Hans Peter Lorenz

Investigation of TiN as an interlayer for diamond deposition on steel

Abstract To develop a diffusion barrier layer for diamond deposition at high temperature onto steel, samples of steel coated with cathodic-arc-deposited and sputter-deposited titanium nitride were tempered under diamond-deposition conditions at temperatures up to 950 °C. Hardness of the steel and the adhesion were affected, no visible changes could be detected on sputtered TiN. Diamond was deposited by microwave plasma chemical vapour deposition onto steel samples coated with cathodic-arc-deposited TiN using substrate temperatures from 520 °C to 950 °C. The arc-deposited TiN is not free enough from defects, so at temperatures > 700 °C different reaction products can be observed and analyzed by electron-probe microanalysis. Depending on the temperature iron-chromium-carbon compounds and iron oxides can be seen, TiN reacts to become TiC x N y , and in some areas TiN delaminates.

Influence of intermediate layers and base materials on adhesion of amorphous carbon and metal-carbon coatings

Abstract Metal carbon (Me : C) and hydrogen-containing amorphous carbon (a-C : H) layers offer interesting possibilities for coating of tools because of their remarkable tribological features. But normally adhesion to steels used as base materials for tools is very low. A hybrid physical vapour deposition (PVD)-plasma chemical vapour deposition (PCVD) process was used to deposit zirconium (Zr)/intermediate layer/Zr : C. The a-C : H layers were deposited in a parallel plate reactor by PCVD with RF plasma. The graded Zr : C coating adheres well to various steels, very low adhesion is observed to a cobalt-containing steel and to cobalt-based hard metals. a-C : H adheres very well to silicon, glass, and aluminium (Al), but delamination in the bulk of the base material can occur due to high compressive stress. Adhesion to steel can be improved by thin layers of Al and tungsten (W), but different mechanisms seem to be the reasons for the improvement. The adhesion to hard metals increases with increasing WC content.

Deposition of ternary hard compounds with a graded composition by the use of a hybrid source ion-plating technique

Abstract Different ternary compounds consisting of two metals (type (M1 M2)X) were deposited by the use of a hybrid ion-plating deposition set-up with two cathodic sources, namely an arc source and a magnetron source. Simultaneous ablation from these two elemental metallic sources allows deposition of ternary compounds in a broad range of coating compositions without using expensive alloy sources. Deposition of graded coatings with different concentrations of the individual metals M, and M2 in the thickness of the film can be easily controlled by changing the source power of the individual sources during the deposition process. The usefulness of the process is demonstrated by deposition examples of various ternary compounds, such as (Ti, A1)N, (Ti, Cr)N, (Ti, Nb)N, (Ti, Ta)N, (Ti, W)N, (Ti, Zr)N, (Cr, A1)N, (Cr, Ta)N and (Cr, W)N.

Influence of process parameters on the size of the bias-nucleated area for diamond deposition with plasma-enhanced chemical vapour deposition

Abstract Diamond deposition experiments on polished silicon were made with microwave plasma chemical vapour deposition using bias-enhanced nucleation. The aim was to investigate the size dependence of the nucleated area on the process parameters. The nucleation density distribution across the border of nucleated/not nucleated and the effects observed with the bias current are discussed by means of a model given in the literature. The dependencies of the size of the prenucleated area on substrate temperature, pressure, and bias voltage are described and discussed. With sufficiently high bias voltage, for example —300 V, a 3″ wafer can be prenucleated throughout the whole area. At low substrate temperatures the bias prenucleation cannot be used as both nucleation density and nucleated area are too small for practical applications.