Sample size effects on the performance of sub-wavelength metallic thin-film bolometers

This paper presents how reducing the width and length of a bolometer’s sensing core affects its performance. Bolometer devices made of thin films of platinum with various lateral dimensions—widths ranging from 300 nm to 4 μm and lengths ranging from 300 nm to 19 μm were tested. Some are significantly smaller in size than the wavelengths they are exposed to, coming from a blackbody source with a λ peak of 2.74 μm. A resonance effect is revealed for samples of specific dimensions, where the performance is enhanced. Further, a strong increase in responsivity appears when the sample’s width is narrowed, whereas specific detectivity remains independent of any change in dimensions. We believe that some of these features are due to plasmonic effects, which may explain the high performance reached by smaller samples. It seems that graphene could be subject to similar geometrical effects to our thin-film bolometers.