Violet/blue photoluminescence from CeO2 thin film

CeO2 thin film was fabricated by dual ion beam epitaxial technique. The violet/blue PL at room temperature and lower temperature was observed from the CeO2 thin film. After the analysis of crystal structure and valence in the compound was carried out by the XRD and XPS technique, it was inferred that the origin of CeO2 PL was due to the electrons transition from Ce4f band to O2p band and the defect level to O2p band. And these defects levels were located in the range of 1 eV around Ce4f band.

The PL "violet shift" of cerium dioxide on silicon

CeO2 thin film was fabricated by dual ion beam epitaxial technique. The phenomenon of PL violet shift at room temperature was observed, and the distance of shift was about 65 nm. After the analysis of crystal structure and valence in the compound were carried out by XRD and XPS technique, it was concluded that the PL shift was related with valence of cerium ion in the oxides. When the valence of cerium ion varied front tetravalence to trivalence, the PL peak position would move from blue region to violet region and the phenomenon of "violet shift" was observed.

Growth and photoluminescence of epitaxial CeO2 film on Si (111) substrate

A CeO2 film with a thickness of about 80nm was deposited by a mass-analysed low-energy dual ion beam deposition technique on an Si(111) substrate. Reflection high-energy electron diffraction and x-ray diffraction measurements showed that the film is a single crystal. The tetravalent state of Ce in the film was confirmed by x-ray photoelectron spectroscopy measurements, indicating that stoichiometric CeO2 was formed. Violet/blue light emission (379.5 nm) was observed at room temperature, which may be tentatively explained by charge transitions from the 4f band to the valence band of CeO2.

1.55μm Fabry-Perot Thermo-Optical Tunable Filter with amorphous-Si as Cavity

A 1.55μm Fabry-Perot (F-P) thermo-optical tunable filter is fabricated. The cavity is made of amorphous silicon (a-Si) layer grown by electron-beam evaporation technique. Due to the excellent thermo-optical property of a-Si, the refractive index of the F-P cavity will be changed by heating; the transmittance resonant peak will therefore shift substantially. The measured tuning range is 12nm, FWHM (full-width-at-half-maximum) of the transmission peak is 9nm, and heating efficiency is 0.1K/mW. The large FWHM is mainly due to the non-ideal coating deposition and mirror undulation. Possible improvements to increase the efficiency of heating are suggested.

Structure and properties of InAs/AlAs quantum dots for broadband emission

The InAs quantum dots (QDs) on an AlAs layer are grown on GaAs substrates by molecular beam epitaxy technique. The properties of materials and optics of such QD structures have been investigated by cross sectional transmission electron microscopy and photoluminescence (PL) techniques. It is discovered that the inhomogeneous strain filed mainly exists below InAs QDs layers in the case of no wetting layer. The full width at half maximums (FWHMs) and intensities of PL emission peaks of InAs QDs are found to be closely related to the thickness of the thin AlAs layers. The InAs QDs on an eight monolayer AlAs layer, with wide FWHMs and large integral intensity of PL emission peaks, are favorable for producing broadband QD superluminescent diodes, external-cavity QD laser with large tuning range.

Precision measurement of excited spectra of oxygen ions

Spectra of the ionized oxygen atom were researched with the Pro-500i monochromator equipped with CCD. The beam foil method was used at energy of 2 MeV in a 2 x 1.7 Tandem accelerator. In this work, we report 201 spectral lines determined in the region 250-350 nm, and most spectral lines were attributed to n, l energy level transitions from O II to O IV atoms. Our experimental results are in good agreement with existing theoretical calculations. Many lines reported in this paper have not been measured in past experiments, and a majority of them are week transitional lines.

Spectra for electric-dipole Delta n=0 transitions in highly ionized sulfur ions

Spectra for Delta n = 0 transitions of the type 2s(2)2p(k)-2s2p(k+1) or 2s2p(k)-2p(k+1) from highly ionized sulfur produced in beam-foil excitation are investigated and compared to similar spectra measured with other types of light sources. In the experiment, fifty lines have been identified, of which eleven lines are new and accurately measured. Analysis of spectra was based on comparisons with other experimental results and calculated values.

Iron XII to XXII spectra measurements between 250 and 400 angstrom

This paper reports laboratory measurements of the spectrum of the most abundant transition Fe ions in the universe. Spectrum of iron of low-lying excited states has been observed in the wavelength range 250-400 angstrom at Chinese Institute of Atomic Energy on the HI-13 tandem accelerator with beams of 130 MeV. A number of spectral lines have been mainly classified as transitions of magnesium-, sodium-, neon-, fluorine-like ions. A total of 54 lines have been measured. Most of them have been mainly ascribed to 3s3p(k)-3p(k+1), 3s(2)3p(k)-3s3p(k+1), 2p(5)3s-2p(5)3p, 3s3d-3p3d and 2p(5)3p-2p(5)3d resonance transitions. These spectral lines have been identified, among which 21 are new and accurately measured. The analysis of the spectra was based on a comparison with other experimental results and calculated values. (c) 2010 Elsevier Ltd. All rights reserved.

Electrochemistry of vanadium hexacyanoferrate film

Two stable redox couples, accompanying clear color switches between yellow green and blue, can be observed when the VHCF-coated film platinum electrodes are cyclic potential scanned in 3.6 M H2SO4 and 0.2 M K2SO4 electrolyte solution. Electrochemical results and in situ Fourier transfer infrared (FT-IR) spectroscopy demonstrate that the redox reaction of the electroactive iron sites is related to the first redox couple (E-1/2 = 0.81 V) while the second redox couple (E-1/2 = 1.01 V) is due to the redox reactions of the electroactive vanadyl ions. Under the proper conditions, such as in high acidic solutions or thin films (deposition time is less than 2 min) and so on, the third redox couple (E-1/2 = 0.89-0.94 V) can be observed on the cyclic voltammograms, which originates from the redox reactions of the interstitial vanadyl ions. This electrochemical reaction mechanism is investigated by in situ probe beam deflection technique, exchange of K+ ions accompanies with redox reaction of the iron sites, but for redox reaction of the vanadyl ions, both H+ ions, K+ ions and water molecules are involved.

Surface roughness characterization of soft x-ray multilayer films on the nanometer scale

The soft x-ray reflectivity of multilayer films is affected by the surface roughness on the transverse nanometer scale. Scanning tunneling microscopy (STM) is an ideal instrument for providing high-lateral-resolution roughness measurements for soft x-ray multilayer films that cannot be obtained with other types of instruments on the transverse nanometer scale. The surface roughnesses of Mo/Si, Mo/C, and W/Si soft x-ray multilayer films prepared by an ion-beam-sputtering technique were measured with a STM on the vertical and transverse attributes. The film roughnesses and average spatial wavelengths added to the substrates depend on the multilayer film fabrication conditions, i.e., material combinations, number of layers, and individual layer thickness. These were estimated to lead to a loss of specular reflectivity and variations of the soft x-ray scattering angle distribution. This method points the way to further studies of soft x-ray multilayer film functional properties and can be used as basic guidance for selecting the best coating conditions in the fabrications of soft x-ray multilayer films. (C) 1996 American Vacuum Society.

HYPERFINE-STRUCTURE OF SOME ODD PARITY LEVELS IN THE THULIUM SPECTRUM

The laser-atomic-beam spectroscopy technique has been used to make measurements of the hyperfine structure in some odd parity levels of thulium by stepwise excitation. With the experimental results the magnetic dipole hyperfine constants A for the four levels in the configurations 4f12 5d6s6p and 4f12 (H-3(5))6s2 6p3/2 and for two intermediate levels have been obtained.

Circular brass foil failed by plugging opposite to direction of incident laser beam

The peripheries of circular foils of 30 mm in diameter and 0.1 mm thick are fixed while their surfaces are subjected to a long pulsed laser over a central region that may vary from 2 mm to 6 mm in diameter. Failure is observed and classified into three stages; they are referred to as thermal bulging, localized shear deformation, and perforation by plugging. A distinct feature of the failure mode is that bulging and plugging occurred in the direction opposite to the incident laser beam. Such a phenomenon can be expected to occur for a laser intensity threshold value of about 0.61 x 10(6) W/cm(2) beyond which local melting of the material begins to take place.

Technique for diagnosing x-ray laser beam quality by use of the moire signal

We present what we believe is a novel technique based on the moire effect for fully diagnosing the beam quality of an x-ray laser. Using Fresnel diffraction theory, we investigated the intensity profile of the moire pattern when a general paraxial beam illuminates a pair of Ronchi gratings in the quasi-far field. Two formulas were derived to determine the beam quality factor M-2 and the effective radius of curvature R-e from the moire pattern. On the basis of the results, the far-field divergence, the waist location, and the radius can be calculated further. Finally, we verified the approach by use of numerical simulation. (C) 1999 Optical Society of America [S0740-3232(99)01502-1].

Formation of arrayed holes on metal foil and metal film by multibeam interfering femtosecond laser beams

We report on an optical interference method to fabricate arrayed holes on metal nickel foil and aluminum film deposited on glass substrate by means of five-beam interference of femtosecond laser pulses. Optical microscope and scanning electron microscope observations revealed that arrayed holes of micrometre-order were fabricated on both metal foil and metal film. The present technique allows one-step, large-area, micrometric processing of metal materials for potential industrial applications.