C.T. Kuo

Crystalline SiCN: a hard material rivals to cubic BN

Abstract Growth and mechanical properties of SiCN materials prepared by microwave plasma enhanced chemical vapor deposition (CVD) as well as electron cyclotron resonance plasma CVD are reported. Large (several tens of microns), well-faceted ternary SiCN crystals were grown by microwave plasma-enhanced chemical vapor deposition, whereas amorphous SiCN films were deposited by ECR-CVD. The ternary crystalline compound (C; Si)xNy exhibits a hexagonal structure and consists of a network wherein the Si and C are substitutional elements. While the N content of the crystalline compound is about 50 at.%, the extent of Si substitution varies and can be as low as 10 at.%. The amorphous SiCN films contain only about 30 at.% N. Nano-indentation studies were employed to investigate the mechanical properties of the SiCN materials. From the load versus displacement curves, we estimated the hardness and the effective modulus of the SiCN crystals to be around 30 and 321.7 GPa, respectively. The corresponding values for the amorphous SiCN were around 22 and 164.4 GPa, respectively. These values are well above most reported values for CN films.

Deposition of silicon carbon nitride films by ion beam sputtering

Abstract Silicon carbon nitride films have been successfully synthesized at a temperature below 100°C from an adenine(C5N5H5)-silicon-mixed target sputtered by Ar ion beam. The effects of Ar ion sputtering voltage, area ratio of Si to adenine in the mixed target and nitrogen atom addition during deposition on the film growth are investigated. XPS, XRD, and ellipsometry were employed to characterize the composition, chemical bonding, structure, and optical property of the films. The growth characteristic and film properties of the silicon carbon nitride films are also compared with those of the carbon nitride films deposited from an adenine target to elucidate the effect of silicon incorporation. The silicon content of the resultant films increased significantly as the area ratio of Si to adenine increased, whereas a higher Ar ion voltage led to a lower level of silicon incorporation, presumably due to differential sputtering yield of Si and adenine. XPS chemical state analysis revealed multiple bonding structures for every element in the SiCN films, of which possible implications are given. XRD studies showed that only amorphous films for Si-rich SiCN were obtained, while the films with low Si incorporation and deposited at high Ar ion beam voltage contained nanocrystallites. Furthermore, the refractive index of the SiCN films increased with increasing silicon content. The appearance of the nanocrystalline structure in the films led to a reduction in the refractive index.

High purity nano-crystalline carbon nitride films prepared at ambient temperature by ion beam sputtering ☆

High purity nano-crystalline carbon nitride films have been successfully deposited by ion beam sputtering. A novel bio-molecular C-N compound, 6-aminopurine, of which the characteristic features include covalent C-N bonding, high N/C ratio and a six-membered ring structure similar to that in the hypothetical C 3 N 4 crystal, has been employed as the target material. The films can be deposited onto a variety of substrates, such as copper, silver, stainless steel, nickel and silicon wafer at ambient temperature. SAM examination indicates a high nitrogen-to-carbon ratio at about 0.51. XPS, IR and Raman studies reveal that the chemical bonding structures consist mainly of sp 3 -hybridized carbon as well as sp 2 -hybridized nitrogen and carbon. Both TEM and SAM mapping investigations indicate that the film contains a very dense and homogenous distribution of nano-crystalline grains. However, the structures of these crystals are yet to be determined since their TEM diffraction patterns only matched partially with the calculated pattern for β-C 3 N 4 .

Wear behaviour of various diamond-coated cutting tools under different deposition conditions

Abstract A hot-filament-assisted chemical vapour deposition system was used to deposit diamond films on cemented carbide cutting tools with Co contents ranging from 6% to 22%. The surface roughness and friction coefficient of the films were measured under different deposition conditions. A block-on-ring tribotester and scanning electron microscopy were adopted to characterize the tribological behaviour and the film morphology. The results indicate that the cutting performance of the diamond-coated tools is closely related to the friction coefficient and surface roughness of the film and that the friction coefficient is a function of the surface roughness and film quality. For the 6% Co substrate the film deposited under 0.5% CH4 concentration shows the best film quality and the lowest friction coefficient and its surface roughness is within the optimum range 0.06-0.25 μm; therefore it shows better cracking resistance and wear resistance.