C. Hammerl

Formation of titanium carbide by high-fluence carbon ion implantation

Abstract Titanium carbide has been prepared by high fluence carbon ion implantation in titanium at temperatures between −70°C and 450°C. The carbon ion dose has been varied between 1.2 and 36 × 1017 C+-ions/cm2 and the ion energy between 30 and 180 keV. The carbon concentration distribution, the structure, the morphology and the microhardness have been examined with Rutherford backscattering, transmission electron microscopy, X-ray diffraction and nanoindentation, respectively. The concentration distribution of carbon is characterized by a symmetric Gaussian profile for doses up to 12×1017C+-ions/cm2 and a more and more asymmetrical profile for higher fluences. The evolution of the concentration distribution is discussed on basis of swelling and sputtering. Precipitates of the titanium carbide phase can be observed after implantation at −70°C with doses ⩾3×1017C+-ions/cm2. The average diameter of the TiC precipitates is a function of ion dose, temperature and duration of annealing. A significant increase of the hardness in the near surface region of implanted samples can be detected. The measured hardness values depend strongly on ion dose, annealing conditions and the hardness of the unimplanted titanium.

Synthesis of buried metal oxide films by high fluence oxygen ion implantation into metals

Abstract Oxygen implantations with a fluence of 1×10 18 O + / cm 2 and energies of 300 and 400 keV were performed in titanium and molybdenum at temperatures between 300°C and 350°C. Chemical composition was investigated using Rutherford backscattering spectrometry (RBS) and TRIDYN simulations. Phase analysis by means of X-ray diffraction and morphology studies utilizing cross-sectional transmission electron microscopy (XTEM) were carried out. The formation of a buried MoO2 layer in molybdenum and a TiO layer in titanium could be observed.

STUDY OF THE CARBON CONCENTRATION DISTRIBUTION IN IRON AND TITANIUM AFTER LOW-TEMPERATURE CARBON ION IMPLANTATION

Abstract Carbon ion distribution profiles after implantation in iron and titanium were extensively investigated using Rutherford Backscattering Spectrometry (RBS) and Elastic Recoil Detection Analysis (ERDA). Ion energy and fluence were varied over large ranges using target temperatures of less than −70°C. In both systems a retention of a gaussian-like implantation profile was found up to very high fluences. Unexpected high values of local carbon concentration were obtained for high fluences. Results were compared to Monte Carlo simulations using the dynamical code TRIDYN. Additionally the influence of subsequent annealing on the carbon distribution was studied. The diffusive behaviour was found to be very different in both systems. The iron–carbon system shows strong rearrangement of carbon atoms and tries to achieve local concentrations of 25 at.% upon thermal treatment. In the corresponding temperature regime no significant carbon diffusion in titanium takes place.

Dependence of the doping efficiency on material composition in n-type a-SiOx:H

Abstract Amorphous hydrogenated silicon suboxides (a-SiO x :H) deposited by plasma enhanced chemical vapour deposition (PECVD) have a band gap which can be tuned from 1.9 to 3.0 eV by varying the oxygen content from 0 to 50 at.%. n- and p-type doping is realised by adding PH 3 and B 2 H 6 , respectively, to the source gases SiH 4 , H 2 and CO 2 . Alloying with increasing amounts of oxygen reduces the mean co-ordination number 〈 r 〉 from a value close to 4 (a-Si:H) to approximately 2.7, which gradually approaches the ideal value of 〈 r 〉=2.4 for network glasses. Thus the incorporation of dopant atoms into electrically active, fourfold co-ordinated sites becomes more unlikely with increasing [O]. As a consequence the conductivity, defect density and doping efficiency in phosphorus doped n-type SiO x undergo drastic changes and show increasingly intrinsic character for higher oxygen concentrations. The dependence of the doping efficiency on average co-ordination 〈 r 〉 is examined in a quantitative manner.

Electronmicroscopical Study of the Formation of Iron Carbide Phases After High-fluence Carbon Ion Implantation into Iron at Low Temperatures

Carbon ions were implanted with energies between 50 and 150 keV into thin iron layers at temperatures of –10 °C and –70 °C. Formation of iron carbide phases was studied as a function of fluence, which was varied from 1.2 × 10 17 C + -ions/cm 2 up to 1.4 × 10 18 C + -ions/cm 2 . The sequence of phase transformation during subsequent annealing to temperatures of up to 450 °C was also investigated. Detailed analysis of structure and morphology was done by cross-sectional transmission electron microscopy and electron diffraction experiments. The existence of metastable iron carbide phases, θ-Fe 3 C, Χ-Fe 5 C 2 , η-Fe 2 C, and also the amorphous phase Fe(C), after high-fluence carbon ion implantation and the transformation of the formed metastable phases by subsequent annealing into the θ-Fe 3 C phase are demonstrated.

Characterization of Plasma Immersion Deposited Multilayer Coatings by Ion Beam Techniques Combined with Energy Filtered Transmission Electron Microscopy

Multilayered and nanostructured coatings of amorphous carbon (DLC), silicon composite multilayers and nanocluster containing films today have great potential for applications as hard coatings, wear reduction layers and as diffusion barriers in biomaterials. Plasma immersion ion implantation and deposition (PIII&D) is a powerful technique to synthesize such films. The quantitative nanoscale analysis of the elemental distribution in such multielemental films and thin film stacks however is demanding. In this paper it is shown how the high spatial resolution capabilities of energy filtered trans-mission electron microscopy (EFTEM) chemical analysis can be combined with accurate and standard-less concentration determination of ion beam analysis (IBA) techniques like Rutherford Backscattering Spectroscopy (RBS) and Elastic Recoil Detection Analysis (ERDA) to achieve absolute and accurate multielement concentration profiles in complicated nanomaterials.