Lithium depth profiling in thin electrochromic WO3 films

Li profiles in sol-gel prepared electrochromic WO3 thin films have been cha racterized using three different techniques: neutron depth profiling (NDP), secondary ion mass spectrometry (SIMS), and elastic recoil detection (ERD) . The results have been evaluated with respect to their concentration sensi tivity and depth resolution. NDP and SIMS led to comparable results in term s of the shape of the profiles. The NDP results were quantified by using a calibration sample. NDP has the advantage that it is a quantitative nondest ructive technique while SIMS has a very high sensitivity and depth resoluti on. Another advantage of NDP is that there is very little risk of neutron-i nduced Li migration during the measurement because of the very low energy o f the incoming thermal neutrons. ERD was found to have a limited depth reso lution, attributable to deterioration of the sample as a result of ion bomb ardment. However, the absolute amount of Li can be very accurately quantifi ed with this technique. (C) 1999 American Vacuum Society. [S0734-2101(99)00 601-6].