UDC 548.512

A. Glaser, S. M. Rosiwal (Nürnberg, Germany)

Chemical vapor infiltration of porous substrates with diamond by using a new designed hot-filament plant

We designed a new hot-filament plant which features some new operating states for chemical vapor infiltration with diamond. Complete infiltration of porous substrates with diamond by using standard hot filament plants is not possible. Chemical vapor infiltration with diamond is limited by the overgrowing diamond layer at the surface primarily caused by high recombination rates of atomic hydrogen on surfaces. As a consequence, the pore mouth is closed before the pore is completely infiltrated («bottleneck» effect). Porous substrates were infiltrated by using a forced flow through the substrate. In order to achieve good infiltration results, it was necessary to use very low methane concentrations.

UDC 548.5

J. Hirmke, S. Schwarz (Erlangen-Nürnberg) F. Hempel, G. D. Stancu, J. Röpcke (Greifswald, Germany) S. Rosiwal (Erlangen-Nürnberg)

Diamond volume crystal growth in HF-CVD and monitoring gas phase with laser absorption spectroscopy

In hot-filament CVD we synthesized single diamond crystals up to 100 µm in diameter [1]. In order to enhance growth rate and impede growth defects, it is intended to employ a new gas feeding system. This allows CH4 to be separately applied from H2 to the reactor locally at the substrate position. The effect of this concept on the gas phase was analyzed by Infrared Tuneable Diode Laser Absorption Spectroscopy (IR-TDLAS). The changes in species concentrations of CH4, CH3 and C2H2 with the substrate distance from filaments as well as first growth results are shown.

UDC 621.793.7

I. Sh. Trakhtenberg, A. B. Vladimirov, A. P. Rubstein, V. A. Yugov, V. B. Vykhodets, T. E. Kurennykh (Ekaterinburg, Russia) A. G. Gontar, V. N. Tkach, S. N. Dub (Kiev, Ukraine) K. Uemura (Tokyo, Japan)

Mechanical properties of CNx coatings obtained by carbon arc sputtering

Internal stresses σ0, friction coefficients f and microhardness were measured in diamond-like coatings obtained by vacuum-arc sputtering of carbon target at different nitrogen pressures in a work chamber during deposition on metallic substrates. The dependence of these parameters on nitrogen concentration in coatings can be used in practical deposition of strengthening and friction coatings for improvement of their tribological properties. The correlation between mechanical properties of diamond-like and CNx coatings was established.

UDC 621.793.1

A. P. Rubshtein, I. Sh. Trakhtenberg, E. G. Volkova, A. B. Vladimirov, V. A. Yugov (Ekaterinburg, Russia) A. G. Gontar, V. N. Tkach (Kiev, Ukraine)

Structure of CNx films (0 ≤ x ≤ 0.5) deposited by arc sputtering of graphite

The structure of a-C and CNx coatings 1—3 µ thick deposited on metal substrates by arc-pulse sputtering of graphite target in nitrogen background at P= (10-2—5)Pa was studied by transmission electron microscopy and scanning electron microscopy. Concentration and depth distribution of nitrogen in CNx depend on progressive saturation of graphite target. Nitrogen-free coatings (x=0) consist of amorphous matrix with multiwalled nanotubes. Structure of carbon nitride coatings depends on nitrogen concentration. Over the range of Cn/Cc < 0.15 and Cn/Cc > 0.4CNx coatings are amorphous. The structure of CN0.15 < x < 0.4 is a mixture of two types of amorphous domains, one of which is decorated by microcrystalline inclusions. The same structured inclusions were found on graphite target modified by electric arc. The obtained results allow understanding the dependence of the CN0≤x≤0.5 coatings properties on nitrogen concentration.

UDC 621.793.1

J. E. Klemberg-Sapieha, P. Jedrzejowski, L. Martinu(Montreal, Quebec, Canada)

Mechanical and optical characteristics of superhard nanocomposite TiN/a—Si3N4 and TiCN/a—SiCN coatings produced by PECVD

There is a continuous need for new hard and superhard (H > 40GPa) materials for applications ranging from protective coatings for cutting tools and aerospace to automobile industries, MEMS and others. In this work nanocomposite hard coatings fabricated by plasma-enhanced chemical vapor deposition from TiCl4/SiH4/CH4/N2/H2/Ar gas mixtures were found to possess unique properties such as superhardness, high toughness, and interesting optical properties and colors. The mechanical characteristics such as hardness and Young’s modulus were determined by depth-sensitive indentation. Film microstructure was studied by XRD, SEM, TEM, ERD-TOF, XPS, and AFM. Optical properties like color, refractive index and extinction coefficient were evaluated using combined spectrophotometry and spectroscopic ellipsometry. This multitechnique approach allowed us to determine the structure-property relationships. We have shown that nc-TiN/a—Si3N4 exhibits a hardness of 45GPa, while the novel nc-TiCN/a—SiCN provides a hardness of 57 GPa in addition to a very high resistance to plastic deformation (1.8 GPa).

UDC 621.793.3

T. Meziani, P. Colpo, F. Rossi (Ispra, Italy)

PECVD of diamond-like carbon (a-C:H) from the decomposition of methane in a high-density inductively coupled discharge

The paper describes an experimental investigation of the diamond-like carbon deposition process from methane precursor with an innovative high-density inductively coupled plasma source. It appears that a high plasma density allows a fast growth of diamond-like carbon coatings exhibiting a high hardness. In contrast to what is usually found in the literature, it seems that the ion species participate significantly to the growth of the carbon film when exposed to a high ion flux.

UDC 548.75:539.26

M. A. Vesaghi, M. Nazari (Tehran, Iran)

XPS and IR study of carbon thin films prepared under negative substrate DC voltage bias

Hydrogenated amorphous carbon (a-C:H) thin films were prepared on glass substrates at different applied DC voltage bias by the HF-CVD method. Other factors of deposition were kept constant. The IR and XPS spectra of the films were obtained. By the deconvolution of the IR and XPS spectra sp³/sp² ratio calculated. The sp³/sp² ratio varies nonlinearly with bias voltage and it has a minimum and maximum in the 0—70 V range of the bias voltage.

UDC 544.526.5:539.216

L. Sedláková, M. Horáková, P. Hájková, A. Kolouch, J. Karásek, P. Špatenka (Liberec, Czech Republic)

Photocatalytic properties of titanium oxide-based films deposited by PECVD

Titanium oxide-based photocatalytic films and their application have been the subject of growing interest in recent years. Properties of these films are significantly influenced by applied deposition methods.

This article is focused on varying parameters of the plasma-enhanced chemical vapor deposition method and their influence on resulting thin titanium oxide films. Depositions were carried out with varying bias, substrate temperature and substrate type. Resulting samples of titanium oxide films were tested for their photocatalytic properties. The test method was based on decomposition of model organic substance, acid orange II. The film thickness was measured by a mechanical profiler.

UDC 533.924:678.742.2-492.2

J. Hladík, M. Jodas, A. Kolouch, P. Špatenka (Liberec, Czech Republic)

Penetration of active particles into the powder

This work is aimed at investigation of the penetration of the plasma modification deep under the upper level of a polyethylene (PE) powder. It has been proved that during modification of powder using a low pressure and low temperature plasma the treatment penetrates under the powder stack layer. This penetration decreases with pressure and increases with the process time.

UDC 539.216:537.533.2

Z. Znamirowski (Wroclaw, Poland) E. Staryga, G. W. Bäk, D. Jarzynska (Lódz, Poland) K. Nikliborc (Wroclaw, Poland) A. Karczemska (Lódz, Poland) M.Green (London, UK)

Emission properties of DLC films on Si substrates

DLC films were deposited on polished both n-type and p-type silicon substrates. The silicon resistivity was ≈ 0.02Ωcm. Some of the DLC films 20nm thick were deposited on the n-type Si surface with the submicron cones. SEM and Raman spectroscopy were used for structural investigations. Field electron emission occurs after dielectric breakdown, except for the samples with Si cones for which the emission seems to originate from SiC formed during the first stage of electron emission. It seems that too much sp² graphite phase may give rise to the observed increase in the turn-on field from 50V/mm up to 150V/mm.

UDC 548.5

E. Dumiszewska, W. Strupinski, K. Zdunek (Warsaw, Poland)

Interaction between dislocations density and carrier concentration of gallium nitride layers

We investigated the problem of oxygen-dislocations interaction and its influence on carrier concentration in GaN layers. We achieved the samples with various dislocation density. Then we checked carrier concentration by means of Hall measurements. The samples with a higher EPD were characterized by a higher electron concentration. We assumed that oxygen diffuses along the threading dislocation lines, acts as a shallow donor and influences unintentional doping. Hence, the more dislocations present in GaN layers, the higher carrier concentration.

UDC 533.924:661.571

T. Bieniek, R. B. Beck, A. Jakubowski, P. Konarski, M.Cwil (Warsaw, Poland) P. Hoffmann, D. Schmeisser (Cottbus, Germany)

Formation of oxynitride layers in a RF plasma planar reactor for future Si and SiC MOS structures

Experiments presented in this work are a part of an extended study that examines the possibility of fabrication of oxynitride layers for future Si and SiC MOS structures by nitrogen implantation from RF plasma and subsequent plasma oxidation process.

In order to avoid analysis of more complex SiC MOS devices, at this stage, the experiments were performed using silicon substrates. The obtained layers were characterized by means of ellipsometry, XPS and SIMS. The results of electrical characterization of MOS test structures fabricated with investigated layers used as gate dielectric, are also discussed.

UDC 615.472.3:621.922.029

L. Klimek, M. Kochanowski, M. Romanowicz (Lódz, Poland)

Abrasive wear of diamond-coated dental burs and its impact on the parameters of the finished surface

The aim of this study was to evaluate the character and the abrasive wear rate of the dental diamond tools as well as their influence on the parameters of enamel surface of the tooth.

UDC 615.472.3:621.9.029

L. Klimek, K. Banaszek (Lódz, Poland)

The mechanisms of wear in burs with diamond grits

The aim of the study was to observe changes in dental burs with diamond grits after cutting and elucidate the nature of bur wear.

UDC 537.533.2:546.26-162

E. Staryga, D. Jarzynska (Lódz, Poland) K. Fabisiak, A. Banaszak (Bydgoszcz, Poland)

Field emission from diamond and diamond-like carbon films

Field emission from diamond and diamond-like carbon thin films deposited on silicon substrates has been studied. The diamond films were synthesized using hot filament chemical vapor deposition technique. The diamond-like carbon films were deposited using the radio frequency chemical vapor deposition method. Field emission studies were carried out using asphere-to-plane electrode configuration. Theresults of field emission were analyzed using the Fowler-Nordheim model. It was found that the diamond nucleation density affected the field emission properties. The films were characterized using standard scanning electron microscopy, Raman spectroscopy, and electron spin resonance techniques. Raman spectra of both diamond and diamond-like films exhibit spectral features characteristic of these structures. Raman spectrum for diamond films exhibit a well-defined peak at 1333cm–1. Asymmetric broad peak formed in diamond-like carbon films consists of D-band and G-band around 1550 cm–1 showing the existence of both diamond (sp³ phase) and graphite (sp2 phase) in diamond-like carbon films.