Diamond Surface Research Articles

Enhancing colloidal stability of nanodiamond via surface modification with dendritic molecules for optical sensing in physiological environments

Pre-treatment of diamond surface in low-temperature plasma for oxygenation and in acids for carboxylation was hypothesized to promote the branching density of the hyperbranched glycidol polymer. This was expected to increase the homogeneity of the branching level and suppress interactions with proteins. As a result, composite nanodiamonds with reduced hydrodynamic diameters that are maintained in physiological environments were anticipated. Surfaces of 140-nm-sized nanodiamonds were functionalized with oxygen and carboxyl groups for grafting of hyperbranched dendritic polyglycerol via anionic ring-opening polymerization of glycidol. The modification was verified with Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Dynamic light scattering investigated colloidal stability in pH-diverse (2–12) solutions, concentrated phosphate-buffered saline, and cell culture media. Thermogravimetric analysis of nanodiamonds-protein incubations examined non-specific binding. Fluorescence emission was tested across pH conditions. Molecular dynamics simulations modeled interparticle interactions in ionic solutions. The hyperbranched polyglycerol grafting increased colloidal stability of nanodiamonds across diverse pH, high ionic media like 10 × concentrated phosphate-buffered saline, and physiological media like serum and cell culture medium. The hyperbranched polyglycerol suppressed non-specific protein adsorption while maintaining intensive fluorescence of nanodiamonds regardless of pH. Molecular modelling indicated reduced interparticle interactions in ionic solutions correlating with the improved colloidal stability.

Microstructure and finite element analysis of Mo2C-diamond/Cu composites by spark plasma sintering

Abstract Mo2C layer was generated on the diamond surface via vacuum micro-evaporating, which was used as the reinforcement particles to fabricate diamond/Cu composites by spark plasma sintering (SPS). The effect of evaporation parameters on the forming of Mo2C, and the holding time on diamond/Cu composites fabrication is studied. Combined with the experiment and finite element analysis (FEA), the holding time on diamond/Cu composites influence on the thermal conductivity (TC) of composites is further discussed. The results show that the Mo2C area on the diamond surface would gradually enlarge and cover the diamond surface evenly with the increment in evaporation time and temperature, better vacuum micro-evaporating parameters were given as 1,000°C for 60 min. The fractures in the diamond/Cu composites are mainly ductile fractures on copper and diamond falling out from the Mo2C interface. It was found that sintering time would significantly influence the dissipation property of diamond/Cu composites. A comprehensive parameter for SPS was obtained at 900°C, 80 MPa for 10 min, the relative density (RD) and TC of the composites obtained under the parameter were 96.13% and 511 W/(m K). A longer sintering time would damage the Mo2C interlayer and further decrease the bonding between copper matrix and diamond particles, which would lower the RD and TC of composites. It can be obtained from the comparison of simulation results and experimental results that the FEA result is closer to the experimental results due to the gaps with low heat conduction, and the air in the gaps is added in the simulation process.

Prehydrated Electrons Activated by Continuous Electron Transfer Stemmed from Peracetic Acid Homolysis Mediated by Diamond Surface Defects for Enhanced PFOA Destruction.

Research on the use of peracetic acid (PAA) activated by nonmetal solid catalysts for the removal of dissolved refractory organic compounds has gained attention recently due to its improved efficiency and suitability for advanced water treatment (AWT). Among these catalysts, nanocarbon (NC) stands out as an exceptional example. In the NC-based peroxide AWT studies, the focus on the mechanism involving multimedia coordination on the NC surface (reactive species (RS) path, electron reduction non-RS pathway, and singlet oxygen non-RS path) has been confined to the one-step electron reaction, leaving the mechanisms of multichannel or continuous electron transfer paths unexplored. Moreover, there are very few studies that have identified the nonfree radical pathway initiated by electron transfer within PAA AWT. In this study, the complete decomposition (kobs = 0.1995) and significant defluorination of perfluorooctanoic acid (PFOA, deF% = 72%) through PAA/NC has been confirmed. Through the use of multiple electrochemical monitors and the exploration of current diffusion effects, the process of electron reception and conduction stimulated by PAA activation was examined, leading to the discovery of the dynamic process from the PAA molecule → NC solid surface → target object. The vital role of prehydrated electrons (epre-) before the entry of resolvable electrons into the aqueous phase was also detailed. To the best of our knowledge, this is the first instance of identifying the nonradical mechanism of continuous electron transfer in PAA-based AWT, which deviates from the previously identified mechanisms of singlet oxygen, single-electron, or double-electron single-path transfer. The pathway, along with the strong reducibility of epre- initiated by this pathway, has been proven to be essential in reducing the need for catalysts and chemicals in AWT.

Oxygen functionalized diamond nanocone arrays coupling cobalt phthalocyanine for enhanced electrochemical CO2 reduction

The development of high-efficiency catalysts plays a crucial role in advancing CO2 electroreduction techniques. Among potential candidates, diamond-based electrocatalysts show promise due to their broad electrochemical windows, which effectively suppress competitive hydrogen evolution and ensure high CO2 reduction efficiency. In this study, we report an integrated electrode composed of oxygen-terminated diamond nanocone (ODcone) with CoPc-molecules anchoring (CoPc/ODcone). The CoPc/ODcone electrodes exhibited remarkable performance, achieving a maximum Faradaic efficiency (FE) of 94.1% for CO at −0.97 V vs reversible hydrogen electrode (RHE), and maintaining an FECO higher than 80% over a wide potential range of −0.67 V to −1.07 V vs RHE. The outstanding performance of the CoPc/ODcone electrode can be attributed to the synergistic effects between the nanostructured diamond surface and the CoPc catalyst. The hydroxyl-rich nature of the diamond surface facilitates the anchoring of CoPc molecules and bonding with Co atoms in CoPc. Simultaneously, the nanostructured diamond with sharp tips enhances CO2 adsorption, thereby improving the catalyst's performance. This study provides valuable insights into the utilization of non-metallic carbon materials, particularly diamond, as metal-free catalysts in CO2 electrochemical reduction and tackles challenges such as low current density and poor Faradaic efficiency, thus contributing to the advancement of more effective catalysts for CO2 electroreduction.

Formation of low-dimensional nanopit structures on atomically flat surfaces of diamond (111) by nickel nanoparticles

Diamond nanoprocessing technologies are essential for the development of diamond-based devices. However, the existing etching processes damage the diamond crystal, adversely affecting the characteristics of the corresponding device. Herein, we focused on the Ni–C solid-solution reaction as a nondamaging fabrication method. Ni films (10, 3, and 1 nm) were deposited on atomically flat surfaces (AFSs) of diamond (111) and annealed under H2 gas flow. The Ni film aggregated into particles, and as the particle size decreased, Ni particles moved around, etching the diamond surface. Interestingly, when the diameter of the Ni nanoparticles was less than a few tens of nanometers, they dug one-dimensional (1D) nanopits with a linear trench shape on diamond AFS. We discuss the mechanism for the formation of these 1D nanopits in detail from the perspective of the etching-morphology dependence on the annealing time, Ni thickness, and gas atmosphere. The results of this study will improve our understanding of the Ni–C solid-solution reaction at the nanoscale and promote the development of damage-free nanofabrication techniques for diamond-based device applications.

A theoretical study on dopants substituted on the H-terminated surface regulating the threshold concentration of nitrogen for accelerating diamond growth

Nitrogen is widely believed to accelerate the diamond growth by chemical vapor deposition (CVD). While there is currently no consensus on the reaction mechanism of nitrogen increasing the growth rate of CVD diamond. In this work, we have proposed a chemical adsorption model formed by substitutional nitrogen on the H-terminated surface of diamond. The first principles calculations based on density functional theory are used to systematically study the effects of substitutional nitrogen on several key features (i.e., surface absorption energy, geometric structure, atomic charge, electron bond population, and electron density) of the H-terminated surfaces. The results indicate that nitrogen substituted on the H-terminated surface are probably more favorable for hydrogen desorption, which can not only affect the properties of directly bonding adjacent species, but also cause changes in the geometric and electronic properties around the surface by electron transfer or forming additional covalent bonds. Furthermore, compared with single nitrogen doping, the co-doped structures formed by adding boron or phosphorus at a relatively low N/H ratio on the H-terminated surface could enhance or weaken the stability of the diamond surface, that is, weaken or enhance the desorption process of hydrogen. It is therefore proved the existence of a regulatory effect on the threshold concentration required for nitrogen to accelerate diamond growth.

Photochemical modification of a diamond surface using a pulsed UV laser as the energy source

The use of an excimer benchtop pulsed UV laser as the energy source for the photochemical modification of the surface of diamond films is reported. Boron-doped nanocrystalline diamond (NCD) films were deposited on Si wafers via plasma-enhanced chemical vapour deposition (PECVD). The as-deposited films were characterised by scanning electron microscopy (SEM), Raman spectroscopy, and X-ray diffraction (XRD). Following characterisation, the surfaces of the films were subjected to a photochemical reaction with 2,2,2-trifluoroethyl undec-10-enoate using two different sources of radiation: a benchtop UV lamp (254 nm) and a KrF excimer pulsed UV laser (248 nm). The photochemically treated films were characterised by contact angle measurements and X-ray photoelectric spectroscopy (XPS) using non-treated films as a control. The use of a pulsed UV laser source was shown to reduce the photochemical reaction time from several hours to a few minutes.

Benchmarking diamond surface preparation and fluorination via inductively coupled plasma-reactive ion etching

Diamond, renowned for its exceptional semiconducting properties, stands out as a promising material for high-performance power electronics, optics, quantum, and biosensing technologies. This study methodically investigates the optimization of polycrystalline diamond (PCD) substrate surfaces through Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE). Various parameters, including gaseous species, flow rate, coil power, and bias power were tuned to understand their impact on surface morphology and chemistry. A thorough characterization, encompassing chemical, spectroscopic, and microscopic methods, shed light on the effects of different ICP-RIE conditions on surface properties. CF4/O2 plasma emerged as a viable treatment for achieving smooth PCD surfaces with minimal etch pit formation. Most notably, surface fluorination, a critical aspect of increasing chemical and thermal stability, was successfully accomplished using CF4, SF6, and other F-containing plasmas. The fluorine concentration and surface chemistry variations were studied, with high resolution X-ray Photoelectron Spectroscopy unveiling differences amongst the sp2 C phase, sp3 C phase, C–O, CO, and C–F bonds. Time-of-flight secondary Ion Mass Spectrometry (ToF-SIMS) and depth-profile analysis unveiled a consistent surface fluorination pattern with CF4/O2 treatment. Furthermore, contact angle measurements showcased heightened hydrophobicity. This study provides valuable insights into precise diamond surface engineering, important for the development of future diamond-based semiconductor technologies.

Low-Cost Preparation of Diamond Nanopillar Arrays Based on Polystyrene Spheres.

Diamond nanopillar arrays can enhance the fluorescence collection of diamond color centers, playing a crucial role in quantum communication and quantum sensing. In this paper, the preparation of diamond nanopillar arrays was realized by the processes of polystyrene (PS) sphere array film preparation, PS sphere etching shrinkage control, tilted magnetron sputtering of copper film, and oxygen plasma etching. Closely aligned PS sphere array films were prepared on the diamond surface by the gas-liquid interfacial method, and the effects of ethanol and dodecamethylacrylic acid solutions on the formation of the array films were discussed. Controllable reduction of PS sphere diameter is realized by the oxygen plasma etching process, and the changes of the PS sphere array film under the influence of etching power, bias power, and etching time are discussed. Copper antietching films were prepared at the top of arrayed PS spheres by the tilted magnetron sputtering method, and the antietching effect of copper films with different thicknesses was explored. Diamond nanopillar arrays were prepared by oxygen plasma etching, and the effects of etching under different process parameters were discussed. The prepared diamond nanopillars were in hexagonal close-rowed arrays with a spacing of 800 nm and an average diameter of 404 nm, and the spacing, diameter, and height could be parametrically regulated. Raman spectroscopy and photoluminescence spectroscopy detection revealed that the prepared diamond nanopillar array still maintains polycrystalline diamond properties, with only a small amount of the graphite phase appearing. Moreover, the prepared diamond nanopillar array can enhance the photoluminescence of diamond color centers by approximately 2 times. The fabrication method of diamond nanopillar array structures described in this article lays the foundation for quantum sensing technology based on diamond nanostructures.

Nitridation of diamond(111) surface by density functional theory.

Density functional theory was employed to examine the adsorption and thermal evolution of nitrogen species on diamond(111) impacted by microwave N2 plasma. On bare domains of diamond, as represented by the models of C(111)-2 × 1 and graphite-like C(111), N2(ad) is identified as the major surface species; the desorption of N2(ad) proceeds on both models via a concerted process of breaking two C-N bonds. By contrast, there is evidence of the formation of (NH)2(ad) via the insertion reaction of microwave N2 plasma on hydrogenated domains of diamond, as represented by the models of C(111)-2 × 1-H and C(111)-1 × 1-H. Interestingly, contrasting dynamics of desorption of (NH)2(ad) are presented on these two models, that is, via sequential breaking of two C-N bonds on C(111)-2 × 1-H and via concerted breaking of both C-N bonds on C(111)-1 × 1-H. Our results demonstrate that the observed diversity of surface nitrogen species in composition, bonding, vibration, and desorption in prior experiments is linked to domains of a variety of surface terminations and reconstructions on diamond(111).

Transformation of the diamond surface with a thin iron coating during annealing and transport properties of the formed conductive layer

In our study, we annealed polycrystalline diamond films with nanometer-thick iron coatings. Based on analysis of X-ray photoelectron spectroscopy data the presence of two catalytic processes was suggested. One is the continuous absorption of sp3 carbon by iron nanoparticles with subsequent extrusion of the sp2 phase from the formed iron carbide, which leads to the creation of deep tracks into the diamond bulk that are filled with graphite stacks. The other process involves a thin layer of iron carbide on the surface and results in the creation of sp2 layers, which are made up of fused graphene-like patches and are oriented mainly along the surface of the diamond film. For the sample annealed at 800 °C for 1 h, the sp2 layers formed exhibit semi-metallic conductivity with quantum corrections caused by disorders. At the same time, no evidence of iron contribution in conductivity of the annealed Fe-coated film was detected, implying that upon transforming the diamond, iron moved quite deep into the bulk. In addition, the formed conductive layer on the diamond surface shows mechanical stability, ensuring the reproducibility of conductivity measurements even after six months of storage in air. The study has revealed the potential for targeted metal-assisted formation of sp2 carbon-based conducting pathways on diamond surfaces for electronic devices.

Multifunctional Nanodiamond Interfacial Layer for Ultra‐Stable Zinc‐Metal Anodes

AbstractAchieving reversible plating/stripping of zinc (Zn) anodes is crucial in aqueous Zn‐ion batteries (AZIBs). However, undesired dendrite growth and parasitic side reactions severely deteriorate battery lifespan. The construction of stable protective coating is an effective strategy to enhance anode stability. In this study, a multifunctional nanodiamond (ND) inorganic layer is designed and constructed on both Zn and Cu electrodes that can both effectively inhibit dendrite growth and suppress Zn anode corrosion. Experimental results and theoretical calculations demonstrate that this artificial protective layer, with ultra‐high surface energy, enables the controlled creation of abundant nucleation sites (in the order of 1012 cm−2) for the homogenization of ion flux and electric field on the anode. It is found that zinc ions preferentially adhere to the diamond surfaces with lower diffusion barriers, leading to uniform zinc deposition. A symmetric cell with the ND‐protected Zn (Zn‐ND) anode exhibits reversible plating/stripping behavior for an impressive duration of over 3600 h at 1 mA cm−2. Furthermore, the MnO2||Zn full battery retains 90% of its initial capacity after 3500 cycles at 2 A g−1, and assembled hybrid capacitor operates smoothly over 65 000 cycles at 10 A g−1. These results underscore the potential of this coating as a promising solution for achieving highly stable Zn anodes for aqueous batteries.

Highly Sensitive and Selective Detection of L-Tryptophan by ECL Using Boron-Doped Diamond Electrodes.

L-tryptophan is an amino acid that is essential to the metabolism of humans. Therefore, there is a high interest for its detection in biological fluids including blood, urine, and saliva for medical studies, but also in food products. Towards this goal, we report on a new electrochemiluminescence (ECL) method for L-tryptophan detection involving the in situ production of hydrogen peroxide at the surface of boron-doped diamond (BDD) electrodes. We demonstrate that the ECL response efficiency is directly related to H2O2 production at the electrode surface and propose a mechanism for the ECL emission of L-tryptophan. After optimizing the analytical conditions, we show that the ECL response to L-tryptophan is directly linear with concentration in the range of 0.005 to 1 µM. We achieved a limit of detection of 0.4 nM and limit of quantification of 1.4 nM in phosphate buffer saline (PBS, pH 7.4). Good selectivity against other indolic compounds (serotonin, 3-methylindole, tryptamine, indole) potentially found in biological fluids was observed, thus making this approach highly promising for quantifying L-tryptophan in a broad range of aqueous matrices of interest.

XPS analysis of molecular contamination and sp2 amorphous carbon on oxidized (100) diamond

The efficacy of oxygen (O) surface terminations on diamond is an important factor for the performance and stability for diamond-based quantum sensors and electronics. Given the wide breadth of O-termination techniques, it can be difficult to discern which method would yield the highest and most consistent O coverage. Furthermore, the interpretation of surface characterization techniques is complicated by surface morphology and purity, which if not accounted for will yield inconsistent determination of the oxygen coverage. We present a comprehensive approach to consistently prepare and analyze oxygen termination of surfaces on (100) single-crystalline diamond. We report on x-ray photoelectron spectroscopy (XPS) characterization of diamond surfaces treated with six oxidation methods that include various wet chemical oxidation techniques, photochemical oxidation with UV illumination, and steam oxidation using atomic layer deposition (ALD). Our analysis entails a rigorous XPS peak-fitting procedure for measuring the functionalization of O-terminated diamond. The findings herein have provided molecular-level insights on oxidized surfaces in (100) diamond, including the demonstration of clear correlation between the measured oxygen atomic percentage and the presence of molecular contaminants containing nitrogen, silicon, and sulfur. We also provide a comparison of the sp2 carbon content with the O1s atomic percentage and discern a correlation with the diamond samples treated with dry oxidation which eventually tapers off at a max O1s atomic percentage value of 7.09 ± 0.40%. Given these results, we conclude that the dry oxidation methods yield some of the highest oxygen amounts, with the ALD water vapor technique proving to be the cleanest technique out of all the oxidation methods explored in this work.

Formation of a Boron‐Oxide Termination for the (100) Diamond Surface

Formation of a Boron‐Oxide Termination for the (100) Diamond Surface

Fabrication of lateral diamond MOSFET with buried pn-junctions by diamond surface planarization based on carbon solid solution into nickel

New fabrication processes for buried p+-type diamond using etching techniques based on the solid-solution reaction of carbon with nickel were proposed and demonstrated. Specifically, an inversion-channel diamond metal-oxide-semiconductor field-effect transistors (MOSFETs) with source and drain regions buried in the body were fabricated, and their operation were confirmed. An etching process using etching techniques based on the solid-solution reaction of carbon with nickel was applied to realize trench formation and planarization after the growth of a p+-type diamond. The fabricated MOSFET exhibited drain current density equivalent to that of conventional MOSFET with source and drain p+-type regions deposited as islands on an n-type body, and ideal field-effect transistor characteristics with linear and saturation regions, and the drain current density was controlled by the gate voltage. However, the surface protrusion structure owing to the incomplete planarization process limited the device characteristics. The proposed fabrication processes for buried layers are expected to function as an important selective doping technique for diamond electronic devices such as ion implantation.

Formation of Diamond Films with Different Grain Sizes on TiO2 Nanotubes and Its Field Emission Properties

Diamond films with different grain sizes are deposited on TiO2 nanotube (TNT) arrays prepared by anodic oxidation using a microwave plasma chemical vapor deposition reactor. The scanning electron microscope, X‐Ray diffractometer, and Raman results indicate that the diamond film is successfully deposited and that the substrate undergoes a phase transition due to the diamond deposition temperature, resulting in the rutile phase becoming dominant with lower energy bandgap and work function. Notably, after 5 h of deposition, a relatively continuous microcrystalline film is formed on the TNTs, and the diamond grains change from spherical to pyramidal and show excellent electron field emission behavior, with a low turn‐on field of 0.5 V μm−1 and a current density of 85.9 μA cm−2. In addition, the deposition environment of the nanocrystalline diamond has a large impact on the substrate morphology, resulting in a blocked electron transport path, which reduces the overall field emission performance. The enhanced performance is attributed to the synergistic effect between the highly efficient 1D electron path of the TNTs, the negative electron affinity of the diamond surface, and the lower work function of rutile TiO2.

Global flattening realization and kinematic analysis of UV-assisted low-speed 3D dynamic friction-polished diamonds

Diamond has attracted extensive attention from many scholars because of its unique properties. However, there are still bottlenecks in how to achieve high efficiency polishing and global flattening of diamond which restrict its application. The aim of this study is to obtain a globally homogeneous flattened diamond surface in macro dimension by introducing a compound motion of the polished workpiece. It is shown that ultra-smooth diamond surface machining with global flattening can be realized by UV-assisted low-speed dynamic friction polishing technique, and the typical roughness is 0.175 nm as measured by 3D optical surface profiler. These experimental results demonstrate that the catalytic phase transition process of UV light is the underlying mechanism to realize the diamond surface polishing under low rotational speed conditions. Additionally, the composite motion of the diamond sample with the metal disk brings large enhancement to the effect of polishing global flattening on the sample surface. The theoretical and experimental studies in this paper provide novel ideas for achieving efficient and polished global flattening of diamond.

Nanocrystalline Diamond Lateral Overgrowth for High Thermal Conductivity Contact to Unseeded Diamond Surface

We demonstrate unseeded lateral overgrowth of nanocrystalline diamond as a way of increasing the thermal conductivity of thin layers of diamond. The technique can be used as a way of growing diamond on top of semiconductors, creating a thin layer of high thermal conductivity diamond in direct contact with semiconductors and allowing for the encasement of GaN in high thermal conductivity diamond.

Efficient manufacture of high-performance electroplated diamond wires utilizing Cr-coated diamond micro-powder

The slicing of silicon ingots using electroplated diamond wires is a fundamental process in the creation of semiconductor devices such as chips and photovoltaic cells. Composite electroplating, a process that uses nickel (Ni) plating to fix diamond particles onto a steel wire, is a critical step in the manufacturing of these diamond wires. In this work, chromium (Cr)-coated diamond was used to achieve rapid and high-quality composite electroplating, thereby aiding the production of high-performance diamond wire saws. The Cr-coated diamond micro-powder was prepared utilizing vacuum slow evaporation technology at a temperature of 850 °C. This resulted in a uniform and firm Cr coating that was firmly bonded to the diamond surface via Cr3C2. Subsequent electrochemical tests were conducted in the composite electroplating bath. Linear scanning voltammetric curves revealed that the Cr-coated diamond was capable of inducing a more positive shift in the overpotential of Ni deposition, thus enhancing the reaction beyond that of uncoated diamond micro-powder. Additionally, the electrochemical impedance spectra indicated a decrease in charge transfer resistance during composite electroplating, attributable to the conductivity of the Cr-coated diamond. Electroplated diamond wires incorporating Cr-coated diamond demonstrated a greater abrasive density per unit length. SEM results showed that Ni was able to deposit on the Cr-coated diamond surface, resulting in the abrasives being completely covered by the Ni plating. The Cr-coated diamond wire exhibits a stronger resistance to abrasive detachment after cutting, which could increase the diamond-protrusion of the wire. The utilization of Cr-coated diamond micro-powder as an abrasive is anticipated to enhance the manufacturing efficiency of diamond wires and improve product quality, thereby promoting advancements in hard and brittle material processing technology.