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Graphite-based metal transition-layer substrates hold great potential for preparing large-area diamond films and achieving crack-free release. In this study, a five-inch crack-free free-standing diamond film was prepared on a graphite substrate with a sacrificial Mo/Ti double-layer transition layer using direct-current arc plasma jet chemical vapor deposition (DC jet CVD). The interfacial bonding and diffusion behavior between the diamond and the transition layers were investigated. The effect of abundant metal particles and elemental diffusion between layers on film adhesion and stress release are discussed and analyzed. The surface of Ti layer prepared by the multi-arc ion-plating contains numerous metal particles that provide a template for the fine-crystalline Mo layer. Metal particles are encapsulated and embedded in the diamond and act as anchors that ensure the stability of the substrate–diamond bond during high-temperature deposition. After deposition, those metal particles act as weak points and play crucial stress-release roles. Mutual elemental diffusion occurs between the Ti, Mo, and diamond layers. Ti penetrates the Mo layer to form a continuous 140-nm-thick thin layer during the initial deposition period, facilitating diamond nucleation. Carbon from the plasma and diamond diffuses into the metal transition layer. Thermal stress generated between the diamond and the graphite substrate is released by destroying the metal transition layer with high thermal expansion coefficient and low elastic modulus during cooling from the deposition temperature. Cracks rapidly propagate along the interface between destroyable transition layers and graphite substrate, which results in the liftoff of a fully crack-free diamond film. [Display omitted] [ABSTRACT FROM AUTHOR]

Reducing the self-heating of SiC- and GaN/SiC-based high-powered devices by integrating diamond films offers promising performance enhancement of these devices. However, such a reduction strategy faces serious problems, such as diamond nucleation on SiC and stress accumulation greater than 10 GPa. In this work, a SiN x dielectric layer (∼50 nm) was coated onto the C polar face of a 4H–SiC wafer using microwave plasma chemical vapor deposition (MPCVD) to improve direct dense diamond nucleation and growth, significantly reduce the stress, and build Si–C(SiC)⋯Si⋯C(diamond) bond bridges. This SiN x thin layer, prepared by activating Si ions under Ar/N plasma during magnetron sputtering, gave rise to local Si 3 N 4 crystal features and a low effective work function (EWF) for promoting surface dipoles with electronegative carbon-containing groups. In the H plasma environment during diamond growth, the local Si 3 N 4 crystal was amorphized, and the N atoms escaped as a result of atomic H and the high temperature. At the same time, C atoms diffused into the SiN x and formed C–Si bonds (49.7% of the total C bonds) by replacing N–Si and Si–Si, thus increasing the direct nucleation density of the diamond grains. The diamond thin film grew rapidly and uniformly, with a grain size of approximately 2 μm in mixed orientation, and the stress of the 2-inch SiC-on-diamond wafer was extremely low (to ∼0.1–0.2 GPa). In comparison, partially connected diamond grains (>10 μm) on the bare SiC in the preferential (110) orientation resulted in a film with twin-grain features and significant stress, which was associated with the hexagonal lattice interface of 4H–SiC. These results are considered the material and surface/interface bases for actively controlling wafer fabrication and enhancing the heat dissipation of SiC and GaN/SiC electronics. [ABSTRACT FROM AUTHOR]

Electronic and mechanical properties, and their biocompatibility, make diamond-based materials promising biomedical applications. The cost required to produce high quality single crystalline diamond films is still a hurdle to prevent them from commercial applications, but the emergence of polycrystalline diamond (PCD) films grown by chemical vapour deposition (CVD) method has provided an affordable strategy. PCD films grown on silicon wafer have been used throughout and were fully characterised by SEM, XPS, Raman spectroscopy and FTIR. The samples contain nearly pure carbon, with impurities originated from the CVD growth and the silicon etching process. Raman spectroscopy revealed it contained tetrahedral amorphous carbon with small tensile stress. The sp2 carbon content, comprised between 16.1 and 18.8%, is attributed to the diamond grain boundaries and iron-catalysed graphitisation. Antibacterial properties of PCD films were performed with two model bacteria, i.e. Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) using direct contact and shaking flask methods. The samples showed strong bacteriostatic properties against S. aureus and E. coli with the direct contact method and no influence on planktonic bacterial growth. These results suggest that the bacteriostatic mechanism of PCD films is linked to their surface functional groups (carbon radicals and –NH 2 and –COOH groups) and that no diffusible molecules or components were involved. [ABSTRACT FROM AUTHOR]

[Display omitted] • The La-doped Er 2 O 3 anti-reflection films was prepared by the power of magnetron sputtering. • The compound of La 2 O 3 formed along the grain boundary of the columnar crystal structure of the polycrystalline film. • The highest hardness and yield strength of the La-doped Er 2 O 3 film was two times higher than that of pure Er 2 O 3 film. • The transmittance of the La-doped Er 2 O 3 anti-reflection films only decreased 1% after erosion. The composition and microstructure consisting of anti-reflection films was obtained by the power of magnetron sputtering. X-ray photoelectron spectroscopy (XPS) and High-resolution transmission electron microscopy (HRTEM) provided evidence to support that the doping La element exists as oxide in the grain boundaries of the matrix Er 2 O 3 films. The undoped and La-doped Er 2 O 3 films show a columnar crystal structure of the main cubic (2 2 2) plane. Twinning and a large number of dislocations show up in the undoped Er 2 O 3 films due to the competitive growth of the columnar crystal. In addition, the La-doped Er 2 O 3 films show a lower roughness (RMS) value in comparison with undoped Er 2 O 3 films. The grain size of columnar crystals decreases significantly with increasing La concentration in the La-doped Er 2 O 3 films. The fine grains resulted in the La-doped Er 2 O 3 films developing high mechanical and impact resistance properties, with an increase in hardness from 12.6 ± 2.1 GPa to 26.1 ± 3.4 GPa and the eroding area rate decreasing from 38.9 % to 1.9 %. Moreover, the La-doped Er 2 O 3 anti-reflection films on the chemical vapor deposition (CVD) diamond substrate maintained 74 % transmittance in the long-wavelength infrared range of 8–12 μm after sand eroding. [ABSTRACT FROM AUTHOR]