Cytotoxicity of Boron-Doped Nanocrystalline Diamond Films Prepared by Microwave Plasma Chemical Vapor Deposition

Boron-doped nanocrystalline diamond（NCD） exhibits extraordinary mechanical properties and chemical stability,making it highly suitable for biomedical applications.For implant materials,the impact of boron-doped NCD films on the character of cell growth（i.e.,adhesion,proliferation） is very important.Boron-doped NCD films with resistivity of 10-2Ω·cm were grown on Si substrates by the microwave plasma chemical vapor deposition（MPCVD） process with H2 bubbled B2O3.The crystal structure,diamond character,surface morphology,and surface roughness of the boron-doped NCD films were analyzed using different characterization methods,such as X-ray diffraction（XRD）,Raman spectroscopy,scanning electron microscopy（SEM） and atomic force microscopy（AFM）.The contact potential difference and possible boron distribution within the film were studied with a scanning kelvin force microscope（SKFM）.The cytotoxicity of films was studied by in vitro tests,including fluorescence microscopy,SEM and MTT assay.Results indicated that the surface roughness value of NCD films was 56.6 nm and boron was probably accumulated at the boundaries between diamond agglomerates.MG-63 cells adhered well and exhibited a significant growth on the surface of films,suggesting that the boron-doped NCD films were non-toxic to cells.

Catalyst-Free Growth of Graphene by Microwave Surface Wave Plasma Chemical Vapor Deposition at Low Temperature

Catalyst-free graphene films has been synthesized by microwave (MW) surface wave plasma (SWP) chemical vapor deposition (CVD) using hydrogenated carbon source on silicon substrates at low temperature (500℃). The synthesized process is simple, low-cost and possible for application on transparent electrodes, gas sensors and thin film resistors. Analytical methods such as Raman spectroscopy, transmission electron microscopy (TEM) and four points prove resistivity measurement and UV-VIS-NIR spectroscopy were employed to characterize properties of the graphene films. The formation of multilayer of graphene on silicon substrate was confirmed by Raman spectroscopy and TEM. It is possible to grow graphene directly on silicon substrate (without using catalyst) due to high radical density of MW SWP CVD. In addition, we also observed that the hydrogen had significant role for quality of graphene.

Growth of mirror-like ultra-nanocrystalline diamond(UNCD)films by a facile hybrid CVD approach

In this study, growth of mirror-like ultra-nanocrystalline diamond（UNCD） films by a facile hybrid CVD approach was presented. The nucleation and deposition of UNCD films were conducted in microwave plasma CVD（MPCVD） and direct current glow discharge CVD（DC GD CVD） on silicon substrates, respectively. A very high nucleation density（about 1×10^11 nuclei cm^-2） was obtained after plasma pretreatment. Furthermore, large area mirrorlike UNCD films of Φ 50 mm were synthesized by DC GD CVD. The thickness and grain size of the UNCD films are 24 μm and 7.1 nm, respectively. In addition, the deposition mechanism of the UNCD films was discussed.

High-Rate Growth and Nitrogen Distribution in Homoepitaxial Chemical Vapour Deposited Single-crystal Diamond

High rate （〉 50 μm/h） growth of homoepitaxial single-crystal diamond （SCD） is carried out by microwave plasma chemical vapour deposition （MPCVD） with added nitrogen in the reactant gases of methane and hydrogen, using a polyerystalline-CVD-diamond-film-made seed holder. Photolumineseenee results indicate that the nitrogen concentration is spatially inhomogeneous in a large scale, either on the top surface or in the bulk of those as-grown SCDs. The presence of N-distribution is attributed to the facts： （i） a difference in N-incorporation efficiency and （ii） N-diffusion, resulting from the local growth temperatures changed during the high-rate deposition process. In addition, the formed nitrogen-vacancy eentres play a crucial role in N-diffusion through the growing crystal. Based on the N-distribution observed in the as-grown crystals, we propose a simple method to distinguish natural diamonds and man-made CVD SCDs. Finally, the disappearance of void defect on the top surface of SCDs is discussed to be related to a filling-in mechanism.

Effects of Surface Pretreatment on Nucleation and Growth of Ultra-Nanocrystalline Diamond Films

The effects of different surface pretreatment nmthods on the nucleation and growth of ultra-nanocrystalline diamond （UNCD） fihns grown from focused microwave Ar/CHa/H2 （argon- rich） plasma were systematically studied. The surface roughness, nucleation density, mierostruc- ture, and crystallinity of the obtained UNCD films were characterized by atomic force microscope （AFM）, scanning electron microscopy （SEM）, X-ray diffraction （XRD）, and Raman spectroscopy. The results indicate that the nucleation enhancement was found to be sensitive to the different sur- face pretreatment methods, and a higher initial nucleation density leads to highly smooth UNCD films. When the silicon substrate was pretreated by a two-step method, i.e., plasma treatment followed by ultrasonic vibration with diamond nanopowder, the grain size of the UNCD films was greatly decreased： about 7.5 nm can be achieved. In addition, the grain size of UNCD films depends on the substrate pretreatment methods and roughness, which indicates that the surface of substrate profile has a ＂genetic characteristic＂.

Direct Synthesis of Graphene on Silicon at Low Temperature for Schottky Junction Solar Cells

Graphene thin films synthesized directly at low temperature (550˚C) on silicon substrate by microwave (MW) surface wave plasma (SWP) chemical vapor deposition (CVD) using the cover on substrates for avoiding plasma emission ultraviolet ray’s effect during film deposition. Analytical methods such as Raman spectroscopy, Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM), four-point probe method, and JASCO V-570 UV/VIS/NIR spectrophotometer were employed to characterize the properties of the graphene films. Here, we report that it is possible to grow graphene directly on the silicon substrate (without using catalyst) due to the high radical density of MW SWP CVD. Furthermore, we fabricated graphene/silicon Schottky junction solar cells with an efficiency of up to 6.39%. Compared to conventional silicon solar cells, the fabrication process is greatly simplified;just graphene is synthesized directly on n-type crystalline Si substrate at low temperate.

Preparation and characterization of nano-crystalline diamond films on glass substrate

Adherent nano diamond films were successfully deposited on glass substrate bymicrowave plasma assisted CVD method in H_2-CH_4 and Ar-CH_4 environment. Raman, AFM (Atomic ForceMicroscope), TEM (Transmission Electron Microscope), FTIR, and Nano Indentation techniques were usedfor characterization of the obtained nano diamond films. It was found that the average grain sizewas less than 100 nm with a surface roughness value as low as 2 nm. The nano diamond films werefound to have excellent transparency in visible and IR spectrum range, and were as hard as naturaldiamond. Experimental results were presented. Mechanisms for nano diamond film deposition werediscussed.

Growth behavior of CVD diamond films with enhanced electron field emission properties over a wide range of experimental parameters

In this study, diamond films were synthesized on silicon substrates by microwave plasma enhanced chemical vapor deposition（CVD） over a wide range of experimental parameters. The effects of the microwave power,CH;/H;ratio and gas pressure on the morphology, growth rate, composition, and quality of diamond films were investigated by means of scanning electron microscope（SEM）, X-ray diffraction（XRD）, Raman spectroscopy and X-ray photoelectron spectroscopy（XPS）. A rise of microwave power can lead to an increasing pyrolysis of hydrogen and methane, so that the microcrystalline diamond film could be synthesized at low CH;/H;levels. Gas pressure has similar effect in changing the morphology of diamond films, and high gas pressure also results in dramatically increased grain size. However,diamond film is deteriorated at high CH;/H;ratio due to the abundant graphite content including in the films. Under an extreme condition of high microwave power of 10 kW and high CH;concentration, a hybrid film composed of diamond/graphite was successfully formed in the absence of N;or Ar,which is different from other reports. This composite structure has an excellent measured sheet resistance of 10-100 Ω/Sqr. which allows it to be utilized as field electron emitter. The diamond/graphite hybrid nanostructure displays excellent electron field emission（EFE） properties with a low turn-on field of 2.17 V/μm and β= 3160, therefore it could be a promising alternative in field emission applications.