First AlGaN Free-Standing Wafers

2003 ◽  
Vol 764 ◽  
Author(s):  
Yu.V. Melnik ◽  
V.A. Soukhoveev ◽  
K.V. Tsvetkov ◽  
V.A. Dmitriev
Keyword(s):  
Single Crystal ◽  
Hydride Vapor Phase Epitaxy ◽  
X Ray Diffraction ◽  
Free Standing ◽  
X Ray ◽  
Transmission Electron ◽  
Temperature Development ◽  
Intense Luminescence ◽  
Uv Emitters ◽  
First Time

AbstractSingle crystal AlGaN bulk materials have been fabricated, for the first time. AlGaN thick (up to 0.6 mm) layers were grown by hydride vapor phase epitaxy on SiC substrates. The substrates were removed resulting in free-standing AlGaN wafers up to 0.5 inch in diameter. Fabricated AlGaN wafers were investigated by x-ray diffraction, transmission electron microscopy (TEM), and cathodoluminescence. X-ray diffraction and TEM studies confirmed single crystal structure of grown material. Based on x-ray diffraction results, AlN concentration in grown material was estimated of about 35 mol.%. Cathodoluminescence measurements demonstrated a number of peaks in UV spectral region with the most intense luminescence at a wavelength of about 325 nm (100 K). The wafers demonstrated n-type conductivity with electron concentration in the 1017 cm-3 range at room temperature. Development of AlGaN substrates with controlled alloy composition may lead to stress-free device epitaxial structures for AlGaN-based transistors and UV emitters and sensors.

AlN Wafers Fabricated by Hydride Vapor Phase Epitaxy

1999 ◽  
Vol 595 ◽  
Author(s):  
Andrey Nikolaev ◽  
Irina Nikitina ◽  
Andrey Zubrilov ◽  
Marina Mynbaeva ◽  
Yuriy Melnik ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Vapor Phase ◽  
Vapor Phase Epitaxy ◽  
Hydride Vapor Phase Epitaxy ◽  
X Ray Diffraction ◽  
Free Standing ◽  
X Ray ◽  
Si Substrates ◽  
Transmission Electron ◽  
Thick Layers

AbstractWe report on AlN wafers fabricated by hydride vapor phase epitaxy (HVPE). AlN thick layers were grown on Si substrates by HVPE. Growth rate was up to 60 microns per hour. After the growth of AlN layers, initial substrates were removed resulting in free-standing AlN wafers. The maximum thickness of AlN layer was about 1 mm. AlN free-standing single crystal wafers with a thickness ranging from 0.05 to 0.8 mm were studied by x-ray diffraction, transmission electron microscopy, optical absorption, and cathodoluminescence.

scholarly journals AlN Wafers Fabricated by Hydride Vapor Phase Epitaxy

2000 ◽  
Vol 5 (S1) ◽  
pp. 432-437 ◽  
Author(s):  
Andrey Nikolaev ◽  
Irina Nikitina ◽  
Andrey Zubrilov ◽  
Marina Mynbaeva ◽  
Yuriy Melnik ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Vapor Phase ◽  
Vapor Phase Epitaxy ◽  
Hydride Vapor Phase Epitaxy ◽  
X Ray Diffraction ◽  
Free Standing ◽  
X Ray ◽  
Si Substrates ◽  
Transmission Electron ◽  
Thick Layers

We report on AlN wafers fabricated by hydride vapor phase epitaxy (HVPE). AlN thick layers were grown on Si substrates by HVPE. Growth rate was up to 60 microns per hour. After the growth of AlN layers, initial substrates were removed resulting in free-standing AlN wafers. The maximum thickness of AlN layer was about 1 mm. AlN free-standing single crystal wafers with a thickness ranging from 0.05 to 0.8 mm were studied by x-ray diffraction, transmission electron microscopy, optical absorption, and cathodoluminescence.

scholarly journals 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 ◽  
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.

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

Materials ◽  
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.

scholarly journals Eightfold Electrophilic Methylation of Octacyanotungstate [W(CN)8]4−/3−: Preparation of Homoleptic, Eight-coordinate Methylisocyanide Complexes [W(CNMe)8]4+/5+

2021 ◽  
Author(s):  
Malte Sellin ◽  
Susanne Margot Rupf ◽  
Ulrich Abram ◽  
Moritz Malischewski
Keyword(s):  
Sulfur Dioxide ◽  
Single Crystal ◽  
Epr Spectroscopy ◽  
X Ray Diffraction ◽  
Liquid Sulfur ◽  
Methyl Fluoride ◽  
X Ray ◽  
First Time ◽  
Ir And Raman ◽  
Methyl Triflate

Homoleptic eight-fold coordinated methylisocyanide complexes of W(IV) and W(V) have been prepared for the first time. The reaction of [NBu4]4[W(CN)8] with methyl triflate MeOTf gives [W(CNMe)8][OTf]4. The even stronger methylating mixture of methyl fluoride MeF and arsenic pentafluoride AsF5 in liquid sulfur dioxide SO2 is able to fully alkylate both [NBu4]4[W(CN)8] and [NBu4]3[W(CN)8]. The paramagnetic octakis(methylisocyanide)- tungsten(V) [W(CNMe)8][AsF6]5 is thermally highly unstable above −30 °C. All compounds have been characterized via single-crystal X-ray diffraction, IR and Raman, as well as NMR or EPR spectroscopy<br>

Boron Nitride Nanotubes: Nanoparticles Functionalization and Junction Fabrication

2007 ◽  
Vol 7 (2) ◽  
pp. 530-534 ◽  
Author(s):  
Chunyi Zhi ◽  
Yoshio Bando ◽  
Guozhen Shen ◽  
Chengchun Tang ◽  
Dmitri Golberg
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Boron Nitride ◽  
Boron Nitride Nanotubes ◽  
X Ray Diffraction ◽  
Carbon Nanostructure ◽  
Wet Chemistry ◽  
X Ray ◽  
Transmission Electron ◽  
First Time

Adopting a wet chemistry method, Au and Fe3O4 nanoparticles were functionalized on boron nitride nanotubes (BNNTs) successfully for the first time. X-ray diffraction pattern and transmission electron microscopy were used to characterize the resultant products. Subsequently, a method was proposed to fabricate heterojunction structures based on the particle-functionalized BNNTs. As a demonstration, BNNT-carbon nanostructure, BNNT-ZnO and BNNT-Ga2O3 junctions were successfully fabricated using the functionalized particles as catalysts.

scholarly journals Two Dibenzoquinones from the Fungus Acremonium cavaraeanum

2017 ◽  
Vol 12 (11) ◽  
pp. 1934578X1701201
Author(s):  
Qiao Xu ◽  
Miao-Miao Zhang ◽  
Shu-Zhen Yana ◽  
Lu-Fen Cao ◽  
Qiang Lia ◽  
...  
Keyword(s):  
Single Crystal ◽  
2D Nmr ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Time

Two symmetrical dibenzoquinone derivatives were isolated from solid cultures of the fungus Acremonium cavaraeanum. Compound 1 was new and identified as 2,7-dihydroxy-3,6,9-trimethyl-9 H-xanthene-1,4,5,8-tetraone. Compound 2 was 3,3’,6,6’-tetrahydroxy-4,4’-dimethyl-1,1’-bi- p-benzoquinone, i.e. oosporein, which was reported from A. cavaraeanum for the first time. The structure of the dibenzoquinone (1) was unambiguously elucidated using a combination of MS, IR, 1D- and 2D-NMR, and the dibenzoquinone (2) was further determined by single-crystal X-ray diffraction.

O,O-diethyl O-[2-(dimethylamino)ethyl] phosphorothioate: structural evidence of the decomposition product and its oxalate salt

2019 ◽  
Vol 234 (9) ◽  
pp. 613-621
Author(s):  
Marc André Althoff ◽  
Jörn Frederik Martens ◽  
Marco Reichel ◽  
Manfred Metzulat ◽  
Thomas Matthias Klapötke ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Title Compound ◽  
Analytical Methods ◽  
Decomposition Product ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rearrangement Process ◽  
Study Support ◽  
First Time

Abstract The molecular and single crystal structure of O,O-diethyl O-[2-(dimethylamino)ethyl] phosphorothioate oxalate, as determined by single crystal X-ray diffraction studies, is described for the first time; although this compound is well-known by industry and research from the mid-20th century. The known decomposition product of pure O,O-diethyl O-[2-(dimethylamino)ethyl] phosphorothioate could also be structurally characterized. Additionally, the compounds are characterized by recent analytical methods e.g. NMR. The findings of our study support the thesis that the isolated decomposition product must be a by-product of the thiono-thiolo rearrangement process of the title compound.

scholarly journals Formation of ZnO/Zn0.5Cd0.5Se Alloy Quantum Dots in the Presence of High Oleylamine Contents

Nanomaterials ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 999
Author(s):  
Yi-An Chen ◽  
Kuo-Hsien Chou ◽  
Yi-Yang Kuo ◽  
Cheng-Ye Wu ◽  
Po-Wen Hsiao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantum Dots ◽  
Particle Size ◽  
X Ray Diffraction ◽  
One Pot ◽  
X Ray ◽  
Transmission Electron ◽  
Average Size ◽  
Alloy Quantum Dots ◽  
First Time

To the best of our knowledge, this report presents, for the first time, the schematic of the possible chemical reaction for a one-pot synthesis of Zn0.5Cd0.5Se alloy quantum dots (QDs) in the presence of low/high oleylamine (OLA) contents. For high OLA contents, high-resolution transmission electron microscopy (HRTEM) results showed that the average size of Zn0.5Cd0.5Se increases significantly from 4 to 9 nm with an increasing OLA content from 4 to 10 mL. First, [Zn(OAc)2]–OLA complex can be formed by a reaction between Zn(OAc)2 and OLA. Then, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) data confirmed that ZnO is formed by thermal decomposition of the [Zn(OAc)2]–OLA complex. The results indicated that ZnO grew on the Zn0.5Cd0.5Se surface, thus increasing the particle size. For low OLA contents, HRTEM images were used to estimate the average sizes of the Zn0.5Cd0.5Se alloy QDs, which were approximately 8, 6, and 4 nm with OLA loadings of 0, 2, and 4 mL, respectively. We found that Zn(OAc)2 and OLA could form a [Zn(OAc)2]–OLA complex, which inhibited the growth of the Zn0.5Cd0.5Se alloy QDs, due to the decreasing reaction between Zn(oleic acid)2 and Se2−, which led to a decrease in particle size.

Refinement of the layered titanosilicate AM-1 from single-crystal X-ray diffraction data

2007 ◽  
Vol 63 (11) ◽  
pp. i186-i186 ◽  
Author(s):  
Stanislav Ferdov ◽  
Uwe Kolitsch ◽  
Christian Lengauer ◽  
Ekkehart Tillmanns ◽  
Zhi Lin ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Hydrogen Bonding ◽  
Single Crystal ◽  
Single Crystals ◽  
Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
First Time ◽  
Ir And Raman ◽  
Bonding Scheme

The structure of the layered noncentrosymmetric titanosilicate AM-1 (also known as JDF-L1, disodium titanium tetrasilicate dihydrate), Na4Ti2Si8O22·4H2O, grown as small single crystals without the use of organics, has been refined from single-crystal X-ray diffraction data. The H atom has been located for the first time, and the hydrogen-bonding scheme is also characterized by IR and Raman spectroscopy. All atoms are in general positions except for the Na, the Ti, one Ti-bound O, one Si-bound O and the water O atoms (site symmetries 2, 4, 4, 2 and 2, respectively).

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