Study on Cubic GaN Growth on (001) Rutile TiO2 Substrates by ECR-MBE

ABSTRACTGaN layers were grown on a (001) rutile TiO2 substrate by electron cyclotron resonance plasma-excited molecular beam epitaxy. For the first time, c-GaN with a preferential growth orientation was obtained. Based on the results from electron diffraction and X-ray diffraction analysis, we found that c-GaN with the growth direction of [110] was grown on the TiO2 substrate. The formation of c-GaN was also confirmed by cathodoluminescence, in which a luminescence peak was observed at 3.24eV.

Download Full-text

Influence of Time and Temperature on Directional Growth of MoO3

Materials Science Forum ◽

10.4028/www.scientific.net/msf.869.1001 ◽

2016 ◽

Vol 869 ◽

pp. 1001-1006

Author(s):

Claudia Ferreira da Silva ◽

André Lima e Silva ◽

Francisco Xavier Nobre ◽

Edson Cavalcanti Silva Filho ◽

Luiz de Sousa Santos Jr. ◽

...

Keyword(s):

Glacial Acetic Acid ◽

Molybdenum Trioxide ◽

Orthorhombic Phase ◽

Growth Direction ◽

X Ray Diffraction ◽

Directional Growth ◽

Preferential Growth ◽

X Ray ◽

Preferential Growth Direction ◽

Characteristic Modes

Two-dimensional microstructures of molybdenum trioxide (MoO3) were synthesized by heptamolybdate tetrahydrate ammonium acidification, followed by calcination. A solution of the precursor compound heptamolybdate tetrahydrate ammonium acidified to pH 3,5 using glacial acetic acid followed by hydrothermal treatment for 150, 180 and 200 °C for 1, 6 and 12 hours. Then, the intermediate was calcined at 300 °C for varying time 6 and 12h to obtain MoO3. X-ray diffraction revealed that the crystals grew with crystalline structure corresponding to the orthorhombic phase of MoO3 (a-MoO3) as major phase, with a preferential growth direction along the planes (0K0). Raman spectroscopy and IR confirmed the formation of the characteristic modes of molybdenum trioxide for stage found. With Scanning Electron Microscopy (SEM) was possible to observe the formation of nanoplates.

Download Full-text

High-Resolution X-Ray Diffraction Analysis of “Devicequality” Cubic GaN Grown on (001)GaAs Substrate Prepared by Atomic-Hydrogen Treatment At “High Temperatures”

MRS Proceedings ◽

10.1557/proc-482-465 ◽

1997 ◽

Vol 482 ◽

Cited By ~ 3

Author(s):

A. Yoshikawa ◽

Z. X. Qin ◽

H. Nagano ◽

Y. Sugure ◽

A. W. Jia ◽

...

Keyword(s):

High Resolution ◽

High Temperatures ◽

Atomic Hydrogen ◽

Plasma Source ◽

Hydrogen Treatment ◽

X Ray Diffraction ◽

Reciprocal Space Mapping ◽

X Ray ◽

Cubic Gan ◽

First Time

AbstractCubic GaN (c-GaN) layers were grown by if-plasma source MBE on (001) GaAs prepared by atomic-hydrogen treatment at “high temperatures”, and the structural properties of the epilayers were investigated by the high-resolution X-ray rocking curve and the reciprocal space mapping measurements. The growth temperature was varied from 620 to 740°C. It was found that single domain “device-quality” c-GaN layers could be grown for the first time; the FWHM of the X-ray rocking curves for the (002) c-GaN could be as small as 70 - 90 arcsec and the inclusion of h-GaN phase in the c-GaN epilayers grown at temperatures above 680°C could be less than 4×10-3.

Download Full-text

Magnetic Anisotropy in Single Crystal Terfenol-D Thin Films

MRS Proceedings ◽

10.1557/proc-475-181 ◽

1997 ◽

Vol 475 ◽

Author(s):

V. Oderno ◽

C. Dufour ◽

K. Dumesnil ◽

A. Mougin ◽

Ph. Bauer ◽

...

Keyword(s):

Thin Films ◽

Room Temperature ◽

Growth Direction ◽

X Ray Diffraction ◽

Bulk Alloy ◽

Easy Magnetization ◽

Magnetization Direction ◽

Kerr Rotation ◽

X Ray ◽

First Time

ABSTRACTTb03.Dy0.7Fe2 (known as Terfenol-D) thin films have been epitaxially grown for the first time with [110] as the growth direction. X-Ray diffraction measurements evidence that the films are strained compared to the bulk alloy. Mössbauer spectroscopy and Kerr rotation measurements show that the easy magnetization direction varies from <116> at 4.2 K to around <133> at 300 K. This variation is different from the bulk case (for which the magnetization is along <100> at 4.2 K and along <111> at room temperature). This effect can be qualitatively understood if we consider the influence of the strains induced by epitaxy on the various energy terms which govern the direction of magnetization.

Download Full-text

Unidirectional crystal growth and crystalline perfection ofL-arginine phosphate monohydrate

Journal of Applied Crystallography ◽

10.1107/s0021889812016822 ◽

2012 ◽

Vol 45 (4) ◽

pp. 679-685 ◽

Cited By ~ 8

Author(s):

B. Riscob ◽

Mohd Shakir ◽

N. Vijayan ◽

K. K. Maurya ◽

M. A. Wahab ◽

...

Keyword(s):

Single Crystal ◽

Growth Direction ◽

Wide Frequency Range ◽

Bulk Single Crystal ◽

X Ray Diffraction ◽

Crystalline Perfection ◽

X Ray ◽

Hardness Tester ◽

Device Applications ◽

First Time

A large (∼20 mm diameter and 80 mm length) single crystal of L-arginine phosphate monohydrate (LAP) has been grown for the first time by the unidirectional Sankaranarayanan–Ramasamy method in an aqueous medium in a specially designed constant-temperature bath. The crystal structure has been confirmed by powder X-ray diffraction. The crystalline perfection was assessed by high-resolution X-ray diffractometry (HRXRD) which found that the quality of the grown single crystal is quite good. HRXRD studies along different directions show that the crystal contains a low density of edge-type dislocations formed along the growth direction. The thermal stability was assessed using thermogravimetric/differential thermal analysis. The mechanical behaviour was studied using an Omnitech micro-hardness tester. The dielectric studies were carried out over a wide frequency range of 10 Hz to 5 MHz at room temperature. The characterization studies reveal that the grown bulk single crystal of LAP is suitable for device applications.

Download Full-text

Study of the Preferred Orientation of Hydroxyapatite in Ivory from Zimbabwe and Mammoth Ivory from Siberia

Crystals ◽

10.3390/cryst11050572 ◽

2021 ◽

Vol 11 (5) ◽

pp. 572

Author(s):

Xue Ying Sun ◽

Ming Yue He ◽

Jin Lin Wu

Keyword(s):

Growth Direction ◽

Preferred Orientation ◽

Crystal Formation ◽

Orientation Factor ◽

X Ray Diffraction ◽

X Ray ◽

Angle Bisector ◽

Pole Figures ◽

First Time ◽

Insight Into

In this paper, the pole figures plotted from X-ray diffraction data are employed to analyze the orientation of hydroxyapatite in ivory and mammoth ivory for the first time. The results present evidence of the lamellar structure and the hydroxyapatite appeared as tabular. A preferred orientation of hydroxyapatite was revealed in terms of the calculated orientation factor and the characteristics found in the pole figures. The c-axes of hydroxyapatite are mainly oriented along the growth direction. Both a-axes are on the left of the angle bisector of Retzius. Approximately 25–30° separates the a-axes and the angle bisector of Retzius in ivory, whereas the figure is approximately 10–15° in mammoth ivory. Our work is significant in providing more accurate knowledge of the shapes and organizational state of bio-mineral crystals and providing insight into crystal formation and development in bio-mineralization.

Download Full-text

Composition, Structure and Electrical Resistivity of ZnO1-x Films Deposited by RF Magnetron Sputtering under Various O2/Ar Gas Ratios

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.697.723 ◽

2016 ◽

Vol 697 ◽

pp. 723-726 ◽

Cited By ~ 1

Author(s):

Yang Wang ◽

Zhi Jian Peng ◽

Qi Wang ◽

Xiu Li Fu

Keyword(s):

Electrical Resistivity ◽

Magnetron Sputtering ◽

Rf Magnetron Sputtering ◽

X Ray Diffraction ◽

Preferential Growth ◽

X Ray ◽

Interstitial Zinc ◽

Composition Structure ◽

Ar Gas ◽

Preferential Growth Orientation

ZnO1-x thin films were deposited by RF magnetron sputtering on conducting silicon wafers at room temperature with ZnOn (n≤1) target under an atmosphere of O2/Ar ratio varying from 0 to 2.0. The correlation between composition, structure and electrical resistivity of the obtained films was investigated. X-ray diffraction analysis revealed that the prepared würtzite ZnO1-x films had c-axis preferential growth orientation. When the O2/Ar ratio was lower than 0.5, the main form of defects in the films was oxygen vacancy; when it was 0.5, the composition of the film approached to the stoichiometric ZnO and had the least number of defects; after that, the main type of defects in the films was interstitial zinc. Thus, with increasing O2/Ar ratio, the electrical resistivity of the films increased first and then decreased.

Download Full-text

The Microstructures of the Biomineralized Bivalvia Shells

MRS Proceedings ◽

10.1557/proc-174-101 ◽

1989 ◽

Vol 174 ◽

Cited By ~ 5

Author(s):

L.J. Huang ◽

H.D. Li

Keyword(s):

Electron Spectroscopy ◽

Structural Features ◽

X Ray Diffraction ◽

Vibrational States ◽

Prismatic Layer ◽

Preferential Growth ◽

X Ray ◽

Growth Orientation ◽

Laser Raman ◽

Preferential Growth Orientation

AbstractThe paper presents the detailed study of the structural features of the biomineralized bivalvia shells. The Cristaria plicata(Leach), Anodonta woodianal(Lea) and Lamprotula Leai(Gray) are selected as the prototype in the present study. Scanning electron microscope (SEM), X-ray diffraction, laser Raman spectroscope and electron spectroscopy for chemical analysis (ESCA) are employed to study the structures of the shells. It is found that three different layers of the shells possess distinct morphologies and structures with a clear boundary between every two layers. The prismatic layer can be further divided into two sub–layers. The preferential growth orientation of the biominerahzed phases were different from the natural ones. The Raman spectra present the detailed vibrational states of these biomineralized phases, while ESCA reveals that the chemical environments of the atoms in pearl layer are less varied than those in the other two layers.

Download Full-text

Quartz Crystallite Size and Moganite Content as Indicators of the Mineralogical Maturity of the Carboniferous Chert: The Case of Cherts from Eastern Asturias (Spain)

Minerals ◽

10.3390/min11060611 ◽

2021 ◽

Vol 11 (6) ◽

pp. 611

Author(s):

Celia Marcos ◽

María de Uribe-Zorita ◽

Pedro Álvarez-Lloret ◽

Alaa Adawy ◽

Patricia Fernández ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Crystallite Size ◽

Archaeological Sites ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

Infrared And Raman Spectroscopy ◽

First Time ◽

Geological Formations

Chert samples from different coastal and inland outcrops in the Eastern Asturias (Spain) were mineralogically investigated for the first time for archaeological purposes. X-ray diffraction, X-ray fluorescence, transmission electron microscopy, infrared and Raman spectroscopy and total organic carbon techniques were used. The low content of moganite, since its detection by X-ray diffraction is practically imperceptible, and the crystallite size (over 1000 Å) of the quartz in these cherts would be indicative of its maturity and could potentially be used for dating chert-tools recovered from archaeological sites. Also, this information can constitute essential data to differentiate the cherts and compare them with those used in archaeological tools. However, neither composition nor crystallite size would allow distinguishing between coastal and inland chert outcrops belonging to the same geological formations.

Download Full-text

First Report on the Geologic Occurrence of Natural Na–A Zeolite and Associated Minerals in Cretaceous Mudstones of the Paja Formation of Vélez (Santander), Colombia

Crystals ◽

10.3390/cryst11020218 ◽

2021 ◽

Vol 11 (2) ◽

pp. 218

Author(s):

Carlos Alberto Ríos-Reyes ◽

German Alfonso Reyes-Mendoza ◽

José Antonio Henao-Martínez ◽

Craig Williams ◽

Alan Dyer

Keyword(s):

Natural Zeolite ◽

Scanning Electron Micrographs ◽

Total Sulfur ◽

Zeolite A ◽

X Ray Diffraction ◽

X Ray ◽

Mineral Phases ◽

The World ◽

Porosity And Permeability ◽

First Time

This study reports for the first time the geologic occurrence of natural zeolite A and associated minerals in mudstones from the Cretaceous Paja Formation in the urban area of the municipality of Vélez (Santander), Colombia. These rocks are mainly composed of quartz, muscovite, pyrophyllite, kaolinite and chlorite group minerals, framboidal and cubic pyrite, as well as marcasite, with minor feldspar, sulphates, and phosphates. Total organic carbon (TOC), total sulfur (TS), and millimeter fragments of algae are high, whereas few centimeters and not biodiverse small ammonite fossils, and other allochemical components are subordinated. Na–A zeolite and associated mineral phases as sodalite occur just beside the interparticle micropores (honeycomb from framboidal, cube molds, and amorphous cavities). It is facilitated by petrophysical properties alterations, due to processes of high diagenesis, temperatures up to 80–100 °C, with weathering contributions, which increase the porosity and permeability, as well as the transmissivity (fluid flow), allowing the geochemistry remobilization and/or recrystallization of pre-existing silica, muscovite, kaolinite minerals group, salts, carbonates, oxides and peroxides. X-ray diffraction analyses reveal the mineral composition of the mudstones and scanning electron micrographs show the typical cubic morphology of Na–A zeolite of approximately 0.45 mμ in particle size. Our data show that the sequence of the transformation of phases is: Poorly crystalline aluminosilicate → sodalite → Na–A zeolite. A literature review shows that this is an unusual example of the occurrence of natural zeolites in sedimentary marine rocks recognized around the world.

Download Full-text

The Effect of Surfactant-Modified Montmorillonite on the Cross-Linking Efficiency of Polysiloxanes

Materials ◽

10.3390/ma14102623 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2623

Author(s):

Monika Wójcik-Bania ◽

Jakub Matusik

Keyword(s):

Total Pore Volume ◽

Cross Linking ◽

X Ray Diffraction ◽

X Ray ◽

Transmission Electron ◽

The Cross ◽

Chain Lengths ◽

First Time ◽

Substituent Influence ◽

Benzyl Substituent

Polymer–clay mineral composites are an important class of materials with various applications in the industry. Despite interesting properties of polysiloxanes, such matrices were rarely used in combination with clay minerals. Thus, for the first time, a systematic study was designed to investigate the cross-linking efficiency of polysiloxane networks in the presence of 2 wt % of organo-montmorillonite. Montmorillonite (Mt) was intercalated with six quaternary ammonium salts of the cation structure [(CH3)2R’NR]+, where R = C12, C14, C16, and R’ = methyl or benzyl substituent. The intercalation efficiency was examined by X-ray diffraction, CHN elemental analysis, and Fourier transform infrared (FTIR) spectroscopy. Textural studies have shown that the application of freezing in liquid nitrogen and freeze-drying after the intercalation increases the specific surface area and the total pore volume of organo-Mt. The polymer matrix was a poly(methylhydrosiloxane) cross-linked with two linear vinylsiloxanes of different siloxane chain lengths between end functional groups. X-ray diffraction and transmission electron microscopy studies have shown that the increase in d-spacing of organo-Mt and the benzyl substituent influence the degree of nanofillers’ exfoliation in the nanocomposites. The increase in the degree of organo-Mt exfoliation reduces the efficiency of hydrosilylation reaction monitored by FTIR. This was due to physical hindrance induced by exfoliated Mt particles.

Download Full-text