Search

Damage formation in 370 keV Kr ion-implanted BaWO4 is investigated with Rutherford backscattering spectrometry in channeling mode (RBS/C), performed in a quasi-in situ modus at a cryogenic temperature of 16 K. The obtained results are compared to those for similar experiments done previously at room temperature. The significant differences observed for ion implantation into BaWO4 at these two temperatures can be explained by the mobility of WO3 impurities. Other authors found WO3 to become mobile at temperatures above 240 K. This defect mobility can further account for the strong damage annealing occurring during warming implanted samples from 16 K to room temperature. In this temperature range, only completely amorphized layers remain stable. However, these layers transform into much less damaged layers exhibiting a strong crystalline long-range order during storage at room temperature with time, revealing a kind of self-healing. Another very important finding is the strong damage annealing due to the analyzing He ions during the RBS/C analysis both at 16 K and at room temperature. The analyzing He ions deposit their energy mainly in the electronic system of the target atoms. By applying an analytical thermal spike model, it is shown that the local temperature increase along the trajectory of the analyzing He ions could be responsible for observed damage annealing. The high susceptibility to energy deposition in electronic processes may have implications for any analysis based on energetic electrons. BaWO4 reveals a high radiation resistance at room temperature, which may be relevant for practical application. [ABSTRACT FROM AUTHOR]

Potassium tantalite (KTaO 3) has shown an excellent performance in optoelectronic applications, proving its advantages with respect to fabricating single crystal thin films by ion implantation. This work introduces the damage formation of KTaO3 under 200 keV He ion implantation at room temperature and He bubbles accumulation. Ion implantation-induced lattice damage before and after annealing was quantitatively analyzed by using the Rutherford backscattering spectrometry in channeling technique. The crystals phase analysis of the samples under different fluences was studied by using the X-ray diffraction technique. For 200 keV He ions, the accumulation and migration of He bubbles were induced by the thermal annealing effect under high fluences of He + . The He bubbles appear obviously coarsening and embrittlement with thermal annealing. The blistering phenomenon caused by He ion implantation is the physical basis for the smart-cut technique, which allows the preparation of high-quality single-crystal films. [ABSTRACT FROM AUTHOR]

Near‐infrared (NIR) afterglow is keenly sought in emerging areas including deep‐tissue imaging and night‐vision surveillance, while only few successes in powder phosphors are achieved through solid‐state calcination. In this work, a perovskite single crystal, namely Cs2Na0.2Ag0.8InCl6:Yb3+, is grown in solution via a simple hydrothermal reaction. Through a co‐doping strategy involving both Na+ and Yb3+, dual‐band emission in the visible and NIR region is activated by self‐trapped excitons (STE) and lanthanide ions, respectively. Importantly, the total photoluminescence quantum yield (PL QY) of both bands is boosted to ≈82%. Intriguingly, a long‐lasting afterglow at the NIR band (≈7200 s) and a simultaneous photochromism is observed after ceasing the excitation. Importantly, the transparency of crystals exhibit a pronounced contrast in the decoloration process, enabling a quantitative analysis of photochromism at varied temperatures. On the other hand, the transparent crystals enable the design of a light‐storage battery free of reabsorption, featuring a linear power output with crystal loading. This work proposes a new paradigm to quantitatively correlate the afterglow traps to photochromism, opening many possibilities to practical applications of NIR‐afterglow transparent crystals. [ABSTRACT FROM AUTHOR]

Luminescent zero-dimensional perovskites of Cs4PbBr6 have spurred a great deal of interest on their photoluminescence (PL) origin in the last few years. Regardless of the ongoing debate, it is interesting to realize that only a Br-based zero-dimensional phase was found to be highly luminescent, while its Cl and I counterparts remain elusive. In this study, we report a luminescent Cs4PbI6 zero-dimensional perovskite having both a sharp red emission and a sharp excitation peak. The phase-pure nanocrystal exhibited a polycrystalline nature whereby lattice boundary or active defects may form, leading to an Urbach tail in the absorption peak. A single-particle imaging technique reveals the heterogeneous emission behavior from particle to particle. A temperature-dependent photoluminescence measurement was performed to evaluate the exciton binding energy (172 meV), which classified the nature of the exciton as a Frenkel type. Compared to that of its 3D-counterpart CsPbI3 nanocrystals, the PL of Cs4PbI6 exhibits a robust resistance to both the ion exchange and photobleaching effect. Our study brings a new luminescent member to the zero-dimensional perovskite family, which may inspire more endeavors to exploit those relative phosphors and to unravel the corresponding luminescent origins. [ABSTRACT FROM AUTHOR]

We propose a high-index-contrast AlGaAs microring waveguide for efficient second harmonic generation (SHG) under near-infrared pump. The good overlap occurs between the fundamental modes of pump and second harmonic wave owing to the strong field confinement. The phase matching and resonance conditions can be satisfied through choosing appropriate height and width of the waveguide. In order to deal with the depleted-pump situation and pulse-pumped nonlinear progress, we investigate the wavelength conversion progress by employing the discrete numerical method. The dependence of conversion efficiency on coupling coefficient, pump power and pump wavelength under continuous-wave pump are analysed systematically, and the conversion efficiency can be up to 0.45 for large-scale coupling coefficients with dB/cm under 30 mW pump. In addition, the pulse-pumped SHG progress is also simulated. Such discrete method also has potential in investigating other resonator-enhanced second-order or third-order nonlinear processes. [ABSTRACT FROM AUTHOR]

The doping of rare earth elements revolutionized applications of optoelectronic devices. Europium (Eu) ions acting as activators can provide the fundamental effect on luminescence of host materials. We investigate photoluminescence, lattice damage formation of Eu-implanted potassium titanyl phosphate (KTiOPO4) crystals using 400-keV Eu ions with a fluence of 5 × 1015 ions / cm2 at room temperature. Effective doping is achieved in the depth range of about 50 to 200 nm from the surface of KTiOPO4 crystal, and the luminescent activity of Eu ions is inhibited due to significant implantation damage. However, the samples showed intense luminescence emission at room temperature through the lattice recovery after annealing at 600°C and 700°C. The lattice damage of as-implanted and annealed samples was investigated by Rutherford backscattering spectrometry in channeling configuration. Furthermore, the relative strain depth curves of Eu implanted KTiOPO4 samples at different annealing temperatures were studied using the high resolution x-ray diffraction and Raman spectra. The present research reveals that Eu implanted KTiOPO4 samples have great prospects in the field of optical applications and waveguide quantum reservoirs. [ABSTRACT FROM AUTHOR]

Abstract: A method named intensity calculation method (ICM), which is based on beam propagation method (BPM) and image processing, was carried out to reconstruct the extraordinary refractive index profile (RIP) of single-mode planar waveguide in lithium niobate (LiNbO3), which was fabricated by multi-energy megaelectron-volt (MeV) O2+ ion implantation. In addition, it has been proved reasonable that the alternation of extraordinary refractive index induced by ion implantation into LiNbO3 is mainly due to the degradation of polarization and reduction of material physical density. As a result, the possible extraordinary RIP of the double-mode planar waveguide could be reconstructed using BPM according to such a hypothesis and the calculated guiding mode values. The end-fire coupling and m-line arrangements were carried out to obtain the near-field modal patterns and dark-mode spectra of waveguides, respectively. [Copyright &y& Elsevier]