Dear Joyce
The maximum error in thickness i can expect is 100 Angstrom. I
have also observed some spherical balls in my film under optical
microscope. The size of each ball or island is around 0.1micron. What i am
expecting is that as we are deposting gold film on substrate by thermal
evaporation each particulate of gold on substrate is connected by tangling
bond. As we increase the temperature these tangled bonds break and
particulate
tries to minimise it surface free energy and aquire sphereical shape. I am
not finding any island for gold film aneealed at 250 C.
_______________________________________________________________________________
Gurvinderjit Singh Ahluwalia Tel: +91-0731-488656
Laser Materials Division Fax: +91-0731-488650
Centre for Advanced Technology email: gjit@cat.ernet.in
Indore - 452 013 INDIA
_______________________________________________________________________________
On Wed, 22 May 2002, Joyce Wong wrote:
> Hello,
>
> Just to echo what's been discussed--I've played with a ~9000 angstrom thick
> heater (Ti-Pt-Au evaporated on LSN and with Au being the primary
> current-carrying layer at 8000 angstrom thick). I power-cycled it within
> 15VDC; and over time, little tiny "white" dots were observed on the heater
> surface. Then I fried it by juicing it with 18VDC. The damaged zone turned
> into a "white belt," and I looked at it under an SEM and found that there
> were a lot of little "islands" formed where there used to be smooth
> continuous gold. But the thing is that I couldn't tell whether they were
> islands or valleys. So I really don't know whether it's gold that's beaded
> up, or silicon has diffused to the top and vice versa for the gold.
>
> Does anyone have any insight into this, or have come across any relating
> paper? I have kept the pictures, but I'm not sure if we're supposed to
> attach anything with our email to the listserve.
>
> joyce
>
> >Allow me to add to my original answer. I am quite sure this is what is
> >happening, though I am a little surprised that it would occur for a 1000
> >angstrom film. Gurvinderjit- are you sure of this thickness?
> >
> >I used to make a form of tunneling sensor just this way- depositing 300-500
> >angstrom gold films on a glass slide, then heating the suface until the
> >uniform gold film broke apart and migrated to form discrete but closely
> >spaced "islands". I then filled the space in between with one of several
> >organic semiconducting films to enhance the tunneling efficiency as they
> >were exposed to various VOC's.
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