scholarly journals The Transformation from (111) to (100): A Routine to Large-Scale Epitaxial Diamond

2020 ◽  
Author(s):  
Yang Wang ◽  
Weihua Wang ◽  
Shilin Yang ◽  
Jiaqi Zhu
Keyword(s):  
Large Scale ◽  
Diamond Films ◽  
Diamond Growth ◽  
Nucleation Density ◽  
Diamond Synthesis ◽  
First Principle ◽  
High Quality ◽  
First Principle Calculations ◽  
Large Size ◽  
Experimental Researches

Diamond is a material with excellent performances which attracts the attention from researchers for decades. Pt (111), owing to its catalytic activity on diamond synthesis, is regarded to be a candidate for diamond hetero-epitaxity, which can enhance nucleation density. Molten surface at diamond growth temperature can also improve mobility and aggregation capability of primitive nuclei. Generally, (100)-oriented is welcomed for the achivement of high quality and large size diamond, since the formation of defects and twins are prevented. First-principle calculations and experimental researches were carried out for the study of transformation of orientation. The transformation from {111} to {100}-oriented diamond has been observed on Pt (111) substrate, which can be promoted by the increase of carbon source concentration and substrate temperature. The process is energetic favorable, which may provides a way towards large-scale (100) diamond films.

A sequential Raman analysis of the growth of diamond films on silicon substrates in a microwave plasma assisted chemical vapor deposition reactor

1997 ◽  
Vol 12 (10) ◽  
pp. 2686-2698 ◽  
Author(s):  
L. Fayette ◽  
B. Marcus ◽  
M. Mermoux ◽  
N. Rosman ◽  
L. Abello ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Sequential Analysis ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Diamond Growth ◽  
Internal Stresses ◽  
Nucleation Density ◽  
Silicon Substrates

A sequential analysis of the growth of diamond films on silicon substrates in a microwave plasma assisted chemical vapor deposition (CVD) reactor has been performed by Raman spectroscopy. The plasma was switched off during measurements, but the substrate heating was maintained to minimize thermoelastic stresses. The detectivity of the present experimental setup has been estimated to be about a few tens of μmg/cm2. From such a technique, one expects to analyze different aspects of diamond growth on a non-diamond substrate. The evolution of the signals arising from the substrate shows that the scratching treatment used to increase the nucleation density induces an amorphization of the silicon surface. This surface is annealed during the first step of deposition. The evolution of the line shape of the spectra indicates that the non-diamond phases are mainly located in the grain boundaries. The variation of the integrated intensity of the Raman signals has been interpreted using a simple absorption model. A special emphasis was given to the evolution of internal stresses during deposition. It was verified that compressive stresses were generated when coalescence of crystals took place.

Implementation of CVD Diamond Growth Methods for Selective and Efficient Formation of Color-Centers in Diamond

2015 ◽  
Vol 1728 ◽  
Author(s):  
Stefano Gay ◽  
Giacomo Reina ◽  
Ilaria Cianchetta ◽  
Emanuela Tamburri ◽  
Mariglen Angjellari ◽  
...  
Keyword(s):  
Diamond Films ◽  
Cvd Diamond ◽  
Structural Features ◽  
Diamond Growth ◽  
Color Centers ◽  
Diamond Synthesis ◽  
Substrate Preparation ◽  
Photoluminescence Emission ◽  
Diamond Phase ◽  
Growth Methods

ABSTRACTWe report here on the chemical methodologies that are being settled in our labs for the insertion in diamond of foreign atoms and consequent creation of fluorescent defects. The inclusion of Si, Cr, Ge, able to produce color centers, is directly obtained during the process of diamond synthesis by means of a CVD technique. The deposition of the diamond films takes place on substrates of different nature, treated following procedures specifically settled to control the insertion of the different species. The photoluminescence emission from a series of diamond samples grown on different substrates (Si, Ge and Ti) has been investigated and is discussed with reference to the morphological/structural features of the diamond phase and to the experimental procedures adopted for substrate preparation.

scholarly journals ActDES – a curated Actinobacterial Database for Evolutionary Studies

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Jana K. Schniete ◽  
Nelly Selem-Mojica ◽  
Anna S. Birke ◽  
Pablo Cruz-Morales ◽  
Iain S. Hunter ◽  
...  
Keyword(s):  
Large Scale ◽  
Gene Family Evolution ◽  
Comparative Genomic ◽  
High Quality ◽  
Genomic Databases ◽  
Content Type ◽  
Bioactive Natural Products ◽  
Large Size ◽  
Large Numbers ◽  
Evolutionary Studies

Actinobacteria is a large and diverse phylum of bacteria that contains medically and ecologically relevant organisms. Many members are valuable sources of bioactive natural products and chemical precursors that are exploited in the clinic and made using the enzyme pathways encoded in their complex genomes. Whilst the number of sequenced genomes has increased rapidly in the last 20 years, the large size, complexity and high G+C content of many actinobacterial genomes means that the sequences remain incomplete and consist of large numbers of contigs with poor annotation, which hinders large-scale comparative genomic and evolutionary studies. To enable greater understanding and exploitation of actinobacterial genomes, specialized genomic databases must be linked to high-quality genome sequences. Here, we provide a curated database of 612 high-quality actinobacterial genomes from 80 genera, chosen to represent a broad phylogenetic group with equivalent genome re-annotation. Utilizing this database will provide researchers with a framework for evolutionary and metabolic studies, to enable a foundation for genome and metabolic engineering, to facilitate discovery of novel bioactive therapeutics and studies on gene family evolution. This article contains data hosted by Microreact.

A new design of tungsten carbide tools with diamond coatings

1996 ◽  
Vol 11 (9) ◽  
pp. 2220-2230 ◽  
Author(s):  
Volker Weihnacht ◽  
W.D. Fan ◽  
K. Jagannadham ◽  
J. Narayan ◽  
C-T. Liu
Keyword(s):  
Wear Resistance ◽  
Tungsten Carbide ◽  
Nickel Aluminide ◽  
Diamond Films ◽  
Diamond Growth ◽  
Nucleation Density ◽  
High Temperature Strength ◽  
Binder Phase ◽  
Chemical Vapor Deposition Diamond ◽  
Diamond Coatings

We have designed tungsten carbide tools with a new binder, which makes them suitable for advanced diamond tool coatings. The new tool substrates, made of tungsten carbide and nickel aluminide as binder phase, are produced by sintering and hot isostatic pressing, and also by combustion synthesis. The high temperature strength of nickel aluminide is key to superior tool performance at elevated temperatures. More importantly, nickel aluminides reduce the formation of graphite and promote diamond growth during chemical vapor deposition. Diamond films are deposited on the new tool substrates to investigate the nucleation density, adhesion, and wear resistance. The diamond coatings are characterized by scanning electron microscopy and Raman spectroscopy. The graphitizing tendency due to cobalt in the tungsten carbide tools was found to be a limitation to improve adhesion of diamond films. The new tool substrates with nickel aluminide binder have been found to exhibit good adhesion and wear resistance. The implications of these results in advanced cutting tools are discussed.

Selective Growth of Polycrystalline Diamond Thin Films

1992 ◽  
Vol 282 ◽  
Author(s):  
R. Ramesham
Keyword(s):  
Plasma Etching ◽  
Microwave Plasma ◽  
Diamond Films ◽  
Polycrystalline Diamond ◽  
Selective Growth ◽  
Diamond Growth ◽  
Nucleation Density ◽  
Substrate Type ◽  
Temperature Growth ◽  
Single Crystal Diamond

ABSTRACTMicrowave plasma assisted CVD is employed to grow diamond films using a gas mixture of H2 and CH4on various substrates. Diamond has a tendency not to nucleate growth on mirror-smooth finished substrates irrespective of the substrate type (except single crystal diamond). We have developed various processes to enhance the nucleation density of the diamond substantially by damaging or seeding the surface of the substrates. Several process techniques such as 1. silicon nitride and silicon dioxide process, 2. ultrasonic agitation process, 3. selective seeding of diamond by electroplating of Cu, 4. patterning of diamond films by air-microwave plasma etching, etc., were developed to achieve the patterns of diamond on various substrates. Selective growth of doped diamond and low temperature growth of diamond for microelectronic applications have also been achieved by using the above processes (1 and 2). Details on selective diamond growth processes and the morphology of as-deposited selective diamond by SEM are presented.

scholarly journals Flux Method Growth of Large Size Group IV–V 2D GeP Single Crystals and Photoresponse Application

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 235
Author(s):  
Shuqi Zhao ◽  
Tongtong Yu ◽  
Ziming Wang ◽  
Shilei Wang ◽  
Limei Wei ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Single Crystals ◽  
High Performance ◽  
Group Iv ◽  
X Ray Diffraction ◽  
High Quality ◽  
Practical Applications ◽  
Large Size ◽  
Growth Method ◽  
Polarized Raman

Two-dimensional (2D) materials driven by their unique electronic and optoelectronic properties have opened up possibilities for their various applications. The large and high-quality single crystals are essential to fabricate high-performance 2D devices for practical applications. Herein, IV-V 2D GeP single crystals with high-quality and large size of 20 × 15 × 5 mm3 were successfully grown by the Bi flux growth method. The crystalline quality of GeP was confirmed by high-resolution X-ray diffraction (HRXRD), Laue diffraction, electron probe microanalysis (EPMA) and Raman spectroscopy. Additionally, intrinsic anisotropic optical properties were investigated by angle-resolved polarized Raman spectroscopy (ARPRS) and transmission spectra in detail. Furthermore, we fabricated high-performance photodetectors based on GeP, presenting a relatively large photocurrent over 3 mA. More generally, our results will significantly contribute the GeP crystal to the wide optoelectronic applications.

scholarly journals A First-Principle Study of Monolayer Transition Metal Carbon Trichalcogenides

2021 ◽  
Author(s):  
Muhammad Yar Khan ◽  
Yan Liu ◽  
Tao Wang ◽  
Hu Long ◽  
Miaogen Chen ◽  
...  
Keyword(s):  
Phonon Dispersion ◽  
Magnetic Ordering ◽  
Dimensional Structure ◽  
First Principle ◽  
Two Dimensional ◽  
Biaxial Strain ◽  
Half Metallic ◽  
First Principle Calculations ◽  
Potential Applications ◽  
External Strain

AbstractMonolayer MnCX3 metal–carbon trichalcogenides have been investigated by using the first-principle calculations. The compounds show half-metallic ferromagnetic characters. Our results reveal that their electronic and magnetic properties can be altered by applying uniaxial or biaxial strain. By tuning the strength of the external strain, the electronic bandgap and magnetic ordering of the compounds change and result in a phase transition from the half-metallic to the semiconducting phase. Furthermore, the vibrational and thermodynamic stability of the two-dimensional structure has been verified by calculating the phonon dispersion and molecular dynamics. Our study paves guidance for the potential applications of these two mono-layers in the future for spintronics and straintronics devices.

Tiered Sampling

2021 ◽  
Vol 15 (5) ◽  
pp. 1-52
Author(s):  
Lorenzo De Stefani ◽  
Erisa Terolli ◽  
Eli Upfal
Keyword(s):  
Large Scale ◽  
Analysis Of Algorithms ◽  
Base Layer ◽  
Single Edge ◽  
Real World Data ◽  
High Quality ◽  
Large Graphs ◽  
Massive Graphs ◽  
Variance Estimate ◽  
Low Probability

We introduce Tiered Sampling , a novel technique for estimating the count of sparse motifs in massive graphs whose edges are observed in a stream. Our technique requires only a single pass on the data and uses a memory of fixed size M , which can be magnitudes smaller than the number of edges. Our methods address the challenging task of counting sparse motifs—sub-graph patterns—that have a low probability of appearing in a sample of M edges in the graph, which is the maximum amount of data available to the algorithms in each step. To obtain an unbiased and low variance estimate of the count, we partition the available memory into tiers (layers) of reservoir samples. While the base layer is a standard reservoir sample of edges, other layers are reservoir samples of sub-structures of the desired motif. By storing more frequent sub-structures of the motif, we increase the probability of detecting an occurrence of the sparse motif we are counting, thus decreasing the variance and error of the estimate. While we focus on the designing and analysis of algorithms for counting 4-cliques, we present a method which allows generalizing Tiered Sampling to obtain high-quality estimates for the number of occurrence of any sub-graph of interest, while reducing the analysis effort due to specific properties of the pattern of interest. We present a complete analytical analysis and extensive experimental evaluation of our proposed method using both synthetic and real-world data. Our results demonstrate the advantage of our method in obtaining high-quality approximations for the number of 4 and 5-cliques for large graphs using a very limited amount of memory, significantly outperforming the single edge sample approach for counting sparse motifs in large scale graphs.

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