In situ measurement of lithium movement in thin film electrochromic coatings using cold neutron depth profiling

Direct analysis of lithium movement within multilayer thin-film electrochro mic (EC) coatings has been performed by cold neutron depth profiling (CNDP) , Transfer of lithium between a counter-electrode layer and an EC tungsten trioxide layer controls the optical density of the EC coating. The lithium profiles have been measured using the CNDP instrument at the Center for Neu tron Research at the National institute of Standards and Technology, The li thium depth profiles are based on measurement of the energy of alpha partic les from the Li-6(n,alpha)H-3 reaction, The alpha particles lose energy as they exit the film and this energy loss pro, ides direct measurement of the depth of the originating lithium nucleus. In this case, in situ measuremen ts were taken with different bias voltages on the film layers. The bias cau ses the lithium to migrate between different layers, changing the optical d ensity of the films. A great advantage of the CNDP technique is that it is non-destructive, which allows repeated observation of the lithium movement. Results of simultaneous optical transmission measurements and lithium prof ile measurements are reported. Copyright (C) 1999 John Wiley & Sons, Ltd.