Type IIa Diamond Research Articles

Molecular Recognition of Aflatoxin M1 in Water and Milk Samples

AbstractTwo stochastic microsensors based on diamond paste modified with 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) were proposed for the molecular recognition of aflatoxin M1 in water and milk samples. Two types of diamond were used: a monocrystalline diamond powder (1 μm) (DP) and a nanopowder of monocrystalline diamond (10 nm) (nDP) for the design of the stochastic microsensors. The microsensors were incorporated as combined stochastic microsensors (a microcell containing the stochastic microsensor and the Pt wire, and a Ag/AgCl sensor) in a platform used for monitoring of waste waters and milk samples. The platforms were used for the fast screening of water and milk samples for the qualitative and quantitative analysis of aflatoxin M1 at very low concentration levels (up to 0.001 fg/L). The linear concentration ranges were wide, being able to cover concentrations between 0.001 fg/L to 20 μg/L. The highest sensitive microsensor (sensitivity of 4.74×1010 s mg−1 L) was the one based on nDP. The results provided by the platforms were in agreement with those obtained by utilization of standard method (ISO certified methods (HPLC/fluorescence method)), recoveries being higher than 99.00 % and RSD lower than 1.00 % proving that the method can be reliable used for molecular recognition of aflatoxin M1 in water and milk samples.

N+ ion beam irradiation as a strategy to enhance the electrical conductivity of polycrystalline diamond thin films

100 keV 14N+ ion beam (at fluences of 1016 and 1017 ions/cm2) irradiation was used to alter the sp2 bonded carbon networks (as revealed by Raman scattering analysis) and incorporate N atoms into the surface and sub-surface regions (as revealed by Rutherford backscattering analysis) in the typical polycrystalline diamond films and as a consequence, the electrical conductivity of the diamond thin films was enhanced several orders in comparison to the as-deposited film. The enhancement in electrical conductivity was achieved with negligible morphological and structural changes in the diamond thin film. This work demonstrates an easy and effective way of altering the electrical conductivity of diamond thin films to a required sub-surface depth.

Плазмохимическое осаждение алмазоподобных пленок на поверхности монокристаллического высоколегированного алмаза

AbstractThe plasma-chemical deposition of diamond-like carbon (DLC) films onto heavily boron-doped single-crystal p -type diamond (the concentration ~10^20 cm^–3) in CH_4 + Ar plasma is conducted. The deposition rate is 7 nm min^–1. The elemental composition and properties of the films are studied in detail. It is found that the films are enriched with hydrogen, possess a density of 2.4 g cm^–3, and exhibit an ultrasmooth surface (with a roughness of 0.4 ± 0.2 nm).

Tribological Behavior of Diamond Coatings against Carbon Fiber Reinforced Plastics under Dry Conditions

The frictional resistance and machining quality when cutting carbon fiber reinforced plastics (CFRP) laminates are associated with tribological behavior of tool materials. In the present study, the tribological properties of three types of monolayer microcrystalline diamond (MCD) coatings, nanocrystalline diamond (NCD) coatings and dual-layer MCD/NCD coatings sliding against CFRP are investigated under dry lubricated conditions using the rotational friction tester. The coefficients of friction (COF), wear rate and worn surfaces of the contacted surfaces are analyzed for the MCD-CFRP, NCD-CFRP and MCD/NCD-CFRP contacting pairs. The results show that compared with the monolayer MCD and NCD, the bilayer of MCD/NCD coating displays the lowest COF with the value of ~0.13, it is 42% and 55% of the values for MCD and NCD coatings. Due to the rough surfaces of MCD, the wear debris of CFRP on MCD samples exhibits the plowing effect. While for the NCD and MCD/NCD samples, the wear fragments display the planar shapes. The wear rate of CFRP against MCD is more than twice that of CFRP against NCD, due to the excellent loading capacity. While the wear rate of CFRP against MCD/NCD is about twice than that of CFRP-NCD pairs. The bilayer of MCD/NCD combines the excellent advantages of high hardness of MCD and the smooth surface of NCD. It shows the broad application potential for the bilayer coatings.

Study on growth characteristics of Ib-type diamond in an Fe–Ni–C–S system

FeS is the main sulfur-containing compound in natural diamond inclusions.

Synthesis of diamond co-doped with B and S under high pressure and high temperature and electrical properties of the synthesized diamond

As is well known, diamond is extensively used in many fields, because of its excellent properties, such as its hardness, high thermal conductivity, high electron and hole mobility, high breakdown field strength and large band gap (5.4 eV). However, its application in semiconductor area needs to be further understood, because it is irreplaceable by conventional semiconductor materials, especially in the extreme working conditions. Furthermore, the preparation of n-type diamond semiconductors is still an unsolved problem. The reason is that an effective donor element has not yet been found. Recently, both the theoretical and experimental studies show that it is difficult to obtain n-type diamond semiconductor with excellent properties by doping single element in the synthetic system. In this paper, diamond single crystals co-doped with B and S are successfully synthesized in FeNiMnCo-C system at a pressure of 6.5 GPa and temperature ranging from 1280 ℃ to 1300 ℃, by using temperature gradient method. The impurity defects in the synthesized diamond single crystals are characterized by Fourier infrared absorption spectra and the results indicate that the corresponding characteristic absorption peaks of B and S are located at 1298 cm<sup>–1</sup> and 847 cm<sup>–1</sup>, respectively. Furthermore, the absorption attributed to B-S group is not detected. The N concentration of the synthesized diamond crystals decreases to 195 ppm, resulting from the incorporation of B and S impurities into the diamond lattices. Additionally, the electrical properties of the typical diamond single crystals are measured in virtue of Hall effects at room temperature. The measurement results display that the electrical conductivity of the diamond doped with B is obviously enhanced, resulting from the involvement of the S when B addition amount is fixed in the synthesis system. Hall mobility of the corresponding diamond crystals increases from 12.5 cm<sup>–2</sup>·V<sup>–1</sup>·s<sup>–1</sup> to 760.87 cm<sup>–2</sup>·V<sup>–1</sup>·s<sup>–1</sup>. And then, the relative proportion of S and B will determine the p/n properties of the obtained diamond. In order to further study the electrical properties of diamond, first-principles calculations are adopted and the theoretical calculation results show that the impurity elements involved in the obtained diamond can affect the band structures of the synthetic diamond crystals, which is consistent with the experimental result.

Orientation Dependence of Hardness and Reduced Modulus of Single Crystal Sapphire Surface Measured by Nanoindentation

Nowadays, industrial products are downsized, and the structure of materials is controlled with the nanometer precision, and it becomes very important to measure the mechanical properties of local area of bulk material. Especially the hardness and the elastic modulus are important mechanical properties. The orientation dependence of hardness and reduced modulus of single crystal sapphire surface was investigated by nanoindentation. The conventional technique to measure the hardness of materials using an optical micrometer cannot evaluate mechanical properties of a local region of several µm or less. However, nanoindentation can measure mechanical properties of very small surface area of materials, and is expected to detect the micro structure dependence of mechanical properties. Nanoindentation uses very small indenter made of diamond, and measures the indentation depth. The measured depth is converted to the indented area size using the area function. The area function of the indenter can be obtained using a standard material (fused quartz) in advance. Therefore nanoindentation can measure the indented area size without using an optical micrometer. In this report, it was shown that the nanoindentation could detect the structure dependence of mechanical properties of materials. The specimen was a single crystal sapphire with c - axis surface, and the indenter was Berkovich type diamond tip. It was confirmed that the nanoindentation hardness was the lowest, and the reduced modulus was the largest, when the ridge line of indenter was oriented to the m - axis of single crystal. The nanoindentation could detect the structure dependence of a local area of mechanical properties materials.

Deformation and drag force of model square fish cages in a uniform flow

Model experiments were carried out to investigate the performance of different types of 1:8.3-scale model square fish cages in a uniform flow. The model cages were designed using different netting materials, mesh types, and cage depths. Shape deformation, volume reduction, and drag force were used as key parameters to characterize the cage performance. The results indicate that cages using polyethylene netting for the four sides and wire-netting for the bottom generally show better performance than those composed entirely of polyethylene netting; specifically, the former undergoes less shape deformation and volume reduction than the latter. The mesh type (square or diamond mesh) had a noticeable effect on shape deformation and drag force but a limited effect on cage volume reduction. Moreover, for the cages with wire-netting bottom and polyethylene sides, the bottom net tended to drift parallel to its undisturbed orientation when the sides were composed of square mesh netting. In contrast, the bottom net drifted obliquely upward on the downstream side when diamond mesh netting was used for the side nets. It was also confirmed that drag force per unit volume of the cages with wire-netting bottom was larger than that for the cages composed entirely of polyethylene netting.

Polycrystalline diamond films with tailored micro/nanostructure/doping for new large area film-based diamond electronics

This paper describes processes developed to change two key electrical properties (electrical resistivity and carrier type) of ultrananocrystalline diamond (UNCD) to microcrystalline diamond (MCD) films. The results show that the electrical properties of the investigated polycrystalline diamond films depend on the grain size and plasma treated grain boundary networks interfaces and external films' surfaces, in which hydrogen, fluorine or nitrogen can be incorporated to tailor electrical carriers-type to tune the electrical properties. Exploring the feasibility of modulating the resistivity of polycrystalline diamond films via tailoring of grain size, surface chemistry and nitrogen or fluorine incorporation into films' grain boundaries and external surfaces may enable applications of these diamond films as active or heat dissipation layers on micro/nano-electronic devices. This work can open the pathway to enabling an industrial process for new diamond-based electronics, since polycrystalline diamond films can be grown with extreme uniformity on 300 mm diameter Si wafers, used in manufacturing of current Si-based micro/nano-electronic devices.

Substrate Effects on Charge Carrier Transport Properties of Single‐Crystal CVD Diamonds and an 8 mm Square Radiation Energy Spectrometer

In an effort to enlarge a sensitive area of a diamond radiation energy spectrometer, a self‐standing chemical vapor deposition (CVD) single crystal is grown on an 8‐mm‐square “general grade” CVD single‐crystal diamond substrate fabricated by Element Six Ltd. The growth conditions that achieved a μτ product of 3 × 10−4 cm2 V−1 for holes in a CVD single‐crystal diamond grown on a high‐pressure and high‐temperature (HP/HT) type IIa single‐crystal diamond substrate elsewhere are adopted. The charge collection efficiency (CCE) of 99.9% for both charge carriers, and 0.39% and 0.5% of energy resolution for holes and electrons are achieved using 5.486 MeV alpha particles. Uniformity of the energy resolution is sufficient for the use of a radiation energy spectrometer. However, μτ products of (5.0 ± 0.4) × 10−5 and (1.8 ± 0.2) × 10−5 cm2 V−1 for holes and electrons are obtained, respectively. These values are approximately one order of magnitude smaller than the μτ products of the CVD single crystal grown on a HP/HT type IIa diamond substrate using the same growth conditions.

Visible-light excited red-emitting vacancies at carbon interstitials as indicators of irradiated and annealed Type Ia diamonds

During the last decades many studies have been carried out to investigate how point defects and aggregates respond and evolve in natural Type Ia diamonds as a result of treatments, and a number of underlying mechanisms have been identified and interpreted. However, the analysis of radiation-induced creation/ionization of defects, as well as their migration and aggregation in secondary defect structures, often requires experimental approaches which can hardly constitute a simple-to-use diagnostic tool for the identification of artificially treated diamonds. Here we disclose a novel simple indicator of artificial exposure of Type Ia diamonds to ionizing radiations and subsequent annealing. This indicator consists in narrow photoluminescence lines in the red region, between 681 and 725 nm, we recently found to result from vacancies trapped by interstitial carbon aggregates and platelets. Our results demonstrate that interstitial structures become sites of vacancy trapping – by thermal migration of radiation-induced vacancies – only when diamond undergoes treatments. We give the rigorous validation of the new spectroscopic probe of artificial treatments analysing photoluminescence and infrared absorption spectra of well-known H1b and H1c centres in a hundred samples. Importantly, the method is based on emission lines which do not require neither high photon-energy excitation nor cryogenic temperatures.

Precise measurements of diamond lattice constant using Bond method

Precise lattice constant measurements based on the Bond method for various types of diamond were performed with a recently reported compensation technique. For the measurements, a calibrated Si single crystal was used as a reference; it was placed in a chamber whose temperature was carefully controlled below the standard deviation σ of ±0.1 °C, including thermo-couple fluctuation of ±0.06 °C for ±σ, X-ray wavelength calibration was performed using the monochromator temperature. A calibration was also carried out for the instrumental value depending on the Bragg angle and it was applied to the 004 diffraction peak of diamond. The lattice constant of high quality insulating undoped IIa type diamond was 3.567095 ± 0.000017 Å (±2σ), which was larger than the previous data derived without above mentioned calibrations. The measurements were carried out for various types of diamond including high pressure high temperature (HPHT) grown crystals as well as crystals grown by the chemical vapor deposition (CVD) method.

Type IIa Diamond Formation

The petrological model of type IIa diamond formation is proposed. By the model these diamonds were formed from fluids on the last stages of kimberlite magma formation at 600–700°C and in the range of 20–30 kbar. The model explains the main specific of the type IIa diamonds. They are the enrichment of light carbon, low nitrogen content, the absence of silicate inclusions, the large size and cleanliness, a high degree of desorption.

The Effect of Three Dimensional Printed Infill Pattern on Structural Strength

Bu çalışmanın amacı; Ergiterek Yığma ile Modelleme tekniğiyle (FDM-Fused Deposition Modeling), Polilaktik Asit (PLA-PolylacticAcid) malzeme kullanılarak oluşturulan dolgu geometrisinin mukavemete olan etkisinin analiz edilmesi ve kıyaslanmasıdır. Kıyaslama ve analiz için; yaygın olarak kullanılmasından dolayı doğrusal (linear), altıgen (hexagonal) ve elmas (diamond) tipi geometriler seçilmiştir. Çekme testi numuneleri Bilgisayar Destekli Tasarım (CAD-ComputerAided Design) metotları kullanarak hazırlanmış ve Bilgisayar Destekli Mühendislik (CAE-Computer Aided Engineering) yöntemleriyle analiz edilmiştir. Çekme testi simülasyonu için tüm numuneler %50 doluluk oranıyla hazırlanmıştır. Örneklerin kabuğu (shell) 0,8 mm kalınlıkta oluşturulmuştur. 3B baskı numuneleri, doğrusal, altıgen ve elmas tipi dolgu türleriyle tasarlanmış ve üretilmiştir. Analiz ve baskı süresini azaltmak için katman yükseklikleri 0,4 mm olarak seçilmiştir. Ayrıca, baskı ürünlerinden daha iyi sonuçlar alabilmek için piramit olarak adlandırılan yeni bir geometrik dolgu tipi tasarlanmıştır. Gerçekçi çekme testi simülasyonu oluşturmak için numunelere 8 adımda, 0,04 mm değerinde düğümsel (nodal) yer değiştirmeler uygulanmıştır. Mukavemete etkisi olan anahtar parametreler simülasyon sonuçlarından elde edilmiştir.Elde edilen sonuçlar; oluşan maksimum gerilimin, dökme PLA ile oluşturulan numune için 7,6 ile 68,6 MPa aralığında olduğu halde, elmas dolgulu numune için 112,3 MPa'ya kadar yükseldiğini göstermiştir. Diğer bir önemli nokta olarak, elmas dolgulu numunenin stres değeri, beşinci aşamada ham malzemenin son çekme mukavemetine (UTS-Ultimate Tensile Strength) yakın olan 70,7 MPa değerine ulaşmış olmasıdır. Numunelerin %50 doluluk oranıyla üretilmesinden dolayı UTS değerleri 35 MPa olarak kabul edilerek simülasyonun üçüncü veya dördüncü basamaklarında kırıldığı sonucuna varılabilir. Oluşturulan farklı dolgu geometrilerinde; yaklaşık 2 ile 12 MPa aralıktaki gerilme farkları birinci ve beşinci adımlar arasında gözlemlenmiştir. En yüksek gerilim elmas geometri için oluşmuştur. Bu durum en düşük yoğunluk ve geometriye bağlı olarak açıklanabilir. Sonuç olarak, yapısal mukavemet değerlendirmesi (Altıgen> Doğrusal> Elmas) şeklinde elde edilmiştir.

Crystalline quality distributions of the type IIa diamond substrate and the CVD diamond layer processed by chemical mechanical polishing using a SiO2 wheel

We have grown a high-quality type-IIa single-crystal diamond substrate, which had a large (001) growth sector with a dislocation-free area of 3.5 × 3.5 mm2, and strong free exciton (FE) emissions were observed by cathodoluminescence (CL), while dislocations, stacking faults, and defect-related CL emissions at 340 and 400 nm were observed in the (111) growth sector. After CVD growth on the off-angled type-IIa substrate processed by SiO2 chemical mechanical polishing, the intensity of the FE emission became 3 times higher and the electronic quality became more homogeneous, indicating that a high-quality CVD layer was successfully grown and the lateral growth eliminated the evolution of point defects in the substrate. On the other hand, the CVD layer on the (111) growth sector had hillocks and defect-related CL emissions, indicating that the stacking faults have a highly negative effect on the electronic quality of the CVD layer compared with the dislocations.

Kimberlites distribution in Angola and prospective areas for new discoveries

Based on a comprehensive analysis of kimberlite pipes of Angola, including the near surface structural setting, deep lithospheric structure, pipe morphology and emplacement, mineralogical and petrographic features, diamond characteristics and locations of secondary deposits four geographical regions have been outlined within Angola representing four types of diamond bearing potential. These areas include high diamond bearing potential pipes, possible potential, no potential, and unclear potential areas. It was found that the depth of magmatism and diamond potential of kimberlites increases from the Atlantic coast in southwestern Angola into the continent in the north-easterly direction. Areas prospective for the discovery of new primary diamond deposits have been identified.

Chemical-vapor deposited ultra-fast diamond detectors for temporal measurements of ion bunches.

This article reports on the development of thin diamond detectors and their characterization for their application in temporal profile measurements of subnanosecond ion bunches. Two types of diamonds were used: a 20 μm thin polycrystalline chemical vapor deposited (CVD) diamond and a membrane with a thickness of (5 ± 1) μm etched out of a single crystal (sc) CVD diamond. The combination of a small detector electrode and an impedance matched signal outlet leads to excellent time response properties with a signal pulse resolution (FWHM) of τ = (113 ± 11) ps. Such a fast diamond detector is a perfect device for the time of flight measurements of MeV ions with bunch durations in the subnanosecond regime. The scCVD diamond membrane detector was successfully implemented within the framework of the laser ion generation handling and transport project, in which ion beams are accelerated via a laser-driven source and shaped with conventional accelerator technology. The detector was used to measure subnanosecond proton bunches with an intensity of 108 protons per bunch.

In situ high-pressure spectroscopic studies using moissanite (4H-SiC) anvils

We examined the Raman scattering and IR absorption spectroscopy of 4H-SiC and its performance as an anvil material for high-pressure UV-visible absorption spectroscopic measurements. The first- and second-order Raman peaks of 4H-SiC and diamond do not coincide. 4H-SiC does not have obvious signals from 2330-5000 cm-1, suggesting that 4H-SiC anvils are beneficial for high-pressure studies of samples whose Raman signals locate in the region of diamond. Above 1800 cm-1, the transmitted signal of 4H-SiC in the IR absorption spectra, measured through 4.6 mm thickness is much higher than that of type IIa diamond. An in situ high-pressure UV-visible absorption spectroscopy study on CdI2 was carried out up to 28.0 GPa using 4H-SiC anvil cells (4H-SAC) with a 400 μm culet and the acquired band gap narrowed with increasing pressure. These results show that 4H-SiC has an excellent performance in high-pressure spectroscopic studies.

Clustering of hydrogen, phosphorus, and vacancies in diamond: A density functional theory analysis

Phosphorus-doped $n$-type diamond is currently one of the most promising wide-band-gap materials for next-generation high-power electronics and optoelectronics. Artificial diamond growth methods such as chemical vapor deposition involve hydrogen-containing precursors; therefore, the hydrogen atoms can be simultaneously introduced into the diamond lattice as a contamination and form complexes with other defects. In this work, we used the spin-polarized, hybrid density functional theory method to investigate the electronic structure, stability, and magnetic and optical properties of phosphorus, vacancy, and hydrogen clusters in diamond. Our results indicate a thermodynamic driving force for the formation of previously unidentified phosphorus-vacancy-hydrogen complexes that can be electrically, magnetically, or optically active centers. We found an unusual extremely large hyperfine coupling with the $^{31}\mathrm{P}$ nuclei ($Ag2$ GHz) for some of the investigated defects that requires further experimental verification. Finally, we demonstrate that the ${\text{PV}}_{2}{\text{H}}^{0}$ complex has two metastable triplets between the ground- and excited-state singlets, and it may exhibit a highly selective spin decay channel to a ground state, which makes the defect a promising candidate for realizing long-living solid-state quantum memory. These results provide deep insight into the donor compensation effect associated with vacancy-related clusters, and they may be useful in future identification of P-related defects suitable for quantum information processing applications.

On the origin of large type IIa gem diamonds

The processes of formation of some diamond types still raise contentious issues, mainly on the origin of the largest diamond crystals recovered from kimberlites. These diamonds constitute less than 2% of worldwide resources and correspond to rare type IIa. They possess some peculiar features: (i) silicate and oxide inclusions are extremely rare, (ii) their δ13C ranges from −17 to −21‰. The detailed estimation of the Premier pressure-temperature-oxygen fugacity parameters and the physic-chemical modeling of diamond growth-dissolution processes suggest that extra-large diamonds have multiple origins. Their formation may occur from lower mantle to crustal depths. Their main building-up takes place from fluids in the pegmatitic veins solidified along the contacts of kimberlite magma at a crustal depth. The model explains the main features of the largest kimberlitic diamonds, i.e. their great sizes, light δ13C signatures, low nitrogen contents, high degree of resorption, absence of mantle-derived mineral inclusions and their occurrence in the form of rare isolated crystals in the host kimberlite.