Artykuły w czasopismach: „Defects - Single Crystalline Oxides”

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Wittkämper, Florian, André Bikowski, Klaus Ellmer, Konrad Gärtner i Elke Wendler. "Energy-Dependent RBS Channelling Analysis of Epitaxial ZnO Layers Grown on ZnO by RF-Magnetron Sputtering". Crystals 9, nr 6 (4.06.2019): 290. http://dx.doi.org/10.3390/cryst9060290.

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The transparent conducting oxides ZnO and ZnO:Al are interesting materials for a wide range of applications. Several of these applications need a large area, single crystalline, and specially doped thin layers. A common technique for the fabrication of those layers is RF (radio frequency) -magnetron sputtering. The investigation of the crystal quality of such layers requires methods of analysis that are destruction free and that are able to obtain information about the concentration and type of defects versus depth. One such option is the Rutherford backscattering spectroscopy (RBS) in channelling mode. In this work, we exploit the channelling effect and its energy dependence, which are sensitive to the type of defects. By using appropriate software and measuring RBS channelling spectra with different beam energies, we were able to determine the depth distribution of point defects and dislocation loops. The presence of dislocation loops was proven using other previously applied analysis methods. The main advantage of RBS in channelling mode is the quantification of point defects, which can be important for defining the electrical and optical properties of such layers. The technique demonstrated is applicable to other defective crystals or thin crystalline layers.

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Trimble, L. E., G. K. Celler, D. G. Schimmel, C. Y. Lu, S. Nakahara i P. M. Fauchet. "The nature of residual stress, defects, and device characteristics for thick single-crystalline Si films on oxidized Si wafers". Journal of Materials Research 3, nr 3 (czerwiec 1988): 514–20. http://dx.doi.org/10.1557/jmr.1988.0514.

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Recently it was reported that high quality, 10–100 μm thick, single-crystalline Si films were formed on oxidized single-crystalline Si wafers by the lateral epitaxial growth over oxide (LEGO) process. Although this recrystallization process is reliable and reproducible, periodic regions of dislocations in the otherwise relatively dislocation-free Si film were not well understood. In this paper, therefore, the film stress and defect properties are investigated in detail, and devices made in recrystallized wafers are compared with devices in conventional wafer structures. Stress levels were found to be too low to cause defects, with TEM data suggesting an impurity mechanism (SiO2 precipitation) for small dislocation loops and slight crystalline misorientation for long dislocation lines in the periodic, defective areas. Device results confirmed that LEGO is a viable alternative to the dielectric isolation (DI) technology.

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Wang, Z. L., Z. W. Pan i Z. R. Dai. "Structures of Oxide Nanobelts and Nanowires". Microscopy and Microanalysis 8, nr 6 (grudzień 2002): 467–74. http://dx.doi.org/10.1017/s1431927602010383.

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We have recently reported the synthesis of one-dimensional nanobelt structures of ZnO, SnO2, In2O3, CdO, Ga2O3, and PbO2 by evaporating the desired commercial metal oxide powders at high temperatures (Science (2001), 291, 1947). The as-synthesized oxide nanobelts are pure, structurally uniform, single crystalline, and most of them free from dislocations. The beltlike morphology appears to be a unique and common structural characteristic for the family of semiconducting oxides. In the present article, we focus on the twin and stacking fault planar defects found in oxide nanobelts and nanowires although they are rarely observed. Some interesting and unique growth morphologies are presented to illustrate the roles played by surface energy and kinetics in growth. It is shown that the surfaces of the oxide nanobelts are enclosed by the low-index, low-energy crystallographic facets. The growth morphology is largely dominated by the growth kinetics.

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Nandanapalli, Koteeswara Reddy, Devika Mudusu i Sungwon Lee. "Defects-free single-crystalline zinc oxide nanostructures for efficient photoelectrochemical solar hydrogen generation". International Journal of Hydrogen Energy 45, nr 51 (październik 2020): 27279–90. http://dx.doi.org/10.1016/j.ijhydene.2020.07.138.

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Locke, Christopher, Christopher L. Frewin, Jing Wang i Stephen E. Saddow. "Growth of Single Crystal 3C-SiC(111) on a Poly-Si Seed Layer". Materials Science Forum 615-617 (marzec 2009): 157–60. http://dx.doi.org/10.4028/www.scientific.net/msf.615-617.157.

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A novel method for growing highly-crystalline 3C-SiC on an oxide release layer via a poly-Si seed layer is reported. Silicon carbide’s potential role as a ubiquitous material for MEMS fabrication lies in its dual role as an electronic and mechanical material. Unfortunately, due to residual stresses and crystal defects stemming from the large lattice constant mismatch and the thermal expansion coefficient difference between SiC and Si, the use of SiC in Si-based MEMS fabrication techniques has been very limited. The growth of 3C-SiC on a poly-Si seed layer deposited on oxide on (111)Si substrates (i.e., p-Si/ SiO2/(111)Si) provides an alternative fabrication method to expensive, traditional SOI bonding techniques for producing free-standing 3C-SiC MEMS structures. 3C-SiC grown with a poly-Si seed layer on SiO2 should experience reduced residual stress and far fewer defects due to the compliance of the SiO2 layer. Although poly-Si is utilized as a seed layer in this process, a well-ordered monocrystalline 3C-SiC layer was achieved and the process and film properties reported.

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WHITFIELD, PAMELA, i LYNDON MITCHELL. "X-RAY DIFFRACTION ANALYSIS OF NANOPARTICLES: RECENT DEVELOPMENTS, POTENTIAL PROBLEMS AND SOME SOLUTIONS". International Journal of Nanoscience 03, nr 06 (grudzień 2004): 757–63. http://dx.doi.org/10.1142/s0219581x04002620.

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Powder X-ray diffraction has become a cornerstone technique for deriving crystallite size in nanoscience due to speed and "simplicity". Unfortunately, this apparently simple technique commonly has unexpected problems. Anisotropic peak broadening related to crystallite shape, defects, and microstrain occurs frequently in nanomaterials and can significantly complicate the analysis. In some instances, the usage of the conventional single peak approach would give erroneous results, and in others, this type of analysis is not even possible. A number of different nanocrystalline oxides have been examined to determine their crystallite sizes by different techniques. They differ in terms of crystal symmetry, crystallinity, density, and present different challenges with regard to size analysis.

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Nyborg, M., Ilia Kolevatov, G. C. Vásquez, K. Bergum i E. Monakhov. "Dominant defects and carrier transport in single crystalline cuprous oxide: A new attribution of optical transitions". Journal of Applied Physics 130, nr 17 (7.11.2021): 175701. http://dx.doi.org/10.1063/5.0059406.

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Litovchenko, V. G., I. P. Lisovskyy, M. Voitovych, Andrey V. Sarikov, S. O. Zlobin, V. P. Kladko i V. Machulin. "Study of the Mechanisms of Oxygen Precipitation in RTA Annealed Cz-Si Wafers". Solid State Phenomena 156-158 (październik 2009): 279–82. http://dx.doi.org/10.4028/www.scientific.net/ssp.156-158.279.

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In this paper, the influence of the rapid thermal annealing of single crystalline Cz-Si wafers on the evolution of the concentration of interstitial oxygen as well as oxygen in precipitated oxide phase was investigated by infrared spectroscopy. The wafers were preliminary furnace annealed to create the precipitate seeds. The concentration of interstitial oxygen was shows to decrease considerably as a result of annealing during up to 40 min together with the growth of the concentration of precipitated oxygen. This effect depended on the purity and defect structure of initial wafers. The kinetic model was developed to account for the observed effects based on the modification of the solubility level for interstitial oxygen induced by defects as well as its diffusivity. Obtained results of simulation agree well with the experimental data.

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Webb, Matthew, Tao Ma, Allen H. Hunter, Sean McSherry, Jonathan Kaufman, Zihao Deng, William B. Carter i in. "Geometric defects induced by strain relaxation in thin film oxide superlattices". Journal of Applied Physics 132, nr 18 (14.11.2022): 185307. http://dx.doi.org/10.1063/5.0120176.

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Functional thin film superlattices with stability in extreme environments can lead to transformative performance in optical and thermal applications such as thermophotovoltaics. In this work, key issues associated with defects that prevent layer-by-layer growth in epitaxial, low-miscibility oxide superlattices are investigated. Layer protrusions, approximately 8 nm wide and 3 nm thick, arise from a strain relaxation mechanism in 8 nm bilayer superlattices of Ba(Zr0.5Hf0.5)O3/MgO and propagate through the subsequent superlattice layers forming an inverted pyramid structure that is spatially phase offset from the matrix. The density and size of these defects scales with the number of interfaces in the sample, indicating that surface roughness during growth is a significant factor in the formation of these defects. In situ high temperature transmission electron microscopy (1000 °C, in vacuo) measurement reveals that phase decomposition of Ba(Zr0.5Hf0.5)O3 and decoherence of the superlattice is nucleated by these defects. This work highlights that achieving optimum growth conditions is imperative to the synthesis of single-crystalline superlattices with sharp interfaces for optimized performance in extreme environments.

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Murshed, M. Mangir, Pei Zhao, Evgeny Alekseev, Ashfia Huq i Thorsten Gesing. "Lattice thermal expansion of complex oxides with intrinsic anharmonicity". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C161. http://dx.doi.org/10.1107/s2053273314098386.

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The lattice thermal expansion of crystalline solids cannot be adequately modeled by Grüneisen approximation using either Einstein single harmonic frequency or Debye frequency spectrum because a true phonon spectrum does not follow either of the two kinds. The Debye model misfits to many observations due to the fact that real solids comprises of axial anisotropy, lattice waves with dispersion at the Brillouin zone boundaries, low/high frequency optical vibrations in excess of the Debye spectrum. The actual frequency distribution is a complicated function of frequency instead of a simple parabolic Debye spectrum. The frequency distribution can be simplified using power series [1] leading to singularities before and after the Debye cutoff frequency. Using multiple Debye or Einstein oscillators, or their mixtures, is also common practice to better describe the lattice expansion, however, these models extremely suffer from intrinsic anharmonicity in particular at high temperatures. It was demonstrated that even the noble monoatomic solids required inclusion of anharmonic terms in the harmonic model to better explain the observed values [2]. Worse even, when anharmonicity becomes dominant due to formation of vacancies and defects, anomalies of hard/soft modes or change of stereochemical activities of lone electron pairs (LEPs) as function of temperature. Herein we approach an extended Grüneisen approximation that includes harmonic, quasiharmonic and intrinsic anharmonic potentials to describe the internal energy of the crystal as function of temperature. The model has been applied to several complex oxides with LEPs (Bi2Ga4O9[3]) along with axial negative thermal expansion (PbFeBO4) and rigid-unit-modes (KAsW2O9) reported here. The metric parameters were obtained from quality data collected from temperature-dependent neutron and X-ray powder diffractions.

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Zaumseil, P., A. Giussani i T. Schroeder. "Laboratory-based characterization of heteroepitaxial structures: Advanced experiments not needing synchrotron radiation". Powder Diffraction 25, nr 2 (czerwiec 2010): 92–98. http://dx.doi.org/10.1154/1.3392302.

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It is demonstrated that a complex X-ray characterization of semiconductor films epitaxially grown on metal oxide buffer layers and Si(111) substrates is possible using laboratory-based equipment. This is demonstrated with epi-germanium on Pr2O3 as buffer material. Pole figure measurements prove that epi-Ge layers are nearly single crystalline with exactly the same in-plane orientation (type A) as the Si(111) substrate, while the lattice of the oxide layer is 180° rotated around the [111] surface normal (type B). Only a small fraction (less than 0.6 vol %) of the epi-Ge exhibits type B rotation twins. The main structural defects are microtwin lamellas lying in {111} planes 70.5° inclined to the wafer surface. The different in-plane orientation of the Si substrate and epi-Ge on one side and the Pr2O3 buffer layer on the other side allows a very sensitive analysis of strain and defects even for a 10-nm oxide layer buried under a 100-nm Ge. The epi-Ge layers are nearly fully relaxed and the Pr2O3 buffer layer is compressively strained. Due to the existing defects the Ge (111) planes are tilted in a characteristic pattern relative to the Si substrate.

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Stopyra, M., D. Niemiec i G. Moskal. "Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates". Archives of Metallurgy and Materials 61, nr 2 (1.06.2016): 1249–54. http://dx.doi.org/10.1515/amm-2016-0206.

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Abstract A2B2O7 oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho2Zr2O7 and praseodymium zirconate Pr2Zr2O7 via Polymerized-Complex Method (PCM). Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C) fine-crystalline, single-phase material is obtained. Thermal diffusivity was measured in temperature range 25-200°C, Ho2Zr2O7 exhibits lower thermal diffusivity than Pr2Zr2O7. Additionally, PrHoZr2O7 was synthesized. The powder in as-calcined condition is single-phase, but during the sintering decomposition of solid solution took place and Ho-rich phase precipitated. This material exhibited the best insulating properties among the tested ones.

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KEDIA, SUNITA, i R. VIJAYA. "PHOTOLUMINESCENCE OF ZINC OXIDE INVERSE PHOTONIC CRYSTAL". International Journal of Nanoscience 10, nr 01n02 (luty 2011): 171–75. http://dx.doi.org/10.1142/s0219581x11007727.

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Three-dimensional photonic crystals prepared by self-assembly method from polymethyl methacrylate colloids are infiltrated with zinc oxide ( ZnO ) prepared using sol–gel technique. The polymer template is removed by chemical method and heat treatment to obtain inverse photonic crystals of ZnO . The inverse crystal fabricated by the chemical method is further heated at high temperature and the X-ray diffraction establishes the presence of single-crystalline ZnO . The photoluminescence is recorded from the inverse photonic crystals by exciting them with He–Cd laser at 325 nm. The as-prepared inverse crystals show only UV emission while the inverse crystal obtained by the chemical route and treated at high temperature shows the visible emission due to oxygen vacancy defects.

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Chen, Yu-Yang, Shu-Meng Yang i Kuo-Chang Lu. "Synthesis of High-Density Indium Oxide Nanowires with Low Electrical Resistivity". Nanomaterials 10, nr 11 (23.10.2020): 2100. http://dx.doi.org/10.3390/nano10112100.

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In this study, indium oxide nanowires of high-density were synthesized by chemical vapor deposition (CVD) through a vapor–liquid–solid (VLS) mechanism without carrier gas. The indium oxide nanowires possess great morphology with an aspect ratio of over 400 and an average diameter of 50 nm; the length of the nanowires could be over 30 μm, confirmed by field-emission scanning electron microscopy (SEM). Characterization was conducted with X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence spectrum (PL). High-resolution TEM studies confirm that the grown nanowires were single crystalline c-In2O3 nanowires of body-centered cubic structures. The room temperature PL spectrum shows a strong peak around 2.22 eV, originating from the defects in the crystal structure. The electrical resistivity of a single indium oxide nanowire was measured to be 1.0 × 10−4 Ω⋅cm, relatively low as compared with previous works, which may result from the abundant oxygen vacancies in the nanowires, acting as unintentional doping.

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Zhu, Jiaxin, Jung-Woo Lee, Hyungwoo Lee, Lin Xie, Xiaoqing Pan, Roger A. De Souza, Chang-Beom Eom i Stephen S. Nonnenmann. "Probing Vacancy Behavior in Complex Oxide Heterostructured Films". ECS Meeting Abstracts MA2018-01, nr 32 (13.04.2018): 1931. http://dx.doi.org/10.1149/ma2018-01/32/1931.

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Oxygen vacancies (Vo•• ) play a critical role in the transport mechanisms within complex oxides, analogous to electrons and holes within semiconductors. Systems including memristors, all-oxide electronics, and electrochemical cells comprise substrate-supported thin films either in metal-insulator-metal or complex oxide heterostructure configurations. As well-studied defect chemistry dictates mixed electronic/ionic functionality, improving oxide-oxide interfaces necessitates a direct, spatial understanding of vacancy distributions that define electrochemically active regions. Here we show that vacancies deplete over large, micron-level distances within single crystalline perovskite Nb-doped SrTiO3 substrate (Nb:SrTiO3) substrates after typical vacuum film deposition and post-annealing processes. We demonstrate the conversion of the surface potential across a four-layer strontium titanate / yttria-stabilized zirconia (STO/YSZ) heterostructured film to spatially defined (< 100 nm) [Vo•• ] profiles within STO through a unique combination of high temperature (500 °C), in situ scanning probes and classic semiconductor energy band diagram model analysis. Further comparison between room temperature and high temperature potential profiles clearly distinguishes between electronic-dominant and activated, ionic-dominant transport characteristics within the oxide layers. Consequently, we determined that oxygen scavenging by deposited films during pulsed laser deposition significantly reduce the Nb:STO, which is then partially reoxidized in the ambient environment during cooling. The results presented herein i) introduce the means to spatially resolve quantitative vacancy distributions across oxide films, and ii) pose the mechanism by which oxide thin film getters both enhance then deplete vacancies within the underlying substrate.

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Demazeau, Gérard, Alain Largeteau i Stéphane Darracq. "Review. New Trends in Solvothermal Crystal Growth at theMacro- and Nanoscale". Zeitschrift für Naturforschung B 65, nr 8 (1.08.2010): 1007–14. http://dx.doi.org/10.1515/znb-2010-0806.

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Solvothermal processes, as compared to hydrothermal processes, enlarge the scope of the employed solvents from aqueous to non-aqueous media, the objective being to extend the possibilities for the preparation and/or the crystal growth of non-oxide materials. During the last fifteen years solvothermal crystal growth of materials has been investigated at two different levels: (i) the macroscopic scale, with the preparation of large single crystals of functional materials for specific applications, (ii) the nanoscale, involving the elaboration of single-crystalline nanocrystallites well defined in size and morphology, and particularly adapted to nanodevices. In the first domain, two main factors have been studied: (i) the influence of the thermodynamical parameters governing the solvothermal processes, and (ii) the purity of the components (nutrient, solvent, etc.), the main objective being to reduce drastically the density of defects inside the single crystals. In the second domain, strong efforts have been made: (i) to control the nano-size, but mainly, (ii) to induce specific morphologies, in particular 1D, appropriate to the relative nanotechnologies

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R, Suresh, Indira Priyadharshini T, Thirumal Valavan K i Justin Paul M. "Role of annealing temperature on the properties of SrO nanoparticles by precipitation method". NanoNEXT 1, nr 1 (30.12.2020): 18–23. http://dx.doi.org/10.34256/nnxt2013.

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Strontia nanoparticles are successfully prepared by chemical precipitation method. The SrO nanoparticles are characterized by XRD, UV-DRS and I-V analysis. X-ray diffraction peaks reveal the single-phase polycrystalline tetragonal structure with preferential orientation along (2 0 2) direction. Influence of annealing temperature strongly induce the growth of peak which indicates the increased intensity of (202) peak. The heat treatment strongly distresses the growth of triplet peaks (002), (101) and (110) whereas the same augment the growth of (202) and (310). Strontium oxide nanoparticles would allow more light for absorption in UV region due to its rough surface whereas the same would allow moderate light absorption in visible region due to its high packing density. The expansion and contraction of Sr-O bonds leads to a high crystalline nature with its purity at 322 nm. It is proposed that strain and surface defects in SrO nanocrystal take place due to different absorption edge.

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Papadogianni, Alexandra, Takahiro Nagata i Oliver Bierwagen. "The electrical conductivity of cubic (In_1−xGa_x)₂O₃ films (x ≤ 0.18): native bulk point defects, Sn-doping, and the surface electron accumulation layer". Japanese Journal of Applied Physics 61, nr 4 (16.03.2022): 045502. http://dx.doi.org/10.35848/1347-4065/ac4ec7.

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Abstract The alloying of the group-III transparent semiconducting sesquioxides In2O3 and Ga2O3 can lead to a modulation of the properties of the parent compounds, e.g. the shallow- and deep-donor character of the oxygen vacancy or the presence and absence of a surface electron accumulation layer, respectively. In this work, we investigate the effect of alloying on the electron transport properties of unintentionally-doped single-crystalline and textured bixbyite (In1−x Ga x )2O3 thin films annealed in oxygen and vacuum with Ga contents up to x = 0.18. Hall effect measurements demonstrate a surprising increase in electron density due to native defects with added Ga, possibly induced by Ga-related unit-cell distortions. Based on the measured electron mobility we assign this increase to oxygen vacancies rather than Ga-interstitials. The large electron density of >7 × 1019 cm−3 in vacuum-annealed, Ga-containing films would place the 2+/0 transition level of the O-vacancy in our films at least 340 meV above the conduction band minimum. A combined investigation based on hard and soft X-ray photoelectron spectroscopy measurements demonstrates the existence of the surface electron accumulation layer for all alloy films irrespective of annealing and, hence, no depletion up to x = 0.18. Comparison of Hall and Seebeck measurements confirms negligible contribution of the SEAL to the electron transport in the few-100 nm thick, unintentionally-doped films. Finally, we additionally demonstrate a single-crystalline (In0.92Ga0.08)2O3:Sn film, as a possible transparent conductive oxide with a wider band gap than that of (Sn-doped) In2O3, with transport properties similar to those of ITO.

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Zaumseil, P., A. Giussani, O. Seifarth, Tzanimir Arguirov, M. A. Schubert i T. Schroeder. "Characterization of Semiconductor Films Epitaxially Grown on Thin Metal Oxide Buffer Layers". Solid State Phenomena 156-158 (październik 2009): 467–72. http://dx.doi.org/10.4028/www.scientific.net/ssp.156-158.467.

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Silicon and germanium films epitaxially grown on metal oxide buffer layers on Si(111) substrates are characterized by different X-ray techniques, transmission electron microscopy and Raman spectroscopy. Pr2O3 and Y2O3 or a combination of both is used as buffer material. X-ray pole figure measurements and grazing incident X-ray diffraction prove that epi-semiconductor layers can be grown single crystalline with exactly the same in-plane orientation as the Si(111) substrate. Epi-Ge layers show a small fraction (less than 0.5 vol. %) of so-called type B rotation twin regions located near the oxide-Ge interface. The main structural defects for both epi materials are micro twin lamellas lying in {111} planes 70° inclined to the wafer surface that may reach through the whole layer from the oxide interface to the surface. Furthermore, TEM confirms the existence of stacking faults and threading dislocations. X-ray grazing incident diffraction and Raman measurements show that epi-Ge layers on Pr2O3 buffer are nearly fully relaxed, while epi-Si layers on Y2O3/Pr2O3 double buffer are compressive strained depending on their own thickness and the thickness of the underlying Y2O3 layer. It is demonstrated that the epi-layer quality can be improved by post-deposition annealing procedures.

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Tsuchiya, Masaru, Nestor A. Bojarczuk, Supratik Guha i Shriram Ramanathan. "Transmission electron microscopy studies on structure and defects in crystalline yttria and lanthanum oxide thin films grown on single crystal sapphire by molecular beam synthesis". Philosophical Magazine 90, nr 9 (21.03.2010): 1123–39. http://dx.doi.org/10.1080/14786430903292415.

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Félix, Rocío, Marco Peres, Sergio Magalhães, Maria Rosario Correia, Armando Lourenço, Teresa Monteiro, Rafael García i Francisco M. Morales. "The Role of Edge Dislocations on the Red Luminescence of ZnO Films Deposited by RF-Sputtering". Journal of Nanomaterials 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/970545.

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The existence of extended defects (i.e., dislocations) in inorganic semiconductors, such as GaN or ZnO, responsible for broad emission peaks in photoluminescence analysis remains unresolved. The possible assignments of these luminescence bands are still matter of discussion. In this study, two different zinc oxide samples, grown under different oxygen partial pressures and substrate temperatures, are presented. Epitaxial and structural properties were analysed by means of X-ray diffraction and transmission electron microscopy techniques. They confirm that the layers are single-phase with a good crystalline quality. Nevertheless, a different density of threading dislocations, with a higher contribution of edge dislocations, was found. Photoluminescence spectroscopy has been used to investigate the optical properties. The steady state luminescence spectra performed at 14 K evidenced the donor bound exciton recombination and deep green and red emission bands. The red band with a maximum at 1.78 eV was found to be stronger in the sample grown at lower oxygen pressure which also shows higher density of threading dislocations. From the temperature and excitation density dependence of the red band, a donor acceptor pair recombination model was proposed, where hydrogen and zinc vacancies are strong candidates for the donor and acceptor species, respectively.

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Rudolph, Peter. "Defect mastering - one of the topic challenges for crystal growth". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C32. http://dx.doi.org/10.1107/s2053273314099677.

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The quality of single crystals, epitaxial layers and devices made there from are very sensitively influenced by structural and atomistic deficiencies generated during the crystal growth. Crystalline imperfections comprise point defects, dislocations, grain boundaries, second-phase particles. Over more than a half-century of the development of crystal growth, most of the important defect-forming mechanisms have become well understood [1-2]. As a result, the present state of technology makes it possible to produce crystals of remarkably high quality. However, that is not to say that all problems are already solved. For instance, in comparison with silicon the point defect dynamics in semiconductor and oxide compounds is not nearly as well understood. The density of equivalent defect types and antisites in each sub-lattice is determined by deviation from stoichiometry. Their charge state depends on the Fermi level position leading via interaction with dopants to certain compensation level and complex formation. One measure proves to be the in situ control of stoichiometry. Due to high-temperature dislocation dynamics heterogeneous dislocation substructures are formed. Both, acting thermo-mechanical stress and given point defect situation force the dislocation to glide and climb. In the course of enthalpy minimization the long-range character of dislocation interaction produces agglomerates and patterns with polygonized cell walls, i.e. small angle grain boundaries [3]. Thanks to the rules of correspondence of Taylor and Kuhlmann-Wilsdorf one is able to estimate the interaction between shear stress, dislocation density and cell diameter (Fig.). In epitaxy the Nye tensor, describing dislocation distribution inhomogeneity, affects the layer stress considerably. The growth under minimum stress, solution hardening and in situ stoichiometry control are effective counteracting methods. One of the most serious consequences during cooling down of as-grown crystals is the point defect condensation in precipitates and micro-voids decorating dislocation patterns or inducing high mechanical misfit stress that generates dislocation loops. It proves to be favourable to anneal the crystal a few degrees below the melting point in order to dissolve the particles and re-diffuse their into the crystal matrix.

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Merckling, Clement, Islam Ahmed, Tsang Hsuan Tsang, Moloud Kaviani, Jan Genoe i Stefan De Gendt. "(Invited) Integrated Perovskites Oxides on Silicon: From Optical to Quantum Applications". ECS Meeting Abstracts MA2022-01, nr 19 (7.07.2022): 1060. http://dx.doi.org/10.1149/ma2022-01191060mtgabs.

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With the slowing down of Moore’s law, related to conventional scaling of integrated circuits, alternative technologies will require research effort for pushing the limits of new generations of electronic or photonic devices. Perovskite oxides with the ABO3 chemical formula have a very wide range of interesting intrinsic properties such as metal-insulator transition, ferroelectricity, pyroelectricity, piezoelectricity, ferromagnetic and superconductivity. For the integration of such oxides, it is of great interest to combine their properties with traditional electronic, memory and optical devices on the same silicon-based platform. In the context of high-speed chip-to-chip optical interconnects, compact high-resolution beam steering and video-rate RGB hologram generation require the integration of fast and efficient optical modulators on top of silicon CMOS devices. For these applications the integration of high quality electro-optical materials A defect-free material-stack deposition on silicon wafers is hence required. Among the possible materials options, barium titanate (BaTiO3) is one promising candidate due to its large intrinsic Pockels coefficients that can be obtained. In a first part of the talk, we will review the different options to integrate BaTiO3 on Silicon substrate though different templates to control the polarization direction and discuss the influence on the physical, electrical and optical properties. Then in the second section we will discuss the use of perovskites oxide in the field of topological based qubits which is one of the promising methods for realizing fault-tolerant computations. It is recognized that superconductor/topological insulator heterostructure interfaces may be a perfect host for the exotic “Majorana” particles. These have relevant topological protection nature as required for processing information. Therefore, the physics at the superconductor/topological insulator heterostructure interface need to be studied further, starting at the material level. In this work, a candidate material Barium Bismuthate (BBO) is studied utilizing the Oxide Molecular Beam Epitaxy (MBE) process. The perovskite structure provides opportunity for easily tailored functionality through substitutional doping. Incorporation of potassium into the lattice of BBO results in a superconducting phase with Curie temperature as high as ~ 30K. In addition, BBO is according to DFT based studies, predicted to form topological surface states when doped with Fluorine. In our work, we integrate BBO perovskite on Si(001) substrate, using an epitaxially grown strontium titanate (STO) single-crystalline buffer layer and discuss the structural and chemical properties of the heterostructure will be established by utilizing physical characterization techniques such as AFM, and TEM in later stages. This will go hand in hand with the understanding of the ARPES studies and related surface reconstruction of BBO observed by RHEED as a criterion for the high-quality films. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (grant agreements No 864483 and 742299)”.

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Fernandez, Erwin, Dennis Friedrich, Roel van De Krol i Fatwa Abdi. "Alternate-Target Layer-By-Layer Pulsed Laser Deposition of Epitaxial BiVO₄ Thin Films". ECS Meeting Abstracts MA2022-01, nr 36 (7.07.2022): 1559. http://dx.doi.org/10.1149/ma2022-01361559mtgabs.

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Bismuth vanadate (BiVO4) has emerged as one of the highest performing metal oxide photoelectrodes for solar energy-to-fuels applications [1, 2]. This achievement has been largely attributed to the development of high-quality synthesis techniques. Specifically, epitaxial synthetic routes to producing lattice-matched, near single-crystalline quality BiVO4 with minimal extrinsic defects have been essential to understand the fundamental and PEC properties of BiVO4 that are inaccessible by conventional bulk synthesis techniques. In addition, epitaxial synthesis may also be employed as a strategy to further improve the PEC properties of BiVO4 through, for instance, altering the band structure and enhancing the carrier dynamics by strain engineering. Hence, the ability to produce high-quality single-phase epitaxial BiVO4 films is desirable. To date, molecular beam epitaxy (MBE), chemical vapor deposition (CVD), and pulsed laser deposition (PLD) [3] have been used to fabricate epitaxial BiVO4 thin films, with PLD having the advantage of relatively simple experimental setup and material versatility. However, an oft-noted drawback in conventional PLD using single oxide targets is off-stoichiometry in the deposited films; this is especially so for BiVO4 which requires a Bi-rich compound target to achieve a stoichiometric BiVO4 film [4]. This problem is also expected in general for multinary oxides composed of elements with very different ablation properties. To alleviate the limitations of conventional PLD, we employ for the first time alternate-target layer-by-layer PLD as a more elegant approach to produce high quality epitaxial BiVO4 films. Briefly, constituent oxide targets are alternately ablated by an excimer laser (λ= 248 nm) to build the desired film one unit cell thick at a time. Stoichiometry is controlled by the number of shots corresponding to a specified laser fluence for the constituent oxide target. To demonstrate the method, we deposited epitaxial BiVO4 films onto (001)-oriented yttrium-stabilized zirconia (YSZ) using 4N-pure Bi2O3 and V2O5 targets. Films grown are single phase BiVO4 as shown by x-ray diffraction. Out-of-plane diffraction peaks indexed to BiVO4(00l) suggests epitaxy of the film onto the substrate; reciprocal space maps of the asymmetric BiVO4(208) and YSZ(204) peaks further confirm the BiVO4(001) || YSZ(001) epitaxial relationship (top figure). Rocking curves of the BiVO4 (004) peak (FWHM ~ 0.015-0.041) indicate high crystalline perfection of the BiVO4 film, almost approaching that of the YSZ substrate (FWHM ~ 0.010). Thickness dependent-rocking curve studies reveal that BiVO4 films are strained to the substrate for film thicknesses under 22 nm; above this critical thickness, film relaxation ensues. In turn, the resulting optoelectronic properties of the BiVO4 film is dictated by its relaxation state. The optical band gap narrows with film relaxation as observed with spectroscopic ellipsometry. Moreover, steady-state photoluminescence emission spectroscopy reveals a sub-bandgap state (A 2, bottom figure) associated with strained BiVO4 films, on top of a state consistent with band-to-band recombination (B1 ). A higher energy sub-bandgap state (A 1, bottom figure) develops as the film relaxes. The implications of the relaxation state on the charge carrier dynamics and photoelectrochemical properties of BiVO4 will be discussed. Figure: (top) reciprocal space maps of the asymmetric BiVO4(208) and YSZ(204) peaks; (bottom) photoluminescence emission spectra of strained and relaxed BiVO4 films. References: [1] Pihosh, Y., Turkevych, I., Mawatari, K. et al. Photocatalytic generation of hydrogen by core-shell WO3/BiVO4 nanorods with ultimate water splitting efficiency. Sci Rep 5, 11141 (2015) [2] Kim, J., Jang, JW., Jo, Y. et al. Hetero-type dual photoanodes for unbiased solar water splitting with extended light harvesting. Nat Commun 7, 13380 (2016) [3] Zhang, Y., Li, G. Recent Advances of Epitaxial BiVO4 Thin Film: Preparation and Physical and Photoelectrochemical Properties. Braz J Phys 50,185 (2020). [4] Rettie, A. J. E., Mozaffari, S., McDaniel, M. D., Pearson, K. N., Ekerdt, J. G., Markert, J. T., & Mullins, C. B. Pulsed Laser Deposition of Epitaxial and Polycrystalline Bismuth Vanadate Thin Films. J Phys Chem C 118(46), 26543 (2014) Figure 1

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25

Kim, Shin-Ik, Hyung-Jin Choi, Gwangyeob Lee, Chang Jae Roh, Inki Jung, Soo Young Jung, Ruiguang Ning i in. "3D architectures of single-crystalline complex oxides". Materials Horizons 7, nr 6 (2020): 1552–57. http://dx.doi.org/10.1039/d0mh00292e.

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We proposed 3D architectures of complex oxides as a way to derive novel properties: various 3D shapes were formed by self-shaped free-standing membranes, and curvature-induced polarization in an otherwise nonpolar material was observed.

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Suihkonen, Sami, Siddha Pimputkar, Sakari Sintonen i Filip Tuomisto. "Defects in Single Crystalline Ammonothermal Gallium Nitride". Advanced Electronic Materials 3, nr 6 (10.03.2017): 1600496. http://dx.doi.org/10.1002/aelm.201600496.

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Dieckmann, Rüdiger. "Point Defects and Diffusion in Nonstoichiometric Metal Oxides". MRS Bulletin 16, nr 12 (grudzień 1991): 27–32. http://dx.doi.org/10.1557/s0883769400055317.

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This article briefly reviews the relationships between point defects and ion diffusion in nonstoichiometric ionic crystals, with special emphasis on cubic oxides. It focuses on crystalline materials with negligibly small concentrations of nonequilibrium defects such as dislocations and grain boundaries. First, the concepts used to analyze the point defect structure and the diffusion of ions in nonstoichiometric crystals will be discussed. Then, specific oxides will be considered as examples. These oxides are manganosite, Mn1−ΔO, and spinels of the type Me3−δO4 with Fe and Mn cations, respectively.

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Furuta, Mamoru, i Yusaku Magari. "(Invited, Digital Presentation) Nondegenerate Hydrogen-Doped Polycrystalline Indium Oxide (InOx:H) Thin Films for High-Mobility Thin Film Transistors". ECS Meeting Abstracts MA2022-02, nr 35 (9.10.2022): 1266. http://dx.doi.org/10.1149/ma2022-02351266mtgabs.

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Transparent metal oxide semiconductors (OSs) have been extensively investigated for use as the active channel layer of thin film transistors (TFTs) for next-generation flat-panel displays, nonvolatile memories, image sensors, and pH sensors, to name a few. Among OSs, the amorphous In–Ga–Zn–O (IGZO) has attracted particular attention for TFT applications owing to its high field effect mobility (μFE) of more than 10 cm2V−1s−1, steep subthreshold swing (S.S.), extremely low off-state current, large-area uniformity, and good bias stress stability. Although the μFE of an IGZO TFT is approximately one order of magnitude higher than that of an amorphous Si TFT, further improvement of the μFE of OS TFTs is required to expand their range of applications as an alternative to polycrystalline Si TFT. Single-crystalline In2O3 has a Hall mobility as high as 160 cm2V−1s−1, which makes amorphous (a-) or polycrystalline (poly-) InOx a potential material for enhancing the μFE of OS TFTs. However, undoped InOx thin films is known as a degenerate semiconductor with high background electron density of over 1020 cm-3, which is attributed to the presence of native defects, such as oxygen vacancies, making them unsuitable for a channel material of OS TFTs. In this presentation, nondegenerate hydrogen-doped polycrystalline InOx (poly-InOx:H) thin films were successfully prepared by low-temperature solid phase crystallization (SPC). A degenerate amorphous InOx:H thin film was deposited by sputtering in Ar, O2, and H2 gases, and an amorphous to polycrystalline phase transition (SPC) of the film was achieved after PDA at more than 175 °C. By PDA at 250 °C in air, a nondegenerate poly-InOx:H film could be obtained with a carrier density as low as 2.4 × 1017 cm−3, which is approximately three orders of magnitude lower than that of the initial a-InOx:H film. The TFTs with a 50 nm thick nondegenerate poly-InOx:H channel could be fully depleted by a gate electric field. A maximum μFE of 125.7 cm2V−1s−1 was exhibited by the TFT with the poly-InOx:H channel. The use of a nondegenerate poly-InOx:H film is a promising approach to boost the μFE of OS TFTs.

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Lankhorst, Martijn H. R., Henny J. M. Bouwmeester i Henk Verweij. "Thermodynamics and Transport of Ionic and Electronic Defects in Crystalline Oxides". Journal of the American Ceramic Society 80, nr 9 (20.01.2005): 2175–98. http://dx.doi.org/10.1111/j.1151-2916.1997.tb03107.x.

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Vilar, Rui, i Edson Costa Santos. "Structure of NiCrAlY Coatings Deposited on Oriented Single Crystal Superalloy Substrates by Laser Cladding". Advanced Materials Research 278 (lipiec 2011): 503–8. http://dx.doi.org/10.4028/www.scientific.net/amr.278.503.

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In the present work single and multiple layer NiCrAlY coatings were produced by laser cladding on (100) single-crystalline substrates of SRR99 Ni-based superalloy. Detailed structural characterisation and texture analysis by optical microscopy, scanning electron microscopy, X-ray diffraction and Rutherford backscattering showed that the NiCrAlY coatings consisted essentially of gamma phase with yttrium oxide (Y2O3) and a small proportion of yttrium–aluminium garnet (Al5Y3O12) precipitated in the interdendritic regions. The coatings presented a columnar dendritic structure grown by epitaxial solidification on the substrate and inherited the single-crystalline nature and the orientation of the substrate. The coating material also showed a mosaicity and a defect density similar to those of the substrate. It can be expected that the protective effect of these coatings against oxidation is greatly enhanced compared with polycrystalline coatings because high diffusivity paths, such as grain boundaries, are eliminated in single-crystalline coatings, thus reducing mass transport through the coating.

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Li, Ming, P. H. Kes, S. F. W. R. Rycroft, C. J. van der Beek i M. Konczykowski. "Origin of linear extended defects in single crystalline Bi2Sr2CaCu2O8". Physica C: Superconductivity 408-410 (sierpień 2004): 25–26. http://dx.doi.org/10.1016/j.physc.2004.02.021.

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LANKHORST, M. H. R., H. J. M. BOUWMEESTER i H. VERWEIJ. "ChemInform Abstract: Thermodynamics and Transport of Ionic and Electronic Defects in Crystalline Oxides". ChemInform 28, nr 52 (2.08.2010): no. http://dx.doi.org/10.1002/chin.199752334.

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Steinmetz, D., E. Neu, J. Meijer, W. Bolse i C. Becher. "Single photon emitters based on Ni/Si related defects in single crystalline diamond". Applied Physics B 102, nr 3 (19.02.2011): 451–58. http://dx.doi.org/10.1007/s00340-011-4402-x.

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Ni, Hai, i Xiao Dong Li. "Synthesis, Structural and Mechanical Characterization of Amorphous and Crystalline Boron Nanobelts". Journal of Nano Research 1 (styczeń 2008): 10–22. http://dx.doi.org/10.4028/www.scientific.net/jnanor.1.10.

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Amorphous and crystalline (rhombohedral structure with [111] growth direction) boron nanobelts were synthesized by the vapor-liquid-solid technique. Their structure and chemical compositions were studied by various electron and atomic force microscopy techniques. Most amorphous and crystalline belts have a width to thickness ratio of 2 and are covered with a layer of amorphous silicon oxide. The crystalline belt cores are defect-free single crystals. Gold catalyst thickness and synthesis temperature are the two prominent parameters determining structure of the synthesized nanobelts. The elastic modulus and hardness were measured using nanoindentation and atomic force microscopy three-point bending techniques. The indentation elastic modulus and hardness were measured to be 92.84.5 GPa and 8.40.6 GPa for amorphous belts, and 72.73.9 GPa and 6.80.6 GPa for crystalline ones, respectively. The three-point bending elastic moduli were found to be 87.83.5 GPa and 72.22.4 GPa for amorphous and crystalline, respectively. The measured mechanical properties are 4-5 times lower than those of the counterpart bulk materials.

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Williams, David R. M., i Avi Halperin. "Hairpin Defects in Liquid-Crystalline Polymers". MRS Bulletin 20, nr 9 (wrzesień 1995): 39–41. http://dx.doi.org/10.1557/s0883769400034916.

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Conventionally, the term “defects” in liquid-crystalline systems refers to microscopic faults in the orientational order, which are usually visible optically. These are discussed in other articles in this issue. Our use of the term defect is entirely different. The defects we shall be considering, “hairpins,” occur on the scale of several angstroms and are abrupt reversals in the trajectory of a single liquid-crystalline-polymer (LCP) chain (Figure 1). In comparison to conventional defects, the direct observation of hairpin defects is much more difficult, yet their presence has important effects. Among the affected properties are the dimensions and the elasticity of the chains, the elastic behavior of the bulk nematic, and its dielectric response. Their presence should also give rise to a family of interfacial phase transitions in solutions of LCPs in nematic solvents. In turn, these are of interest in the design of liquid-crystalline displays. Hairpins in LCPs are superficially reminiscent of similar configurations in proteins and in homopolymers that undergo fold crystallization. These similarities are misleading because hairpins in proteins are permanent structures due to the chemical bonds. The folds in crystalline polymers are also fixed structures. In marked contrast, hairpin defects are mobile topological excitations that are created and annihilated continuously. Our emphasis in this article is on main-chain, semiflexible, nematic LCPs, consisting of mesogenic monomers joined by flexible spacer chains (Figure la). These polymers combine the orientational order of monomeric nematics with the flexibility and randomness inherent in polymers. The appearance of an oriented, nematic phase can be controlled either by temperature or by concentration.

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Taylor, Seth T., John Mardinly i Michael A. O'Keefe. "HRTEM Image Simulations for the Study of Ultrathin Gate Oxides". Microscopy and Microanalysis 8, nr 5 (październik 2002): 412–21. http://dx.doi.org/10.1017/s1431927602020123.

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We have performed high resolution transmission electron microscope (HRTEM) image simulations to qualitatively assess the visibility of various structural defects in ultrathin gate oxides of MOSFET devices, and to quantitatively examine the accuracy of HRTEM in performing gate oxide metrology. Structural models contained crystalline defects embedded in an amorphous 16-Å-thick gate oxide. Simulated images were calculated for structures viewed in cross section. Defect visibility was assessed as a function of specimen thickness and defect morphology, composition, size, and orientation. Defect morphologies included asperities lying on the substrate surface, as well as “bridging” defects connecting the substrate to the gate electrode. Measurements of gate oxide thickness extracted from simulated images were compared to actual dimensions in the model structure to assess TEM accuracy for metrology. The effects of specimen tilt, specimen thickness, objective lens defocus, and coefficient of spherical aberration (Cs) on measurement accuracy were explored for nominal 10-Å gate oxide thickness. Results from this work suggest that accurate metrology of ultrathin gate oxides (i.e., limited to several percent error) is feasible on a consistent basis only by using a Cs-corrected microscope. However, fundamental limitations remain for characterizing defects in gate oxides using HRTEM, even with the new generation of Cs-corrected microscopes.

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37

Yeom, Eun Joo, Seong Sik Shin, Woon Seok Yang, Seon Joo Lee, Wenping Yin, Dasom Kim, Jun Hong Noh, Tae Kyu Ahn i Sang Il Seok. "Controllable synthesis of single crystalline Sn-based oxides and their application in perovskite solar cells". Journal of Materials Chemistry A 5, nr 1 (2017): 79–86. http://dx.doi.org/10.1039/c6ta08565b.

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Li, Xiao, José A. Martínez-González, Juan P. Hernández-Ortiz, Abelardo Ramírez-Hernández, Ye Zhou, Monirosadat Sadati, Rui Zhang, Paul F. Nealey i Juan J. de Pablo. "Mesoscale martensitic transformation in single crystals of topological defects". Proceedings of the National Academy of Sciences 114, nr 38 (5.09.2017): 10011–16. http://dx.doi.org/10.1073/pnas.1711207114.

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Liquid-crystal blue phases (BPs) are highly ordered at two levels. Molecules exhibit orientational order at nanometer length scales, while chirality leads to ordered arrays of double-twisted cylinders over micrometer scales. Past studies of polycrystalline BPs were challenged by the existence of grain boundaries between randomly oriented crystalline nanodomains. Here, the nucleation of BPs is controlled with precision by relying on chemically nanopatterned surfaces, leading to macroscopic single-crystal BP specimens where the dynamics of mesocrystal formation can be directly observed. Theory and experiments show that transitions between two BPs having a different network structure proceed through local reorganization of the crystalline array, without diffusion of the double-twisted cylinders. In solid crystals, martensitic transformations between crystal structures involve the concerted motion of a few atoms, without diffusion. The transformation between BPs, where crystal features arise in the submicron regime, is found to be martensitic in nature when one considers the collective behavior of the double-twist cylinders. Single-crystal BPs are shown to offer fertile grounds for the study of directed crystal nucleation and the controlled growth of soft matter.

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Hayashi, Kei, Sota Kawamura, Yusuke Hashimoto, Noboru Akao, Zhicheng Huang, Wataru Saito, Kaichi Tasaki, Koichi Hayashi, Tomohiro Matsushita i Yuzuru Miyazaki. "Effects of Oxygen on Lattice Defects in Single-Crystalline Mg2Si Thermoelectrics". Nanomaterials 13, nr 7 (30.03.2023): 1222. http://dx.doi.org/10.3390/nano13071222.

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Lattice defect engineering has attracted attention due to its ability to develop thermoelectric materials with low thermal conductivity. For Mg2Si single crystals (SCs), Si vacancy (VSi) defects can be introduced and consequently result in the formation of dislocation cores. These lattice defects confer Mg2Si SCs with a lower thermal conductivity compared to Mg2Si polycrystals. To reveal a mechanism for the stabilisation of VSi in the Mg2Si SCs, we investigated the effects of oxygen (O) on lattice defects by performing electronic structure calculations, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and photoelectron holography. On the basis of these calculations, we predicted that O stabilised the formation of VSi when it was located at the Si site or at an interstitial site. All experiments confirmed the presence of O inside the Mg2Si SCs. However, O was suggested to be located not at the specific site in the crystal lattice of Mg2Si but at dislocation cores. The interaction between O and the dislocation cores in the Mg2Si SC is expected to immobilise dislocation cores, leading to the stabilisation of VSi formation.

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Peng, Bin, Ren-Ci Peng, Yong-Qiang Zhang, Guohua Dong, Ziyao Zhou, Yuqing Zhou, Tao Li i in. "Phase transition enhanced superior elasticity in freestanding single-crystalline multiferroic BiFeO3 membranes". Science Advances 6, nr 34 (sierpień 2020): eaba5847. http://dx.doi.org/10.1126/sciadv.aba5847.

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The integration of ferroic oxide thin films into advanced flexible electronics will bring multifunctionality beyond organic and metallic materials. However, it is challenging to achieve high flexibility in single-crystalline ferroic oxides that is considerable to organic or metallic materials. Here, we demonstrate the superior flexibility of freestanding single-crystalline BiFeO3 membranes, which are typical multiferroic materials with multifunctionality. They can endure cyclic 180° folding and have good recoverability, with the maximum bending strain up to 5.42% during in situ bending under scanning electron microscopy, far beyond their bulk counterparts. Such superior elasticity mainly originates from reversible rhombohedral-tetragonal phase transition, as revealed by phase-field simulations. This study suggests a general fundamental mechanism for a variety of ferroic oxides to achieve high flexibility and to work as smart materials in flexible electronics.

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Medvedeva, Julia E. "Role of morphology in defect formation and photo-induced carrier instabilities in amorphous indium oxide". Applied Physics Letters 121, nr 26 (26.12.2022): 261902. http://dx.doi.org/10.1063/5.0128941.

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Ab initio molecular dynamics liquid-quench simulations and hybrid density functional calculations are performed to model the effects of room-temperature atomic fluctuations and photo-illumination on the structural and electronic properties of amorphous sub-stoichiometric In2O2.96. A large configurational ensemble is employed to reliably predict the distribution of localized defects as well as their response to the thermal and light activation. The results reveal that the illumination effects on the carrier concentration are greater in amorphous configurations with shorter In–O bond length and reduced polyhedral sharing as compared to the structures with a more uniform morphology. The obtained correlation between the photo-induced carrier density and the reduction in the number of fully coordinated In-atoms implies that metal oxides with a significant fraction of crystalline/amorphous interfaces would show a more pronounced response to illumination. Photo-excitation also produces In–O2–In defects that have not been previously found in sub-stoichiometric amorphous oxides; these defects are responsible for carrier instabilities due to overdoping.

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Huang, Xiege, Wenying Deng, Xiaolian Zhang, Sergey I. Morozov, Guodong Li, Pengcheng Zhai i Qingjie Zhang. "Enhancing the shear strength of single-crystalline In4Se3 through point defects". Scripta Materialia 211 (kwiecień 2022): 114507. http://dx.doi.org/10.1016/j.scriptamat.2022.114507.

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Wu, Di, Lijun Wu, Dongsheng He, Li-Dong Zhao, Wei Li, Minghui Wu, Min Jin i in. "Direct observation of vast off-stoichiometric defects in single crystalline SnSe". Nano Energy 35 (maj 2017): 321–30. http://dx.doi.org/10.1016/j.nanoen.2017.04.004.

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Krawczyk, J., A. Tondos, W. Bogdanowicz i R. Paszkowski. "Structural Defects of Initial Crystallization Areas in Single-Crystalline Turbine Blades". Powder Metallurgy and Metal Ceramics 56, nr 7-8 (listopad 2017): 481–86. http://dx.doi.org/10.1007/s11106-017-9919-z.

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Fomenko, V. S. "Electronic work function of sintered and single-crystalline high-temperature superconducting oxides". Powder Metallurgy and Metal Ceramics 32, nr 2 (luty 1993): 178–81. http://dx.doi.org/10.1007/bf00560050.

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Mfon, Rebecca Emmanuel, Simon R. Hall i Andrei Sarua. "Effect of Ocimum gratissimum plant leaf extract concentration and annealing temperature on the structure and optical properties of synthesized zinc oxide nanoparticles". EDUCATUM Journal Of Science, Mathematics And Technology 7, nr 1 (31.01.2020): 1–13. http://dx.doi.org/10.37134/ejsmt.vol7.1.1.2020.

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Zinc oxide nanoparticles biosynthesized using two concentrations of Ocimum gratissimum (Og) plant leaf extracts were annealed at two different temperatures. Their UV-Vis absorbance peaks at 372 nm - 375 nm indicate a blue shift in excitonic absorption and their optical energy band gap values were in the range 3.22 eV – 3.31 eV. SEM images show the nanoparticles to be polydispersed and of a wide range of sizes with smaller nanoparticles clustering around bigger micrometer- sized ones with sharp edges. An annealing temperature of 400 resulted in the sintering of the nanoparticles but nanoparticles annealed at 250 had porous surfaces suggesting a possible use in gas sensor applications. XRD patterns show that the ZnO nanoparticles have the hexagonal wurtzite structure and are of good crystalline structure. Obtained crystallite sizes increased with annealing temperature and were in the range 14 nm to 29 nm. FTIR spectra show phenols, amines and aldehydes as the available reducing agents involved in the nanoparticle synthesis. The photoluminescence (PL) spectra show two emission peaks: a UV emission peak at 369 -381 nm indicating that the zinc oxide nanoparticles exhibited band-edge photoluminescence and a green emission peak at 523 nm – 538 nm suggesting the presence of defects from singly ionized oxygen vacancies. The PL peak intensities were dependent on the annealing temperatures with the UV- emission peaks for higher annealing temperatures exhibiting a spectral shift towards lower wavelengths. Plant leaf extracts concentration and the annealing temperatures used affect the structure and optical properties of the synthesized ZnO nanoparticles.

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Wang, Xingyu, Chunlin Ma, Weiping Zhou i Weishi Tan. "Crystalline Orientation-Dependent Ferromagnetism in N+-Implanted MgO Single Crystal". Materials 15, nr 20 (18.10.2022): 7274. http://dx.doi.org/10.3390/ma15207274.

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Samples of (110), (100), and (111) MgO single crystals were implanted with 70 keV N ions at room temperature. All as-implanted samples showed room temperature hysteresis in magnetization loops. The observed saturation magnetization (Ms) was 0.79 × 10−4 emu/g, 1.28 × 10−4 emu/g, and 1.5 × 10−4 emu/g for (110), (100) and (111) orientation implanted-MgO and follows the relation Ms(111) > Ms(100) > Ms(110), indicative of crystalline orientation-dependent ferromagnetism in N-implanted MgO. The samples were characterized by X-ray photoelectron spectroscopy (XPS), high resolution X-ray diffraction (HRXRD), reciprocal space mapping (RSM), and photoluminescence (PL). The results indicated that the amount of N-substitute-O and N-interstitial defects in these three N-implanted MgO samples showed the same changing tendency as compared with Ms data. Thus, we conclude that the N-substitute-O and N-interstitial defects may play a crucial role in controlling the N+-implanted-induced ferromagnetism.

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FECHT, H. J., i Z. FU. "AMORPHIZATION OF HYDRIDED Fe2Er-SINGLE-CRYSTALS TRIGGERED BY A LATTICE INSTABILITY". Modern Physics Letters B 05, nr 01 (10.01.1991): 1–11. http://dx.doi.org/10.1142/s0217984991000022.

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Specific heat measurements at constant concentration of hydrided, initially single-crystalline Fe2Er powder samples exhibit a lambda-type anomaly during the transition from the crystalline to the amorphous state. The logarithmic temperature-dependence of the specific heat results from local fluctuations in the crystalline phase, rather than thermally activated lattice defects. This is suggestive of an instability underlying the “melting” transition to a glass that has been predicted if vitrification occurs in the vicinity of the extrapolated triple point between crystal, liquid and glass.

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Popescu, Madalina, Roxana Piticescu, Eugeniu Vasile, Dragos Taloi, Mirela Petriceanu, Maria Stoiciu i Viorel Badilita. "The Influence of Synthesis Parameters on FeO(OH) / Fe2O3 Formation by Hydrothermal Techniques". Zeitschrift für Naturforschung B 65, nr 8 (1.08.2010): 1024–32. http://dx.doi.org/10.1515/znb-2010-0808.

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In this paper, a hydrothermal method of high-pressure and low-temperature synthesis conditions is presented as a simple single-step technique to obtain crystalline nanoparticles of iron oxides. The aim of this work has been to demonstrate the influence of the main synthesis parameters on the formation of nanosized Fe2O3 particles using statistical methods and to establish the most significant effects. Based on mathematical pre-modeling calculations, the best reaction conditions for the hydrothermal process have been chosen, and controlled crystalline nanostructures of iron oxides could be prepared

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Liu, Qing, Youwei Yan, Xiangcheng Chu, Yiling Zhang, Lihong Xue i Wuxing Zhang. "Graphene-induced growth of single crystalline Sb2MoO6sheets and their sodium storage performance". J. Mater. Chem. A 5, nr 40 (2017): 21328–33. http://dx.doi.org/10.1039/c7ta07111f.

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Pure and single crystalline Sb₂MoO₆sheets can be hydrothermally synthesizedviathe induction of graphene oxides, and the Sb₂MoO₆/RGO composite exhibits excellent cyclability and rate performance as the anode in a sodium ion battery.

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