The blue-green photoluminescence emitted by pure and electron-doped strontium titanate under intense pulsed near-ultraviolet excitation is studied experimentally, as a function of excitation intensity and temperature. Both emission spectra and time-resolved decays of the emission are measured and analyzed in the framework of simple phenomenological models. We find an interesting blue-to-green transition occurring for increasing temperatures in pure samples, which is instead absent in doped materials. The luminescence yield and decay rate measured as a function of temperature can be modeled well as standard activated behaviors. The leading electron-hole recombination process taking place in the initial decay is established to be second-order, or bimolecular, in contrast to recent reports favoring a third-order interpretation as an Auger process. The temporal decay of the luminescence can be described well by a model based on two interacting populations of excitations, respectively identified with interacting defect-trapped (possibly forming excitons) and mobile charges. Finally, from the measured doping and sample dependence of the luminescence yield, we conclude that the radiative centers responsible for the luminescence are probably intrinsic structural defects other than bulk oxygen vacancies.
We report emergence of photoluminescence at room temperature in trigonal $Cs_3Bi_2Br_9$ at high pressures. Enhancement in intensity with pressure is found to be driven by increase in distortion of $BiBr_6$ octahedra and iso-structural transitions. Electronic band structure calculations show the sample in the high pressure phase to be an indirect band gap semiconductor. The luminescence peak profile show signatures related to the recombination of free and self trapped excitons, respectively. Blue shift of the both peaks till about 4.4 GPa are due to the exciton recombination before relaxation d…
An electron spin resonance (ESR) and photoluminescence signal is observed in the as grown single crystal of stishovite indicating the presence of defects in the non-irradiated sample. Photoluminescence of the as received stishovite single crystals exhibits two main bands - a blue at 3 eV and an UV at 4.75 eV. Luminescence is excited in the range of optical transparency of stishovite (below 8.75 eV) and, therefore, is ascribed to defects. A wide range of decay kinetics under a pulsed excitation is observed. For the blue band besides the exponential decay with a time constant of about 18 μs an a…
Emerging technologies are demanding innovative properties of glasses. In this work, Cerium Oxide is used as a dopant in Zinc-Tellurite samples and its effects on the properties of the glass are investigated. Thermal analysis and x-ray diffraction confirmed the amorphous nature of all samples. The bivalent nature of Cerium is investigated spectroscopically and a strong redshift induced by the dopant is attributed to charge transfers O$^{2-}{\rightarrow}$Ce$^{4+}$, while the 4f-5d transition of Ce$^{3+}$ could not be identified in absorption or luminescence measurements. Yellow/red (570/650 nm) …
The Closer, the Better: Engineering RGB Thermometric Performance in Tb3+, Eu3+-Doped MOFs
Institute of Low Temperature and Structure Research, Polish Academy of Sciences（波兰科学院低温与结构研究所）；Institute of Materials Science, Vietnam Academy of Science and Technology（越南科学技术院材料科学研究所）
Spatially-resolved luminescence and crystal structure of single core-shell nanowires measured in the as-grown geometry
我们报道了单个的、生长态的核-多壳GaAs/In $_{0.15}$ Ga $_{0.85}$ As/GaAs/AlAs/GaAs纳米线的结构和光学性质之间的直接相关性。通过分子束外延在预先图案化的Si（111）衬底上制造，在一排良好分离的成核位置上，可以在生长的几何形状中访问单个纳米线。通过同步辐射纳米探针X射线衍射技术监测轴向111布拉格反射，揭示了沿纳米线生长轴的多型体分布。对于相同的纳米线，空间分辨的发射特性，通过阴极发光高光谱线扫描在扫描电子显微镜。相关的两个测量，我们揭示了一个蓝移的壳量子阱发射能量结合的发射强度增加的片段表现出的混合结构的交替纤锌矿和锌的堆叠相比，纯晶体多型体。这种混合结构的存在下，独立地证实了横截面透射电子显微镜。
Cathodoluminescence spectra were measured to determine the characteristics of luminescence bands and carrier dynamics in beta-Ga2O3 bulk single crystals. The CL emission was found to be dominated by a broad UV emission peaked at 3.40 eV, which exhibits strong quenching with increasing temperature; however, its spectral shape and energy position remain virtually unchanged. We observed a super-linear increase of CL intensity with excitation density; this kinetics of carrier recombination can be explained in terms of carrier trapping and charge transfer at Fe impurity centres. The temperature-dep…
Vacuum-Sealed Thermal Treatment Regulates Trap States and Red Persistent Luminescence in CaTiO3: Pr3+,Al3+ Phosphors
State Key Laboratory of Integrated Optoelectronics, Key Laboratory of UV Light-Emitting Materials and Technology of Ministry of Education, School of Physics, Northeast Normal University（集成光电子学国家重点实验室，教育部紫外发光材料与技术重点实验室，物理学院，东北师范大学）
Chemically _ driven isothermal close space vapour transport was used to prepare pure MoO2 films which were eventually converted to MoO3 by annealing in air. According to temperature_dependent Raman measurements, the MoO2/MoO3 phase transformation was found to occur in the 225 _ 350 oC range; no other phases were detected during the transition. A clear change in composition and Raman spectra, as well as noticeable modifications of the band gap and the absorption coefficient confirmed the conversion from MoO2 to MoO3. An extensive characterization of films of both pure phases was carried out. In…
