Very Black Infrared Detector from Vertically Aligned Carbon Nanotubes and Electric-Field Poling of Lithium Tantalate

Abstract

Vertically aligned multiwall carbon nanotubes were grown by water-assisted chemical vapor deposition on a large-area lithium tantalate pyroelectric detector. The processing parameters are nominally identical to those by which others have achieved the "world's darkest substance" on a silicon substrate. The pyroelectric detector material, though a good candidate for such a coating, presents additional challenges and outcomes. After coating, a cycle of heating, electric field poling, and cooling was employed to restore the spontaneous polarization perpendicular to the detector electrodes. The detector responsivity is reported along with imaging as well as visible and infrared reflectance measurements of the detector and a silicon witness sample. We find that the detector responsivity is slightly compromised by the heat of processing and the coating properties are substrate dependent. However, it is possible to achieve nearly ideal values of detector reflectance uniformly less than 0.1% from 400 nm to 4 microm and less than 1% from 4 to 14 microm.