We present a short survey of the optical properties of primary radiation-induced point defects in alkali halides, simple oxides and some ABO3 perovskites. We discuss in details the optical properties of single electron F and F + centers in rock-salt (f.c.c.) alkali halides and oxides and show that the Mollwo–Ivey law well-known for the F-type centers in alkali halides may be extended for other rock-salt structure insulators. We also discuss the major differences in point defect production mechanisms in halides and oxides. We show that the Rabin–Klick diagram may be generalized for a whole family of alkali halides. The F-type center migration and aggregation into metal colloids in alkali halides and oxides is also discussed.

Basic properties of the F-type centers in halides, oxides and perovskites

In the electron energy loss spectra for amorphous, atomic layer deposited (ALD) Al2O3 film, a peak at 64 eV was observed First principle quantum chemical simulation shows that it relates to excitation of neutral oxygen vacancy in Al2O3 The 291 eV luminescence excited in a band near 60 eV in amorphous Al2O3 is similar to that in bulk crystals which is associated with neutral oxygen vacancy Thus, the amorphous ALD Al2O3 film is oxygen deficient and the oxygen vacancy parameters are similar in crystalline and amorphous Al2O3

Oxygen deficiency defects in amorphous Al2O3

The present work describes various defects-induced tunable emission behavior of MgAl2O4 compounds obtained after annealing at different temperatures through a sol–gel combustion route. Multiple defect centers, such as F, F2, F+, and F22+ and different shallow and deep defects were found to be present inside the band gap, as confirmed by the lifetime and time-resolved emission spectroscopy (TRES) studies. The tunable emission characteristic at different annealing temperatures could be linked with the phase behavior of the spinel. Excitation wavelength variation suggested that a photoconversion process of F to F+ centers was involved with λex = 250 nm, followed by a trapping–de-trapping mechanism of the released electrons within different trap states. An exchange mechanism of electrons in between conduction band and shallow states was also observed at room temperature, which was absent at low temperature, as indicated by the emission profile. These observations render it to be a potential optical-based ther...

An Insight into the Various Defects-Induced Emission in MgAl2O4 and Their Tunability with Phase Behavior: Combined Experimental and Theoretical Approach

Mirror-turn axis of the sixth order (ternary inversion axis)


Three axes of the second order normal to it


Three symmetry planes normal to the axes of the second order and intercrossing along the axis of the highest order


Symmetry center

Properties of Sapphire

Amorphous aluminum oxide Al$_2$O$_3$ (a-Al$_2$O$_3$) layers grown by various deposition techniques contain a significant density of negative charges. In spite of several experimental and theoretical studies, the origin of these charges still remains unclear. We report the results of extensive Density Functional Theory (DFT) calculations of native defects - O and Al vacancies and interstitials, as well as H interstitial centers - in different charge states in both crystalline $\alpha$-Al$_2$O$_3$ and in a-Al$_2$O$_3$. The results demonstrate that both the charging process and the energy distribution of traps responsible for negative charging of a-Al$_2$O$_3$ films [M. B. Zahid et al., IEEE Trans. Electron Devices 57, 2907 (2010)] can be understood assuming that the negatively charged O$_{\textrm{i}}$ and V$_{\textrm{Al}}$ defects are nearly compensated by the positively charged H$_{\textrm{i}}$, V$_{\textrm{O}}$ and Al$_{\textrm{i}}$ defects in as prepared samples. Following electron injection, the states of Al$_{\textrm{i}}$, V$_{\textrm{O}}$ or H$_{\textrm{i}}$ in the band gap become occupied by electrons and sample becomes negatively charged. The optical excitation energies from these states into the oxide conduction band agree with the results of exhaustive photo-depopulation spectroscopy (EPDS) measurements [M. B. Zahid et al., IEEE Trans. Electron Devices 57, 2907 (2010)]. This new understanding of the origin of negative charging of a-Al$_2$O$_3$ films is important for further development of nanoelectronic devices and solar cells.

The origin of negative charging in amorphous Al$_2$O$_3$ films: The role of native defects

The colour centres introduced in sapphire crystals by neutron irradiation and by thermochemical treatment exhibit polarized luminescence. In neutron-irradiated crystals an absorption band at 4.1 eV and luminescence bands at 2.45 and 3.8 eV are due to one type of centres, most probably interstitial aluminium ions. Other donor-type centres give rise to an absorption band at 2.75 eV and a luminescence band at 2.2 eV. In magnesium containing crystals similar centres absorbing at 2.93 eV and emitting at 2.35 eV can be introduced by thermochemical treatment in reducing atmosphere. The preliminary study of the red luminescence indicates its connection with the absorption bands at 3.45 and 3.8 eV.



[Russian Text Ignore]

Visible Luminescence of Colour Centres in Sapphire

The polarization diagrams of the luminescence at 400 nm of colour centres in YAG crystals have been measured under excitation in absorption bands at 370 and 235 nm. The results suggest that the centre is most likely to be a one-electron centre involving an oxygen vacancy and a perturbing agent in the adjacent Al(Oh) site.

https://iopscience.iop.org/article/10.1088/0953-8984/3/28/021/pdf

Polarization of luminescence of colour centres in YAG crystals

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

J. A. Valbis

Author Tools

Chat about Author

Papers

Visible Luminescence of Colour Centres in Sapphire

Polarization of luminescence of colour centres in YAG crystals