Single Crystal Diamond Plates Research Articles

Infrared vertical external cavity surface emitting laser threshold magnetometer

Nitrogen-vacancy (NV) centers have considerable promise as high sensitivity magnetometers; however, they are commonly limited by inefficient collection and low contrasts. Laser threshold magnetometry (LTM) enables efficient collection and high contrasts, providing a path toward higher sensitivity magnetometry. We demonstrate an infrared LTM using an ensemble of NV centers in a single-crystal diamond plate integrated into a vertical external cavity surface emitting laser. The laser was tuned to the spin-dependent absorption line of the NV centers, allowing for optical readout by monitoring the laser output power. We demonstrate a magnetic sensitivity of 7.5 nT/Hz in the frequency range between 10 and 50 Hz. Furthermore, the contrast and the projected photon shot noise limited (PSNL) sensitivity are shown to improve significantly by operating close to the lasing threshold, achieving 18.4% and 26.6 pT/Hz near the threshold. In addition, an unexpected saturable absorption phenomenon was observed near the threshold, which enhanced the contrast and projected PSNL sensitivity.

Determination of the Strain Tensor and the Elastic Stress Fields in a Diamond Plate with a High Bending Curvature Using Local Laue Diffraction Data

Cylindrically bent diamond single-crystal plates have a great potential for creating energy dispersive spectrometers and focusing crystal monochromators. When they are designed, it is necessary to take into account the significant stresses that appear on bending the plates. The strain tensor and the elastic stress fields in a cylindrically bent single-crystal (110) diamond plate are calculated. The calculations are based on experimental data obtained by local Laue diffraction. The calculation results can be used to design new X-ray optical devices with the ability to control their parameters.

Evaluation of Local Stress Distributions and Dislocations Around Petal Patterns Observed in CVD Single Crystal Diamond Plates

Evaluation of Local Stress Distributions and Dislocations Around Petal Patterns Observed in CVD Single Crystal Diamond Plates

Temperature-dependent electrical and structural characterization of laser-induced graphitic microwires in CVD diamond

An array of 2500 vertical graphitic microwires was fabricated within a single-crystal diamond plate with the purpose of creating distributed electrically conductive structures intended for the development of electronic devices operating at high temperatures. To this end, the structural, morphological, and electrical properties of the diamond/graphite system were investigated as a function of temperature up to 550 °C, by means of optical and secondary electron microscopy (SEM), micro-Raman spectroscopy and current-voltage measurements. The vertical microstructuring of the diamond bulk was obtained by a laser-induced phase transition from diamond to graphite by means of ultra-short laser pulses (100 fs duration, 800 nm wavelength, 1 kHz repetition rate). As inferred from SEM micrographs, the graphitic wires display a high-aspect-ratio with length of approximately 200 μm and diameter of about 10 μm. The electrical resistivity of the single microwire is estimated to be 0.49 ± 0.15 Ω cm at room temperature, then decreasing linearly with temperature with a coefficient of approximately −1 × 10−2 K−1. Raman spectroscopy results point out the absence of structural alterations after high-temperature operations.

Dissolving Diamond: Kinetics of the Dissolution of (100) and (110) Single Crystals in Nickel and Cobalt Films

We report a study of the kinetics of dissolution of (100) and (110) single-crystal diamond plates (“D(100)” and “D(110)”) in thin films of nickel (Ni) and cobalt (Co). This dissolution occurs at the metal–D(100) or metal–D(110) interface and was studied in the presence and also in the absence of water vapor at temperatures near 1000 °C. The single-crystal D(100) dissolves in Ni, and also in Co, in the temperature range 900–1050 °C. The dissolution is too slow to measure below 900 °C. In an argon (Ar) atmosphere (under an Ar(g) flow at 1000 sccm and 1 atm pressure, with no water vapor present in the reaction chamber) and at any temperature in the range 900–1050 °C, the metal film is rapidly saturated with dissolved carbon (C), thin graphite films form on the free metal surface and at the metal–D interface during heating at or above 650 °C, and the dissolution of the diamond then stops. For addition of water vapor, its partial pressure was controlled by using a water bubbler immersed in a constant temperature bath and Ar(g) was used as the carrier gas. We discovered two different regimes (I and II) for the kinetics of dissolution of D(100) and D(110), in which the rate-determining step was the removal of carbon atoms on the open metal surface (regime I, lower partial pressure of water vapor) or dissolution of diamond at the metal–diamond interface (regime II, higher partial pressure of water vapor) that yielded different Arrhenius parameters. Time-of-flight-secondary ion mass spectrometry depth profiles show the concentration gradient of C from a certain depth into the metal film surface down to the M–D(100) interface, and residual gas analyzer measurements show that the gas products formed in the presence of water vapor on the metal surface are CO and H2. It was found that the rate of dissolution of diamond in Co was higher than that in Ni for both D(100) and D(110) and for both regimes I and II, and possible reasons are suggested. We also found that D(111) could not be dissolved at the Ni/D(111) and Co/D(111) interface in the presence of water vapor (over the same range of sample temperatures). The reaction paths for dissolution of C at the M–D(100) or M–D(110) interface and for removal of C from the free surfaces of Ni and Co were assessed through density functional theory modeling at 1273 K.

The single-crystal diamond trap (SCDT): a new method to determine the composition of high-P\u2013T fluids

In view of recently reported discrepancies in mineral solubility results obtained with the classical diamond trap method, an alternative approach to quantify the composition of high P–T fluids was developed. In this approach the high P–T fluids are trapped in laser-drilled holes within single-crystal diamond plates and subsequently analyzed by LA–ICP–MS using the same pit size as the one that was used to drill the holes, which allows more rigorous testing of the data reproducibility than in the case of the classical diamond trap, where the fluid resides in a large, open network. To reduce the spikiness of the LA–ICP–MS signals and minimize element fractionation, the aqueous solution within the holes was allowed to evaporate, and the solid residue was melted to a glass. Because this results in the partial loss of the internal standard elements that are usually used for quantifying the LA–ICP–MS signals we developed a new quantification procedure that works without any internal standard in the fluid but instead uses the carbon signal produced by the epoxy that was filled into the holes after melting the precipitates. The new method was first tested on holes filled with epoxy resins doped with known amounts of chemicals, then on holes filled with known amounts of minerals that were subsequently melted, and finally on real high P–T mineral solubility experiments at 1.0 GPa and 700–900 °C in the quartz–H2O and olivine–enstatite–H2O systems, for which reliable reference data exist. In all 15 experiments the measured concentrations agree within 1–21% (avg. 13%) with the reference values. In contrast, four mineral solubility experiments that were performed at identical conditions with the classical diamond trap method returned concentrations that deviated by 7–56% (avg. 28%) from the reference value. Furthermore, a strong fractionation effect that has been observed during the ablation of albite + H2O in a classical diamond trap is efficiently prevented in our single-crystal diamond trap (SCDT) approach. On the downside, we observe significant mobility of alkalies during the melting step in our approach.

Optical grating and THz polarizer based on normal grade single crystal diamond fast fabricated by fs laser

In this paper, we have researched the fs laser induced the phase transition in the normal grade single crystal diamond plates. The results show that the optical properties and electric properties of the irradiated region closely relate to the degree of the phase transition. We have succeeded in fabricating the optical gratings on the surface and inside of the diamond plates even though only partial material in the irradiated region phase-transforms from single crystal phase to amorphous phase. The gratings can be used as terahertz polarizers likewise. The modulation depths are 53% at 1.6 THz and 40% at 2.52 THz, which can be further improved by optimizing the fabrication parameters and the fill factors of gratings. We have also fabricated the electric wire on the surface of the normal grade diamond plate.

Diffractive optical elements in single crystal diamond.

We demonstrate the design, fabrication, and experimental characterization of near-field binary phase transmission diffractive optical elements (DOEs) in single crystal diamond. Top-hat and arbitrary pattern DOE beam shapers were numerically optimized using an iterative Fourier transform algorithm (IFTA). Commercially available single crystal diamond plates (3mm×3mm×0.3mm) were patterned using hardmask deposition (α-Si), e-beam lithography, and O2 plasma-based diamond reactive ion etching. The resulting binary phase relief patterns were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Experimental characterization of the single crystal diamond DOEs in transmission at λ=532nm confirms excellent uniformity of the resulting top-hat beam profile as required in copper welding applications.

ОСОБЛИВОСТІ ВИГОТОВЛЕННЯ РОТОРА ДЛЯ ПОПЛАВКОВОГО ГІРОСКОПА В УМОВАХ ВИРОБНИЦТВА

The problem of ensuring the performance of high-precision parts of navigation systems, while forming their surfaces by turning, has become extremely urgent today. The use of wide-ranging numerically controlled machine tools for precision spherical surfaces is promising, provided the required shape accuracy and roughness are required. Practical experience with the use of synthetic single-crystal interchangeable diamond plates has shown the need to find technological solutions related to reducing the surface roughness under certain conditions. The article presents the basic data on the technological capabilities of instrument production of manufacturing the parts for mechanical gyros-copes. The algorithm and technological sequence of manufacturing and providing the necessary properties to the surfaces of gyroscope rotor parts made of D16 and B95 aluminum alloys are presented. A description of the manufacturing sequence is given, indicating the tools and equipment used during the operation. A detailed description of geometric parameters of the variable plates with the indica-tion of manufacturers is given. A series of experiments has been conducted to determine the cutting modes by carbide and diamond tools. The influence of flow, speed and depth of cutting have been determined to ensure the minimum roughness of spherical surface of float gyroscope rotor for specific processing conditions. The results of the roughness measurements after polishing the surface obtained with diamond sharpening are presented. The results obtained can be used in the production, in the design of technological processes for the manufacture of parts made of aluminum alloys which have high-precision spherical surfaces. In addition, additional confirmation of the influence of the radius of rounding of the main cutting edge on the roughness of the machined surface has been obtained.

High‐Pressure High‐Temperature Single‐Crystal Diamond Type IIa Characterization for Particle Detectors

Various samples of multisectoral high‐pressure high‐temperature (HPHT) single‐crystal diamond plate (IIa type) (4 × 4 × 0.53 mm) are tested for particle detection applications. The samples are investigated by X‐ray diffractometry, photoluminescence spectroscopy, Raman spectroscopy, Fourier‐transform infrared, and visible/ultraviolet (UV) absorption spectroscopy. High crystalline perfection and low impurity concentration (in the {100} growth sector) are observed. To investigate detector parameters, circular 1.0 and 1.5 mm diameter Pt Schottky barrier contacts are created on {111} and {100} growth sectors. On the backside, a Pt contact (3.5 × 3.5 mm) is produced. The {100} growth sector is proved to be a high‐quality detector: the full width at half maximum energy resolution is 0.94% for the 5.489 MeV 226Ra α‐line at an operational bias of +500 V. Therefore, it is concluded that the HPHT material {100} growth sector is used for radiation detector production, whose quality is not worse than the chemical vapor deposition method or specially selected natural diamond detectors.

Analysis of doping anisotropy in multisectorial boron-doped HPHT diamonds

A set of single-crystal multisectorial diamond plates, cut from boron-doped high-pressure high-temperature (HPHT) grown crystals, was investigated using admittance spectroscopy methods. The results of admittance measurements demonstrate that the density of free charge carriers in one multisectorial crystal may differ by more than 50 times depending on the growth face and it correlates with boron concentration derived from IR absorption studies. For the first time we have obtained different activation energy for boron in sectors within one single crystal. Based on the experimental data, the difference in impurity capture coefficients along the (111) and (001) faces were numerically estimated for the established HPHT growth process.

Characteristics of hydrogen-terminated single crystalline diamond field effect transistors with different surface orientations

Diamond has great potential applications in high-power, high-frequency semiconductor devices because of its wide band gap (5.5 eV), high thermal conductivity (22W/(cm·K)), and high carrier mobility (4500 cm<sup>2</sup>/(V·s) for electron, and 3800 cm<sup>2</sup>/(V·s) for hole). It has been widely considered as an ultimate semiconductor. From the analysis of our previous work, we find that the output current of field effect transistor based on hydrogen-terminated polycrystalline diamond is usually larger than that based on single crystal diamond, and that the preferential orientations of the polycrystalline diamond are mainly <inline-formula><tex-math id="Z-20200108113531-1">\begin{document}$ \langle 110\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20191013_Z-20200108113531-1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20191013_Z-20200108113531-1.png"/></alternatives></inline-formula> and <inline-formula><tex-math id="Z-20200108113531-2">\begin{document}$ \langle 111\rangle $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20191013_Z-20200108113531-2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2-20191013_Z-20200108113531-2.png"/></alternatives></inline-formula> shown by XRD results. Therefore, in order to further analyze the effect of surface orientation on the device performance of hydrogen-terminated diamond field effect transistor (FET), we study the devices fabricated respectively on the (110) plane and (111) plane single crystal diamond plates obtained from a single 3.5-mm-thick single crystal diamond grown by the microwave plasma chemical vapor deposition on the high-pressure high-temperature synthesized diamond substrate. Prior to processing the device, these diamond plates are characterized by atomic force microscope, Raman spectra and photoluminescence (PL) spectra. The results of Raman and PL spectra show that (110) plane and (111) plane plates originating from the same CVD single crystal diamond have no significant difference in optical property. Then the normally-on hydrogen-terminated diamond FET with a gate length of 6 μm is achieved. The device on (111) plane delivers a saturation drain current of 80.41 mA/mm at a gate voltage <i>V</i><sub>GS</sub> = –4 V, which is approximately 1.4 times that of the device on (110) plane. Meanwhile, the on-resistance of the device on (111) plane is 48.51 Ω·mm, and it is only 67% of the device on (110) plane. Analyses of the capacitance-voltage show that the hole concentration of the gated device on (110) plane and (111) plane are 1.34 × 10<sup>13</sup> cm<sup>–2</sup> and 1.45 × 10<sup>13</sup> cm<sup>–2</sup>, respectively, approximately at the same level. In addition, the hole density of the device on both (110) and (111) plane increase near-linearly with the increase of gate voltage from the threshold voltage to – 4 V, indicating that the control effect of the gate on the carrier in the channel is uniform. The possible reason for the higher saturation drain current as well as the lower on-resistance of the device on (111) plane is that its sheet resistance is lower.

Multiple enlarged growth of single crystal diamond by MPCVD with PCD-rimless top surface**Project supported by the National Key Research and Development Program of China (Grant Nos. 2018YFB0406504 and 2016YFB0400105) and the National Postdoctoral Program for Innovative Talents, China (Grant No. BX20190263).

We report the simultaneous enlarged growth of seven single crystal diamond (SCD) plates free from polycrystalline diamond (PCD) rim by using a microwave plasma chemical vapor deposition (MPCVD) system. Optical microscope and atomic force microscope (AFM) show the typical step-bunching SCD morphology at the center, edge, and corner of the samples. The most aggressively expanding sample shows a top surface area three times of that of the substrate. The effective surface expanding is attributed to the utilization of the diamond substrates with (001) side surfaces, the spacial isolation of them to allow the sample surface expanding, and the adoption of the reported pocket holder. Nearly constant temperature of the diamond surfaces is maintained during growth by only decreasing the sample height, and thus all the other growth parameters can be kept unchanged to achieve high quality SCDs. The SCDs have little stress as shown by the Raman spectra. The full width at half maximum (FWHM) data of both the Raman characteristic peak and (004) x-ray rocking curve of the samples are at the same level as those of the standard CVD SCD from Element Six Ltd. The nonuniformity of the sample thickness or growth rate is observed, and photoluminescence spectra show that the nitrogen impurity increases with increasing growth rate. It is found that the reduction of the methane ratio in the sources gas flow from 5% to 3% leads to decrease of the vertical growth rate and increase of the lateral growth rate. This is beneficial to expand the top surface and improve the thickness uniformity of the samples. At last, the convenience of the growth method transferring to massive production has also been demonstrated by the successful simultaneous enlarged growth of 14 SCD samples.

Selection of CVD Diamond Crystals for X-ray Monochromator Applications Using X-ray Diffraction Imaging

A set of 20 single crystal diamond plates synthesized using chemical vapor deposition (CVD) was studied using X-ray diffraction imaging to determine their applicability as side-bounce (single-reflection) Laue monochromators for synchrotron radiation. The crystal plates were of optical grade (as provided by the supplier) with (001) nominal surface orientation. High dislocation density was found for all samples. Distortions in the crystal lattice were quantified for low-index Laue reflections of interests using rocking curve topography. Maps of effective radius of curvature in the scattering plane were calculated using spline interpolation of the rocking curve peak position across the studied plates. For several selected plates, nearly flat regions with large effective radius of curvature were found ( R 0 ≳ 30 − 70 m, some regions as large as 1 × 4 mm 2 ). The average width of the rocking curve for these regions was found to be about 150 μ rad (r.m.s.). These observations suggest that the selected CVD diamond plates could be used as intermediate-bandwidth monochromators refocusing the radiation source to a specific location downstream with close to 1:1 distance ratio.

Calibration of a 6Li diamond-sandwich spectrometer with quasi-monoenergetic neutrons

In the present article we describe calibration measurements of the compact neutron spectrometer at the PTB quasi-monoenergetic neutron reference fields. The spectrometer is based on two diamond detectors enclosing a 6 Li neutron converter. The conversion occurs through the 6 Li(n,t) 4 He reaction, featuring the Q -value of 4.8 MeV. The incident neutron energy is measured through the sum of energies of the two conversion reaction products: t and α . The prototype used in this work was based on two 4 × 4 mm 2 100 μ m thick single crystal CVD commercial diamond plates. The measurements were performed in the fission spectrum domain at five different neutron energies varying from 0.3 up to 2 MeV. The obtained data showed a very good neutron energy reconstruction, i.e. in agreement with its reference values within statistical uncertainties or with absolute deviations below 11 keV. The energy resolution of the spectrometer was found to be about 100 keV (RMS) with a small (about 9 keV/MeV) rising trend towards higher energies. The measured detection efficiency was found to be compatible with predictions based on analytical calculations and on Geant4 simulations within 3% statistical and 4% systematic uncertainty.

Femtosecond pulsed laser fabrication of a novel SCD grinding tool with positive rake angle

Ablating a single-crystal diamond (SCD) plate with a femtosecond laser to fabricate a novel abrasive regularly arranged binder-less face grinding tool with acute inclination angle at the edge of the micro grains was proposed in this paper. A Ti:Sapphire femtosecond laser with a wavelength of 1030 nm and a pulse width of 250 fs was used for the ablation experiments. The effects of processing parameters, especially the ablation track pitch on the ablation surface quality of the diamond, were investigated in advance. Based on the optimal processing parameters, an array of square frustum microabrasive with grain inclination angle of approximately 100° was fabricated on the surface of SCD according to the predesigned laser scanning path. The microabrasive array was subsequently ablated to reduce the inclination angle at the edge of the micrograins to approximately 80°, and a novel abrasive regularly arranged binder-less diamond face grinding tool with positive rake angle which was expected to decrease the grinding force and improve the surface quality of hard and brittle materials had been fabricated for the first time.

X-ray reflectivity of chemically vapor-deposited diamond single crystals in the Laue geometry.

The absolute X-ray reflectivity of chemically vapor-deposited (CVD) single-crystal diamond plates was measured in the Laue geometry in the double-crystal non-dispersive setting with an asymmetric Si beam-conditioner crystal. The measurements were supplemented by rocking-curve topography. The measured reflectivity curves are examined in the framework of the Darwin-Hamilton approach using a set of two independent parameters: the characteristic thickness of mosaic blocks and their average angular misorientation. Owing to strong extinction effects, the width of the reflectivity curves does not directly represent the average misorientation of the blocks. Two different sets of parameters were found for the 111 asymmetric reflection in the two different scattering configurations (beam compression and beam expansion). Analysis of the rocking-curve topographs shows that this discrepancy can be attributed to inhomogeneity of the diamond crystal microstructure.

Fabrication of (111)-faced single-crystal diamond plates by laser nucleated cleaving

Single-crystal diamond plates with surfaces oriented in a (111) crystal plane are required for high-performance solid-state device platforms ranging from power electronics to quantum information processing architectures. However, producing plates with this orientation has proven challenging. In this paper, we demonstrate a method for reliably and precisely fabricating (111)-faced plates from commercially available, chemical-vapor-deposition-grown, type-IIa single-crystal diamond substrates with (100) faces. Our method uses a nanosecond-pulsed visible laser to nucleate and propagate a mechanical cleave in a chosen (111) crystal plane, resulting in faces as large as 3.0mm × 0.3mm with atomically flat surfaces, negligible miscut angles, and near zero kerf loss. We discuss the underlying physical mechanisms of the process along with potential improvements that will enable the production of millimeter-scale (111)-faced single-crystal diamond plates for a variety of emerging devices and applications.

Low-coherence interferometry as a tool for monitoring laser micro- and nanoprocessing of diamond surfaces

We have demonstrated the possibility of using low-coherence tandem optical interferometry for monitoring the local laser processing of diamond surfaces. Noncontact measurements of the optical thickness of single-crystal diamond plates were performed directly during the exposure of the surface to repetitive intense laser pulses. We investigated the dynamics of the thinning of a single crystal in two radically different regimes of laser etching: ablation (KrF excimer laser, λ = 248 nm, τ = 20 ns) and nanoablation (Ti : sapphire laser, λ = 266 nm, τ = 100 fs).

Using Si-doped diamond plate of sandwich type for spatial profiling of laser beam

We demonstrated a laser beam profiling method based on imaging of the laser induced photoluminescence of a transparent single-crystal diamond plate. The luminescence at 738 nm is caused by silicon-vacancy color centers formed in the epitaxial diamond film by its doping with Si during CVD growth of the film. The on-line beam monitor was tested for a cw laser emitting at 660 nm wavelength.