Influences of neutral oxygen vacancies and E′_1 centers on α-quartz

Our calculations demonstrate that the concentration of neutral oxygen vacancies can affect the geometrical structrue,electronic structure, and optical properties of α-quartz. Moreover, the distribution of the neutral oxygen divacancy can also exert some influence on the properties of α-quartz. The dissimilarity and similarities are presented in the corresponding density of state（DOS） and absorption spectrum. In addition, when a higher defect concentration is involved in α-quartz,the influence of E1 center on the geometry of α-quartz becomes more significant. However, the introduction of an E1 center barely results in any improvement compared with the influence produced by the corresponding neutral defect.

Intrinsic luminescence centers in γ- and θ-alumina nanoparticles

In this study, we investigate the photoluminescence （PL） properties of γ and θ-alumina nanoparticles synthesized by the chemical wet method followed by annealing. The obtained experimental results indicate the presence of some favorable near ultraviolet （NUV）-orange luminescent centers for usage in various luminescence applications, such as oxygen vacancies （F, F＋, F2＋, and F2 centers）, OH related defects, cation interstitial centers, and some new luminescence bands attributed to trapped-hole centers or donor-acceptor centers. The energy states of each defect are discussed in detail. The defects mentioned could alter the electronic structure by producing some energy states in the band gap that result in the optical absorption in the middle ultraviolet （MUV） region. Spectra show that photoionazation of F and F2 centers plays a crucial role in providing either free electrons for the conduction band, or the photoconversions of aggregated oxygen va- cancies into each other, or mobile electrons for electrons-holes recombination process by the Shockley-Read-Hall （SRH） mechanism.

Photoluminescence and Raman Spectroscopy Study on Color Centers of Helium Ion-Implanted 4H-SiC

Color centers in silicon carbide(SiC)are promising candidates for quantum technologies.However,the richness of the polytype and defect configuration of SiC makes the accurate control of the types and position of defects in SiC still challenging.In this study,helium ion-implanted 4H-SiC was characterized by atomic force microscopy(AFM),confocal photoluminescence(PL),and confocal Raman spectroscopy at room temperature.PL signals of silicon vacancy were found and analyzed using 638-nm and 785-nm laser excitation by means of depth profiling and SWIFT mapping.Lattice defects(C-C bond)were detected by continuous laser excitation at 532 nm and 638 nm,respectively.PL/Raman depth profiling was helpful in revealing the three-dimensional distribution of produced defects.Differences in the depth profiling results and SRIM simulation results were explained by considering the depth resolution of the confocal measurement setup,helium bubbles,as well as swelling.

Influence of oxygen on photoluminescence of erbium-implanted silicon

The luminescence of silicon doped with trivalent rare earth erbium at about 1.54μmhas attracted considerable attention in recent years, because this emission corresponds tothe minimum attenuation of silica glass fibers and presents the possibilities of integratingelectrical and optical circuits fabricated in silicon-based materials with the maturemanufacturing technology of silicon. Recently it was observed that the presence of