Diamond Etching Research Articles

Effect of holding time on interfacial reaction layer characteristics and mechanical performance of brazed diamonds with Cu-Sn-Ti-Ga filler metals

The diamond joints of the diamond/CuSnTiGa solder system were prepared under the holding time of 3 min, 6 min, 9 min, 12 min, and 15 min, respectively. The effect of brazing holding time on the microscopic morphology, interface characteristics, element distribution changes and mechanical properties of brazing diamond was studied. When the holding time is 6 min, a continuous and uniform TiC reaction layer has been formed at the interface. Etching of diamond and XRD results both proved the formation of TiC. The microhardness results show that when the holding time is 6 min, the maximum hardness at the interface is 318 HV0.1, and the uniformly fluctuating friction coefficient and grinding removal amount are obtained at the holding time of 6 min. Finally, combined with the analysis of the worn surface morphology, the interface reaction of the base brazing filler metal is closely connected, and the filler metal has a high holding force on the diamond. The 6 min heat preservation can effectively improve the bonding strength and wear resistance of the filler metal and the diamond, and meet the expected use requirements.

Spatially selective, solid state etching of diamond using lithographically patterned FeCoB

Nanocrystalline layers of FeCoB (Fe:Co:B = 60:20:20 at atom ratio) enable spatially selective, microstructurally agnostic removal of diamond through a solid-state diffusion reaction. Lithographically fabricated 100-300 nm thick films of FeCoB are deposited on polycrystalline diamond substrates. Heat treatment at temperatures ranging from 700 °C–900 °C for 30 min–90 min are used to trigger the conversion of sp3 to sp2 carbon at the diamond-transition metal interface. The integrity of the solid-state etchant within the thermal processing window underpins the spatial selectivity with which the diamond is removed. Removal of the reaction products using solvothermal etching in an acid solution enables the recovery of the structured diamond surfaces. FeCoB offers material removal rates, which exceeds that possible with just Fe or Co – pointing to the key role of B. The interaction zone was excised using focused ion beam milling and characterized using electron microscopy. In addition, XRD and Raman spectroscopy were performed to study the phase composition of the interaction zone. The role of the transition metal-diamond interface is key to controlling the material removal; the stability of the interface determines the ability to faithfully replicate the ultrafine features that were lithographically patterned in the FeCoB.

Experimental Etching of Diamonds: Extrapolation to Impact Diamonds from the Popigai Crater (Russia)

Diamond etching in high-temperature ambient-pressure experiments has been performed aimed to assess possible postimpact effects on diamonds in impact craters, for the case of the Popigai crater in Yakutia (Russia). The experiments with different etchants, including various combinations of silicate melts, air, and inert gases, demonstrated the diversity of microstructures on {111} diamond faces: negative or positive trigons, as well as hexagonal, round, or irregularly shaped etch pits and striation. The surface features obtained after etching experiments with kimberlitic diamonds are similar to those observed on natural impact diamonds with some difference due to the origin of the latter as a result of a martensitic transformation of graphite in target rocks. Extrapolated to natural impact diamonds, the experimental results lead to several inferences: (1) Diamond crystals experienced natural oxidation and surface graphitization during the pressure decrease after the impact event, while the molten target rocks remained at high temperatures. (2) Natural etching of diamonds in silicate melts is possible in a large range of oxidation states controlled by O2 diffusion. (3) Impact diamonds near the surface of molten target rocks oxidized at the highest rates, whereas those within the melt were shielded from the oxidizing agents and remained unchanged.

Morphogenesis of mesoscopic surface patterns formed in polarized two-photon etching of diamond

Two-photon etching of diamond surfaces is a novel technique for providing controlled removal of atomic layers and nano-patterning the surface. However, the details of the etching mechanism and pattern development are not well understood so that the full capability of the process is unclear. Here, a comprehensive investigation into the dynamics of nanopattern formation on the (100), (110) and (111) facets is reported as a function of polarization, for CVD and HPHT diamond, and for nanosecond and picosecond laser pulse durations. A diverse array of behaviour is observed including sub-wavelength scale structuring with morphologies characteristic of the facet and the selected polarization. As etching proceeds, the anisotropies in the quantum photon-lattice interaction are imprinted on the emergent patterns on nano and mesoscopic scales. The sum of the results leads to rules for predicting pattern type, roughness and etch rate. We also argue that they support a mechanism for carbon ejection based on the photo-ejection of carbonyl groups from carbonyl-supporting surfaces, defects and atomic-level step edges. The results provide guidance for optically manipulating diamond surfaces and comprise a major step towards a complete model for the process to aid laser direct-write structuring of functional diamond surfaces.

Enhanced etch rate of deep-UV laser induced etching of diamond in low pressure conditions

Ultraviolet laser-induced etching is a method of machining and nanostructuring diamond surfaces in which carbon is removed from the surface via a photochemical process involving oxygen. We show here that using a dry source of oxygen at pressures in the range of 0.01–1 Torr leads to a 10-fold increase in the etch rate compared to etching in atmospheric air. The enhanced etch rate is also found to be accompanied by a marked change in the nanopatterned surface morphology. We developed a rate equation model for the etch rate that provides good agreement with measurements for pressures up to approximately 0.1 Torr. For higher pressures, the reduced etch rate and departure from the model are attributed to the contamination of the diamond surface by trace amounts of water vapor, introduced as an impurity from the gas sources. The results provide a method for markedly increasing the etch rate, as well as a better understanding of the role of gas impurities on the etch mechanism and emergent nanopattern formation.

Investigation of 〈100〉-oriented etching pattern on diamond coated with Ni and Cu

Diamond etching of [Formula: see text] orientation is processed in chemical vapor deposition (CVD) chamber using H2 as reactive gas. Etching process happens on diamond substrates using a variety of etch mask materials including copper and nickel. Scanning electron microscope (SEM) and atomic force microscope (AFM) show different kinds of diamond etching pattern of two mask materials. It is observed that the etching pit of copper is tetrahedron, while the etching pit of nickel is step structure. This indicates diverse etching mechanism of diamond etched by different metal. Observing the surface etching topography of diamond and analyzing the etching mechanism of different metal can help study the growth of diamond by CVD and controllable etching of diamond.

Two‐Step Reactive Ion Etching Process for Diamond‐Based Nanophotonics Structure Formation

Diamond surface modification is one of the most important technological challenges in the creation of diamond quantum photonics devices. It is necessary to fabricate different 3D structures on the crystal surface with both vertical and V‐shaped etching grooves for waveguides, grating couplers, and mesastructures. Herein, the applicability of SF6‐based plasma for diamond processing is studied. SF6 plasma etches diamond five times faster than commonly used Ar/O2 3:1 at the same pressure and bias, but it cannot provide vertical diamond structures due to the ion scattering. Herein, the two‐step plasma processing method is developed with Molybdenum protective masks that provide steep diamond 3D structures with sidewall roughness less than 40 nm and is, therefore, suitable for nanophotonics and other diamond applications. Mo can be chemically patterned by low‐power SF6 plasma and then used as a hardmask for anisotropic etching of diamond in Ar/O2 plasma with a selectivity of 27. Unlike common methods of diamond processing, the proposed two‐step method does not require chlorine.

Role of knock-on in electron beam induced etching of diamond

Electron beam induced etching (EBIE) has recently emerged as a promising direct-write nanofabrication technique. EBIE is typically assumed to proceed entirely through chemical pathways driven by electron-electron interactions. Here we show that knock-on (i.e., momentum transfer from electrons to nuclei) can play a significant role in EBIE, even at electron beam energies as low as 1.5 keV. Specifically, we calculate knock-on cross-sections for H, D, O and CO on the surface of diamond and show experimentally that they affect the kinetics of EBIE performed using oxygen, hydrogen and deuterium etch precursors. Our results advance basic understanding of electron-adsorbate interactions, particularly in relation to EBIE and the related techniques of electron beam-induced deposition and surface functionalisation.

Catalytic etching of {100}-oriented diamond coating with Ni and Cu nanoparticles under hydrogen

Nanopores formed in insulating solid state membrane is of great importance in many fields such as detection of DNA/RNA molecules in their internal environment, probing and manipulating biopolymers. Here, we present an effective and convenient method to form nanopores in diamond etched by self-assembled Ni or Cu nanoparticles in hydrogen atmosphere. With our method, homogeneous nanopores with lateral size in the range of [Formula: see text]–[Formula: see text] were created without using Reactive Ion Etching (RIE) process. In this work, the etching pits of Ni and Cu etched diamond were investigated, respectively. A novel step-like pattern of etching pits was observed on diamond etched by Ni. In order to study the etching process and figure out the etching mechanism of diamond, Scanning Electron Microscopy (SEM) was used to observe the etching morphology. Atomic Force Microscopy (AFM) and Laser Scanning Confocal Microscope (LSCM) were used to visualize the image of diamond etching pits and investigate the step-like pattern. A fixed step height was observed in each pit. Based on these observations and findings, a hypothesis is proposed, which can help to provide a new controllable etching method.

Formation of U-shaped diamond trenches with vertical {111} sidewalls by anisotropic etching of diamond (110) surfaces

U-shaped diamond trenches with vertical {111} sidewalls for power devices were successfully obtained by anisotropic etching of diamond (110) surfaces using Ni films in high-temperature (1000 °C) water vapor. The etching rate for the diamond (110) surfaces was estimated to be 3.8 μm/min on the basis of the relationship between etching time and etching depth of diamond trenches with (110) bottoms. These (110) bottoms gradually disappeared as the etching progressed. Finally, they completely vanished and each diamond trench was surrounded by four vertical {111} sidewalls and two slanted {111} sidewalls. The formation mechanisms of the U-shaped diamond trenches are also discussed on the basis of the experimental results.

Fast smoothing on diamond surface by inductively coupled plasma reactive ion etching

Abstract

Diamond Etching Beyond 10\u2009\u03bcm with Near-Zero Micromasking

To exploit the exceptional properties of diamond, new high quality fabrication techniques are needed to produce high performing devices. Etching and patterning diamond to depths beyond one micron has proven challenging due to the hardness and chemical resistance of diamond. A new cyclic Ar/O2 - Ar/Cl2 ICP RIE process has been developed to address micromasking issues from the aluminium mask by optimising the proportion of O2 in the plasma and introducing a preferential “cleaning” step. High quality smooth features up to, but not limited to, 10.6 μm were produced with an average etched surface roughness of 0.47 nm at a diamond etch rate of 45 nm/min and 16.9:1 selectivity.

Surface etching of diamond powders with electroless Ni-P coating according to phosphorus content

Ni-P coatings with different P content were deposited on the surface of diamond powders with a particle size of about 200 μm by electroless plating. The Ni-Pcoated diamond powders were then annealed at 900 °C in vacuum for 1 h followed by cleaning. The etching properties of the coated diamond powders were investigated. The amount of the Na2H2PO4·H2O reductant was adjusted to obtain Ni-P coating layers with a P content of 5 and 7 wt%. After the coating for 5, 15, and 60 min, the vacuum annealing and coated layer removal processes were carried out. In each process, the microstructure of the coatings was examined using field emission scanning electron microscopy. The elemental compositions of the coating surfaces were examined using energy dispersive X-ray spectroscopy. Ni-P coating layers were evenly coated on the entire surface of the diamond powders, and the coating thickness was proportional to the root square of the coating time. The thickness of the coatings with high P content was two times higher than that of the coatings with low P content for the same coating time. The surface analysis results after annealing revealed that the coatings layer was initially consisted of spherical grain size of 3um. With an increase in the reductant content and coating time, Ni aggregation was observed along with the formation of Ni-Sn-P intermetallic compounds. With an increase in the P content and coating time, the thickness of the Ni-P coating layers increased. However, the etching ratio of the diamond surface decreased, while the etching depth increased. Therefore, the diamond etching profile could be controlled by Ni-P coating process condition.

CVD Diamond Interaction with Fe at Elevated Temperatures.

Chemical vapor deposition (CVD) diamond is a prospective thin film material for cutting tools applications due to the extreme combination of hardness, chemical inertness, and thermal conductivity. However, the CVD diamond cutting ability of ferrous materials is strongly limited due to its extreme affinity to iron, cobalt, or nickel. The diamond–iron interaction and the diffusion behavior in this system are not well studied and are believed to be similar to the graphite–iron mechanism. In this article, we focus on the medium-temperature working range of 400–800 °C of a CVD diamond–Fe system and show that for these temperatures etching of diamond by Fe is not as strong as is generally accepted. The starting point of the diamond graphitization in contact with iron was found around 400 °C. Our results show that CVD diamond is applicable for the cutting of ferrous materials under medium-temperature conditions.

FABRICATION OF WELL-DEVELOPED SURFACE OF SYNTHETIC DIAMOND SINGLE CRYSTALS FOR INCREASING IN SPECIFIC POWER OF BETAVOLTAIC POWER SUPPLIES ON THEIR BASE

The process of the reactive ion etching of synthetic monocrystalline diamond with thick aluminum oxide and aluminum nitride protective masks for increasing the surface of diamond was studied. The etching selectivity of aluminum oxide and aluminum nitride were determined. The relief structures in a shape of ribs with more than 2 µm height, 5 µm period and 45° profile slope were fabricated on diamond surface. These structures increase the effective surface area 1.3 times.

Precision micro-mechanical components in single crystal diamond by deep reactive ion etching

The outstanding material properties of single crystal diamond have been at the origin of the long-standing interest in its exploitation for engineering of high-performance micro- and nanosystems. In particular, the extreme mechanical hardness, the highest elastic modulus of any bulk material, low density, and the promise for low friction have spurred interest most notably for micro-mechanical and MEMS applications. While reactive ion etching of diamond has been reported previously, precision structuring of freestanding micro-mechanical components in single crystal diamond by deep reactive ion etching has hitherto remained elusive, related to limitations in the etch processes, such as the need of thick hard masks, micromasking effects, and limited etch rates. In this work, we report on an optimized reactive ion etching process of single crystal diamond overcoming several of these shortcomings at the same time, and present a robust and reliable method to produce fully released micro-mechanical components in single crystal diamond. Using an optimized Al/SiO2 hard mask and a high-intensity oxygen plasma etch process, we obtain etch rates exceeding 30 µm/h and hard mask selectivity better than 1:50. We demonstrate fully freestanding micro-mechanical components for mechanical watches made of pure single crystal diamond. The components with a thickness of 150 µm are defined by lithography and deep reactive ion etching, and exhibit sidewall angles of 82°–93° with surface roughness better than 200 nm rms, demonstrating the potential of this powerful technique for precision microstructuring of single crystal diamond.

High-selectivity anisotropic etching of single-crystal diamond by H plasma using iron catalysis

A highly selective anisotropic etching method for single-crystal diamond was investigated. After a thin film of Fe was deposited on the diamond surface, it was processed in H plasma activated by microwave plasma-assisted-chemical vapor deposition (MPCVD). Spurred by the high catalytic activity of Fe, the diamond was easily etched, with masked areas (i.e., with no Fe deposition) remaining smooth or barely damaged. The etch rate was 180 nm min−1. This method provides a simple and alternative way for diamond processing and patterning.

Anisotropic diamond etching through thermochemical reaction between Ni and diamond in high-temperature water vapour

Diamond possesses excellent physical and electronic properties, and thus various applications that use diamond are under development. Additionally, the control of diamond geometry by etching technique is essential for such applications. However, conventional wet processes used for etching other materials are ineffective for diamond. Moreover, plasma processes currently employed for diamond etching are not selective, and plasma-induced damage to diamond deteriorates the device-performances. Here, we report a non-plasma etching process for single crystal diamond using thermochemical reaction between Ni and diamond in high-temperature water vapour. Diamond under Ni films was selectively etched, with no etching at other locations. A diamond-etching rate of approximately 8.7 μm/min (1000 °C) was successfully achieved. To the best of our knowledge, this rate is considerably greater than those reported so far for other diamond-etching processes, including plasma processes. The anisotropy observed for this diamond etching was considerably similar to that observed for Si etching using KOH.

Atomic layer deposition frequency-multiplied Fresnel zone plates for hard x-rays focusing

The design and fabrication of Fresnel zone plates for hard x-ray focusing up to 25 keV photon energies with better than 50 nm imaging half-pitch resolution is reported as performed by forming an ultrananocrystalline diamond (UNCD) scaffold, subsequently coating it with atomic layer deposition (ALD) with an absorber/phase shifting material, followed by back side etching of Si to form a diamond membrane device. The scaffold is formed by chemical vapor-deposited UNCD, electron beam lithography, and deep-reactive ion etching of diamond to desired specifications. The benefits of using diamond are as follows: improved mechanical robustness to prevent collapse of high-aspect-ratio ring structures, a known high-aspect-ratio etch method, excellent radiation hardness, extremely low x-ray absorption, and significantly improved thermal/dimensional stability as compared to alternative materials. Central to the technology is the high-resolution patterning of diamond membranes at wafer scale, which was pushed to 60 nm lines and spaces etched 2.2-μm-deep, to an aspect ratio of 36:1. The absorber growth was achieved by ALD of Ir, Pt, or W, while wafer-level processing allowed to obtain up to 121 device chips per 4 in. wafer with yields better than 60%. X-ray tests with such zone plates allowed resolving 50 nm lines and spaces, at the limit of the available resolution test structures.

Bonding performance of self-adhesive flowable composites to enamel, dentin and a nano-hybrid composite.

This study aimed to analyze bond strengths of self-adhesive flowable composites on enamel, dentin and nano-hybrid composite. Enamel, dentin and nano-hybrid composite (Venus Diamond, Heraeus Kulzer, Germany) specimens were prepared. Three self-adhesive composites (Constic, DMG, Germany; Fusio Liquid Dentin, Pentron Clinical, USA; Vertise Flow, Kerr Dental, Italy) or a conventional flowable composite (Venus Diamond Flow, Heraeus Kulzer, Germany, etch&rinse technique) were applied to enamel and dentin. Nano-hybrid composite specimens were initially aged by thermal cycling (5000 cycles, 5-55°C). Surfaces were left untreated or pretreated by mechanical roughening, Al2O3 air abrasion or silica coating/silanization. In half of the composite specimens, an adhesive (Optibond FL, Kerr Dental, Italy) was used prior to the application of the flowable composites. Following thermal cycling (5000 cycles, 5-55°C) of all specimens, shear bond strengths (SBS) and failure modes were analyzed (each subgroup n=16). Statistical analysis was performed by ANOVAs/Bonferroni post hoc tests, Weibull statistics and χ 2-tests (p<0.05). SBS (MPa) of the self-adhesive composites on enamel and dentin were significantly lower (enamel: < 5, dentin: < 3) than those of the conventional flowable composite (enamel: 13.0±5.1, dentin: 11.2±6.3), and merely adhesive failures could be observed. On the nano-hybrid composite, SBS were significantly related to the pretreatment. Adhesive application improved SBS of the conventional, but not of the self-adhesive composites. The self-adhesive composite groups showed less cohesive failures than the reference group; the occurence of cohesive failures increased after surface pretreatment. Bonding of self-adhesive flowable composites to enamel and dentin is lower than bonding to a nano-hybrid composite.