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  • 1
    Electronic Resource
    Electronic Resource
    Stresses in Pt/Pb(Zr,Ti)O3/Pt thin-film stacks for integrated ferroelectric capacitors (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 1926-1933 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of the stresses in a ferroelectric capacitor stack deposited on an oxidized silicon substrate is presented. The capacitor stack was prepared with sputtered Pt bottom and top electrodes and a ferroelectric film of composition PbZrxTi1−xO3 (PZT) with x≈0.5 which was deposited using a modified sol-gel technique. The stresses were determined by the changes in the radius of curvature of the wafer following the deposition steps, during and after annealing treatments, and after etching steps in which the top electrode, the PZT film, and the bottom electrode were successively removed. The largest stress effects are found in the Pt electrodes which are deposited under conditions giving an intrinsic compressive stress. An annealing treatment exceeding 500 °C changed the stress of the bottom electrode from ≈−750 MPa (compressive) to a large tensile stress (≈1 GPa). This stress is largely thermal and is caused by the differences in thermal-expansion coefficients of the Pt film and the Si substrate. The stress of the PZT film is numerically relatively small (below ≈200 Mpa) and it is found to be of both thermal and intrinsic origin. The deposition and annealing of the top electrode has a profound influence on the stress of the PZT film as well as on the electrical properties. The stress behavior of the as-deposited PZT film shows a poling direction mainly in the plane of the substrate. An annealing of the complete capacitor stack changes the poling direction of the ferroelectric film to be perpendicular to the substrate. This explains the observed electrical switching properties of as-prepared as well as annealed ferroelectric capacitors. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.360230
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  • 2
    Electronic Resource
    Electronic Resource
    Ferroelectric properties and fatigue of PbZr0.51Ti0.49O3 thin films of varying thickness: Blocking layer model (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 2405-2413 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferroelectric capacitors having Pt bottom and top electrodes and a ferroelectric film of composition PbZr0.51Ti0.49O3 (PZT) were fabricated and investigated. The PZT films of thicknesses varying from 0.12 to 0.69 μm were prepared by organometallic chemical-vapor deposition. Annealed capacitors were investigated by capacitance, hysteresis, and pulse switching measurements. It is found that the thickness dependence of the reciprocal capacitance, the coercive voltage, and the polarization measured by pulse switching can all be explained by a blocking layer model, in which a dielectric layer of thickness dbl and relative permittivity εbl is situated between the PZT film and an electrode. It is shown that (i) the coercive field is independent of thickness having a value of 2.4 V/μm; (ii) the ratio εbl/dbl is in the range 20–28 nm−1; (iii) the voltage across the blocking layer is proportional to the polarization, Vbl=cP, where c=4.1±0.5 V m2/C; and (iv) the polarization depends on the electric field in the PZT layer, independent of thickness. Pulse switching endurance measurements showed that in the saturation range the fatigue for these ferroelectric capacitors is determined by the pulse voltage and is independent of the thickness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.357589
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  • 3
    Electronic Resource
    Electronic Resource
    High-brightness and high-resolution RHEED system (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 2940-2944 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A RHEED system, consisting of a high-resolution (75-μm FWHM) and high-brightness (10-μA) electron gun, and a phosphor screen with high resolution and good linearity, was developed. The system is based on concepts from projection television. The results show that this setup is particularly useful for obtaining quantitative RHEED patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1140631
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  • 4
    Electronic Resource
    Electronic Resource
    Video system for quantitative measurements of RHEED patterns (1986)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 57 (1986), S. 1363-1367 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Two different signal-processing systems are described for the conversion of reflection high-energy electron diffraction (RHEED) patterns, displayed on a phosphor screen, into quantitative data. Both systems are based on the use of a sensitive video camera. One system using a multichannel boxcar integrator is particularly suited to simultaneous temporal measurements of different RHEED beams and integrated line intensities, while the other can be applied to fast data acquisition of line profiles. The system performance is illustrated and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138601
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  • 5
    Electronic Resource
    Electronic Resource
    Preparation and ferroelectric properties of PbZr0.53Ti0.47O3 thin films by spin coating and metalorganic decomposition (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2290-2298 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Films with a composition PbZr0.53Ti0.47O3 were prepared on different platinum bottom electrodes using a spin-coating process followed by metalorganic decomposition. The film morphology and structure were characterized by scanning electron microscopy and x-ray diffraction analysis. The morphology was strongly influenced by the heat cycle used to form the PbZr0.53Ti0.47O3 layer. Fast heating and high-fire temperatures produced smooth films, while slow heating and low-fire temperatures gave films having a rosette perovskite phase and an inter-rosette second phase. The films were characterized electrically by measuring hysteresis loops and capacitance and conductance versus bias voltage and by pulse-switching measurements. The dependence of the switched and nonswitched polarization on the number of switching cycles (i.e., the fatigue behavior) is found to be much better for fast-heated than for slowly heated films. Switching lifetimes exceeding 1011 cycles were measured. The type of platinum bottom electrode used was found to have a large influence on the ferroelectric properties of the lead zirconate titanate films.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349422
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  • 6
    Electronic Resource
    Electronic Resource
    Improvement of the optical properties of metalorganic chemical vapor deposition grown GaN on sapphire by an in situ SiN treatment (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 2390-2392 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effect of an in situ SiN treatment of sapphire substrates on the optical properties of GaN films grown by metalorganic chemical vapor deposition. The SiN deposition, partially covering the substrate, forms a mask for the formation of nanoscale auto-organized GaN islands. These islands formed upon an increase of the temperature after deposition of a GaN buffer layer on this mask. A photoluminescence study of the GaN epilayers obtained by lateral overgrowth of these islands shows significant enhancement of the luminescence emission intensity of the near band edge peaks and a reduction of the full width at half maximum of the donor bound exciton (D0X) peak by 32% down to 4 meV compared to in our standard process. The GaN films grown using SiN treatment are highly stressed as evidenced by a blueshift of 10 meV in the D0X peak energies. Photoelectrochemical etching in aqueous solution of KOH was applied to reveal the dislocation density. The density of "whisker-like" etch features, which form due to the presence of dislocations, was reduced from 6×109 cm−2 in standard GaN films to 8×108 cm−2 in the GaN layers grown with the optimized SiN treatment. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1409277
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  • 7
    Electronic Resource
    Electronic Resource
    High rate epitaxial lift-off of InGaP films from GaAs substrates (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2131-2133 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Centimeter sized, crack-free single crystal InGaP films of 1 μm thickness were released from GaAs substrates by a weight-induced epitaxial lift-off process. At room temperature, the lateral etch rate of the process as a function of the applied Al0.85Ga0.15As release layer thickness was found to have a maximum of 3 mm/h at 3 nm. Using 5-nm-thick AlAs release layers, the etch rate increased exponentially with temperature up to 11.2 mm/h at 80 °C. Correlation of the experimental data with the established theoretical description of the process indicate that the model is qualitatively correct but fails to predict the etch rates quantitatively by orders of magnitude. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126276
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  • 8
    Electronic Resource
    Electronic Resource
    Optical investigation of shallow acceptor states in GaN grown by hydride vapor-phase epitaxy (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 4109-4111 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The evolution of low-temperature photoluminescence (PL) spectra with the thickness of the layer (3–400 μm) is investigated on high-quality GaN grown by hydride vapor-phase epitaxy. With increasing layer thickness, three acceptor bound exciton peaks are found to reduce in intensity, although the impurity concentrations, measured by secondary ion mass spectrometry, do not depend on the sample thickness. The observed acceptor transitions are attributed to intrinsic defects, originating from the substrate/layer interface and decreasing in density with the thickness of the layer. The optical properties, studied by reflectance, temperature and excitation power dependent PL, are compared to those of homoepitaxial GaN films grown by metalorganic chemical vapor deposition. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1427151
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  • 9
    Electronic Resource
    Electronic Resource
    Exciton-related photoluminescence in homoepitaxial GaN of Ga and N polarities (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 2355-2357 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A photoluminescence (PL) study of GaN homoepitaxial layers grown by metal–organic chemical-vapor deposition demonstrates the high optical quality of N-face layers deposited on vicinal (0001¯) GaN substrates. In contrast to broad PL emission in exact (0001¯) layers, narrow-bound (0.9 meV) and free- (A and B) excitonic transitions are observed. By following the PL spectra as a function of temperature and excitation power, the main optical transitions in the Ga- and the misoriented N-face layers are found to be the same. Observed differences are related to the distinct creation of donor and acceptor states in the samples of different polarities. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.126344
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  • 10
    Electronic Resource
    Electronic Resource
    Pulse measurements on ferroelectric capacitors simulating memory switching (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 3326-3328 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Pulse switching investigations of ferroelectric PbZr0.44Ti0.56O3 capacitors prepared by organometallic chemical vapor deposition were done to simulate a ferroelectric memory. The released charge from the ferroelectric capacitor was measured with a reference capacitor, representing the bitline capacitances in a memory. A large reference capacitor will result in complete switching at low voltages, but gives a small detection signal. For a small reference capacitor partial switching and substantial backswitching of the ferroelectric material occurs. Here, a higher detection signal and improved endurance ((approximately-greater-than)1012 cycles) are found. Scaling the results indicates the feasibility of 0.2 μm2 capacitors operating at 3 V. © 1994 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.112381
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