To investigate electrically-active deep levels in high-resistivity single-crystalline diamond, particle-induced charge transient spectroscopy (QTS) techniques were performed using 5.5MeV alpha ...particles and 9MeV carbon focused microprobes. For unintentionally-doped (UID) chemical vapor deposition (CVD) diamond, deep levels with activation energies of 0.35eV and 0.43eV were detected which correspond to the activation energy of boron acceptors in diamond. The results suggested that alpha particle and heavy ion induced QTS techniques are the promising candidate for in-situ investigation of deep levels in high-resistivity semiconductors.
Sub-millimeter-sized radio photoluminescence (RPL) glass bead microdosimeters using Ag and Cu activators were developed for micrometer-scale dose measurement in particle therapy. To obtain the ...desired size of RPL glass beads, the RPL glasses containing Ag or Cu activators were heated with carbon microparticles. The elemental composition of RPL glass beads with diameters of 400μm were evaluated by particle-induced X-ray emission analysis using proton microbeam probe with different energy of 1.7 and 3MeV. A nearly uniform elemental distribution was observed in both the Ag and Cu dosimeters indicating the uniform distribution of activator ions, which create the luminescence centers. These results indicate that the sub-millimeter-sized RPL glass bead dosimeters possess the basic properties required for particle dosimetry.
In this paper, a modified and easy finite-difference time-domain (FDTD) method based on a regular cartesian Yee's lattice is developed for calculating the dispersion diagram of triangular lattice ...photonic crystals (PCs). Our method uses the standard central-difference equation, which is very easy to implement in any computing environment. The Bloch periodic boundary conditions are applied on the sides of the unit cell by translating the periodic boundary conditions to match with the directions of periodicity in the triangular lattice. Complete and accurate bandgap information is obtained by using this FDTD approach. Convergence, accuracy, and stability analysis were carried out, which ensures the reliability of this method. Numerical results for 2-D TE/TM modes in triangular lattice PC are in good agreement with results from 2-D plane wave expansion method. To ease the practical application of this method, clear explanations on the computer implementation are also provided.
A focused 750keV proton microbeam was used to fabricate an embedded Mach-Zehnder (MZ) optical waveguide in a polydimethylsiloxane (PDMS) film for interferometer application. The sample position was ...precisely controlled by a mechanical stage together with scanning microbeam to form an embedded MZ waveguide structure within an area of 0.3mm40mm. The MZ waveguides with core size of 8 mu m was successfully embedded in PDMS film at a depth of 18 mu m by 750keV proton microbeam with fluences from 10 to 100nC/mm2. The MZ waveguides were coupled with an IR fiber-laser with a center wavelength of 1550nm and evaluated by using the transmitted intensity images from an IR vidicon camera. The results indicate that the embedded MZ waveguide structure in PDMS achieved single spot light propagation, which is necessary for building optical switching circuits based on polymer MZ waveguides.
Thulium-doped tantalum-oxide (Ta2O5:Tm) thin films were prepared using a simple co-sputtering method. A remarkable photoluminescence peak having a wavelength of around 800nm due to Tm3+ was observed ...from a film annealed at 900°C for 20min. The δ-Ta2O5 (hexagonal) phase of the Ta2O5:Tm sputtered film is very important for obtaining strong photoluminescence.
Co-sputtered tantalum (V) oxide and yttrium (III) oxide (Ta2O5:Y2O3) thin films were fabricated using radio-frequency magnetron sputtering for the first time, and their photoluminescence (PL) and ...X-ray diffraction properties were evaluated. Broad PL spectra from 380 to 800nm were observed only from films annealed at 700°C. The maximum PL intensities were found around a wavelength of 500nm regardless of the Y concentrations of the films, and the films annealed at 700°C were primarily amorphous phases. It seems that the broad PL spectra from the Ta2O5:Y2O3 films originated from oxygen vacancies of Ta2O5 and Y2O3 particles that may be produced in Ta2O5 by co-sputtering.
Erbium, europium, and cerium co-doped tantalum oxide (Ta2O5:Er, Eu, Ce) thin films were prepared using a simple co-sputtering method, and yellow light emission was observed by the naked eye from a ...sample annealed at 900 °C for 20 min. The hexagonal Ta2O5 phase is very important, but the hexagonal CeTa7O19 phase should be avoided to obtain strong yellow light emission from Ta2O5:Er, Eu, Ce films. The co-sputtered films can be used as high-refractive-index and yellow-light-emitting materials of autocloned photonic crystals that can be applied to novel light-emission devices, and they will also be used as anti-reflection and down-conversion layers toward high-efficiency silicon solar cells.
Erbium and cerium co-doped tantalum-oxide (Ta2O5:Er, Ce) thin films were fabricated using radio-frequency co-sputtering of Ta2O5, Er2O3, and CeO2 for the first time. Enhanced green-light emission due ...to Er3+ that seems to be sensitized by Ce3+ was observed from the film annealed at 900 °C for 20 min. From XRD measurements of the films, the β-Ta2O5 (orthorhombic), δ-Ta2O5 (hexagonal), and (201) Ta2O5 phases seem to be very important for obtaining green PL from them. Such Ta2O5:Er, Ce co-sputtered films can be used as high-refractive-index materials of autocloned photonic crystals that can be applied to novel green-light-emitting devices, and they will also be used as multi-functional coating films that can work both as anti-reflection and down-conversion films for realizing high-efficiency silicon solar cells.
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