Use of an ultra-high resolution magnetic spectrograph for materials research

A brief description is given of a magnetic spectrograph for RBS and ERD analysis with MeV beams, delivered by a Tandem accelerator. With a number of examples of thin layer analysis it is shown that the spectrograph is uniquely suited for the measurement of concentration depth profiles up to a depth of about 50 nm. The positions of light and heavy atoms in epitaxial layers can be determined by using blocking, or channeling/blocking geometries in ERD or RBS measurements. Such determinations are especially interesting for samples with shallow interfaces and delta-doped layers. It is also shown that the impact-parameter dependence of energy loss and charge exchange in ion-solid interactions can be determined from measurements at samples with submonolayer coverage of elements at the surface, single crystalline samples, or (in transmission geometries) very thin layers. Some features of this spectrograph are compared with those of a selection of other high-resolution analyzers

On combining surface and bulk passivation of SiN\u3csub\u3ex\u3c/sub\u3e:H layers for mc-Si solar cells

\u3cp\u3eA route, as followed by ECN, is described for development of SiN\u3csub\u3ex\u3c/sub\u3e:H layers deposited by microwave (MW) PECVD, which are suited for surface and bulk passivation of mc-Si solar cells. First research was focussed on surface passivation and this resulted in the development of SiN layers that were Si-rich and where the hydrogen is mainly bonded to silicon atoms. A disadvantage of such Si-rich layers is their large absorption at shorter wavelengths, which make them unsuitable as front side AR coatings. Further, these layers appeared to be less suitable for bulk passivation. The next step therefore was the development of SiN layers for bulk passivation. For good bulk passivation of solar cells by means of a thermal anneal of the SiN layers, we found that SiN layers with high N-H bonding concentrations are required. Fine-tuning of the deposition conditions of these layers, finally resulted in the development of a SiN layer type which combines the three desired properties: low absorption (good anti-reflection coating), good surface passivation (S\u3csub\u3eeff\u3c/sub\u3e on FZ wafers less than 50 cm/s) and good bulk passivation.\u3c/p\u3

A round robin characterisation of the thickness and composition of thin to ultra-thin AlNO films

International audienceA round robin characterisation of the thickness and composition of thin to ultra-thin AINO films was organised. Thirteen participant groups used various ion beam analysis (IBA) techniques to determine quantitatively the thickness, areal density and concentration of aluminium, nitrogen and oxygen in films with thicknesses ranging nominally from 1 to 100 nm. Most of the ratios reported are not statistically different from the reference values, and only very seldom are large deviations observed. It was not possible to identify a given technique or a group of techniques as being more reliable for analysing the ultra-thin samples. Unexpected deviations in some results reflect a need for further measurements of fundamental quantities, namely cross-sections and stopping powers in energy ranges useful for IBA. Furthermore, precise measurements of beam fluence and detector solid angle would lead to improvements in the accuracy of some of the quantities reported, particularly areal densities. (C) 2004 Elsevier B.V. All rights reserved