Diamond Morphology Research Articles

Morphology, defects and electrical properties of boron-doped single crystal diamond under various oxygen concentration

In this work, high quality boron-oxygen co-doped homoepitaxial diamond has been proposed. The morphology of diamond was smooth and flat with the O2/H2 ratios less than 1%. The X-ray diffraction, Photoluminescence and Raman spectroscopy illustrated that the substitution of oxygen into diamond lattice could inhibit nitrogen related defects and improve the crystallinity. The Raman mapping showed that tensile stress were formed from film surface to substrate. Under the O2/H2 ratio of 1%, the mobility of 892 cm2/V·s at boron concentration of 4.7 × 1017 cm−3 were obtained, which showed decent electrical properties.

Morphology and FTIR Characteristics of the Alluvial Diamond from the Yangtze Craton, China

A total of 48 natural alluvial diamonds from the Yangtze Craton, China, also called Hunan diamonds, were studied using morphology and IR spectroscopy. These diamond samples, collected downstream of the Yuan River, Hunan Province, with unknown host-rock source(s), were observed by scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR). Most Hunan diamonds are monocrystal forms of octahedra, tetrahexahedra (THH) and dodecahedra; octahedral–rhom-dodecahedral transitional behaviors and irregular forms are also visible. Trigons and tetragons, terraces and shield-shaped laminae are surface features that frequently indicate dissolution and reabsorption; green and brown spots, network patterns, and other mechanical abrasion marks are typical evidence of long-time deposition and transportation of Hunan diamonds. The main types of Hunan diamonds are type IaAB and type Ⅱa. Diamond samples have a wide range of total nitrogen content (Ntot) from 196–1094 ppm. Two populations are distinguished by two-peak distribution models of NA (A-center concentrations) and %B (proportion of aggregated nitrogen). Hunan diamonds are low in structure hydrogen (0.03–4.67 cm−1, mostly below 1 cm−1) and platelets (0.23–17 cm−1, mostly below 2 cm−1). Moreover, there is a significant positive correlation between the hydrogen correlation peak and Ntot, which is similar to Argyle diamonds. The temperature conditions of the diamond formation have been estimated at 1075–1180 °C, mainly conforming to the kimberlite diamond range. Besides, some samples with slightly higher temperatures are close to the ultramafic-related Juina diamonds. Therefore, the FTIR characteristics analysis and comparison indicate the multiple sources of Hunan diamonds.

Diamond morphology CuO nanomaterial’s elastic properties, ADMET, optical, structural studies, electrical conductivity and antibacterial activities analysis

Copper oxide nanoparticles (CuO NPs) with well-defined diamond-shaped morphology were prepared efficaciously through co-precipitating method. The elastic constants such as Young’s modulus (E), Bulk modulus (K), Shear modulus (G), Poisson’s ratio and linear compressibility were calculated using the Voigt theory. Furthermore, to quantify sub-atomic descriptors just as to overview nuclear components, Absorption, Distribution, Metabolism, Excretion and Toxicity (ADMET) boundaries, Bioactivity radar and scores are determined utilizing Swiss ADME and ADMET pointers. An assessment on electrical conductivity of CuO nano fluids comprising various concentrations, particle size and nano fluid temperature was made. The nano fluids containing 100 nm CuO has higher electrical conductivity whereas in 150 nm of CuO size, it declines. Nano sized CuO NPs have wide transmission ranges with a UV cutoff wave-length of 235 nm from optical studies. As a function of the wavelength, optical conductivity (σ), Energy gap (Eg), absorption coefficient (α), extinction coefficient (k), refractive index (n) and reflectance (R) were determined. The novel diamond shaped CuO nano particles exhibited virtuous antibacterial action against foodborne pathogens, Escherichia Coli (E. coli) and Listeria monocytogenes (L. monocytogenic) compounds. Thus, the CuO NPs has potential to be employed in medical field, food packaging applications and in wastewater treatment to control the spread of above-mentioned pathogenic microbes.

Diamond formation during sulfidation of metal–carbon melts

Experimental studies modeling the mechanism of diamond crystallization during sulfidation of metal–carbon melts were performed on a multi-anvil high-pressure apparatus BARS at pressure of 6.3 GPa, temperature range of 1270–1470 °C, and run duration of 20 to 35 h. Sandwich experiments with layer filling were carried out using schemes FeS2-[Fe(Fe90Ni10) + C]-FeS2, FeS2-Ol-[Fe90Ni10 + C]-Ol-FeS2 and S-Ol-[Fe90Ni10 + C]-Ol-S. The experiments have revealed that crystallization of diamond and/or graphite occurs during sulfidation of a metal–carbon melt either due to mixing of metal–carbon and sulfide melts or due to influx of sulfur from external sources through a polycrystalline olivine layers. Transport of a sulfur fluid or a metal–sulfide–carbon melt through a silicate matrix occurs through the intergranular space and microcracks as well as by recrystallization of olivine. Sulfidation is accompanied by a decrease in the solubility of carbon and leads to supersaturation that is necessary for crystallization of diamond or graphite. The inhibitory effect of the sulfide component is the cause for changes in the diamond morphology and transition of carbon phase crystallization from diamond to metastable graphite. The synthesized diamond crystals are classified as low-nitrogen or nitrogen-free diamonds. The revealed regularities may be used to explain the genesis of diamonds with central inclusions and nitrogen-free CLIPPIR diamonds.

Surface Morphology and Microstructure Evolution of Single Crystal Diamond during Different Homoepitaxial Growth Stages.

Homoepitaxial growth of step-flow single crystal diamond was performed by microwave plasma chemical vapor deposition system on high-pressure high-temperature diamond substrate. A coarse surface morphology with isolated particles was firstly deposited on diamond substrate as an interlayer under hillock growth model. Then, the growth model was changed to step-flow growth model for growing step-flow single crystal diamond layer on this hillock interlayer. Furthermore, the surface morphology evolution, cross-section and surface microstructure, and crystal quality of grown diamond were evaluated by scanning electron microscopy, high-resolution transmission electron microcopy, and Raman and photoluminescence spectroscopy. It was found that the surface morphology varied with deposition time under step-flow growth parameters. The cross-section topography exhibited obvious inhomogeneity in crystal structure. Additionally, the diamond growth mechanism from the microscopic point of view was revealed to illustrate the morphological and structural evolution.

Metamorphic microdiamond formation is controlled by water activity, phase transitions and temperature

Metamorphic diamonds hosted by major and accessory phases in ultrahigh-pressure (UHP) metamorphic terranes represent important indicators of deep subduction and exhumation of continental crust at convergent plate boundaries. However, their nucleation and growth mechanisms are not well understood due to their small size and diversity. The Bohemian microdiamond samples represent a unique occurrence of monocrystalline octahedral and polycrystalline cubo-octahedral microdiamonds in two different metasedimentary rock types. By combining new and published data on microdiamonds (morphology, resorption, associated phases, carbon isotope composition) with P–T constraints from their host rocks, we demonstrate that the peak P–T conditions for the diamond-bearing UHP rocks cluster along water activity-related phase transitions that determine the microdiamond features. With increasing temperature, the diamond-forming medium changes from aqueous fluid to hydrous melt, and diamond morphology evolves from cubo-octahedral to octahedral. The latter is restricted to the UHP-UHT rocks exceeding 1100 °C, which is above the incongruent melting of phengite, where microdiamonds nucleate along a prograde P–T path in silicate-carbonate hydrous melt. The observed effect of temperature on diamond morphology supports experimental data on diamond growth and can be used for examining growth conditions of cratonic diamonds from kimberlites, which are dominated by octahedra and their resorbed forms.

Reaction thickness between diamond and silicon under 5 GPa

The thickness of the silicon carbide layer around diamond grains in the reaction sintering process of diamond/SiC composites starting from diamond and silicon was investigated at 1100–1400 °C and 5 GPa using two different sample assemblies. Dense silicon carbide layers with thicknesses from 60 nm to 350 nm were observed using energy dispersive spectrometry (EDS) and X-ray diffraction (XRD) analysis. This demonstrated that the thickness of the silicon carbide layer increased with increasing sintering temperature and time. The surface morphology of diamond grains/single-crystal diamond wafers eroded by liquid silicon was analysed by field emission scanning electron microscopy (FESEM), and it was found that SiC growth was controlled by the diffusion of silicon and carbon atoms through the existing layer of SiC.

Wear characteristics of diamond segments on multi-blade combination saw with different diameters in granite sawing

In this paper, the wear characteristics of diamond segments adopted to multi-blade combination circular saw with different diameters were compared and investigated in the process of granite through an experiment. Load model with a diameter as the variable of combination saw was established based on the maximum undeformed chip thickness of a single particle. Combined with the load model, scanning electron microscope, laser microscope and vernier calipers were used to comprehensively analyze the wear characteristics of segment form the aspects of the wear morphology of diamond and metal matrix, the particle protrusion height, and the abrasion loss of segment. The results indicated that load nonuniformity of diamond generated by diameters change of saw blade was the main reason for segment wear discrepancy of large and small diameter saw blade when rocks were sawed by combination saw, and abrasion loss of segment adopted to small diameter saw blade was significantly higher than that of large-diameter saw blade. Diameter variation of saw blade in combination saw caused the different wear mechanism of diamond in segment, pulled-out and macro-fractured crystals were dominant in small-diameter saw blade, then the proportion of whole particles increased in segment used to the saw blade of large diameter. Particle protrusion height was related to the diameter in the combination saw. The high protrusion height of particles existed in the large-diameter saw blade.

FEATURES OF GARNET AND CLINOPYROXENE IN DIAMONDIFEROUS ECLOGITES FROM THE UDACHNAYA KIMBERLITE PIPE, YAKUTIA: METASOMATOSIS EVIDENCE

Mineralogy of diamondiferous eclogite xenolites showing metasomatosis evidence from the Udachnaya kimberlite pipe is discussed. The paper also reviews features of diamonds they contain, compositions of primary garnets and omphacites as well as alteration of structural and species compositions of original garnets and clinopyroxenes during metasomatosis. Based on pyrope structure update, two-phase garnet composition is suggested, which is mostly represented by complex pyrope associated with Ca-pyrope. In all samples, primary omphacite is replaced by another clinopyroxene variety depleted in Na2O, which is typical of partial melting products. Geothermometry results suggested that the eclogites formed within a temperature range of 1,000–1,2000 °C. Based on diamond morphology, data on total N content in diamonds and its aggregation, multiple stages of diamond formation in eclogites and the most probable growth of later diamond generations impacted by metasomatizing mantle fluids containing carbon are postulated. It is suggested that certain diamond formation stages probably had a time gap of several hundred million years.

Fabrication of low stress GaN-on-diamond structure via dual-sided diamond film deposition

The fabrication of GaN-on-diamond structure by the process of diamond growth on GaN technology is becoming more and more attractive for high-power GaN devices. However, due to the high-temperature steps employed during the GaN epitaxial layer transfer process, significant stress accumulates in the GaN-on-diamond structure and induces the formation of cracks or deformations in the GaN layer. To improve the stress characteristics of the GaN layer, in this work, dual-sided diamond film deposition was carried out to accomplish the GaN-on-diamond structure. The surface morphology, interface microstructure and crystal quality of diamond on GaN were analyzed by using scanning electron microscopy, atomic force microscopy, transmission electron microscopy and X-ray diffraction. The results showed that the stress accumulation originating from the GaN epitaxial layer transfer process was effectively alleviated as compared with other reporteds in the literature and that the crystal quality of the GaN was only slightly altered. The stress relaxation was attributed to the low-quality diamond used as the temporary carrier during the GaN transfer process. In addition, a thin SiC transition layer in the interface is also beneficial in alleviating the mismatch between the coefficients of thermal expansion for the GaN and the diamond.

Effect of Ni2O3 on diamond crystal growth in an Fe–Ni–C system under high temperature and high pressure

In this paper, the oxygen-containing diamond large single crystals were successfully synthesized by adding Ni2O3 to the Fe–Ni–C system under HPHT. The oxygen affects the P–T conditions for diamond synthesis, and morphology of diamond.

Crystallomorphological and Crystallochemical Indicators of Diamond Formation Conditions

An analytical review of the results of experimental studies of diamond crystallization and dissolution in systems with different compositions and mantle P–T parameters is presented. It is shown that the diamond morphology and the set of defect-impurity centers depend to a great extent on the composition of crystallization medium. Specific crystallomorphological and crystallochemical features of diamond that are typical of certain conditions are revealed. The genetic informativeness of some diamond characteristics and possibility of their use as indicators of the composition of crystallization and dissolution media and oxygen fugacity in diamond-origin processes are substantiated based on the experimentally established regularities in the “conditions–properties” system.

Optimum conditions for electrochemical deposition of 3-D mesoporous platinum framework

Here, we report a systematic investigation of the effect of experimental parameters on the structure, morphology and electrochemically active surface area of 3-D mesoporous platinum (Pt) framework. Template-assisted deposition of the mesoporous Pt framework is achieved using phytantriol-based inverse bicontinuous cubic phase of double diamond morphology (QIID) with Pn3m symmetry. Platinum is deposited electrochemically using hexachloroplatinic acid solution present within the aqueous domains of the cubic phase template. Deposition conditions, particularly the deposition potentials, are shown to significantly affect the surface morphology, porosity and electrochemically active surface area of the deposited Pt framework. Furthermore, the effect of underlying substrate on the structure and morphology of the mesoporous Pt framework is also investigated.

Regulation mechanism of catalyst structure on diamond crystal morphology under HPHT process**Project supported by the National Natural Science Foundation of China (Grant No. 11804305), the Natural Science Foundation of Chongqing, China (Grant No. cstc2019jcyj-msxmX0391), the Science and Technology Research Program of Chongqing Municipal Education Commission, China (Grant No. KJ201901405), and the Open Project of State Key Laboratory of Superhard Materials,

To elucidate the regulation mechanism of catalyst geometry structure to diamond growth, we establish three catalyst modes with different structures. The simulation results show that with the decrease of the protruding height of the catalyst, the low-temperature region gradually moves toward the center of the catalyst, which causes the distribution characteristics of the temperature and convection field in the catalyst to change. The temperature difference in vertical direction of the catalyst decreases gradually and increases in the horizontal direction, while the catalyst convection velocity has the same variation regularity in the corresponding directions. The variation of temperature difference and convection velocity lead the crystal growth rate in different crystal orientations to change, which directly affects the crystal morphology of the synthetic diamond. The simulation results are consistent with the experimental results, which shows the correctness of the theoretical rational analysis. This work is expected to be able to facilitate the understanding of catalyst structure regulation mechanism on diamond morphology and the providing of an important theoretical basis for the controllable growth of special crystal shape diamond under HPHT process.

Surface termination, crystal size, and bonding-site density effects on diamond biosensing surfaces

Diamond's properties, such as chemical stability and low biofouling rates, make it an ideal material for developing more adequate biosensing technology for single-use bioreactors. We propose a simplistic approach to covalently functionalizing diamond and evaluating the effects of different variables on the sensitivity of the bioactive surface. We hypothesize that by maximizing sensitivity, we can maximize the signal-to-noise ratio of the biosignal. Three different methods of achieving an oxygenated surface on diamond with varying crystal sizes is investigated to see which results in the most active biointerface. Surface termination species were confirmed post‑oxygenation with X-ray Photoelectron Spectroscopy. The diamond was then functionalized with a biotinylated monolayer, which was treated with gold-conjugated streptavidin to quantify the available bonding sites. After complete biofunctionalization, detection sensitivity of IL-8 and antibody density were assessed with ELISA and electrochemical impedance spectroscopy for quantification of sites with functional antibodies. The contradicting correlations between diamond morphology and percentage of CO bonds lead us to conclude that the effectiveness of oxygen-termination method is independent of diamond morphology. Through quantifying bonding sites, it was found that both the number of available sites and active sites increased with increasing crystal size. This result is suspected to be directly correlated to the hybridization of the diamond-carbon material in that functional species prefer sp3 carbon over sp2. Therefore, a diamond film with the largest possible crystals is predicted to have a higher detection sensitivity in biosensing applications.

Carrier mobility enhancement on the H-terminated diamond surface

The surface conductivity on the H-terminated diamond is still an interesting topic in the field of diamond electronics. Until now, the carrier mobility in the conductive channel has been limited to below 200cm2/Vs due to the various surface scattering mechanisms. In this paper, a high mobility conductive channel on the H-terminated diamond surface was reported. Firstly, the high quality diamond films were deposited on the commercial CVD diamond substrates. After polishing, the H-termination was obtained by hydrogen plasma treatment. The surface morphology of the H-terminated diamond was observed by atomic force microscope (AFM) and scanning electron microscope (SEM). The crystal quality on the diamond surface was characterized by Raman spectroscopy. The impurities in the crystals were tested by photoluminescence spectroscopy. The surface conductivity of H-terminated diamond was monitored comprehensively by Hall test. It can be found that the sheet resistance decreases much and the carrier mobility increases dramatically after the hydrogen plasma treatment and mechanical cleaning. The maximum mobility value is up to 365cm2/Vs with carrier density of 2.9 × 1012 cm−2, which is the highest value reported. Raman spectra of diamond surface show that a peak appears at 1121.4 cm−2 after the hydrogen plasma treatment, which corresponds to the nanocrystal diamond or carbon clusters of sp3 bonded material. The corresponding mobility enhancement mechanism on the H-terminated diamond surface was proposed.

How do diamonds grow in metal melt together with silicate minerals? An experimental study of diamond morphology

Abstract. The origin and evolution of metal melts in the Earth's mantle and their role in the formation of diamond are the subject of active discussion. It is widely accepted that portions of metal melts in the form of pockets can be a suitable medium for diamond growth. This raises questions about the role of silicate minerals that form the walls of these pockets and are present in the volume of the metal melt during the growth of diamonds. The aim of the present work was to study the crystallization of diamond in a complex heterogeneous system: metal-melt–basalt–carbon. The experiments were performed using a multianvil high-pressure apparatus of split-sphere type (BARS) at a pressure of 5.5 GPa and a temperature of 1500 ∘C. The results demonstrated crystallization of diamond in metal melt together with garnet and clinopyroxene, whose chemical compositions are similar to those of eclogitic inclusions in natural diamond. We show that the presence of silicates in the crystallization medium does not reduce the chemical ability of metal melts to catalyze the conversion of graphite into diamond, and, morphologically, diamond crystallizes mainly in the form of a cuboctahedron. When the content of the silicate material in the system exceeds 5 wt %, diamond forms parallel-growth aggregates, but 15 wt % of silicate phases block the crystallization chamber, preventing the penetration of metallic melt into them, thus interrupting the growth of diamond. We infer that the studied mechanism of diamond crystallization can occur at lower-mantle conditions but could also have taken place in the ancient continental mantle of the Earth, under reducing conditions that allowed the stability of Fe–Ni melts.

Effect of sulfur on diamond growth and morphology in metal–carbon systems

Sulfur additives inhibit diamond crystallization in the Fe–Ni–C system at 6 GPa and 1400 °C and affect the diamond crystal morphology and nitrogen impurity content.

Challenges in Processing Diamond Wire Cut and Black Silicon Wafers in Large-Scale Manufacturing of High Efficiency Solar Cells

Texturing of diamond wire cut wafers using a standard wafer etch process chemistry has always been a challenge in solar cell manufacturing industry. This is due to the change in surface morphology of diamond wire cut wafers and the abundant presence of amorphous silicon content, which are introduced from wafer manufacturing industry during sawing of multi-crystalline wafers using ultra-thin diamond wires. The industry standard texturing process for multi-crystalline wafers cannot deliver a homogeneous etched silicon surface, thereby requiring an additive compound, which acts like a surfactant in the acidic etch bath to enhance the texturing quality on diamond wire cut wafers. Black silicon wafers on the other hand require completely a different process chemistry and are normally textured using a metal catalyst assisted etching technique or by plasma reactive ion etching technique. In this paper, various challenges associated with cell processing steps using diamond wire cut and black silicon wafers along with cell electrical results using each of these wafer types are discussed.

Bismuth modified boron doped diamond electrode for simultaneous determination of Zn, Cd and Pb ions by square wave anodic stripping voltammetry: Influence of boron concentration and surface morphology

The optimization of electrode properties is an inseparable part of the analytical process which can highly improve the quality of obtained results in electrochemical sensing methods. This paper investigates the role of doping level, morphology and structure of boron-doped diamond (BDD) electrodes in electrochemical sensing of heavy metals in the presence of bismuth. To study the influence of doping level and morphology, a large set of BDD films with varying boron-to-carbon and carbon-to-hydrogen ratios in the deposition gas mixture was grown using hot filament chemical vapor deposition method. The set was used for fabrication of electrodes (the active area 0.43 mm2 was opened in 400 nm SiO2 by standard optical lithography) for simultaneous electrochemical determination of zinc, cadmium and lead. Square wave anodic stripping voltammetry was utilized for this purpose. The influence of BDD properties on limit of detection (LOD) and sensitivity (S) of the electrodes was also investigated. The highest sensitivity was observed for electrodes prepared with 10 000 ppm boron-to-carbon ratio and lower methane concentrations. The findings prove the importance of selecting an appropriate electrode prior to progressing to electrochemical measurements.