Thermal expansion coefficient of single crystal silicon from 7 K to 293 K

Understand

We measured the absolute lengths of three single crystal silicon samples by means of an imaging Twyman-Green interferometer in the temperature range from 7 K to 293 K with uncertainties of about 1 nm.

• From these measurements we extract the coefficient of thermal expansion with uncertainties in the order of $1\times 10^{-9} {\rm /K}$.
• To access the functional dependence of the length on the temperature usually polynomials are fitted to the data.
• Instead we use a physically motivated model equation with 7 fit parameters for the whole temperature range.