Quantum cascade laser based spectroscopic ellipsometry for advanced material investigation

Description

Resume : Conventional optical techniques applied in the fingerprint region of the mid-infrared (MIR) spectral range typically rely on thermal emitters. Such sources are characterized by low brightness, which finds expression in poor signal-to-noise ratios (SNR), long acquisition times and insufficient spatial resolution. By exploiting high-brightness broadband MIR laser sources, however, the limits of conventional instruments can be exceeded by orders of magnitude. The application of a spectrally tunable MIR quantum cascade laser (QCL) for spectroscopic ellipsometry is presented. The QCL based ellipsometer is outperforming state-of-the-art FTIR ellipsometers in terms of SNR by a factor of 290. This exceptional noise performance allows to acquire high-resolution (1 1/cm) broadband (900 1/cm – 1204 1/cm) ellipsometry spectra in less than a second (887 ms), which designates a reduction in acquisition time by a factor of 66,000 compared to reference measurements performed with a state-of-the-art instrument. The great benefit of this approach is illustrated by monitoring molecular reorientation during the stretching of a 6 µm Polypropylene film at sub-second temporal resolution. In addition, we demonstrate the advanced investigation of semiconductor materials by means of spectroscopic transmission ellipsometry measurements at continuously varying angle of incidence and sample orientation – likewise enabled by the available brightness of the applied QCL.

Period	01 Jun 2021
Event title	E- MRS Spring Meeting 2021
Event type	Conference
Location	AustriaShow on map