A very neat way to measure the thermal expansion coefficient of such a thin
film is to use m-line spectroscopy.  By coupling into one or more TE guided
modes of the film, heating and measuring the angular shift in the m-lines,
you can evaluate very accurately the thermal expansion coefficient of the
film. Rememeber however, you do need to know the refractive index of the of
the SiO2 film at the particular wavelenth of interest.

Another way is simply to place the sample film in the arm of a Michelson (or
other type) interferometer. Adjusting the temperature of the film, and
measuring the shift in the resulatnt interference fringes, will also allow
the change of thickness per degree kelvin, to be evaluated. This is probably
a simpler method as possible changes in the refractive index with
temperature, are already accounted for by directly measruing the change in
the optical path length (i.e. fringe shifts).

Regards,

Karl Cazzini (Ph.D)




-----Original Message-----
From: fye@oakind.com 
To: MEMS@ISI.EDU 
Date: Saturday, October 30, 1999 3:39 PM
Subject: Measure thermal expansion coefficience of thin film


>
>
>
>I am interested to know the ways to measure thermal expansion coefficience
>of thin film like
>SiO2 with thickness of 2000A - 5000A.
>
>Thank you for your information.
>
>Fan Ye
>fye@qlaser.com
>
>
>