Plasma Chemical Vapor Deposition Technique Research Articles

Microcontact printing fabrication of diamond MEMS cantilevers on silicon substrate

Diamond shows great potentials as an ultimate material candidate for application in microelectromechanical systems (MEMS). In this work, we report microcontact printing (μCP) transfer as a facile technique to fabricate diamond MEMS cantilever arrays. We started from the Deryaguin–Landau–Verwey–Overbeek (DLVO) principles and formulated a colloidal “ink” that contains nanodiamonds (NDs) seeds well dispersed in polymethyl methacrylate/acetone. The NDs seeds were then transfer printed onto a silicon (100) substrate by using a flexible polydimethylsiloxane (PDMS) stamp with predefined pattern. The densely packed NDs pattern (∼109 cm−2) enables facile and selected-area growth of diamond with microwave plasma chemical vapor deposition (MPCVD) technique. A diamond film with minimal graphite contaminants and low residual stresses was obtained after growth at 1118 K for 3 h. The diamond cantilevers were released from the substrate by wet chemical etching using KOH (40 % wt.) and isopropyl alcohol (10 % vol.). An examination of the vibrational kinetics indicates that the diamond film has a high Young's modulus (∼795 GPa) and the cantilevers exhibit consistently distributed resonant frequencies and high quality factors in ambient air. The method opens the door for large-scale, cost-effective production of uniform diamond MEMS devices for sensor and quantum applications.

Robust diamond-embedded microwave antenna for optimizing quantum sensing using nitrogen-vacancy center ensembles

The nitrogen-vacancy (NV) color center in diamond has emerged as a promising candidate for quantum sensing. In this study, we propose a diamond-embedded metal antenna for magnetic detection utilizing NV center ensembles. Our approach involved employing nanofabrication and microwave plasma chemical vapor deposition techniques to fabricate the metal antenna and diamond epilayer. By directly embedding the antenna into the diamond, we effectively minimize external environmental interference, leading to improved device stability and reusability. Moreover, this integration enhances the device's compactness, making it highly suitable for on-chip quantum sensing applications. The innovative antenna design holds great potential for the development of future integrated quantum sensing devices based on NV centers in diamond.

Structural and optical properties of micro-diamonds with SiV− color centers

Isolated, micro-metre sized diamonds are grown by micro-wave plasma chemical vapour deposition technique on Si(001) substrates. Each diamond is uniquely identified by markers milled in the Si substrate by Ga+ focused ion beam. The morphology and micro-grain structure analysis, indicates that the diamonds are icosahedral or bi-crystals. Icosahedral diamonds have higher (up to = 2.3 GPa), and wider distribution ( = 4.47 GPa) of hydrostatic stress built up at the micro-crystal grain boundaries, compared to the other crystals. The number and spectral shape of SiV− colour centres incorporated in the micro-diamonds (MDs) is analysed, and estimated by means of temperature dependent photoluminescence measurements, and Monte Carlo simulations. The Monte Carlo simulations indicates that the number of SiV− colour centres is a few thousand per MD.

Morphological changes of carbon thin films with nitrogen doping synthesized by microwave-excited surface wave plasma CVD

Nitrogen (N) doped graphene-based materials are of significant interest for various applications, such as, catalytic reactions, tribological energy generation, sensor devices and other electronic device applications. Most recently, the catalytic and noncatalytic growth of graphene structures at a low substrate temperature were explored by using the microwave-excited surface wave plasma (MW-SWP) chemical vapor deposition (CVD) technique. In this study, growth of carbon thin films is investigated by the MW-SWP CVD technique with nitrogen doping at various temperatures on the insulating substrates. It is obtained that partially graphitized carbon thin films can be obtained at a temperature as low as 150 °C on the quartz substrates. Interestingly, the morphological changes are observed with nitrogen doping and change in synthesis temperature for the carbon thin films grown by the MW-SWP CVD method. The partially graphitized carbon thin films form irregular morphologies at a lower temperature, while the morphology transforms with increase in temperature. At a certain growth temperature (500 and 700 °C), the carbon film shows granular morphology without addition of nitrogen, whereas the addition of nitrogen reduces the granular morphology and forming planar structures. Thus, these studies reveal the growth of carbon films with control morphology with respect to incorporation of nitrogen, which can be significant to develop carbon films and nanostructures for diverse fields of applications.

Polycrystalline Diamond Coating on Orthopedic Implants: Realization and Role of Surface Topology and Chemistry in Adsorption of Proteins and Cell Proliferation.

Polycrystalline diamond has the potential to improve the osseointegration of orthopedic implants compared to conventional materials such as titanium. However, despite the excellent biocompatibility and superior mechanical properties, the major challenge of using diamond for implants, such as those used for hip arthroplasty, is the limitation of microwave plasma chemical vapor deposition (CVD) techniques to synthesize diamond on complex-shaped objects. Here, for the first time, we demonstrate diamond growth on titanium acetabular shells using the surface wave plasma CVD method. Polycrystalline diamond coatings were synthesized at low temperatures (∼400 °C) on three types of acetabular shells with different surface structures and porosities. We achieved the growth of diamond on highly porous surfaces designed to mimic the structure of the trabecular bone and improve osseointegration. Biocompatibility was investigated on nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD) coatings terminated either with hydrogen or oxygen. To understand the role of diamond surface topology and chemistry in the attachment and proliferation of mammalian cells, we investigated the adsorption of extracellular matrix proteins and monitored the metabolic activity of fibroblasts, osteoblasts, and bone-marrow-derived mesenchymal stem cells (MSCs). The interaction of bovine serum albumin and type I collagen with the diamond surfaces was investigated by confocal fluorescence lifetime imaging microscopy (FLIM). We found that the proliferation of osteogenic cells was better on hydrogen-terminated UNCD than on the oxygen-terminated counterpart. These findings correlated with the behavior of collagen on diamond substrates observed by FLIM. Hydrogen-terminated UNCD provided better adhesion and proliferation of osteogenic cells, compared to titanium, while the growth of fibroblasts was poorest on hydrogen-terminated NCD and MSCs behaved similarly on all tested surfaces. These results open new opportunities for application of diamond coatings on orthopedic implants to further improve bone fixation and osseointegration.

Designing of room temperature diluted ferromagnetic Fe doped diamond semiconductor

Semiconductor devices generally take advantage of the charge of electrons, whereas magnetic materials are used for recording information involving electron spin. To make use of both charge and spin of electrons in semiconductors, a high concentration of magnetic elements can be introduced in nonmagnetic III-V semiconductors to make magnetic semiconductor. In this work, Fe-Diamond was obtained with low solubility by modified microwave plasma chemical vapor deposition technique. Magnetic measurements revealed that the magnetic transition temperature from paramagnetic to ferromagnetic-like is above room temperature. The bandgap of Fe-Diamond is calculated to be 1.65 eV, which indicates that Fe-Diamond is a room temperature diluted ferromagnetic semiconductor.

Battery-like flexible supercapacitors from vertical 3D diamond/graphite composite films on carbon cloth

Flexible supercapacitors (SCs) based on carbon nanomaterials are one of the promising energy storage devices for wearable electron devices. However, their low energy density and cycle stability severely restrict further practical applications. The development of unique capacitor electrodes is expected largely to overcome these challenges. Herein, vertical 3D diamond/graphite (DG) composite films are directly grown on carbon cloth (CC) using a microwave plasma chemical vapor deposition (MPCVD) technique. Thin, straight nanosheets, consisted of diamond as core and graphite as shell, are interlaced with each other to form a 3D porous structure. As a binder- and additive-free electrode material, the DG/CC electrodes are used to construct electrical double layer capacitors (EDLCs) in diluted H2SO4 solution and pseudocapacitors (PCs) using Fe(CN)63−/4- redox electrolytes. Both EDLCs and PCs exhibit large specific capacitance and high capacitance retention. When assembled as all-solid-state flexible symmetric SCs, they offer high full-cell capacitances of 30.4 and 143.6 mF cm−2 at 10 mV s−1 for EDLCs and PCs, respectively. The power densities are 6.3 μW cm−2 and 3.0 mW cm−2 for EDLCs and PCs, together with their energy densities of 3.7 and 86.2 μWh cm−2, respectively. As flexible SCs, the specific capacitance can be completely recovered for EDLCs and has only about 6.7% loss for PCs even after the U-shape bending state. Such vertical 3D porous DG films are thus promising for the construction of high-performance battery-like SCs for an intelligent wearable energy supplier.

In-situ formation, structural transformation and mechanical properties Cr[sbnd]N coatings prepared by MPCVD

This study innovatively employed the microwave plasma chemical vapor deposition (MPCVD) technique to fabricate CrN coatings. The influence of preparation temperature on chemical composition, crystalline phase, morphology, and mechanical properties of the coatings were analyzed systematically. The increase of preparation temperature resulted in the structural transformation of the CrN coatings from the duplex of Cr2N/CrN to the single-phased Cr2N. The coatings with dense and flat surface were obtained at ≤800 °C; however, the decomposition of CrN to Cr2N and N2 led to the formation of pores at ≥850 °C and consequently an increase in friction coefficient and wear. The hardness and elastic modulus increased with increasing temperature because of the structural evolution of the CrN coating and phase transformation. 800 °C was the optimal preparation temperature as the coating exhibited a dense surface and possessed the best overall mechanical properties.

Synthesis, Properties and Aging of ICP-CVD SiCxNy:H Films Formed from Tetramethyldisilazane

Amorphous hydrogenated silicon carbonitride films were synthesized on Si(100), Ge(111), and fused silica substrates using the inductively coupled plasma chemical vapor deposition technique. 1,1,3,3-tetramethyldisilazane (TMDSN) was used as a single-source precursor. The effect of the precursor’s pressure in the initial gas mixture, the substrate temperature, the plasma power, and the flow rate of nitrogen gas as an additional reagent on the film growth rate, element composition, chemical bonding, wettability of film surface, and the optical and mechanical properties of a-SiCxNy:H films was investigated. In situ diagnostic studies of the gas phase have been performed by optical emission spectroscopy during the film deposition process. The long-term stability of films was studied over a period of 375 days. Fourier-transform infrared (FTIR) and X-ray energy dispersive spectroscopy (EDX), and wettability measurements elucidated the oxidation of the SiCxNy:H films deposited using TMDSN + N2 mixture. Films obtained from a mixture with argon had high stability and maintained the stability of element composition after long-term storage in ambient air.

Photocatalytic and Optoelectronic Properties of Polycrystalline Diamond

AbstractPolycrystalline diamonds are grown by microwave plasma chemical vapor deposition techniques. The structures and morphologies are investigated by X‐ray diffraction, Raman, and atomic force microscope. The photocatalytic characterizations show that diamond has a certain degradation ability for rhodamine B, and the degradation rate of nanocrystalline diamond is faster than that of microcrystalline diamond. Diamond based photoconductor‐type photodetector with Au electrode is prepared and it shows high photoresponsivity. This research has opened up new opportunities for diamond in various fields including photocatalysis and photodetectors.

Eigenmode analysis of the waveguide-plasmon structure based on a-Si1-xCx:H layer with 1D gold grating

Resonant structure consisting of waveguide layer with metallic strips array is a promising design for various optical effects control and enhancement at the nanoscale due to its strong resonant properties and light localization phenomena. However, different applications require understanding the nature of eigenmodes of the structure, that possess peculiar properties. In this research, the optical properties of the planar waveguide with one-dimensional periodic gold grating on it was examined. Emitting layer of a-Si1-xCx:H was deposited by plasma chemical vapour deposition technique and the gold array was created by the e-beam lithography. Angle-resolved reflection and photoluminescence spectra in s- and p-polarizations were measured by the Fourier-imaging spectroscopy method. The theoretical analysis was performed to reveal the physical nature of the observed spectral features and their effect on the waveguide layer emitting properties was studied.

Nitrogen-doped carbon nanowalls/diamond films as efficient electrocatalysts toward oxygen reduction reaction

Substitution of commercial Pt/C electrocatalysts with efficient carbon-based ones for oxygen reduction reaction (ORR) still remains a huge challenge. For practical ORR applications it is significant to design robust 3D network nanostructures in that they do not require polymer binders. For conventional powder catalysts, they must be combined with substrate, leading to their shedding and degradation. In this work, vertically-aligned N-doped carbon nanowalls/diamond (N-CNWs/D) films are synthesized by means of a microwave plasma chemical vapor deposition technique, where nitrogen doping is conducted during the growth process and a subsequent facile annealing treatment under Ar atmosphere. The obtained Ar treated N-CNWs/D film exhibits an ORR onset potential of 835 mV (versus reversible hydrogen electrode) in 0.1 mol l−1 KOH solution in a four-electron reaction pathway. It also displays excellent tolerance toward methanol crossover and long-term stability (e.g. a current density loss of only 10% even after 16 h measurement). The boosting ORR performance can be attributed to the activated pyridinic N dopant at abundant edge sites and enlarged electrochemical surface areas of N-CNWs/D films. This work not only develops a controllable strategy to fabricate binder-free carbon-based ORR electrocatalysts, but also paves a way to in-depth understand actual active sites in terms of ORR pathway mechanisms.

Production and Surface Modification of Cellulose Bioproducts.

Petroleum-based synthetic plastics play an important role in our life. As the detrimental health and environmental effects of synthetic plastics continue to increase, the renewable, degradable and recyclable properties of cellulose make subsequent products the “preferred environmentally friendly” alternatives, with a small carbon footprint. Despite the fact that the bioplastic industry is growing rapidly with many innovative discoveries, cellulose-based bioproducts in their natural state face challenges in replacing synthetic plastics. These challenges include scalability issues, high cost of production, and most importantly, limited functionality of cellulosic materials. However, in order for cellulosic materials to be able to compete with synthetic plastics, they must possess properties adequate for the end use and meet performance expectations. In this regard, surface modification of pre-made cellulosic materials preserves the chemical profile of cellulose, its mechanical properties, and biodegradability, while diversifying its possible applications. The review covers numerous techniques for surface functionalization of materials prepared from cellulose such as plasma treatment, surface grafting (including RDRP methods), and chemical vapor and atomic layer deposition techniques. The review also highlights purposeful development of new cellulosic architectures and their utilization, with a specific focus on cellulosic hydrogels, aerogels, beads, membranes, and nanomaterials. The judicious choice of material architecture combined with a specific surface functionalization method will allow us to take full advantage of the polymer’s biocompatibility and biodegradability and improve existing and target novel applications of cellulose, such as proteins and antibodies immobilization, enantiomers separation, and composites preparation.

Porous single-crystal diamond

Porous diamonds have unique application prospects due to their flexible surface functionalities, high surface-area-to-volume ratio and high self-sharpening ability. Porous diamonds are usually prepared through microwave plasma chemical vapor deposition (MPCVD) techniques or through etching by transition metals, which are expensive and inefficient. Here, we report a simple and efficient method to grow large millimetre-scale porous single-crystal diamonds using high-pressure and high-temperature (HP-HT) techniques. The porous diamond crystal growth is driven by minimizing the surface energy through the attachment of small crystals to a large seed crystal surface in a metal solvent. Industrial-scale production of single-crystal porous diamonds is possible with this discovery.

Structural, optical and photoluminescence investigations of nanocrystalline CuO thin films at different microwave powers

Thin films of copper oxide were prepared through two steps: the formation of metallic copper thin films by DC sputtering technique and oxidizing the metallic copper films through microwave plasma chemical vapor deposition technique. X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM) were used to detect the crystalline phases and the films morphology, respectively. Tenorite CuO phase with interlocking between grains were observed and detected. Optical and photoluminescence properties were investigated by UV–Vis-NIR to detect the optical transparency, optical band gap, and refractive index of the prepared films. The optical transmittance of the studied films was resolved by Swanepoel’s procedure due to the presence of the optical interference in such samples. The optical band gap values were observed to decrease from 2.355 to 1.986 eV as the microwave power increase. A strong UV emission at around 358 nm was observed in all CuO samples. Moreover, weak blue and green emission were also observed in the photoluminescence spectra.

Cutting performance of cubic boron nitride-coated tools in dry turning of hardened ductile iron

A novel cubic boron nitride (cBN)-coated silicon nitride(Si3N4) cutting tool was fabricated via the diamond interlayers by electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (MPCVD) technique. The cutting performance of cBN-coated tools was evaluated by dry turning of hardened ductile iron in comparison with the commercially available titanium aluminum nitride (TiAlN)-coated tools. The effects of cutting parameters on the cutting force and cutting temperature were studied. The results showed that the cutting forces increased with the increase of depth of cut but decreased with the increase of cutting speed, while the cutting temperature increased with the increase of cutting speed. Compared to the TiAlN-coated tools under identical turning conditions, the cBN-coated tools had lower cutting force and cutting temperature, and smaller tool wear. The cBN-coated tools delivered excellent cutting performance and prolonged tool life. Furthermore, the wear patterns and wear mechanisms of cBN-coated tools were investigated. It was found that the dominant wear patterns were crater wear on rake face and flank wear land, and the wear mechanisms were demonstrated to be abrasion wear and diffusion wear. The cutting experiments verified that the cBN-coated tools had attractive potentials in the applications for dry turning of refractory metals and hardened ferrous materials.

Improvement in growth yield of single-walled carbon nanotubes with narrow chirality distribution by pulse plasma CVD

A pulse plasma chemical vapor deposition (CVD) technique was developed for improving the growth yield of single-walled carbon nanotubes (SWNTs) with a narrow chirality distribution. The growth yield of the SWNTs could be improved by repetitive short duration pulse plasma CVD, while maintaining the initial narrow chirality distribution. Detailed growth dynamics is discussed based on a systematic investigation by changing the pulse parameters. The growth of SWNTs with a narrow chirality distribution could be controlled by the difference in the nucleation time required using catalysts comprising relatively small or large particles as the key factor. The nucleation can be controlled by adjusting the pulse on/off time ratio and the total processing time.

MICROSTRUCTURE AND MECHANICAL PROPERTY CHARACTERIZATION OF MULTILAYER FREE-STANDING DIAMOND/Mo FILMS

The monolayer diamond film and free-standing diamond/Mo multilayer films were prepared by combining microwave plasma chemical vapor deposition (MPCVD) and double glow plasma surface alloying (DGPSA) techniques. The result shows that the film grain size decreases from 70–80[Formula: see text][Formula: see text]m to [Formula: see text]–20[Formula: see text][Formula: see text]m with the layer number increasing from the monolayer diamond film with a columnar crystal structure to the seven-layer diamond/Mo films, indicating that the Mo interlayer can effectively reduce the grain size. The Mo2C is formed between the Mo and diamond layers, which can improve the bonding strength. The internal stress of these films depends on the number of Mo interlayers and the Mo2C content. Moreover, the fracture strength and abrasion ratio of multilayer diamond films are effectively improved by adding the Mo interlayer. The four-layer diamond/Mo film system has the highest fracture strength and the seven-layer film system has the highest abrasion ratio.

Optimal parameter(s) for the synthesis of nitrogen-vacancy (NV) centres in polycrystalline diamonds at low pressure

Nitrogen-vacancy (NV) centres in diamonds are emerging quantum materials having applications in quantum computing and magnetic field sensing. The ability to synthesize polycrystalline diamond films from chemical vapour deposition technique offers a possibility to grow cheap diamonds with NV centres over large areas. Till date, extensive studies have not been carried out to understand the influence of nitrogen flow rate on the formation of NV centres in polycrystalline diamonds. In this study, we investigate the effect of nitrogen flow rate on the morphology, optical, and electrical properties of polycrystalline diamonds deposited at low pressure. Several samples were prepared in different nitrogen flow regimes using the microwave plasma chemical vapour deposition (MPCVD) technique. The films were characterized using Raman spectroscopy and scanning electron microscopy (SEM). The I–V characteristics of the samples were measured using a point contact method at room temperature. Results obtained showed the formation of both neutral and negatively charged NV centres at an optimum nitrogen flow rate of 10 sccm. An increase in nitrogen flow rate led to a decrease in the electrical resistivity of the films. Furthermore, nitrogen flow rates greater than 20 sccm results to a decrease in the reflectance spectra of samples and a depreciation in the crystalline quality of films. This study is important in benchmarking an optimal parameter space for the growth of nitrogen doped polycrystalline diamonds suitable for sensing applications.

Enhanced oxygen reduction reaction performance of nitrogen-doped carbon nanocages

Microwave plasma chemical vapor deposition (MPCVD) technique was successfully applied to fabricate Nitrogen-doped carbon nanocages (NCNCs) with doping content of 2.94 at.%. The NCNCs treated by HNO3 were characterized by TEM, XPS and Raman technique respectively. The rotating disk electrode voltammetry was used to estimate the oxygen reduction reaction (ORR) performance of nanocages in O2-saturated 0.1 M KOH electrolyte. Our results show that NCNCs possess not only electrocatalytic property comparable to those of commercial Pt/C catalyst, but also higher resistance to methanol crossover and better long-term stability than those of Pt/C. Therefore, NCNCs can be regarded as a very prominent alternative for Pt catalyst in ORR area.