Variable-wavelength frequency-domain terahertz ellipsometry

T. Hofmann, C. M. Herzinger, A. Boosalis, T. E. Tiwald, John A Woollam, Mathias Schubert

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

We report an experimental setup for wavelength-tunable frequency-domain ellipsometric measurements in the terahertz spectral range from 0.2 to 1.5 THz employing a desktop-based backward wave oscillator source. The instrument allows for variable angles of incidence between 30° and 90° and operates in a polarizer-sample-rotating analyzer scheme. The backward wave oscillator source has a tunable base frequency of 107-177 GHz and is augmented with a set of Schottky diode frequency multipliers in order to extend the spectral range to 1.5 THz. We use an odd-bounce image rotation system in combination with a wire grid polarizer to prepare the input polarization state. A highly phosphorous-doped Si substrate serves as a first sample model system. We show that the ellipsometric data obtained with our novel terahertz ellipsometer can be well described within the classical Drude model, which at the same time is in perfect agreement with midinfrared ellipsometry data obtained from the same sample for comparison. The analysis of the terahertz ellipsometric data of a low phosphorous-doped n -type Si substrate demonstrates that ellipsometry in the terahertz spectral range allows the determination of free charge-carrier properties for electron concentrations as low as 8× 1014 cm-3.

Original languageEnglish (US)
Article number023101
JournalReview of Scientific Instruments
Volume81
Issue number2
DOIs
StatePublished - Mar 16 2010

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Ellipsometry
ellipsometry
backward waves
Frequency multiplying circuits
polarizers
Wavelength
Substrates
Charge carriers
image rotation
oscillators
wavelengths
frequency multipliers
Diodes
ellipsometers
Wire
Polarization
Schottky diodes
Electrons
charge carriers
analyzers

ASJC Scopus subject areas

  • Instrumentation

Cite this

Variable-wavelength frequency-domain terahertz ellipsometry. / Hofmann, T.; Herzinger, C. M.; Boosalis, A.; Tiwald, T. E.; Woollam, John A; Schubert, Mathias.

In: Review of Scientific Instruments, Vol. 81, No. 2, 023101, 16.03.2010.

Research output: Contribution to journalArticle

Hofmann, T. ; Herzinger, C. M. ; Boosalis, A. ; Tiwald, T. E. ; Woollam, John A ; Schubert, Mathias. / Variable-wavelength frequency-domain terahertz ellipsometry. In: Review of Scientific Instruments. 2010 ; Vol. 81, No. 2.
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