Mid-Infrared Thermomechanical Sensitivity of Microcantilevers for Application to Infrared Spectroscopy

We report the use of bimaterial microcantilever sensors for sensing narrow-band infrared (IR) radiation generated by a monochromator and its application to IR spectroscopy of polymer films. We selected microcantilever sensors of either silicon or silicon nitride and having a thin metal film coating. To assess the IR measurement capability of these cantilevers, the IR sensitivity to noise ratio (SNR), was measured in the mid-IR fingerprint spectral region (5 - 10 mu m or 1000 - 2000 cm(-1)). The measured SNR was in the range of 8 - 90. We further demonstrated the utility of these sensors by using them to collect an IR absorbance spectrum of 1 mu m thick polycarbonate film. The characteristic IR peaks for this film could be seen, and compare well with conventional Fourier Transform IR (FT-IR) data. The spectral resolution of the cantilever sensors determined to be in the range 32 - 64 cm(-1).