Special Issue "Non-Classical Crystal Growth"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Crystalline Materials".

Deadline for manuscript submissions: closed (1 July 2019).

Special Issue Editor

Guest Editor
Prof. Dr. Wuzong Zhou Website E-Mail
School of Chemistry, University of St Andrews, St Andrews, Fife KY16 9ST, UK
Interests: crystal growth; solid state chemistry; electron microscopy; defects in solids

Special Issue Information

Dear Colleagues,

According to the classical crystal growth theory, established over 100 years ago, a crystal is developed via nucleation and the repeated attachment of building units, which can be atoms, molecules or ions. The polyhedral morphology of crystals can be explained by different growth rates along different crystal orientations. However, many crystals do not follow classical growth routes, forming various morphologies or novel hierarchical structures. For example, fast aggregation of precursor molecules/ions may disturb the environment for the growth of free crystals, leading to so-called reversed crystal growth, forming hollow crystals. When release of the building units relies on a reaction on some particular crystal surfaces, growth orientations can be highly selective, forming dendrites. The formation of some novel morphologies of polycrystalline particles may be driven by inter-particle forces of dipole fields, magnetic fields, etc. In fact, many phenomena of crystal growth have not been well investigated.

This Special Issue on “Non-Classical Crystal Growth” is intended to provide an international forum for scientists to present and discuss various novel crystal growth mechanisms. Better understanding of crystal growth will enable us to better-control crystal size and morphology. Scientists are invited to contribute to this issue in different forms, short communications, full papers, and review articles.

Prof. Dr. Wuzong Zhou
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • non-classical crystal growth
  • selective growth orientations
  • unusual nucleation sites
  • reversed crystal growth
  • formation mechanisms of crystal defects
  • aggregation and re-crystallization

Published Papers (3 papers)

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Research

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Open AccessArticle
Nanodefects in YAG:Ce-Based Phosphor Microcrystals
Crystals 2019, 9(9), 476; https://doi.org/10.3390/cryst9090476 - 11 Sep 2019
Abstract
The present paper focused on the study of spectral–kinetic characteristics of luminescence in two batches of yttrium aluminum garnet (YAG):Ce-based phosphors synthesized in different years by two manufacturers: NPO “Platan” in Russia and “GrandLux” in the People’s Republic of China (PRC). Upon studying [...] Read more.
The present paper focused on the study of spectral–kinetic characteristics of luminescence in two batches of yttrium aluminum garnet (YAG):Ce-based phosphors synthesized in different years by two manufacturers: NPO “Platan” in Russia and “GrandLux” in the People’s Republic of China (PRC). Upon studying the structural characteristics of the phosphors—elemental composition, morphology, and X-ray diffraction (XRD) patterns—it was concluded that both types of YAG:Ce phosphors are highly imperfect. The presence of heterogeneities of different nature was accompanied by the introduction—to compensate for charges and elastic stresses—of intrinsic lattice defects during synthesis. There is a high probability of creating complex defects during phosphor synthesis. Luminescence properties (full width at half maximum (FWHM), spectral position of the emission peaks, excitation spectra of emission, emission decay time) are affected by the nearest environment of the luminescence center; whereas the degree of correlation of defects (distance between the components of the donor–acceptor pair) does not depend on the concentration of impurities, intrinsic defects, and their ratio. The results do not fit into the framework of existing ideas regarding the processes in phosphors as systems with widely distributed luminescence centers. The patterns obtained in the paper are discussed based on a hypothesis according to which a nanodefect phosphorus crystal phase is formed during the synthesis. Full article
(This article belongs to the Special Issue Non-Classical Crystal Growth)
Open AccessArticle
Effect of the Gaseous Atmosphere in GaAs Films Grown by Close-Spaced Vapor Transport Technique
Crystals 2019, 9(2), 68; https://doi.org/10.3390/cryst9020068 - 28 Jan 2019
Abstract
The effect of the gaseous atmosphere in the growth of gallium arsenide (GaAs) films was studied. The films have been grown by close-spaced vapor transport (CSVT) technique in a home-made hot filament chemical vapor deposition (HFCVD) reactor using molecular hydrogen and molecular nitrogen [...] Read more.
The effect of the gaseous atmosphere in the growth of gallium arsenide (GaAs) films was studied. The films have been grown by close-spaced vapor transport (CSVT) technique in a home-made hot filament chemical vapor deposition (HFCVD) reactor using molecular hydrogen and molecular nitrogen as the transport agent. An important point about the gaseous atmosphere is the ease in creating volatile compounds when it makes contact with the GaAs source, this favors the transport of material in a CSVT system. Chemical reactions are proposed in order to understand the significant difference produced from the gaseous atmosphere. The films grown with hydrogen are (almost) continuous and have homogeneous layers with preferential orientation (111). The films grown with nitrogen are granular and rough layers with the coexistence of the orientations (111), (220) and (311) in the crystals. The incorporation of impurities in the films was corroborated by energy dispersive spectroscopy (EDS) showing traces of oxygen and nitrogen for the case of the samples obtained with nitrogen. Films grown in a hydrogen atmosphere show a higher band gap than those grown in a nitrogen atmosphere. With the results of XRD and micro-Raman we observe a displacement and broadening of the peaks, characteristic of a structural disorder. The calculations of the FWHM allow us to observe the crystallinity degree and determine an approximate crystallite size using the Scherrer’s equation. Full article
(This article belongs to the Special Issue Non-Classical Crystal Growth)
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Review

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Open AccessReview
Reversed Crystal Growth
Crystals 2019, 9(1), 7; https://doi.org/10.3390/cryst9010007 - 22 Dec 2018
Abstract
In the last decade, a reversed growth route has been found in many crystal growth processes. In these systems, a single crystal does not develop from a single nucleus. The precursor molecules/ions or nanocrystallites aggregate into some large amorphous or polycrystalline particles. Multiple-nucleation [...] Read more.
In the last decade, a reversed growth route has been found in many crystal growth processes. In these systems, a single crystal does not develop from a single nucleus. The precursor molecules/ions or nanocrystallites aggregate into some large amorphous or polycrystalline particles. Multiple-nucleation on the surface of the amorphous particles or surface re-crystallization of the polycrystalline particles then takes place, forming a single crystal shell with a regular morphology. Finally, the crystallization extends from the surface to the core to form single crystals. This non-classical crystal growth route often results in some special morphologies, such as core-shell structures, hollow single crystals, sandwich structures, etc. This article gives a brief review of the research into reversed crystal growth and demonstrates that investigation of detailed mechanisms of crystal growth enables us to better understand the formation of many novel morphologies of the crystals. Some unsolved problems are also discussed. Full article
(This article belongs to the Special Issue Non-Classical Crystal Growth)
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