Very large third-order optical nonlinearity, χ(3)∼2.5×10−6 esu, measured by a degenerate four wave mixing method using a short pulse (70 picosecond) laser, has been found in the rapid-thermal annealed Au:SiO2 composite films at concentrations below the Au percolation threshold. The dependence of the χ(3) on Au concentration, p, follows a cubic power law. The maximum figure of merit, χ(3)/α (with α being the absorption coefficient) is about 10−11 esu cm. We explain this result as due to local field enhancement arising from the Mie resonance of the Au nanoclusters, with strong interaction between the nanoclusters further promoting the effect.

The wavelength dependence of the third-order nonlinear optical susceptibilities, χ(3), of the Au:TiO2 composite films with Au concentration varying from 15% to 60% (volume fraction), was measured by a degenerate four-wave mixing (DFWM) technique using a probe laser with a pulse width of 200 fs. It was found that, with the wavelength of the probe laser close to the surface plasmon resonance (∼680 nm), both the χ(3) and the figure of merit, χ(3)/α (α is optical absorption coefficient) were significantly enhanced. The maximum value of the χ(3) was 6×10−7 esu and occurred at an Au concentration of about 38%. Femtosecond time-resolved DFWM measurements revealed that the response time of the optical nonlinearity in the Au:TiO2 films is extremely fast. The time-resolved DFWM results suggest that the main physical mechanism involved in the optical nonlinearity in Au:TiO2 films on the femtoseconds time scale is the interband electric–dipole transition, and the hot electron excitation only partially contributes to the χ(3) on the femtosecond time scale and it becomes dominant only in the picosecond region.

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Three sorts of probe laser, which have pulse durations of 200 fs, 35 ps, and 70 ps, were employed in the measurement of the third-order nonlinear optical susceptibility x((3)) in Au:SiO(2) composite films in a degenerate four-wave mixing scheme. We found that the composite films at their absorption peak (~550 nm) had a maximum x((3)) , which depends strongly on the pulse width of the probe laser. The value of x((3)) measured with a 70-ps laser was ~30 times larger than that measured with a 200-fs laser. The time-resolved measurements revealed that the optical nonlinearity on the femtosecond time scale is attributable mainly to contributions from the interband electric-dipole transition (especially at low concentrations) and partly to those from hot electrons rather than being dominated by hot-electron excitation in the picosecond regime.

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Annealing induced coherent evolutions of biaxial strain and antiferromagnetic-insulator phase in La0.625Ca0.375MnO3 films J. Appl. Phys. 112, 063716 (2012) The effect of the top electrode interface on the hysteretic behavior of epitaxial ferroelectric Pb(Zr,Ti)O3 thin films with bottom SrRuO3 electrode J. Appl. Phys. 112, 064116 (2012) Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry Appl. Phys. Lett. 101, 131601 (2012) Applications of pulsed laser ablation for enhanced gold nanofluids Yttrium oxide, Y 2 O 3 , films were prepared by pulsed laser deposition in the presence of oxygen (O 2 ) gas. The microstructures of these films were found to be highly dependent on the deposition temperature and the amount of O 2 gas used during the deposition process. X-ray diffraction ͑XRD͒ analysis showed that the Y 2 O 3 films transformed from amorphous to polycrystalline form when the deposition temperature was increased to 350°C at an O 2 pressure of 0.01 mbar, and an extremely strong XRD peak originated from Y 2 O 3 ͑111͒ orientation was observed when the deposition temperature was increased above 400°C. However, during the deposition at a fixed temperature ͑650°C͒, the Y 2 O 3 films became amorphous when the O 2 pressure was successively increased. For the films deposited on either fused silica or silicon substrate between 150 and 650°C, very smooth surface morphologies with an average surface roughness of 0.4-19 nm have been observed by an atomic force microscopy. UV/Visible spectrometer and Fourier transform infrared analysis have shown that the as-grown Y 2 O 3 films are highly transparent from the UV ͑with a band gap 5.6 eV͒ to the middle infrared region (ϳ15 m). The refractive index of the Y 2 O 3 films measured by a spectroscopic ellipsometer changed from 1.9 to 2.15 with decreasing wavelength. Furthermore, a good waveguiding property has been observed in the as-grown Y 2 O 3 films. The dielectric constant of these Y 2 O 3 films measured by a standard ferroelectric test system is between 11 and 18 depending on the film thickness. A C -V measurement has confirmed that these Y 2 O 3 films are indeed good for metal-insulator-semiconductor device applications.

We have expanded our earlier Monte Carlo model [Phys. Rev. A 38, 2447; J. Crystal Growth 100, 313 {1990)]to three dimensions and included reevaporation after accommodation and growth on dislocation-induced steps. We found again that, for a given set of growth parameters, the critical size, beyond which a crystal cannot retain its macroscopically faceted shape, scales linearly with the mean free path in the vapor. However, the three-dimensional (3D) the systems show increased shape stability compared to corresponding 2D cases. Extrapolation of the model results to mean-free-path conditions used in morphological stability experiments leads to order-of-magnitude agreement of the predicted critical size with experimental findings. The stability region for macroscopically smooth (faceted) surfaces in the parameter space of temperature and supersaturation depends on both the surface and bulk diffusion. While surface diffusion is seen to smooth the growth morphology on the scale of the surface diffusion length, bulk diffusion is always destabilizing. The atomic surface roughness increases with increase in growth temperature and supersaturation. That is, the tendency of surface kinetics anisotropies to stabilize the growth shape is reduced through thermal and kinetic roughening. It is also found that the solid-on-solid assumption, which can be advantageously used at low temperatures and supersaturations, is insufficient to describe the growth dynamics of atomically rough interfaces where bulk diffusion governs the process. For surfaces with an emerging screw dislocation, we find that the spiral growth mechanism dominates at low temperatures and supersaturations.The polygonization of a growth spiral decreases with increasing temperature or supersaturation. When the mean free path in the nutrient is comparable to the lattice constant, the combined effect of bulk and surface diffusion reduces the terrace width of a growth spiral in its center region. At elevated temperatures and supersaturations, 2D nucleationcontrolled growth can dominate in corner and edge regions of a facet, while the spiral growth mode prevails in its center. Thus, in addition to confirming the experimental observation that the critical size of a growing crystal depends on the prevailing growth mechanism, we are able to obtain detailed insight into the processes leading to the loss of face and facet stability.

We have studied the correlation between surface roughening and surface diffusion in kinetic thin-film deposition by Monte Carlo simulation. Through a variation of simulation parameters, we have obtained an optimal deposition window for layer-by-layer