Growth, annealing and thermo-electrical properties of Cd1-xZnxS thin films for microbolometers

Cd1-xZnxS (0<x<0.14) nanocrystalline thin films were grown and tested for use as sensing elements in microbolometer-type uncooled infrared detectors instead of vanadium oxides. Films of thickness 80-700 nm were deposited on SixNy/silicon as well as on glass and SiO2/silicon wafers using both thermal evaporation and MOCVD. The films were characterized by AFM, SIMS and electrical measurements. CdS thin films showed good parameters for use in microbolometer-type infrared uncooled sensors. The thermal coefficient of resistance (TCR) was in the range of 1.1-3.6% for the different film thicknesses. The TCR and electrical resistance of US films were optimized using annealing in different environments (vacuum, nitrogen, hydrogen and NF3) and by using a capping silicon nitride layer. The correlations between grain size, grain boundaries structure and TCR were established. Owing to the nanoscale film structure and thickness, significant grain growth and grain-boundary reconstruction occurred during minute long annealing time at temperatures as low as 200 degrees C. (C) 2007 Elsevier B.V. All rights reserved.