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  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Femtosecond fluorescence depletion spectroscopy of NO2 multiphoton dissociation dynamics (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 7183-7186 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Two-color femtosecond pump–probe spectroscopy has been applied to the multiphoton dissociation of NO2 with a time resolution of ≤350 fs. At laser intensities in the range (similar, equals)3×1012–2×1013 W cm−2 and a wavelength of 400 nm, NO2 absorbs three photons before dissociation. Nascent NO A 2Σ+ product in its n′=0 and 1 vibrational levels is probed by single-photon fluorescence depletion at 800 nm. Analyses of the ultrafast transient behavior at different intensities leads to an estimate of ≤600 fs for formation of NO A 2Σ+ n′=0 and 1. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480046
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  • 3
    Electronic Resource
    Electronic Resource
    Diffraction of high-energy synchrotron radiation (invited) (abstract) : Proceedings of the 5th international conference on synchrotron radiation instrumentation (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 1614-1614 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Diffraction of high-energy synchrotron radiation at energies above 100 keV combines advantages of conventional x-ray diffraction and neutron diffraction. For hard x rays absorption in matter is weak with typical mean free paths of several millimeters. Bulk properties are studied on large samples. With a three-crystal diffractometer an excellent k-space resolution of about 10−5 A(ring)−1 transversal and 10−4 A(ring)−1 longitudinal is achieved. In this contribution the particularities of hard x rays, the instrumental setup, and the k-space resolution are discussed and presented. The potential of the new method will be demonstrated on two examples: magnetic diffraction from MnF2 and the structural phase transition of SrTiO3. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146465
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  • 4
    Electronic Resource
    Electronic Resource
    Magnetism of ultrathin FeCo (001) films on GaAs(001) (2000)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5457-5459 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial Fe34Co66 films in a thickness range from 3 to 100 monolayers (MLs) were grown by molecular beam epitaxy on GaAs(001) at room temperature. The growth was characterized by reflection high energy electron diffraction and x-ray diffraction. The magnetic properties were investigated by alternating gradient magnetometry magneto-optic Kerr effect, and superconducting quantum interference device magnetometry. The films show a strong interface-induced uniaxial in-plane anisotropy with the easy axis along [110]. In addition, the fourfold anisotropy coefficient changes sign around 6 ML i.e., the easy axis of the fourfold anisotropy switches from 〈110〉 to 〈100〉 with decreasing thickness. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.373371
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  • 5
    Electronic Resource
    Electronic Resource
    Nonimaging characterization of imperfect single crystals by means of a three-crystal diffractometer for high energy synchrotron radiation (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 3680-3684 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A three-crystal diffractometer for synchrotron radiation with energies of 100 keV and higher has been used in a nondispersive setting to map out the distribution of Bragg scattered intensity in the scattering plane with very high resolution. By using perfect silicon crystals in symmetrical Laue geometry for reflection 220 as monochromator and analyzer, respectively, a resolution of ≈2×10−4 A(ring)−1 in the direction parallel to the reciprocal lattice vector G220 and of ≈10−5 A(ring)−1 in the direction perpendicular to G220 has been achieved at high counting rates. As a first example the mosaic structure of a plastically deformed silicon crystal has been characterized with respect to its mosaic distribution and lattice parameter fluctuations. Second, the study of a silicon-germanium gradient crystal, produced by means of the chemical vapor deposition technique, demonstrated that the substrate peak could be well separated from the intensity distribution of the gradient crystal. A two-dimensional contour plot of the intensity distribution in the vicinity of 220 shows the variation of the lattice parameters in the gradient crystal, as well as the lattice plane tilts of the substrate and the silicon-germanium layers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352927
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  • 6
    Electronic Resource
    Electronic Resource
    Ag-induced multistep formation on Si(001) (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2185-2187 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The step topography of 4°-misoriented Si(001) surfaces was examined by scanning tunneling microscopy and spot profile analyzing–low-energy electron diffraction. The clean Si(001)-(2×1) surface proves to be a single domain substrate, which is characterized by a regular array of double steps. This step structure is changed dramatically upon adsorption of submonolayer quantities of Ag at ∼700 K. In this case, the formation of multisteps with fourfold, sixfold, and eightfold step heights occurs. The single domain character of the substrate is preserved, now showing a Ag-induced (3×2) reconstruction. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115097
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  • 7
    Electronic Resource
    Electronic Resource
    Low-temperature photoluminescence from CdTe grown by hot-wall epitaxy on GaAs (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1220-1222 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low-temperature near-band-edge photoluminescence of thick (d≈36 μm) (100)CdTe epilayers grown on (100)GaAs substrates is investigated. Besides a dominating bound exciton emission, evidence for free-exciton emission (n=1 and 2) and two electron transitions (TETs) of donor-bound excitons is found. The defect involved in the TET is most likely a gallium-related donor. This is concluded from the TET line wavelength adopting recent bulk CdTe TET data. A new emission line at 781.4 nm (1586.7 meV) is observed. It is tentatively assigned to a TET of a free exciton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.101660
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  • 8
    Electronic Resource
    Electronic Resource
    Solving the structural model for the Si(001)–In(4×3) surface (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 203-205 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The atomic geometry, energetic, and scanning tunneling microscopy (STM) simulations of the In-induced Si(001)-(4×3) surface have been investigated using first-principles total energy calculations. We have studied three distinct (4×3) structural models, which have been proposed based on STM and x-ray diffraction experiments. The energetic stability calculations indicate that the (4×3) model formed by In–Si–In mixed trimer is the most stable structure. In addition, we have simulated the STM images (for occupied states) of these three models. Our STM image for the In–Si–In mixed trimer structure presents a good agreement with the experimentally observed single central protrusion localized on the top-layer Si atom. Also, the calculated equilibrium atomic geometry of the In–Si–In mixed trimer model presents a good agreement with the experimentally obtained x-ray diffraction results. The other two proposed models are energetically less favorable by as much as 0.2 eV/(1×1) compared to the mixed trimer model. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1383275
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  • 9
    Electronic Resource
    Electronic Resource
    Stacking fault effects in pure and n-type doped GaAs (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 907-909 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using ab initio total-energy calculations, we investigate the effects of stacking faults on the properties of dopants in pure and n-type doped GaAs. We find that the Si impurity segregates towards a GaAs stacking fault. A Si atom at a Ga site in the stacking fault, in either a neutral or a negative charge state, is energetically favorable as compared to a Si atom at a Ga site in a crystalline environment by as much as 0.2 eV. We also find that a Si impurity in the stacking fault cannot occupy metastable positions, as occurs in the formation of DX centers. Thus, stacking faults can prevent the formation of DX-like centers in GaAs. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1347005
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  • 10
    Electronic Resource
    Electronic Resource
    Energy selective optically pumped stimulated emission from InGaN/GaN multiple quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 560-562 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optically pumped stimulated emission (SE) from InGaN/GaN multiple quantum wells (MQWs) grown by metalorganic chemical vapor deposition has been systematically studied as a function of excitation photon energy (Eexc) to further understand the origin of SE in these structures. Optically pumped SE was observed for excitation photon energies well below that of the absorption edge of the MQWs, indicating the states responsible for the soft absorption edge in these structures can efficiently couple carriers with the gain region. "Mobility edge"-type behavior in the SE peak was observed as Eexc was varied. The effective mobility edge measured in these SE experiments lies ∼110 meV above the main spontaneous emission peak and ∼62 meV above the SE peak. Tuning the excitation energy below the mobility edge was found to be accompanied by a drastic increase in the SE threshold due to a decrease in the effective absorption cross section. The experimental results indicate that the SE peak observed here has the same microscopic origin as the spontaneous emission peak, i.e., radiative recombination of localized states. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121855
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