> Date:          Tue, 20 Oct 1998 09:22:54 -0400
> From:          andrew lyon 
> Subject:       what am i doing wrong with ti adhesion layers?
> To:            MEMS@ISI.EDU
> Reply-to:      andrew lyon ,
> mems-cc@ISI.EDU

> What am i doing wrong with Ti adhesion layers?  I am thermally
> evaporating 50-100nm Au films on glass substrates with 2-5nm Ti
> adhesion layers.  After a few days, the films turn from reflective
> Au to a frosty white color.  Is this titanium oxidation or some
> other diffusion process I am unfamiliar with?
>

Dear Andrew,
your description is really pointing in the direction of Ti oxidation.
I do not have experience wit Ti adhesion layers myself but I have
observed similar effects with Cr. As I found later, these have also
been described in literature as you may see from the short list below.

Cr or Ti diffuse through the Au film along the grain boundaries and
oxidize at the Au surface. This way, the surface acts a sink for the
underlying metal film and with time passing suck up the whole adhesion
layer. From my own experience I know that the colour of the gold film
clearly changes even with thinnest oxide films on it.

Yours, Kai