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  • 1
    Digitale Medien
    Digitale Medien
    Investigation of the ablated flux characteristics during pulsed laser ablation deposition of multicomponent oxides (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7497-7505 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The ablated flux characteristics of PbZr0.52Ti0.48O3 (PZT), La0.5Sr0.5CoO3 (LSC), and MgO ceramic targets have been studied as functions of the ablation time, the ablation energy, and the chamber gas pressure. The time dependence of the ablation rate shows an initial exponential decay, reaching a steady-state value at longer times. The energy dependence of the ablation rate (in vacuum) reveals a distinct ablation threshold energy for MgO ablation, while for PZT and LSC no ablation threshold is evident. The differences in the ablation characteristics of these materials are explained mainly by differences in their melting points, thermal conductivities, and absorption coefficients. Upon adding O2 gas, a visual change in the color and shape of the PZT ablation plume is evident. The color change indicates a gas phase reaction of the ablated species with the O2 gas, while the shape change implies a change in the angular distribution of the ablated species. We have measured a narrowing of the ablated flux distribution from a PZT target as O2 is added, from a cos40 θ distribution in a low pressure, up to a cos260 θ distribution in an O2 pressure of 300 mTorr. This narrowing, or focusing, of the ablation plume is observed with high laser energies and high pressures of O2 or noble gases. At low laser power, the deposition rate decreases and the plume broadens as the gas pressure is increased. The plume narrowing and plume broadening regimes are both controlled by gas scattering effects. The angular distribution of depositing species, and the ratio of deposition flux to O2 flux, are very different in each of these regimes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.354974
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  • 2
    Digitale Medien
    Digitale Medien
    Uniform deposition of YBa2Cu3O7−δ films over large areas using ion-beam sputtering (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 6952-6957 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Uniform films of YBaCuO have been deposited over 4-in.- (100-mm) diam, unheated Si wafers using ion-beam sputtering of a stoichiometric YBa2Cu3O7−δ target. Rutherford backscattering spectrometry reveals that within a 3-in. diam, the thickness variation is ±2.9%, and the compositional uniformity of Y, Ba, and Cu is ±0.9%, ±5.2%, and ±3.4%, respectively. The average film composition is Y1.03Ba1.88Cu3.09O7−δ. Deposition onto unheated substrates virtually eliminates the problem of the low sticking coefficients of Ba and Cu, and is much simpler for film synthesis and processing. The observed difference from the 1:2:3 target composition is attributed mainly to angular differences in the sputtered-flux distribution of each element. These effects should be minimized by substrate rotation. In order to obtain useful superconducting films, a post-deposition anneal on a suitable substrate or buffer layer is required. Using a relatively low temperature (∼810 °C), low O2 pressure (1.2 Torr) post-anneal, we show that oriented, superconducting films can be obtained on single-crystal MgO and SrTiO3 substrates. Films annealed under these conditions on MgO are predominantly c-axis oriented, whereas those on SrTiO3 are predominantly a-axis oriented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.349822
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  • 3
    Digitale Medien
    Digitale Medien
    Synthesis and characterization of Pb (ZrxTi1−x)O3 thin films produced by an automated laser ablation deposition technique (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5197-5207 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ferroelectric lead zirconium titanate [Pb (ZrxTi1−x)O3] (PZT) thin films have been synthesized by using an automated laser ablation deposition technique with a capability for layer-by-layer or simultaneous deposition of elemental film constituents. The technique is suitable for producing multicomponent and/or multilayered thin films with controlled stoichiometry, such as high-temperature superconductor, ferroelectric, and electro-optic thin films. PZT films were synthesized on MgO (100) by either sequential deposition of layers of ZrO2, TiO2, and PbO, produced by laser ablation of ZrO2, TiO2, and PbO targets, or by simultaneous deposition of all species from ablation of stoichiometric or PbO-rich PZT targets. Films were deposited at 200 °C and subsequently annealed at 600 °C for different periods of time. The orientation, microstructure, surface topography, and composition of the films were characterized by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectrometry, respectively. As-deposited layer films consists of highly oriented (001) PbO layers, from which highly oriented (110) PZT films are produced after postdeposition annealing. On the other hand, laser ablation of bulk PZT targets yields amorphous as-deposited films, which evolve into highly oriented (100) PZT films after postdeposition annealing. Preliminary electrical characterization of the PZT films included polarization hysteresis, fatigue, conductivity (ac and dc), and capacitance versus voltage measurements. From the initial electrical measurements, it appears that the remnant polarization of the layered PZT films is similar to that of the films produced by laser ablation of bulk PZT targets.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.353746
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  • 4
    Digitale Medien
    Digitale Medien
    Microstructure of ultrananocrystalline diamond films grown by microwave Ar–CH4 plasma chemical vapor deposition with or without added H2 (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 90 (2001), S. 118-122 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Ultrananocrystalline diamond (UNCD) films, grown using microwave plasma-enhanced chemical vapor deposition with gas mixtures of Ar–1%CH4 or Ar–1%CH4–5%H2, have been examined with transmission electron microscopy (TEM). The films consist of equiaxed nanograins (2–10 nm in diameter) and elongated twinned dendritic grains. The area occupied by dendritic grains increases with the addition of H2. High resolution electron microscopy shows no evidence of an amorphous phase at grain boundaries, which are typically one or two atomic layer thick (0.2–0.4 nm). Cross-section TEM reveals a noncolumnar structure of the films. The initial nucleation of diamond occurs directly on the Si substrate when H2 is present in the plasma. For the case of UNCD growth from a plasma without addition of H2, the initial nucleation occurs on an amorphous carbon layer about 10–15 nm thick directly grown on the Si substrate. This result indicates that hydrogen plays a critical role in determining the nucleation interface between the UNCD films and the Si substrate. The relation between diamond nuclei and Si is primarily random and occasionally epitaxial. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1377301
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  • 5
    Digitale Medien
    Digitale Medien
    Second harmonic generation in potassium niobate thin films (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 435-438 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Green light produced by second harmonic generation has been observed in an epitaxial orthorhombic KNbO3 thin film planar waveguide produced by ion-beam sputter deposition on a (100)-oriented MgO single crystal substrate. A Nd:YLF laser beam, with a wavelength of 1.053 μm and ∼80 ps, 100 MHz pulses under mode-locked operation, was coupled into the waveguide using a rutile prism, and a green light streak 3–4 mm long was seen in the guide. The TM0 mode of the input beam was phase matched to the TE1 mode of the second harmonic for a film thickness of 2300 A(ring). Second harmonic generation was also observed in a nonwaveguided configuration on thicker (4600–6500 A(ring)) films on both MgO and KTaO3 substrates. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.360622
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  • 6
    Digitale Medien
    Digitale Medien
    Electrical properties of ferroelectric thin-film capacitors with hybrid (Pt,RuO2) electrodes for nonvolatile memory applications (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 2146-2154 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: For Pb(ZrxTi1−x)O3 (PZT) thin-film capacitors to be used in ferroelectric nonvolatile memories, they must have low polarization fatigue and low leakage currents. PZT capacitors fabricated in our laboratory with RuO2 electrodes exhibit excellent polarization fatigue characteristics, but they have large and variable leakage currents (typically 10−3–10−4 A/cm2 at 1 V). On the other hand, PZT capacitors with Pt electrodes have low leakage currents (typically 〈10−9 A/cm2 at 1 V), but they undergo severe polarization fatigue. New (Pt,RuO2) hybrid electrodes which result in PZT capacitors that combine the excellent fatigue behavior of RuO2/PZT/RuO2 with the low leakage currents of Pt/PZT/Pt capacitors have been developed. The hybrid electrodes studied are of two main types: one type consisted of Pt/RuO2 or RuO2/Pt double layers, while the other consisted of a codeposited Pt–RuO2 layer. All capacitors discussed here had an RuO2/PZT/hybrid electrode/MgO heterostructure. It will be shown that capacitors with negligible fatigue (up to 1011 switching cycles) and with leakage currents that are two to four orders of magnitude lower than those of RuO2/PZT/RuO2 capacitors can be achieved. In addition, the capacitors with hybrid electrodes have very small retention loss. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.359572
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  • 7
    Digitale Medien
    Digitale Medien
    Electro-optic characterization of ion beam sputter-deposited KNbO3 thin films (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1964-1966 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The Electro-optic properties of potassium niobate thin films deposited using a computer-controlled ion beam sputtering technique have been studied for the first time. Epitaxial and polycrystalline films were deposited on single crystal magnesium oxide and highly (111) oriented films were deposited on sapphire for the study. All films exhibited a quadratic-like dependence of birefringence shift on the applied electric field. The microstructure of the films and its relation to the observed electro-optic properties is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105033
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  • 8
    Digitale Medien
    Digitale Medien
    Observation of growth modes during metal-organic chemical vapor deposition of GaN (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 3326-3328 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We present real-time surface x-ray scattering measurements during homoepitaxial growth of GaN by metal-organic chemical vapor deposition. We observed intensity oscillations corresponding to the completion of each monolayer during layer-by-layer growth. The growth rate was found to be temperature independent and Ga-transport limited. Transitions between step-flow, layer-by-layer, and three-dimensional growth modes were determined as a function of temperature and growth rate. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.123333
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  • 9
    Digitale Medien
    Digitale Medien
    Studies of film growth processes and surface structural characterization of ferroelectric memory-compatible SrBi2Ta2O9 layered perovskites via in situ, real-time ion-beam analysis (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 2671-2673 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: In situ, real-time studies of layered perovskite SrBi2Ta2O9 (SBT) film growth processes were performed using a time-of-flight ion scattering and recoil spectroscopy (TOF ISARS) technique. These studies revealed two important features related to the synthesis of SBT films via ion-beam sputter-deposition, namely: (a) atomic oxygen originating from a multicomponent SBT target during the sputtering process is incorporated in the growing film more efficiently than molecular oxygen; and (b) the SBT surface appears to be terminated in an incomplete (Bi2O2)2+layer with a top surface of oxygen atoms, which may be responsible for the high resistance to polarization fatigue exhibited by Pt/SBT/Pt capacitors. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.117554
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  • 10
    Digitale Medien
    Digitale Medien
    Spectroscopic analysis of electronically excited species in XeCl excimer laser-induced plasmas from the ablated high-temperature superconductor YBa2Cu3O7 (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 72-74 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Optical spectroscopic analyses have been performed to study luminescence from plasmas produced by ablation of YBa2Cu3O7 single-phase high Tc bulk superconductors exposed to XeCl excimer laser (308 nm) pulses. Only excited atomic neutral and single ionized species (Cu/Cu+, Ba/Ba+, Y/Y+) were observed within the experimental resolution of an optical multichannel analyzer detection system, when irradiating the targets in vacuum (∼10−5–10−4 Torr). Conspicuously absent in the spectra (300–800 nm range) are molecular emission bands that would appear if large excited molecules or fragments were present. Implications of the present results are discussed which relate to an early hypothesis about the laser ablation mechanism and their influence on high Tc film characteristics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.100573
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