ICMCTF2011 Session B1-2: PVD Coatings and Technologies

The results of fundamental studies on the deposition of nanocrystalline diamond (n-D) films by means of pulsed laser deposition (PLD) will be present. The n-D films were deposited on silicon (111) and hard metal by excimer laser ablation from a graphite target at elevated substrate temperatures and in hydrogen background gas. The variation of the microstructure and the properties of the films with temperature was investigated in the range of 100°C to 660°C and with hydrogen pressure in the range of 1 mbar to 7 mbar. With diamond and / or ion bombardment pretreated and non-pretreated substrates were used and the influence of the pretreatment process on the microstructure of the films was investigated. The films were produced at laser fluences between 10 J/cm² and 15 J/cm². The thickness of the films was varied from 100 nm up to 2 microns. The influence of deposition parameters on the n-D growth and the sp²/sp³ bonding ratio was determined by Raman spectroscopy and TEM / EELS analysis and it will be shown that n-D films of good quality can be prepared using proper parameters. The hardness and Young´s modulus were determined using nanoindentation and the optical properties in the UV / VIS range was measured by using photospectrometry. The variation of these properties with deposition parameters and their correlation with the microstructure of the n-D films will also be presented.

We present the effects of pulsed laser irradiation of as-deposited c-BN-films using photons of 157 nm wavelength and 7.9 eV energy, respectively. The films were deposited by pulsed laser deposition (PLD) using a KrF excimer laser of 248 nm wavelength and up to 30 J/cm² laser fluence on the pyrolytic hexagonal boron nitride target with additional ion beam bombardment of the growing films using a mixture of nitrogen and argon ions produced in a r.f. ion source with 700 eV ion energy.

So, alternating deposition of sub-layers and irradiation directly affects the quality of the entire c-BN films.

Furthermore, calculations were done concerning the mean penetration depth of the photons in the c-BN films and, based on these evaluations of laser-induced temperature fields, experiments have been carried out using proper sub-layer thickness. The influence of the irradiation of the films with photons on the intrinsic shear stresses, which limited the film thickness so far, was investigated and will be presented.

High power impulse magnetron sputtering (HIPIMS) is a young technology whose opportunities, advantages and limitations are currently intensely investigated by a number of groups. Here we selected niobium as one of the most interesting materials since thin films of niobium and niobium compounds are used in a diverse range of applications. Pure niobium films are needed for the next generation of superconducting radio-frequency cavities not made from solid niobium. Niobium nitride is a material sometimes incorporated in hard, wear-resistant coatings and multilayers for its added corrosion resistance benefit. Niobium oxide is an attractive high index material for optical and photonics applications. The complex refractive index can be tuned by going to niobium oxynitride. We report on the dramatic changes of the HIPIMS discharge behavior when going from pure metal mode to reactive deposition, and correlate some plasma and film properties. One could expect that HIPIMS with other transition metals exhibit similar features.

Work supported by the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Here, we report on the influence of sinus RF biasing at 1 MHz on the crystallinity of aluminium oxide films. The films are prepared in a RF magnetron discharge, which is excited by 13.56 and 71 MHz frequencies and used for reactive sputtering of an aluminium target. The target is mounted on the powered electrode and the silicon substrate is placed on a biased electrode at the opposite side. The temperature of the substrate is varied and reaches up to 700°C. A feedback loop based on measurements of an Al-atom emission line is used to control the partial pressure of O₂ in the plasma.

The Al₂O₃ films are characterized by FTIR, XPS and XRD. During this study, a combination of arbitrary function biasing scheme and IEDF measurements with a retarding field analyzer has been performed. The results reveal a dependence of the orientation of the crystal structure in the film on the energy distribution of the ions. First results show that the orientation of the crystal structure can be manipulated by the variation of bias voltage. In future, these results are planned to optimize the Al₂O₃ deposition process and to reveal the role of the ion energy in the film growth. The work is funded by DFG within SFB-TR 87.

Face centered cubic (Al_1-xCr_x)₂O₃ solid solution films, with x in the range 0.60<x<0.70, have been deposited using dual reactive RF magnetron sputtering from Al and Cr targets in mixed Ar/O₂ discharge at a substrate temperature of 500°C. The films have a strong <100> preferred orientation. The unit cell parameter is 4.04 Å determined by x-ray diffraction and high resolution transmission electron microscopy techniques. The (Al_1-xCr_x)₂O₃ films are suggested to have a non-stoichiometric NaCl structure with 33% vacancy occupancy on Al/Cr sites. Nanoindentation shows that the films exhibit hardness values up to 26 Gpa and reduced modulus of 220-235 Gpa. In the present work, in-situ annealing studies were performed on as-deposited samples for a series of temperatures up to 1100°C and annealing time of 8 h. The results show that fcc structure remains intact up to 950°C. A gradual phase transformation from fcc to corundum at 1000°C is observed, where annealing for 1-3 h yields a partial transformation and annealing for > 4 h results in complete transformation to alpha-(Al_1-xCr_x)₂O₃. There is no indication of any phase separation into alpha-Cr₂O₃ and alpha-Al₂O₃.