N P Barradas

Bio: N P Barradas is an academic researcher. The author has contributed to research in topics: Surface finish. The author has an hindex of 1, co-authored 1 publications receiving 57 citations.

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.

Improved physics in SIMNRA 7

Abstract: SIMNRA is an analytical code for the simulation of ion beam analysis energy spectra obtained by Rutherford backscattering, non-Rutherford scattering, elastic recoil detection analysis, and nuclear reaction analysis. Improvements of the simulation physics in SIMNRA version 7 include among others the skewness of all energy spread distributions, improved handling of scattering or reaction cross-sections with structure, generalized layer roughness, and sample porosity.

Elemental thin film depth profiles by ion beam analysis using simulated annealing - a new tool

Abstract: Rutherford backscattering spectrometry (RBS) and related techniques have long been used to determine the elemental depth profiles in films a few nanometres to a few microns thick. However, although obtaining spectra is very easy, solving the inverse problem of extracting the depth profiles from the spectra is not possible analytically except for special cases. It is because these special cases include important classes of samples, and because skilled analysts are adept at extracting useful qualitative information from the data, that ion beam analysis is still an important technique. We have recently solved this inverse problem using the simulated annealing algorithm. We have implemented the solution in the `IBA DataFurnace' code, which has been developed into a very versatile and general new software tool that analysts can now use to rapidly extract quantitative accurate depth profiles from real samples on an industrial scale. We review the features, applicability and validation of this new code together with other approaches to handling IBA (ion beam analysis) data, with particular attention being given to determining both the absolute accuracy of the depth profiles and statistically accurate error estimates. We include examples of analyses using RBS, non-Rutherford elastic scattering, elastic recoil detection and non-resonant nuclear reactions. High depth resolution and the use of multiple techniques simultaneously are both discussed. There is usually systematic ambiguity in IBA data and Butler's example of ambiguity (1990 Nucl. Instrum. Methods B 45 160–5) is reanalysed. Analyses are shown: of evaporated, sputtered, oxidized, ion implanted, ion beam mixed and annealed materials; of semiconductors, optical and magnetic multilayers, superconductors, tribological films and metals; and of oxides on Si, mixed metal silicides, boron nitride, GaN, SiC, mixed metal oxides, YBCO and polymers.

Advanced physics and algorithms in the IBA DataFurnace

Abstract: The IBA DataFurnace (NDF) is a general purpose program for analysis of IBA data. It currently includes Rutherford backscattering (RBS), elastic (non-Rutherford) backscattering (EBS), elastic recoil detection analysis (ERDA), non-resonant nuclear reaction analysis (NRA), and particle induced X-ray emission (PIXE). Here we discuss recent developments in the advanced physics capabilities implemented in NDF, supported by advanced algorithms. Examples of real life hard cases are given that illustrate the issues discussed.

“Total IBA” – Where are we?

Abstract: The suite of techniques which are available with the small accelerators used for MeV ion beam analysis (IBA) range from broad beams, microbeams or external beams using the various particle and photon spectrometries (including RBS, EBS, ERD, STIM, PIXE, PIGE, NRA and their variants), to tomography and secondary particle spectrometries like MeV-SIMS. These can potentially yield almost everything there is to know about the 3-D elemental composition of types of samples that have always been hard to analyse, given the sensitivity and the spacial resolution of the techniques used. Molecular and chemical information is available in principle with, respectively, MeV-SIMS and high resolution PIXE. However, these techniques separately give only partial information – the secret of “Total IBA” is to find synergies between techniques used simultaneously which efficiently give extra information. We here review how far “Total IBA” can be considered already a reality, and what further needs to be done to realise its full potential.