Influence of thermal annealing on optical properties and surface morphology of NiOx thin films

NiOx thin films were deposited by reactive DC-magnetron sputtering from a nickel metal target in Ar + O-2 with the relative O-2 content of 5%. Thermal annealing effects on optical properties and surface morphology of NiOx, films were investigated by X-ray photoelectron spectroscopy, thermogravimetric analysis, scanning electron microscope and optical measurement. The results showed that the changes in optical properties and surface morphology depended on the temperature. The surface morphology of the films changed obviously as the annealing temperature increased due to the reaction NiOx -> NiO + O-2 releasing O-2. The surface morphology change was responsible for the variation of the optical properties of the films. The optical contrast between the as-deposited films and 400 degrees C annealed films was about 52%. In addition, the relationship of the optical energy band gap with the variation of annealing temperature was studied. (c) 2006 Elsevier B.V. All rights reserved.

Structure-change-dependent transmittance of PtOx thin film in super-resolution near-field structure: Diffraction effect analysis

To study working mechanism of super-resolution near-field structure (super-RENS) optical disk from a far-field optics view is very necessary because of the actual far-field writing/readout process in the optical disk system. A Gaussian diffraction model based on Fresnel-Kirchhoff diffraction theory of PtOx-type super-RENS has been set up in this Letter. The relationship between micro-structural deformation (change of bubble structure and refractive index profile) with far-field optical response of PtOx thin film has been studied with it in detail. The simulation results are in good agreement with the experimental results reported in literatures with a designed configuration. These results may provide more quantitative information for better understanding of the working mechanism of metal-oxide-type super-RENS. (c) 2007 Elsevier B.V. All rights reserved.

Write-once blue laser recording using silicon doped SbOx thin films prepared by reactive dc-magnetron sputtering

Si:SbOx films have been deposited by reactive dc-magnetron sputtering from a Sb target with Si chips attached in Ar + O-2 with the relative O-2 content 7%. The as-deposited films contained Sb metal, Sb2O3, SiO, Si2O3 and SiO2. The crystallization of Sb was responsible for the changes of optical properties of the films. The results of the blue laser recording test showed that the films had good writing sensitivity for blue laser beam (406.7 nm), and the recording marks were still clear even if the films were deposited in air 60 days, which demonstrated that doping silicon in SbOx films can improve the stability of SbOx films. High reflectivity contrast of about 36% was obtained at a writing power 6 mW and writing pulse width 300 ns. (c) 2007 Elsevier B.V. All rights reserved.

Optical properties of nickel(II)-azo complexes thin films for potential application as high-density recordable optical recording media

Smooth thin films of three kinds of nickel(II)-azo complexes were prepared by the spin-coating method. Absorption spectra of the thin films on K9 glass substrate in the 300-600 nn wavelength region were measured. Optical constants (complex refractive index N = n + ik) and thickness of the thin films prepared on single-crystal silicon substrate in the 300-600 nm wavelength region were investigated on rotating analyzer-polarizer type of scanning ellipsometer, and dielectric constants epsilon (epsilon = epsilon(1) + i epsilon(2)), absorption coefficients a as well as reflectance R of thin films were then calculated at 405 nm. In addition, in order to examine the possible use of nickel(II)-azo complex thin film as an optical recording medium, one of the nickel(II)-azo complex thin film prepared on K9 glass substrate with an Ag reflective layer was also studied by atomic force microscopy and static optical recording. The results show that the nickel(II)-azo complex thin film is smooth and has a root mean square surface roughness of 2.25 nm, and the recording marks on the nickel(II)-azo complex thin film are very clear and circular, and their size can reach 200 nn or less. (c) 2006 Elsevier Ltd. All rights reserved.

Write-once medium with Fe-Doped BiOx thin films for blue laser recording

Fe:BiOx films are fabricated on K9 glass substrates by rf-magnetron sputtering of a BiFeO target under argon atmosphere with increasing sputtering power from 80 to 200 W at room temperature. It is found that the thin films grown at the sputtering power of 160W can be formed at an appropriate deposition rate and have an improved surface morphology. The XPS result reveals that the films investigated are comprised of Bi, Fe and O elements. A typical XRD pattern shows that no phase transition occurs in the films up to 400 degrees C. The results of the blue laser recording test demonstrate that the Fe:BiOx films have good writing sensitivity for blue laser beam (406.7 nm) and good stability after reading 10000 times. The recording marks of 200nm or less are obtained. These results indicate that the introduction of Fe into BiOx films can reduce the mark size and improve the stability of the films.

Structure and properties of amorphous thin film for optical data storage

In this paper the magnetic and magneto-optical properties of amorphous rare earth-transition metal (RE-TM) alloys as well as the magnetic coupling in the multi-layer thin films for high density optical data storage are presented. Using magnetic effect in scanning tunneling microscopy the clusters structure of amorphous RE-TM thin films has been observed and the perpendicular magnetic anisotropy in amorphous RE-TM thin films has been interpreted. Experimental results of quick phase transformation under short pulse laser irradiation of amorphous semiconductor and metallic alloy thin films for phase change optical recording are reported. A step-by-step phase transformation process through metastable states has been observed. The waveform of crystallization propagation in micro-size spot during laser recording in amorphous semiconductor thin films is characterized and quick recording and erasing mechanism for optical data storage with high performance are discussed. The nonlinear optical effects in amorphous alloy thin films have been studied. By photo-thermal effect or third order optical nonlinearity, the optical self-focusing is observed in amorphous mask thin films. The application of amorphous thin films with super-resolution near field structure for high-density optical data storage is performed. (c) 2007 Elsevier B.V. All rights reserved.

Super-resolution scanning laser microscopy with a third-order optical nonlinear thin film

In a configuration of optical far-field scanning microscopy, super-resolution achieved by inserting a third-order optical nonlinear thin film is demonstrated and analyzed in terms of the frequency response function. Without the thin film the microscopy is diffraction limited; thus, subwavelength features cannot be resolved. With the nonlinear thin film inserted, the resolution is dramatically improved and thus the microscopy resolves features significantly smaller than the smallest spacing allowed by the diffraction limit. A theoretical model is established and the device is analyzed for the frequency response function. The results show that the frequency response function exceeds the cutoff spatial frequency of the microscopy defined by the laser wavelength and the numerical aperture of the convergent lens. The main contribution to the improvement of the cutoff spatial frequency is from the phase change induced by the complex transmission of the nonlinear thin film. Experimental results are presented and are shown to be consistent with the results of theoretical simulations.

Si underlayer induced nano-ablation in AgInSbTe thin films

AgInSbTelSi thin films on glass substrates are prepared by dc magnetron sputtering at room temperature. Using Si underlayer as the thermal diffusion layer, the super-resolution nano-ablation holes with a size of 70nm in the AgInSbTe phase change films are obtained by a far-field focused laser experimental setup, with laser wavelength 405nm and objective-lens numerical aperture 0.90. The nano-ablation formation mechanism is analysed and discussed via the thermal diffusion of sample structures.

The origin of the super-resolution via a nonlinear thin film

In laser applications, resolutions beyond the diffraction limit can be obtained with a thin film of strong optical nonlinear effect. The optical index of the silicon thin film is modified with the incident laser beam as a function of the local field intensity n(r) similar to E-2(r). For ultrathin films of thickness d << lambda the transmitted light through the film forms a profile of annular rings. Therefore, the device can be related to the realization of super-resolution with annular pupils. Theoretical analysis shows that the focused light spot appears significantly reduced in comparison with the diffraction limit that is determined by the laser wavelength and the numerical aperture of the converging lens. Analysis on the additional optical transfer function due to the thin film confirms that the resolving power is improved in the high spatial frequency region. (C) 2007 Published by Elsevier B.V.

Reversible Resistance Switching Effect in Amorphous Ge1Sb4Te7 Thin Films without Phase Transformation

We demonstrate a reversible resistance switching effect that does not rely on amorphous-crystalline phase transformation in a nanoscale capacitor-like cell using Ge1Sb4Te7 films as the working material. The polarity and amplitude of the applied electric voltage switches the cell resistance between low- and high-resistance states, as revealed in the current-voltage characteristics of the film by conductive atomic force microscopy (CAFM). This reversible SET/RESET switching effect is induced by voltage pulses and their polarity. The change of electrical resistance due to the switching effect is approximately two orders of magnitude.