Hi Rafael, Al will alloy with refractory metals (W, Mo, Ta) over time when heated. If you look at your filament, I bet it now looks dull grey rather than shiny (like a pure Al coating would appear). I had similar problems and contacted the Kurt Lesker company for advice; they recommended two possibilities to me: 1. Replace the W spring every few runs. Can get expensive over time. 2. Use a boron nitride crucible with an outer coil heater, or a coated box heater. Will require higher operating currents and impose a higher thermal load on your substrate. The company sent me a useful technical brief on evaporating Al; if you want, I can forward it to you directly. Good luck, Mike On Mar 22, 2011, at 4:06, Rafael García Valverde wrote: > Hi everybody, > > We need some advice, critics or suggestion. > > We are trying to thermally evaporate Al layers on glass substrates. We are > using Tungsten filaments in spring form and holding the Al filaments inside > the Tungsten spring. Our vacuum arrives to 10^(-6) mbar and the DC current > is gradually raise to 18-20A (the tungsten filament becomes incandescent), > we keep the DC current until we don't see any Al inside the tungsten spring.. > Apperently everything is right and the first days we achieved some > acceptable layers, but after a few days the Al layers are extremelly thin > (almost invisible). > > Maybe the chamber is dirty? Any possible treatment for cleaning it?