ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of Si1−xGex(001) growth on Si(001)2×1 by gas-source molecular-beam epitaxy from Si2H6 and Ge2H6 (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 6372-6381 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Si1−xGex layers with x ranging from 0 to 0.30 were grown on Si(001)2×1 substrates at temperatures ranging from 450 to 950 °C by gas-source molecular-beam epitaxy (GS-MBE) from Si2H6 and Ge2H6. In the low-temperature surface-reaction-limited growth regime, the deposition rate RSiGe increases with increasing Ge concentration due to an enhancement in the hydrogen desorption rate resulting in a correspondingly higher steady-state dangling bond density. In the high-temperature impingement-flux-limited regime, where the steady-state hydrogen coverage approaches zero, RSiGe is controlled by the Si2H6 and Ge2H6 reactive sticking probabilities S which decrease with increasing Ge2H6 flux but are not strongly temperature dependent. SSi2H6 and SGe2H6 range from 0.036 and 0.28 on Si(001) to 0.012 and 0.094 during growth of Si0.82Ge0.18 at Ts=800 °C. In both growth regimes, large changes in RSiGe require only modest increases in incident Ge2H6 to Si2H6 flux ratios, JGe2H6/JSi2H6, due to Ge segregation which is strongly coupled to the steady state hydrogen coverage. The Ge to Si ratio in as-deposited films increases linearly, while SGe2H6/SSi2H6 remains constant, with increasing JGe2H6/JSi2H6. Hydrogen desorption and Ge segregation rates, together with Si2H6 and Ge2H6 reactive sticking probabilities, were quantitatively determined from D2 temperature-programmed desorption (TPD) measurements. The combined results from film growth kinetics and TPD studies, together with the assumption of linear superposition, were then used to develop a predictive model, with no fitting parameters, for RSiGe(Ts,JSi2H6,JGe2H6) during Si1−xGex GS-MBE. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.368882
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Development of a high-current microwave ion source for Korean Multipurposed Accelerator (abstract) : Proceedings of the 7th international conference on ion sources (1998)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 69 (1998), S. 1015-1015 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A high-current, proton linear accelerator, named as Korean multipurposed accelerator (KOMAC), is being proposed mainly for accelerator-driven transmutation technology (ADTT) by Korea Atomic Energy Research Institute (KAERI). High-current, low emittance continuous power (cw) linear accelerators favor electron cyclotron resonance (ECR) microwave ion sources as an injector (Ref. 〈citeref RID="R1" STYLE="ONLINE"〉1). Recently, these microwave sources are developed and constructed by several institutes especially for high-current cw linear accelerators. A high-density microwave ion source has been designed and constructed as a prototype ion source for the proposed KOMAC linear accelerator. The design of microwave power injection system is similar to that of the 75 keV proton injector at Los Alamos National Laboratory (Ref. 〈citeref RID="R2" STYLE="ONLINE"〉2). A 2.45 GHz, 1.5 kW magnetron source is introduced into the stainless steel plasma chamber with 10 cm diam and 20 cm length through a tapered, double-ridged waveguide and a quartz window. The microwave power supply is separated from the plasma chamber by a high-voltage waveguide break. Axial magnetic fields up to 1 kG can be provided by two sets of water-cooled solenoid coils. A single-hole extraction system is designed for extraction current up to 50 mA at 50 kV extraction voltage. The design and initial operations of the ion source in ECR regimes will be presented. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148744
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Electro-optic characteristics and switching principle of a nematic liquid crystal cell controlled by fringe-field switching (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 2881-2883 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated a nematic liquid crystal cell associated with a homogeneously aligned to twisted transition of a liquid crystal director. In the absence of an electric field, the liquid crystal molecule is homogeneously aligned under the crossed polarizers, and thus the cell appears to be black. When a fringe field induced by interdigital electrodes is applied, liquid crystal molecules rotate in plane even above electrodes and thus the cell transmits light. The device exhibits a high transmittance ratio as well as a wide viewing angle, which solves a long standing problem of low transmittance existing in the conventional in-plane switching mode. We show that the distance between electrodes smaller than the width of an electrode and cell gap is required for generating fringe field with applied voltage and rotating molecules above electrodes. We also investigate the mechanism of fringe-field switching and dependence of electro-optic effect on different cell conditions and dielectric anisotropy of liquid crystal. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122617
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Wide viewing angle, homeotropic nematic liquid-crystal display controlled by effective field (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 470-472 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electro-optic properties of a liquid-crystal display associated with a homeotropic to multidomainlike transition for a liquid crystal with a positive dielectric anisotropy have been investigated. The cell plates are prepared in such a way that, in the absence of an electric field, the liquid-crystal alignment is homeotropic. an electric field created by interdigitated electrodes on both substrates causes a director deformation of a multidomain type. The display shows wide viewing angle, excellent color characteristics, and a fast response time. The molecular director configuration, together with the electro-optic characteristics of the device, are discussed in this letter. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121903
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    High photoresponsivity of a p-channel InGaP/GaAs/InGaAs double heterojunction pseudomorphic modulation-doped field effect transistor (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 584-586 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter, we report the electrical and optical characteristics of p-channel In0.13Ga0.87As double heterojunction pseudomorphic modulation-doped field effect transistor (MODFET) structure grown by gas source molecular beam epitaxy. The Hall mobility and the density of 2-DHGs (two-dimensional hole gases) in the pseudomorphic In0.13Ga0.87As channel were measured to be 250 cm2/V s and 1.9×1012 cm−2 at 300 K, and 5800 cm2/V s and 1.5×1012 cm−2 at 23 K, respectively. The fabricated p-channel MODFET shows a good mobility property which is due to high valence band discontinuity of InGaP/GaAs/InGaAs double barriers. The peak energy in the photoluminescence spectrum from the p-channel pseudomorphic MODFET structure was found to be 1.4 eV (λ=881 nm). The photoresponsivity with this modified pseudomorphic MODFET structure shows outstandingly better than that of a pin photodiode, particularly at low incident optical power. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120813
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Piezoelectric effects on the optical properties of GaN/AlxGa1−xN multiple quantum wells (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3426-3428 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Piezoelectric effects on the optical properties of GaN/AlGaN multiple quantum wells (MQWs) have been investigated by picosecond time-resolved photoluminescence (PL) measurements. For MQWs with well thicknesses 30 and 40 Å, the excitonic transition peak positions at 10 K in continuous wave (cw) spectra are redshifted with respect to the GaN epilayer by 13 and 45 meV, respectively. The time-resolved PL spectra of the 30 and 40 Å well MQWs reveal that the excitonic transition is in fact blueshifted at early delay times due to quantum confinement of carriers. The spectral peak position shifts toward lower energies as the delay time increases and becomes redshifted at longer delay times. We have demonstrated that the results described above are due to the presence of the piezoelectric field in the GaN wells of GaN/AlGaN MQWs subject to elastic strain together with screening of the photoexcited carriers. By comparing experimental and calculation results, we conclude that the piezoelectric field strength in GaN/Al0.15Ga0.85N MQWs has a lower limit value of about 560 kV/cm. The electron and hole wave function distributions have also been obtained. The implication of our findings on the practical applications of GaN based optoelectronic devices is also discussed. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122786
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Electro-optic characteristics of a liquid crystal cell in a homogeneous-to-twisted planar mode (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 858-860 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electro-optic properties of a novel liquid crystal device associated with a homogeneous to twisted-planar (HTP) transition have been investigated. The cell plates are prepared in such a way that in the absence of an electric field the liquid crystal orientation is uniform throughout the cell, and thus between crossed polarizers the cell appears black (off state). When an electric field of a particular configuration is applied, a 90° twist is imposed, and the cell transmits light (on state). It was found that the HTP device exhibits wide viewing angle and excellent color characteristics. The dependence of the electro-optic effect on rubbing directions and cell gap has also been investigated. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.120917
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Field Evaluation of Interfacial and Partitioning Tracers for Characterization of Effective NAPL-Water Contact Areas (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 36 (1998), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The use of surface-active tracers for measuring the interfacial area between no aqueous phase liquids (NAPLs) and water was evaluated in a hydraulically isolated test cell installed in a surficial aquifer located at Hill Air Force Base (AFB), Utah. Interfacial tracers were developed at the University of Florida for quantifying immiscible fluid-fluid interfaces (air-water or NAPL-water) in porous media. Sodium dodecyl benzene sulfonate (SDBS) was used as the interfacial tracer to measure the effective NAPL-water interfacial area (aNw), while 2,2-dimethyl-3-pentanol (DMP) was used as the partitioning tracer to estimate the NAPL saturation (SN). The observed retardation of SDBS and DMP when compared to a nonreactive tracer (bromide or methanol) at eight multilevel sampling locations and one extraction well, was used to quantify the aNw and SN values averaged over the interval between the injection wells and each monitoring point. The NAPL morphology index, defined here as HN= aNw/φSN (φ= porosity), varied significantly within the test cell. In locations where the magnitude of HN was large, the NAPL was assumed to be more or less uniformly spread, providing good contact with the mobile fluid. In contrast, regions with low HN values were assumed to have NAPL that was more heterogeneously distributed as isolated patches providing poor contact with the mobile fluid. The index HN, provided by the combined use of interfacial and partitioning tracers, has important implications for NAPL source region remediation employing in situ flushing technologies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1998.tb02821.x
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Characterization of the surface structure of CH3 and CF3 terminated n-alkanethiol monolayers self assembled on Au{111} (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9134-9147 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Surface elemental and structural characterization of hexadecanethiol and heptadecanethiol (C16 and C17 for short) and 16,16,16-trifluorohexadecanethiol (FC16) self-assembled monolayers (SAMs) on a Au{111} surface have been obtained from time-of-flight scattering and recoiling spectrometry. The clean Au surface was also characterized in order to identify the azimuthal orientation of the SAMs with respect to the substrate. Classical ion trajectory simulations were used to relate the experimental scattering and recoiling data to the surface structure. The scattered and recoiled atoms originate from the outermost five–six atomic layers, and azimuthal anisotropy was observed in the measurements. The results provide a model for the SAMs in which the alkyl chains chemisorb with the S atoms situated above the face-centered-cubic (fcc) threefold sites of the Au{111} surface to form a continuous film with a ((square root of)3×(square root of)3)R30° structure that fully covers the Au surface. The orientation of the molecular axis azimuth of the SAMs relative to the Au azimuthal directions was determined. The data indicate that the molecular chains have specific tilt and twist angles relative to the Au surface and six coexisting domains resulting from the six equivalent tilt directions of the molecular axis. Dramatic changes in the anisotropic patterns of the ion scattering azimuthal scans from the surfaces of the SAMs with different terminations were observed. These phenomena result from the different tilt angles of the CH3 and CF3 groups. The data are consistent with free rotation of both the CH3 and CF3 groups. The C16 SAM exhibited the best azimuthal features and was more resistant to radiation damage from the incident Ar+ scattering beam than the other films. Due to the tilt angle of the SAMs, an "ion's eye view" of the structure, i.e., the positions of the atomic cores as experienced by the incoming keV ions, reveals a regular array of sloping cavities within each unit cell. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477629
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Chemisorption site of methanethiol on Pt{111} (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 9574-9582 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The chemisorption site of the simplest prototypical model alkanethiol compound, methanethiol [CH3SH], on a Pt{111} surface in the temperature range 298–1073 K has been investigated by means of time-of-flight scattering and recoiling spectrometry (TOF-SARS) and low-energy electron diffraction (LEED). TOF-SARS spectra of the scattered and recoiled ions plus fast neutrals were collected as a function of crystal azimuthal rotation angle δ and beam incident angle α using 4 keV Ar+ primary ions. At room temperature, the adsorption of methanethiol produces a partially disordered overlayer that gives rise to a diffuse (3×3)R30° LEED pattern and three-fold symmetry in the scattering profiles. Heating this surface layer results in the sequential dehydrogenation of the methanethiol and the formation of S–C species at elevated temperatures. By ∼373 K, hydrogen is absent from the TOF-SARS spectra and a sharp (3×3)R30° LEED pattern is observed. The model developed from the scattering data is consistent with the preservation of the adsorption site at elevated temperatures, but a change in the S–C bond angle with respect to the surface plane. For the fully dehydrogenated species, the S atoms reside ∼1.6±0.2 Å above the surface in face-centered-cubic (fcc) three-fold sites and the C atoms reside ∼1.5±0.4 Å in hexagonal-close-packed (hcp) three-fold sites. It is proposed that the remarkable stability of this SC adsorbate results from bonding of both the S and C atoms to the surrounding Pt atoms, i.e., a Pt-stabilized SC moiety. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.477619
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...