Single-layer Diamond Research Articles

Enhanced field emission characteristics of WS2 nano-films by diamond film and Mo film

WS2 is a type of transition metal chalcogenide materials (TMDCs) that exhibits exceptional photoelectric properties. Due to its atomically sharp edges, WS2 has the capability to enhance the electric field around its edges, thus presenting significant potential in field emission applications. In this study, the electron beam vapor deposition (EBVD) system and microwave plasma chemical vapor deposition (MPCVD) system were used to prepare a series of single-layer WS2 films，single-layer diamond films and diamond/WS2 nano-composite films on N-type highly doped Si substrate, and Mo/WS2 nano-composite films were prepared on Al2O3 ceramic substrate. Based on the characterization and analysis of the microstructure and chemical composition of each thin film layer in the above film devices, the field emission (FE) characteristics of each thin film device are compared and studied. The results demonstrate that the maximum FE current density of diamond/WS2 nano-composite film device is 912 μA/cm2, which is 2.7 times of the maximum FE current density of Mo/WS2 nano-composite film device 330 μA/cm2, and 3.4 times of the maximum FE current density of the single-layer diamond thin film device 267 μA/cm2. The single layer WS2 film did not exhibit measurable FE performance. The working principles of thin film field emission devices with various structures are introduced. It is considered that the diamond layer plays the role of electron accelerating layer, which not only effectively improves the FE characteristics of diamond/WS2 nanocomposite film, but also improves the repeatability and long-term stability of diamond/WS2 nanocomposite film FE devices.

Development of a novel bulk metallic glass bonded single-layer diamond wheel

A novel manufacturing process was employed to develop a single-layer diamond wheel using bulk metallic glass (BMG) as the matrix and diamond particles as abrasives. BMG effectively prevented graphitisation and damage to the diamond abrasives because of its lower manufacturing temperature and avoidance of brazing flux. The Titanium (Ti) coating on the surface of diamond abrasives facilitated the formation of an interleaved dissolution-diffusion interface between the two constituents, creating mechanical occlusion at the BMG-diamond interface. The strong and tight bonding interface afforded a diamond abrasive joint strength of up to 112.59 N, with the main shear failure mode being transgranular fracture instead of pull-off failure. Furthermore, the manufactured BMG-bonded single-layer diamond wheel predominantly exhibited attritious wear instead of the exfoliation of abrasives when grinding Al2O3 ceramics. Compared with contemporary electroplated grinding wheels, the developed diamond wheel demonstrated a reduction in the normal and tangential grinding forces of 32.64% and 35.86%, respectively, and a 28.22% increase in the grinding ratio, making it an excellent candidate for grinding hard and brittle materials.

Performance of patterned single-layer diamond grinding wheel in grinding of Al-SiCP composites with large infeed

Performance of patterned single-layer diamond grinding wheel in grinding of Al-SiCP composites with large infeed

Analysis of the vibrational characteristics of diamane nanosheet based on the Kirchhoff plate model and atomistic simulations

Single layer diamond—diamane, has been reported with excellent mechanical properties. In this work, molecular dynamics (MD) simulation and Kirchhoff plate model are utilized to investigate the vibrational characteristics of diamane sheets. The mechanical parameters of diamane sheets, including bending stiffness, Young’s modulus, Poisson’s ratio and coefficient of thermal expansion, are calibrated by using MD simulations. The natural frequencies and corresponding modal shapes of the diamane sheets predicted by the Kirchhoff plate model agree well with that obtained from the MD simulations. It is found that the edges exert marginal effect on the modal shapes when free boundary conditions are applied. Additionally, the Kirchhoff plate model considering the thermal expansion provides reasonable prediction for the natural frequencies of the diamane sheets with all boundary clamped under varying temperatures. This study offers valuable insights into the vibrational properties of diamane sheets, from both a simulation and theoretical standpoint. The findings would be beneficial for the design of nanoscale mechanical resonators utilizing these novel carbon materials.

Hot-filament CVD diamond coatings for optical applications

The demand for highly scratch resistant transparent coatings is motivated by the industrial sector of consumer goods for example for the protection of displays, touch-screens, watches, and all kinds of optical instruments. In a wide variety of applications, scratch-free and highly wear-resistant surfaces are the enabling factor for improvement of lifetime and thus sustainability of the products. Diamond with its unique properties such as the highest known hardness, low thermal expansion coefficient and chemical resistance (to acids and bases) [1,2] has outstanding potential for optical applications [3]. The use of thin ultrahard diamond layers with adapted optical properties is expected to enhance the resistance against abrasive wear to a new level. At Fraunhofer IST large-area Hot-Filament Chemical Vapor Deposition (HFCVD) processes have been developed [4,5] and now utilized for depositing highly uniform and transparent diamond coatings on optical components with sizes of up to 200 mm × 200 mm. The use of single-layer diamond coatings is investigated as well as the integration of diamond films into multilayer film stacks combining anti-reflective properties with mechanical stability (strength). Four-layer anti-reflective coatings (Si3N4/SiO2/Diamond/SiO2) entirely deposited with hot-filament/hot-wire processes and their optical and mechanical performance will be presented.

First principles study on thermal conductivity of nitrogen substituted diamane

2D materials have been in the spotlight due to their impressive properties since graphene was successfully synthesized. A single-layered diamond or diamane, which has high thermal conductivity and high stiffness inherited from its bulk counterpart, is a candidate for heat dissipating applications in nanodevices. Unfortunately, non-passivated dangling bonds on the surface of pristine diamane can cause its structural instability. Recent theoretical studies have suggested that site-specific substitution of N for C could stabilize the diamane’s structure without surface termination. Beside its superhard properties inherited from bulk carbon nitrides, thermal properties of N-substituted diamane have not been revealed. In this work, we investigate thermal properties of N-substituted diamane through first principles study. Our results show that there is an emergence of flexural phonon branch, which is regularly seen in 2D materials, and it contributes large thermal conductivity to N-substituted diamane. The thermal conductivity of N-substituted diamane is decreasing as the temperature increasing. At room temperature, it is 33% lower than that of diamond and 15-35% higher than that of hydrogen passivated diamane (H-diamane).

Active laser brazing of diamond onto 45 steel: Diamond flow behavior, microstructure and bonding strength

The paper investigated the influence of an active agent on the distribution and bonding properties of laser brazed abrasive particles experimentally in fabricating a diamond tool. In the design of experiments, fiber laser brazing was applied to make a single-layer diamond tool, 45 steel was used as a substrate, Cr2O3 was used as an active agent, and Ni-Cr alloy was used as a filler metal. The advantages of active laser brazing(A-LB) and conventional laser brazing (LB) are compared and analyzed from the aspects of flow behavior and mechanical properties. The experimental findings demonstrate that the molten metal flowing to the central will cause the diamond particles in A-LB to flow to the central of the molten pool. The diamond and Ni-Cr interface on the A-LB specimen is roughly 10 μm broader than on the LB. A-LB has a higher single particle shear strength than LB. Additionally, the sample of A-LB has superior wear resistance.

Configuration stability and electronic properties of diamane with boron and nitrogen dopants

The structural stability and electronic properties of N-doped and B-N-codoped cubic and hexagonal diamane (single-layer diamond) were investigated based on first-principles methods. The N atom tends to stay in the substitutional site rather than the interstitial site, and the most stable configuration is the structure where the N atom is located at the external substitutional site without H saturation. The B and N atoms codoped in diamane tend to gather to form a covalent bond, where N is saturated by H, since the stability of a lone pair of electrons in N is reduced by the B dopant. Moreover, B and N dopants can adjust the bandgap (0--3.52 eV) and reduce the formation energy (FE) of diamane to promote its synthesis. The formation energies of N-doped diamane are not sensitive to N distributions, and diamane containing a vertical B-N bond has the lowest FE due to the attraction between the N-dopant-induced electron and the B-dopant-induced hole.

Phonon propagation in isotopic diamond superlattices

The out-of-plane thermal conductivity and elastic constant of epitaxial [100] $^{12}\mathrm{C}/^{13}\mathrm{C}$ superlattice diamonds with layer thicknesses of 1, 30, and 100 nm are evaluated by picosecond ultrasound spectroscopy. The measured elastic constants of the superlattices are equivalent to those of single-layer diamond thin films. This result confirms our success in synthesizing superlattice specimens with few defects at the interfaces. Therefore, the phonon transport behavior is governed by the mass difference, not the interfacial defects. The measured thermal conductivity of the superlattices is lower than that of a pure $^{12}\mathrm{C}$ isotope diamond thin film. We estimated the lattice thermal conductivity using the lattice dynamics calculation, attributing the lowered thermal conductivity to the decrease in the phonon group velocity in superlattices. We further consider the effect of mini-umklapp scattering in the superlattice, which explains the dependence of the thermal conductivity on the layer thickness. We reveal that the mini-umklapp scattering effect becomes significant only for an isotope diamond superlattice because of the high Debye temperature and large relative mass difference.

Outstanding elastic, electronic, transport and optical properties of a novel layered material C4F2: first-principles study.

Motivated by very recent successful experimental transformation of AB-stacking bilayer graphene into fluorinated single-layer diamond (namely fluorinated diamane C4F2) [P. V. Bakharev, M. Huang, M. Saxena, S. W. Lee, S. H. Joo, S. O. Park, J. Dong, D. C. Camacho-Mojica, S. Jin, Y. Kwon, M. Biswal, F. Ding, S. K. Kwak, Z. Lee and R. S. Ruoff, Nat. Nanotechnol., 2020, 15, 59–66], we systematically investigate the structural, elastic, electronic, transport, and optical properties of fluorinated diamane C4F2 by using density functional theory. Our obtained results demonstrate that at the ground state, the lattice constant of C4F2 is 2.56 Å with chemical bonding between the C–C interlayer and intralayer bond lengths of about 1.5 Å which are close to the C–C bonding in the bulk diamond. Based on calculations for the phonon spectrum and ab initio molecular dynamics simulations, the structure of C4F2 is confirmed to be dynamically and thermally stable. C4F2 exhibits superior mechanical properties with a very high Young's modulus of 493.19 N m−1. Upon fluorination, the formation of C–C bonding between graphene layers has resulted in a comprehensive alteration of electronic properties of C4F2. C4F2 is a direct semiconductor with a large band gap and phase transitions are found when a biaxial strain or external electric field is applied. Interestingly, C4F2 has very high electron mobility, up to 3.03 × 103 cm2 V−1 s−1, much higher than other semiconductor compounds. Our findings not only provide a comprehensive insight into the physical properties of C4F2 but also open up its applicability in nanoelectromechanical and optoelectronic devices.

Liquid-phase exfoliation of F-diamane-like nanosheets

Fluorinated single-layer diamond (“F-diamond”) is a new form of two-dimensional (2D) carbon allotrope. Herein, poly(dicarbon monofluoride) (C2F)n which is essentially made of stacked layers of “F-diamane” has been synthesized and exfoliated in a variety of solvents to yield well-dispersed ultrathin sheets. Microscopic and spectroscopic analyses revealed that the exfoliated nanosheets retained the “F-diamane”-like structure. The experimental results are also supported by density functional theory (DFT) calculations.

Mechanical Properties of a Single-Layer Diamane under Tension and Bending

Based on atomistic simulations, we investigated the mechanical properties of a single-layer diamond—diamane under tensile and bending deformation. It is found that the layer stacking sequence exert...

Roles of nitrogen substitution and surface reconstruction in stabilizing nonpassivated single-layer diamond

Single-layer diamond or diamane is substituted by N atoms assisting the diamond-like structure to be stabilize without any passivation. One fourth of N substitution in diamane, vertically stacking as NCCC, is found to be stable by surface reconstruction forming Pandey $\pi$ chain structure and has an antiferromagnetic property. Half N substitution in diamane, vertically stacking as NCCN can be stable and prevails the diamane form. Its elastic constants yield high values, for example, its $C_{11}$ is as twice as diamond and its $C_{33}$ is only 21\% lower than diamond. The NCCN phase is a metastable phase at 10 GPa compared with other layered carbon nitride phases showing the possible pathway to be created.

Single layer diamond - A new ultrathin 2D carbon nanostructure for mechanical resonator

The single layer diamond – diamane, a two-dimensional (2D) form of diamond with a bilayer sp3 carbon nanostructure, has been initially predicted in 2009, while its experimental synthesis has only been reported very recently. This work carries out a comprehensive study on the vibrational properties of diamane nanoribbon (DNR) targeting the ultra-sensitive sensing applications. Based on in silico studies, it is found that the DNR resonator possesses a higher natural frequency and a large quality factor (Q-factor) on the order of 105 higher than those of a bilayer nanoribbon resonator. Under pre-tensile strain, the natural frequency of the DNR resonator receives a remarkable increase and its Q-factor maintains a high magnitude yielding to an extremely high figure of merit on the order of 1015. It is further found that the randomly distributed surface hydrogenation exerts negligible influence on the vibrational properties of the DNR resonator. However, an unevenly distributed hydrogenation results in out-of-plane deformation and significantly changes its vibrational properties. It is additionally found that the stacking configuration of the diamane leads to negligible influence on its vibrational properties. This study reveals that the DNR resonator has excellent vibrational properties, which are promising for the construction of ultra-sensitive resonator-based sensors.

Synthesizing single-layer diamond

Thin Films The carbon allotropes of diamond and graphene have different types of bonding that lead to their exceptional properties. Bakharev et al. pull off the impressive trick of making a monolayer carbon film that is diamond-like in its bonding. The authors accomplish this by attaching fluorine atoms to the carbon film, creating “F-diamane.” Diamane is a long-sought-after, but challenging to make, material that should have useful properties. F-diamane may find use in a variety of applications, from microelectronics as a semiconductor to a seed material for growing single-crystal diamond films. Nat. Nanotechol. 15 , 59 (2020).

Boron-dopant enhanced stability of diamane with tunable band gap

The structural, electronic, and superconducting properties of B-doped cubic and hexagonal diamane (single layer diamond) were investigated based on the first-principles methods. B atom tends to stay in the substitutional site, and the most stable configuration is the structure with vertical B–B dimer. The formation energy of B-doped diamane is lower than the counterpart of pristine diamane indicating that B dopant can facilitate the synthesis of diamane. The configurations with vertical B–B dimers are semiconductors with tunable band gaps, which decrease with the B concentration increasing due to the interaction between B–B dimers. For example, the band gap of 3.125 mol% and 6.25 mol% B-doped cubic diamane is 1.82 eV and 1.44 eV, respectively. Moreover, configurations with meta-stable B distributions are metals, which have comparable superconducting transition temperatures with B-doped diamond (~4 K).

High elastic moduli, controllable bandgap and extraordinary carrier mobility in single-layer diamond

Fluorinated single layer diamond is found by first-principles calculations to be a wide-direct bandgap material at the Γ-point, exhibiting a high mechanical strength, adjustable electronic properties and extraordinary carrier mobility at room temperature.

Chemically induced transformation of chemical vapour deposition grown bilayer graphene into fluorinated single-layer diamond.

Notwithstanding the numerous density functional studies on the chemically induced transformation of multilayer graphene into a diamond-like film carried out to date, a comprehensive convincing experimental proof of such a conversion is still lacking. We show that the fluorination of graphene sheets in Bernal (AB)-stacked bilayer graphene grown by chemical vapour deposition on a single-crystal CuNi(111) surface triggers the formation of interlayer carbon-carbon bonds, resulting in a fluorinated diamond monolayer ('F-diamane'). Induced by fluorine chemisorption, the phase transition from (AB)-stacked bilayer graphene to single-layer diamond was studied and verified by X-ray photoelectron, UV photoelectron, Raman, UV-Vis and electron energy loss spectroscopies, transmission electron microscopy and density functional theory calculations.

Mechanical properties and wear behavior of multi-layer diamond films deposited by hot-filament chemical vapor deposition

Diamond films were deposited on cobalt-cemented tungsten carbide (WC-Co) by Hot-Filament Chemical Vapor Deposition (HFCVD). The mechanical properties and wear behavior of single-layer and multi-layer diamond films were compared, based on the difference of diamond crystal formation and internal structure. Adhesive failure modes and critical loads, post-scratch tests, were identified according to the applied load, acoustic emission and friction force. For single-layer diamond films, the samples produced with lower CH4 concentration evidence columnar crystal diamond structure, which exhibit better adhesive properties. The samples produced with 5% CH4 exhibit the lowest hardness, however, due to their higher crystallinity and nucleation density, they exhibit higher toughness. The multi-layer diamond film with 300 nm alternate thickness per interlayer shows the highest critical delamination load (23.22 N). Concerning the multi-layer diamond films, the hardness and Young's modulus increases from 84.13 to 94.01 GPa and 788.65 to 936.26 GPa, respectively, with the alternate thickness change from 100 nm to 600 nm per layer, which indicates that thicker alternate layers lead to higher hardness and toughness. The wear behavior of the nano-crystalline (NCD) single-layer diamond films is potentially related to the less adequate adhesive abilities to the substrate material.

Machining performance of hard-brittle materials by multi-layer micro-nano crystalline diamond coated tools

Abstract Single layer diamond coatings, deposited on cobalt cemented tungsten carbide (WC-Co), with CH4 concentrations of 1%, 3% and 5% were prepared, by hot filament chemical vapor deposition (HFCVD). Moreover, according to the characteristics of different kinds of diamond structure, observed on the single layer coatings, multi-layer crystalline diamond films with micro-nano structures (composed of the 1% and 5%-type coatings) were prepared. The objective was to cumulate the increased interfacial adhesion and mechanical properties of each single layer diamond coating, into one multilayer coating, capable of resisting the efforts present between a milling tool and a hard-brittle material (natural marble). The coating morphology, structure, and resistance to crack propagation of the diamond films were evaluated. Furthermore, cutting tests with diamond-coated tools were performed, while observing the machining life and wear mechanism, on a hard-brittle material (marble). The results on the single layers showed that with the increase of the concentration of CH4, the adhesion to the WC-Co substrate, as well as the resistance to crack propagation is decreasing. The multilayer coating structure shows benefits from the single layer coatings, i.e. improved adhesion to the substrate and inhibition of crack propagation, while the tool life and machining stability are significantly better than the single diamond layer coated tools.