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9 Feb 1998

Volume 72, Issue 6, pp. 627-747

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Simplified analysis of some complex film stacks in x-ray reflectivity

Matthew A. Marcus

Appl. Phys. Lett. 72, 659 (1998); http://dx.doi.org/10.1063/1.120838 (3 pages) | Cited 3 times

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X-ray reflectivity (XRR) is commonly used to measure the thickness, density, and roughness of thin films. XRR can be used on multilayered films, however the data analysis then involves a complex fit. Such fits display many local minima for stacks of more than two layers. It is shown how the modulated diffuse scattering arising from the correlated roughness effect can sometimes be used to measure the thickness of the top film in the stack, hence reducing the size of the parameter space to be searched. Data for three- and four-layer stacks will be presented. © 1998 American Institute of Physics.
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78.20.-e Optical properties of bulk materials and thin films
68.65.-k Low-dimensional, mesoscopic, nanoscale and other related systems: structure and nonelectronic properties
78.70.Ck X-ray scattering

On determining the relevance of athermal nucleation in rapidly quenched liquids

James S. Im, Vikas V. Gupta, and M. A. Crowder

Appl. Phys. Lett. 72, 662 (1998); http://dx.doi.org/10.1063/1.120839 (3 pages) | Cited 9 times

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When a liquid is quenched, classical nucleation theory asserts that at least a fraction of the solid must nucleate by way of the athermal mechanism. In this letter, we show that this fundamental issue regarding the relative rates of athermal and thermal nucleation during a quench can be readily addressed by comparing the instantaneous quench rate that is in effect at any point during the quench, −dT/dt, to kn∗+/(∂n∗/∂T) evaluated at the corresponding temperature. This and additional considerations permit the construction of a nucleation-mechanism diagram that maps out the thermal-mechanism-dominated and athermal-mechanism-dominated domains in the quench-rate–temperature parameter space. By projecting the thermal trajectory of a quench on the diagram, the relevance or irrelevance of the athermal mechanism, as well as the extent to which athermal mechanism participates in the transformation, can be assessed. © 1998 American Institute of Physics.
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64.60.Q- Nucleation
82.60.Nh Thermodynamics of nucleation
64.70.D- Solid-liquid transitions
81.30.Fb Solidification

Control of epitaxial growth for SrBi2Ta2O9 thin films

J. H. Cho, S. H. Bang, J. Y. Son, and Q. X. Jia

Appl. Phys. Lett. 72, 665 (1998); http://dx.doi.org/10.1063/1.120840 (3 pages) | Cited 18 times

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We report the (a00) oriented as well as the (00l) oriented epitaxial SrBi2Ta2O9 thin film grown on (100) LaAlO3 and (200) yttria-stabilized zirconia single crystal substrates. On (100) SrTiO3 single crystal substrate, we only observe the (00l) oriented epitaxial growth of SrBi2Ta2O9 thin film. We infer that the (a00) oriented epitaxial growth results from the strain by the lattice mismatch. The band gaps of the (00l) and the (a00) oriented SrBi2Ta2O9 films are ∼ 3.9 and ∼ 3.5 eV, respectively. The two epitaxial orientations of ferroelectric SrBi2Ta2O9 thin film can provide an opportunity to study the effects on microwave and optical waveguides as well as underlying anisotropic physical properties. © 1998 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.55.-g Dielectric thin films
81.15.Kk Vapor phase epitaxy; growth from vapor phase
81.15.Fg Pulsed laser ablation deposition
77.80.-e Ferroelectricity and antiferroelectricity
42.65.Wi Nonlinear waveguides
42.79.Gn Optical waveguides and couplers
71.20.Ps Other inorganic compounds

Effect of coupling structure of Eu on the photoluminescent characteristics for ZnO:EuCl3 phosphors

Y.-K. Park, J.-I. Han, M.-G. Kwak, H. Yang, S.-H. Ju, and W.-S. Cho

Appl. Phys. Lett. 72, 668 (1998); http://dx.doi.org/10.1063/1.120833 (3 pages) | Cited 22 times

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In this study we have synthesized ZnO:EuCl3 phosphors under various sintering atmospheres and temperatures, and investigated the effect of coupling structure of Eu in ZnO upon the photoluminescent characteristics for the purpose of searching for optimum conditions towards pure red emission. The analysis of x-ray diffraction and photoluminescence spectra measurements indicate that, for ZnO:EuCl3 phosphors sintered in vacuum, Eu exists in the host lattice as EuOCl and effectively quenches the broad-band emission of the ZnO host, consequently isolating the red emission due to Eu3+ ion. © 1998 American Institute of Physics.
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78.55.Et II-VI semiconductors

Cutoff anomalies in light emitted from the tunneling junction of a scanning tunneling microscope in air

R. Pechou, R. Coratger, F. Ajustron, and J. Beauvillain

Appl. Phys. Lett. 72, 671 (1998); http://dx.doi.org/10.1063/1.120841 (3 pages) | Cited 9 times

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Light emission from noble metal tunneling junctions of a scanning tunneling microscope has been detected in air. A spectroscopic study of the photons emitted from Au/Au and PtIr/Au junctions has been performed as a function of the applied bias voltage. A higher-energy emission band, which grows in as a function of bias voltage, has been observed in the recorded spectra. The high energy cutoffs of the recorded spectra do not follow the quantum law hνcutoff = eVsample. © 1998 American Institute of Physics.
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78.66.Bz Metals and metallic alloys
78.40.Kc Metals, semimetals, and alloys
07.79.Cz Scanning tunneling microscopes
68.37.Ef Scanning tunneling microscopy (including chemistry induced with STM)
68.37.Ps Atomic force microscopy (AFM)
68.37.Rt Magnetic force microscopy (MFM)
68.37.Uv Near-field scanning microscopy and spectroscopy

Collinear mirage effect measurement of the thermal diffusivity in Ferronematics

S. M. Shibli, A. L. L. Dantas, and D. Walton

Appl. Phys. Lett. 72, 674 (1998); http://dx.doi.org/10.1063/1.120864 (3 pages) | Cited 2 times

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Thermal diffusivity results obtained for a lyotropic nematic liquid crystal sample doped with different amounts of ferrofluid (ferronematics) are reported. The collinear mirage technique was used for measurements along axes parallel and perpendicular to the director of this anisotropic material. The results show that as the ferrofluid concentration increases the thermal diffusivity decreases, leading to values even lower than those already reported for plain lyotropic nematic liquid crystals. The ratio of the two diffusivities increases as the ferrofluid concentration increases, reaching the exact value theoretically expected, though not achieved experimentally, for plain lyotropic nematic liquid crystals. © 1998 American Institute of Physics.
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61.30.Eb Experimental determinations of smectic, nematic, cholesteric, and other structures
75.50.Mm Magnetic liquids
66.25.+g Thermal conduction in nonmetallic liquids
65.90.+i Other topics in thermal properties of condensed matter (restricted to new topics in section 65)
78.20.N- Thermo-optic effects
78.20.nb Photothermal effects
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