František Fendrych

Growth and characterization of nanodiamond layers prepared using the plasma-enhanced linear antennas microwave CVD system

Industrial applications of plasma-enhanced chemical vapour deposition (CVD) diamond grown on large area substrates, 3D shapes, at low substrate temperatures and on standard engineering substrate materials require novel plasma concepts. Based on the pioneering work of the group at AIST in Japan, the high-density coaxial delivery type of plasmas has been explored (Tsugawa et al 2006 New Diamond Front. Carbon Technol. 16 337–46). However, an important challenge is to obtain commercially interesting growth rates at very low substrate temperatures. In this work we introduce the concept of novel linear antenna sources, designed at Leybold Optics Dresden, using high-frequency pulsed MW discharge with a high plasma density. This type of pulse discharges leads to the preparation of nanocrystalline diamond (NCD) thin films, compared with ultra-NCD thin films prepared in (Tsugawa et al 2006 New Diamond Front. Carbon Technol. 16 337–46). We present optical emission spectroscopy data for the CH4–CO2–H2 gas chemistry and we discuss the basic properties of the NCD films grown.

The mechanical, tribological and optical properties of Ti-C:H coatings, prepared by DC magnetron sputtering☆

Abstract The aim of this work was to determine the correlations between the growth parameters of diamond-like coatings with small amount of titanium (from 10 to 20 at.%) prepared by d.c. magnetron sputtering of the Ti target in a CH4+Ar gas mixture and their mechanical, tribological and optical properties. The composition, microhardness, internal stress, friction coefficient, adhesion and optical properties (Eg, n, k) dependent on methane flow rate, substrate bias and interlayer formation were studied. It was found that the optical properties of Ti-C:H films (Eg, n, k) monotonically approach those for C:H films when the titanium concentration is decreased. This enables us to consider Ti-C:H film as a-C:H film with TiC inclusions, when the Ti concentration is low. An increase in the negative substrate bias voltage to −100 V leads to a considerable increase in layer microhardness, with a slight decrease at a further bias increase to −200 V. The internal stresses are decreased under the same conditions due to the substrate temperature growth. The best coatings had friction coefficients 0.12–0.15, microhardness 14–18 kN/mm2 and demonstrated elastic behaviour and good adhesion. The nature and correlation of these properties are discussed.

The mechanical, tribological and optical properties of CNx coatings prepared by sputtering methods

Abstract CNx coatings were prepared by DC magnetron sputtering at different N2 pressures. Increase of N2 pressure led to the increase of nitrogen content N/C in the films, but decreased their microhardness. Evaluation of optical properties and electron-energy-loss function combining spectroscopic ellipsometry (1.5–4 eV) and VUV reflection spectroscopy (4–14 eV) by means of Kramers-Kronig analysis showed increase of the π-plasmon resonance peak, which indicates enhancement of the amount of π-bonded electrons. It demonstrates increase of sp2 hybridization. The extrapolated energy gap indicates more semimetallic properties of the CNx films due to nitrogenation.

Epithelial cell morphology and adhesion on diamond films deposited and chemically modified by plasma processes

The authors show that nanocrystalline diamond (NCD) thin films prepared by microwave plasma enhanced chemical vapor deposition apparatus with a linear antenna delivery system are well compatible with epithelial cells (5637 human bladder carcinoma) and significantly improve the cell adhesion compared to reference glass substrates. This is attributed to better adhesion of adsorbed layers to diamond as observed by atomic force microscopy (AFM) beneath the cells. Moreover, the cell morphology can be adjusted by appropriate surface treatment of diamond by using hydrogen and oxygen plasma. Cell bodies, cytoplasmic rims, and filopodia were characterized by Peakforce AFM. Oxidized NCD films perform better than other substrates under all conditions (96% of cells adhered well). A thin adsorbed layer formed from culture medium and supplemented with fetal bovine serum (FBS) covered the diamond surface and played an important role in the cell adhesion. Nevertheless, 50-100 nm large aggregates formed from the RPMI medium without FBS facilitated cell adhesion also on hydrophobic hydrogenated NCD (increase from 23% to 61%). The authors discuss applicability for biomedical uses.

The influence of deposition conditions on the growth and mechanical properties of CNxHy films obtained by ECR plasma-activated CVD

Abstract The effects of the main deposition parameters: (1) microwave power (Pw); (2) nitrogen content in a CH4-N2 gas mixture (%N2): and (3) RF-substrate bias (UF) on the growth rate Vg, nitrogen concentration N:C, microhardness H, friction coefficient K and wear resistance of CNxHy, films, deposited by ECR plasma-enhanced CVD, are reported. The plots of Vg versus UF a and N:C versus UF h have peaks at certain values of UF. The maximal values of N:C and Vg of about 0.2 and 1.2 nm s1, respectively, for CNxHy films were obtained. The microhardness of the film increased with the increase of parameter J∼ UF × (%N2), while the influence of nitrogen concentration in the film on its microhardness and tribological properties was not revealed. The microhardness derived from nanoindentation measurements was in the range 3700–7000 N mm2 depending on deposition conditions; the friction coefficient was 0.08–0.4 depending on measuring technique (scratch test or ball-on-disk test) and deposition parameters. Ball-on-disk tests revealed relativly high wear resistance of the best samples at a 5 N normal load. An increase of the load to 20 N noticeably resulted in an increase in the wear. The main factor which greatly influenced CNxHy film properties and the growth mechanisms was the ion bombardment of the film during the growth process.

Nanocrystalline diamond protects Zr cladding surface against oxygen and hydrogen uptake: Nuclear fuel durability enhancement

In this work, we demonstrate and describe an effective method of protecting zirconium fuel cladding against oxygen and hydrogen uptake at both accident and working temperatures in water-cooled nuclear reactor environments. Zr alloy samples were coated with nanocrystalline diamond (NCD) layers of different thicknesses, grown in a microwave plasma chemical vapor deposition apparatus. In addition to showing that such an NCD layer prevents the Zr alloy from directly interacting with water, we show that carbon released from the NCD film enters the underlying Zr material and changes its properties, such that uptake of oxygen and hydrogen is significantly decreased. After 100–170 days of exposure to hot water at 360 °C, the oxidation of the NCD-coated Zr plates was typically decreased by 40%. Protective NCD layers may prolong the lifetime of nuclear cladding and consequently enhance nuclear fuel burnup. NCD may also serve as a passive element for nuclear safety. NCD-coated ZIRLO claddings have been selected as a candidate for Accident Tolerant Fuel in commercially operated reactors in 2020.

Fluorescent Nanodiamonds: Effect of Surface Termination

It has been reported that physico-chemical properties of diamond surfaces are closely related to the surface chemisorbed species on the surface. Hydrogen chemisorption on a chemical vapor deposition grown diamond surface is well-known to be important for stabilizing diamond surface structures with sp 3 hybridization. It has been suggested that an H-chemisorbed structure is necessary to provide a negative electron affinity condition on the diamond surfaces. Negative electron affinity condition could change to a positive electron affinity by oxidation of the Hchemisorbed diamond surfaces. Oxidized diamond surfaces usually show characteristics completely different from those of the H-chemisorbed diamond surfaces. The unique electron affinity condition, or the surface potential, is strongly related to the chemisorbed species on diamond surfaces. The relationship between the surface chemisorption structure and the surface electrical properties, such as the surface potential of the diamond, has been modelled using DFT based calculations.

Novel concepts for Low-pressure, Low-temperature Nanodiamond Growth using MW Linear Antenna Plasma Sources

Industrial applications of PE MWCVD diamond grown on large area substrates, 3D shapes, at low substrate temperatures and on standard engineering substrate materials require novel plasma concepts. Based on the pioneering work of the group at AIST in Japan, highdensity coaxial delivery type of plasmas have been explored [1]. However, an important challenge is to obtain commercially interesting growth rates at very low substrate temperatures. In the presented work we introduce the concept of novel linear antenna sources, designed at Leybold Optics Dresden, using high-frequency pulsed MW discharge. We present data on high plasma densities in this type of discharge (> 10 E11 cm-3), accompanied by data from OES for CH 4 – CO 2 - H 2 gas chemistry and the basic properties of the nano-crystalline diamond (NCD) films grown.

Surface potential of functionalised nanodiamond layers

Carbon nanomaterials especially ultrananocrystalline diamond and nanocrystalline diamond films have attracted more and more interest due to their unique electrical, optical and mechanical properties, which make them widely used for different applications (e.g. MEMS devices, lateral field emission diodes, biosensors and thermoelectrics). Nanocrystalline diamond can also offer novel advantages for drug delivery development. Recent studies have begun to use nanocrystalline diamond for in-vivo molecular imaging and bio-labeling. To enable grafting of complex bio-molecules (e.g. DNA) the surface of ND requires specific fictionalization (e.g. H, OH, COOH & NH 2). Due to the surface dipoles of functionalised nanodiamond band bending at the surface can be easily induced and from the measured band bending we can deduce the type of the fictionalization on the surface. The surface potential of H-terminated and OH terminated nanodiamond layers was investigated by Kelvin probe microscope. From the change of the surface potential value (as the departure of the material surface from the state of electrical neutrality is reflected in the energy band bending) the work function of the H-terminated nanodiamond layer was established to be lower than OH-terminated nanodiamond layer. The surface potential difference can be explained by the surface dipole induced by the electronegativity difference between the termination atoms.