TY - CHAP A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Muller, F. A1 - Dams, Florian A1 - Schreiner, Rupert A1 - Serbun, Pavel A1 - Müller, Günter T1 - Comparison of integral and local field-emission properties of Mo-coated p-Si tip arrays T2 - 2015 28th International Vacuum Nanoelectronics Conference (IVNC), 13-17 July 2015, Guangzhou, China N2 - Silicon tip arrays were fabricated by means of reactive ion etching followed by oxidation for final sharpening and molybdenum thin film coating. The field-emission (FE) properties of these Mo-coated p-Si tip arrays were systemically investigated by different measurement techniques. Integral measurements in diode configuration yielded a turn-on field (for 1 nA) of 22 V/μm and nearly stable FE currents up to 6.6 μA at 38 V/μm. The effective field enhancements factor extracted from the FN plots is about 180. Detailed investigations of these FE arrays were also performed by means of field emission scanning microscopy combined with electron microscopy. A rather limited efficiency of the tips (50% at 1500 V) and FE homogeneity (180 nA at 700 V) might be correlated with the varying morphology of the tips and the presence of oxides. Local I-V measurements of selected single tips revealed both activation and deactivation effects, which finally resulted in nearly reproducible I-V curves. Current stability measurements at a constant voltage showed rather large fluctuations (0.1-1 μA) of the FE current, which could be reduced up to 1.7% by using of a PID-regulated voltage source. SEM images showed unchanged tip shape after the current processing. KW - CATHODES KW - Coatings KW - Current measurement KW - field emission KW - Iron KW - Mo-coated KW - p-Si tip KW - Scanning electron microscopy KW - silicon KW - tip arrays KW - Vacuum technology Y1 - 2015 U6 - https://doi.org/10.1109/IVNC.2015.7225579 SP - 192 EP - 193 PB - IEEE ER - TY - JOUR A1 - Hornberger, Helga A1 - Virtanen, Sannakaisa A1 - Boccaccini, Aldo R. T1 - Biomedical coatings on magnesium alloys BT - a review JF - Acta Biomaterialia N2 - This review comprehensively covers research carried out in the field of degradable coatings on Mg and Mg alloys for biomedical applications. Several coating methods are discussed, which can be divided, based on the specific processing techniques used, into conversion and deposition coatings. The literature review revealed that in most cases coatings increase the corrosion resistance of Mg and Mg alloys. The critical factors determining coating performance, such as corrosion rate, surface chemistry, adhesion and coating morphology, are identified and discussed. The analysis of the literature showed that many studies have focused on calcium phosphate coatings produced either using conversion or deposition methods which were developed for orthopaedic applications. However, the control of phases and the formation of cracks still appear unsatisfactory. More research and development is needed in the case of biodegradable organic based coatings to generate reproducible and relevant data. In addition to biocompatibility, the mechanical properties of the coatings are also relevant, and the development of appropriate methods to study the corrosion process in detail and in the long term remains an important area of research. KW - Magnesium alloyn KW - Biodegradable materials KW - Coatings KW - Conversion KW - Deposition Y1 - 2012 U6 - https://doi.org/10.1016/j.actbio.2012.04.012 VL - 8 IS - 7 SP - 2442 EP - 2455 ER -