We used standard CCD cameras as thermal imaging devices in the very near infrared spectrum (VNIR) to study interference effects during the growth of thermal oxide layers (at temperatures >400°C). We derived a theoretical model from which the determination of the complex index of refraction becomes possible by simply evaluating the emissivity variations caused by the afore mentioned interference effects. Thus, a very precise analysis e.g. of growth rates at nanometer scale is possible.
Left: Emssivity distribution on a steel sample with thin oxidelayer. Middle: Test chamber for emissivity measurements. Right: Film growth curve of an oxide layer on steel at nanometer scale.
Left: emissivity image of a metallic sample during PACVD process. Right: temporal emissivity signals at two different surface positions indicating different thin film growth rates.
Measurement of rapid temperature change at very high temperatures with commercial pyrometers is limited especially by their response times (>1ms) and measurement ranges (< 3000K). Thus a novel type of high temperature measurement system using a high-speed camera as a two-color pyrometer is introduced, characterized by high temporal resolution (10µs – 100µs), temperature range: 1000K – 4000K and high spatial resolution.
Blackbody radiation measurements for absolute temperature measurements
Raman spectroscopy relies on inelastic scattering, or Raman scattering, of monochromatic light, usually from a laser in the visible, near infrared, or near ultraviolet range. The laser light interacts with molecular vibrations, phonons or other excitations in the system, resulting in the energy of the laser photons being shifted up or down. The shift in energy gives information about the vibrational modes in the system. Infrared spectroscopy yields similar, but complementary, information. Spontaneous Raman scattering is typically very weak, and as a result the main difﬁculty of Raman spectroscopy is separating the weak inelastically scattered light from the intense Rayleigh scattered laser light.
Left: Molecular vibrations and energy states. Right: Measurement setup
Sample application: Hardness testing of diamond-like-carbon (DLC) coated steel samples. The shift of the so-called G peak is characteristic for the hardness of the DLC-coating.