Dielectric constant measurement of thin films using goniometric terahertz time-domain spectroscopy

Ming Li, Jeffery Fortin, Jin Y. Kim, G. Fox, F. Chu, T. Davenport, Toh Ming Lu, Xi Cheng Zhang

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Goniometric time-domain spectroscopy (GTDS), employing an ultrashort electromagnetic (EM) pulse technique, has been developed for measuring the dielectric constant of thin films in a broad band of gigahertz to terahertz. An ultrafast optoelectronic system, including an emitter and a detector unit, is constructed with a θ-2θ goniometer. A silicon wafer was analyzed as the reference substrate material. A sharp π phase-shift of the reflected EM wave was observed at the Brewster angle of 73.5° for a bare silicon wafer. The phase shift for a film on the Si substrate is relatively smooth due to its two surfaces' providing a complex reflectance. The dielectric constant of the film on Si, related with angular dependency of the phase shift, can be extracted by means of fitting the curve or measuring slope of the curve near the Brewster angle. The measured dielectric constants of FLARE, TiOx, and PZT film are reported.

Original languageEnglish (US)
Pages (from-to)624-629
Number of pages6
JournalIEEE Journal on Selected Topics in Quantum Electronics
Issue number4
StatePublished - Jul 2001

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering


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