Luminescence offers a sensitive probe of the quality of Nd:YAG laser material both in the bulk and, via cathodoluminescence, in the near surface layers. The spectral signals are primarily from the Nd dopants, but the thermoluminescence spectra reveal traces of impurities such as Tb, Cr and Mn. Control of the electron energy of the cathodoluminescence demonstrates that the outer few micron layers differ significantly in luminescence response from the bulk crystal. The cathodoluminescence signals are influenced by near surface dislocations and solvents from cleaning treatments. The effects are often apparent as discontinuities in the Nd signal intensities at temperatures which match the solid-liquid or liquid-gas phase transitions of contaminants. Additionally there is strong evidence for the inclusion of carbon dioxide, in the form of nanoparticles. At 202 K, the CO2 sublimation temperature, the Nd line intensities change discretely and there are wavelength shifts for some of the emission lines consistent with pressure driven changes in the lattice parameter. Data for x-ray lattice parameters identify a complex and sudden change and expansion of the lattice in this temperature region. The luminescence methods used suggest identification of impurities and gaseous inclusions can be exploited in other insulator materials and examples are cited.
Surface enhanced Raman spectroscopy (SERS) is becoming a paramount analytical mechanism in nanotechnology and biological/chemical detection. However, fabrication of highly sensitive SERS substrates often involves expensive and time‐consuming procedures and the resulting materials require careful handling. Herein, a simple‐to‐manufacture, highly sensitive, and easy‐to‐handle SERS substrate enabled by plasmonic nanopaper decorated with graphene oxide flakes is reported. Owing to the physicochemical properties gathered by this SERS substrate, the nanocomposite leads to a flexible platform facilitating: a) analysis of the model analyte (Rhodamine 6G) via a high energy laser (457 nm) with negligible fluorescent background, which is important to achieve the maximum excitation of the respective localized surface plasmon resonance; b) a charge transferring phenomenon associated to the graphene derivative that, operating in synergy with the previous phenomenon, enhances the SERS signal and allows an analytical limit of detection of 0.13 × 10−9 m, which is about 2900‐fold lower than that obtained with the counterpart substrate made of silver nanoparticle‐decorated nanopaper; c) an ultrastable signal which remains completely constant at least during 50 days. Furthermore, the resulting SERS substrate is amenable to a cost‐efficient and large‐scale production process, which furthers laboratory and real world applications of SERS.
Cathodoluminescence (CL) provides a sensitive analytical probe of the near-surface region of insulating materials, and some new examples of the strengths of the technique are presented using recent data from the University of Sussex. Analysis of float glass shows that by spectral and lifetime resolved data it is possible to separate the emission bands from excitonic, intrinsic imperfections, and impurities in various valence states, as a ftmction of their depth beneath the surface. Correlation of the CL data with those from Mrssbauer, ion beam and other analyses then provides the basis for models of the defect sites. CL from a second glass, ZBLAN, reveals the presence of microcrystallites and growth defects, and the work underpins confidence in the high purity gas levitation method of ZBLAN production. New results on CL of wavelength shifts with crystal field of Mn in carbonates are presented, and of Nd emission from Nd:YAG. The effects are directly linked to surface damage and dislocations caused by sample preparation steps of cutting and polishing. Methods to minimise the damage, by furnace or pulsed laser annealing, and chemical routes, are mentioned. Such surface preparation damage has a profound effect on all CL monitoring, whether for fundamental studies or mineralogical applications. Finally, a route to eliminate such problems is demonstrated, with consequent improvements in luminescence, transmission and laser performance of surface waveguides. The implications of improved surface quality range widely from mineralogical CL imaging through improved photonic materials and epitaxial growth to elimination of surface damage, and additional information.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.