Microstructure and electrical transport in electrodeposited Bi films

The semimetal character of bismuth and its large photon absorbing power make of this element the most suitable absorber material for X-ray low temperature detectors. This application requires coatings of Bi with thicknesses and properties that only electrodeposition methods may achieve. Although there are studies on electrodeposition of bismuth for these detectors and other devices, the process is not straightforward and has not been sufficiently studied in terms of the desired final properties, neither the effect of different parameters is well known or easily reproduced. This work reports the influence of two different electrolytes, of the deposition method, and of heating and stirring on the structure, microstructure and transport properties of bismuth films. Typically, rhombohedral Bi is obtained upon electrodeposition with very good crystallinity, and some crystal preferential orientation, while significant empirical correlations are found among electrochemical parameters, microstructure, and resistivity. Such correlation allows the identification of the deposition parameters for coatings that yield the optimal functional properties.Work financed by the Spanish Ministerio de Economía y Competitividad-MINECO (projects ESP2014-53672-C3-2-P, ESP2016-76683-C3-2-R and ESP2014-59309-JIN), the European Space Agency-ESA (CTP Contract “Optimization of a European TES array”) and the European Commission (H2020 project AHEAD: “Integrated activities for the high energy astrophysics domain”). Personnel from ICMAB acknowledge financial support from MINECO, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496). RMJ wishes to thank MINECO for her FPI contract. We acknowledge also the help of Guillermo Antorrena (INA) on XPS data.Peer reviewe