Abstract
This paper presents the results of preliminary investigations of thin films of KTN (KTa1−xNbxO3) surface acoustic wave (SAW) structures
for their suitability as thermal detectors. The goal is to use the technique for infrared (IR) detection and imaging.
The thin films (0.6 m) of K(Ta1−xNbx)O3 [x = 0.5] epitaxial films were grown and polished on KTaO3 (0 0 1) substrates approximately
1mm thick. SAW resonators with a center frequency of approximately 480MHz were fabricated using these substrates. To form the basis of
comparison to commonly used, thermally sensitive SAW substrates, SAW devices using lithium niobate (LiNbO3) as the substrate material
were also fabricated. The phase response as a function of temperature for the KTN as well as the LiNbO3 SAW devices was measured with a
network analyzer. The largest phase change exhibited by the LiNbO3 was about −4.7◦/◦C, whereas the largest phase change exhibited by the
KTN was about twice as much (11â—¦/â—¦C). Assuming a worst case network analyzer phase resolution of 0.5â—¦, this corresponds to a temperature
resolution of 0.1 â—¦C for the LiNbO3 and 0.05 â—¦C for the KTN. By comparison, typical sensitivity of (uncooled) microbolometers is of the
order of 50 mK. We believe that with improved fabrication and signal processing, the KTN/SAW-based detection approach can achieve a
temperature resolution of better than 50 mK.
