We present a theoretical model and preliminary experimental results on the
dielectric constant measurement of thin films by using differential time-do
main spectroscopy. This technique greatly reduces the minimum measurable th
ickness, and it promises the dielectric constant measurement of mu m-thick
thin films with the frequency range from GHz to THz. (C) 2000 American Inst
itute of Physics. [S0003-6951(00)03922-X].