K. Engel

Bio: K. Engel is an academic researcher from University of Göttingen. The author has contributed to research in topics: Ion & Ion beam mixing. The author has an hindex of 2, co-authored 2 publications receiving 18 citations.

Ion-beam irradiation effects on Ni3N/Si bilayers

Abstract: Nitrides, carbides and oxides are important ceramic materials for wide range of applications in coating, nuclear reactor and semiconductor technology The study of their bonding properties to metals and semiconductors, for instance via ion irradiation, is of great importance In this work, we report on the effects induced by 100 and 450 keV Xe+ ions in 70–100 nm Ni3N layers deposited on Si substrates Low-energy irradiation at 80 K was found to cause a preferential nitrogen loss in the near-surface regions and an increase in surface roughness of the Ni3N film After the 450 keV Xe+ ion irradiation, strong mixing and the formation of Ni2Si and Si3N4 phases were detected at the Ni3N/Si interface These findings demonstrate the dissociation of Ni3N under ion bombardment and the competition of chemical driving forces and collision cascade mixing at the interface

Heavy ion irradiation induced effects in Ni3N/Al bilayers

Abstract: The article reports on the Xe ion beam irradiation studies of Ni3N/Al bilayers at 80 K. The ion-induced modifications were monitored by Rutherford backscattering (RBS), resonant nuclear reaction analysis (RNRA), X-ray diffraction (XRD) and atomic force microscopy (AFM). We found preferential loss of nitrogen from the surface region of the Ni3N top layers. The surface roughness ΔσS and the interface broadening variance Δσint2 increase linearly with the Xe ion fluence Φ. The experimental mixing rate of Δσ 2 /Φ=1.8 nm 4 is explained by considering an enhancement of ballistic mixing due to chemical reactions at the interface.

Rutherford backscattering analysis of thin films and superlattices with roughness

Abstract: Knowledge on the thickness, composition, and interfaces of thin films and multilayers is, in many systems, fundamental for the understanding and optimization of their properties. One of the techniques often applied to such studies is Rutherford backscattering (RBS). However, it has been very difficult to account for the effects of interface roughness in the data obtained, and the alternative has been to develop dedicated data analysis codes for particular problems where roughness plays a determinant role. In this work, the effect of roughness is taken into account in the data analysis by calculating the effect of roughness on the apparent energy resolution as a function of depth. This depends on the exact type of roughness, and three different models have been implemented: inhomogeneous layer thickness, corrugated sample, and rough substrate surface. Interfacial mixing in multilayers can also be analysed with the method developed. Automatic fits to the data can be performed in this way, where the roughness parameters are derived during the fit, providing a new tool for RBS analysis. The code is applied to several systems in order to test its validity and applicability. Systems which are hard to analyse by RBS have been chosen: Si/VS/ Si0.65 Ge0.35 300 nm/ Si0.2 Ge0.8 4 nm/ Si0.65 Ge0.35 15 nm/Si 3 nm thin films, where VS stands for a linearly composition-graded virtual substrate; and MgO /( Fe 25 A/ Co 20 A)10 multilayers.

RBS ANALYSIS OF MBE GROWN SiGe/(001)Si HETEROSTRUCTURES WITH THIN HIGH Ge CONTENT SiGe CHANNELS FOR HMOS TRANSISTORS

Abstract: The growth of Si1-xGex quantum wells with high Ge composition (x>0.5) on Si(001) substrates by MBE is of great interest both for HMOS device applications and fundamental research. One of the possibilities to obtain a high Ge content Si1-xGex channel for mobile carriers, while retaining its strain, is to grow a relaxed Si1-yGey buffer layer on an underlying Si substrate. Such a buffer is termed a virtual substrate (VS), which is a constituent of SiGe metamorphic heterostructures. The effect of annealing on the structure of the Si(001)/VS/Si0.7Ge0.3/Si0.2Ge0.8/Si0.7Ge0.3 heterostructures was studied by grazing angle of incidence RBS. The thickness of the Si0.2Ge0.8 channel is inhomogeneous, which makes the analysis of the data by traditional means very hard. We have developed a model whereby the influence of the thickness inhomogeneity of each layer in the apparent energy resolution as a function of depth can be calculated. Automatic fits to the data were performed, and the roughness parameters, that is, the standard deviation of the thickness inhomogeneity of the relevant layers, were obtained, together with the thickness and stoichiometry of each layer. The results are compared with TEM and high resolution XRD experiments.

Fitting of RBS data including roughness: Application to Co/Re multilayers

Abstract: In this work automated fitting of Rutherford backscattering (RBS) data including the effect of roughness is performed, by calculating the effect of roughness on the apparent energy resolution as a function of depth. This depends on the exact type of roughness, and three different models have been implemented: inhomogeneous layer thickness, corrugated sample, and rough substrate surface. Full automated fitting can be performed including one, or more, of the models, with the roughness parameters (e.g. standard deviation of the thickness of any number of layers), as well as the sample structure, as fitting parameters. The code is applied to the system substrate/Re 50 A/(Co 20 A/Re 5 A)16, which had been studied before by other methods. The results are excellent, providing a new tool for RBS data analysis.