) at 10 K under different excitation conditions using photoluminescence (PL), PL excitation, and time-resolved PL spectroscopy. We found that the PL emission consists of a strong main peak at 2.80 eV and a much weaker and broader secondary peak at ∼2.25 eV. We observed that the peak position blueshifts and the spectral width narrows for the main peak when the excitation energies are varied from 3.81 eV (above the band gap of the AlGaN capping layer) to 2.99 eV (below the band gap of the GaN barrier layers). The intensity ratio of the main peak to the secondary peak also varied with excitation energy. The two observed emission peaks originate from different layers of the MQWs. Time-integrated and time-resolved PL revealed that the InGaN-related spontaneous emission processes are strongly affected by inhomogeneity and carrier localization in the MQWs. From these studies under varying excitation energies, we conclude that interface-related defects and roughness may play an important role in the InGaN-related emission mechanism during the carrier transfer between different layers of the MQWs. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122711
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  • 7
    Electronic Resource
    Electronic Resource
    Erratum: "Recombination dynamics in n-AlxGa1−xAs/n-In0.5Ga0.5P type-II heterostructures" [Appl. Phys. Lett. 73, 1245 (1998)] (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2219-2219 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122431
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  • 8
    Electronic Resource
    Electronic Resource
    Observation of the phase inversion in photoreflectance spectra from ZnSe/GaAs(001) heterostructures (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 1382-1384 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The pump photon energy dependence of photoreflectance (PR) of a ZnSe/GaAs heterostructure has been measured at 77 K. The phase inversion in the PR signal is observed for the pump photon energy when it decreases from above to below the excitonic absorption edge of ZnSe. The observation of the phase inversion in PR is explained in terms of the modulation of the built-in electric field at the interface of the ZnSe/GaAs heterojunction, not at the ZnSe surface. It provides evidence of a built-in triangular-well potential and of hole traps at the ZnSe/GaAs interface. This argument is confirmed by photoreflectance excitation spectroscopy. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122167
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  • 9
    Electronic Resource
    Electronic Resource
    Large optical nonlinearities near the band gap of GaN thin films (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 1504-1506 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The interband optical transitions in single-crystal GaN films grown by metal organic chemical vapor deposition have been studied at 10 K and room temperature using nondegenerate nanosecond optical pump-probe techniques. At low temperatures, strong, well-resolved features are seen in the absorption and reflection spectra corresponding to the 1s A and B exciton transitions. These features broaden and decrease in intensity due to the presence of a high density of photoexcited free carriers and are completely absent in the absorption and reflection spectra as the excitation density, Iexc, approaches 3 MW/cm2, resulting in induced transparency in transmission measurements. The absorption spectra also show induced absorption below the band gap as Iexc is increased. Both the observed induced transparency and induced absorption were found to be extremely large, exceeding 4×104 cm−1 as the pump density approaches 3 MW/cm2 at 10 K. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121040
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  • 10
    Electronic Resource
    Electronic Resource
    Pressure-dependent photoluminescence study of InxGa1−xN (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 2433-2435 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We present the results of pressure-dependent photoluminescence (PL) studies of single-crystal InxGa1−xN (0≤x〈0.15) films grown on top of thick GaN epitaxial layers by metalorganic chemical vapor deposition with sapphire as substrates. PL measurements were performed at 10 K as a function of applied hydrostatic pressure using the diamond-anvil-cell technique. The luminescence emissions from the InxGa1−xN epifilms were found to shift linearly toward higher energy with increasing pressure. By examining the pressure dependence of the PL spectra, the pressure coefficients for the emission structures associated with the direct band gap of InxGa1−xN were determined. The values of the pressure coefficients were found to be 3.9×10−3 eV/kbar for In0.08Ga0.92N and 3.5×10−3 eV/kbar for In0.14Ga0.86N. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120083
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