A photon noise limited sub-mm/far-IR cold telescope in space will require detectors with noise equivalent power (NEP) less than 1x10-19 W/Hz1/2 for imaging applications and at least an order of magnitude lower for spectroscopic studies. The detector NEP can be reduced by lowering the operation temperature and improving the thermal isolation between the bolometer and a heat bath. We report on the fabrication of membrane isolated transition edge sensor bolometers incorporating compact (<50 μm) thermal isolation beams based on phononic filters. Phononic filters are created by etching quasi-periodic nanoscale structures into supporting thermo-mechanical beams. The cross-sectional dimensions of the etched features are less than the thermal wavelength at the operating temperature, enabling coherent phonon transport to take place in one dimension. The phonon stop-band can be tuned by adjusting the scale of the quasi-periodic structures. Cascading multiple filter stages can increase bandwidth and provide improved thermal isolation similar to the function of a multi-stage electrical filter. We describe the fabrication of AlMn based transition edge sensor bolometers on silicon and silicon nitride membranes isolated by one- and two-dimensional phononic filters. The phononic filters are patterned through electron beam lithography and isolated with deep reactive ion etching.
Here we present a solution based functionalization technique for streptavidin (SA) protein conjugation to silicon
nanowires (Si NWs). Si NWs, with a diameter of 110 nm to 130 nm and a length of 5 μm to 10 μm, were functionalized
with 3-aminopropyltriethoxysilane (APTES) followed by biotin for the selective attachment of SA. High-resolution
transmission electron microscopy (HRTEM) and atomic force microscopy (AFM) showed that the Si NWs were
conformally coated with 20 nm to 30 nm thick APTES, biotin, and SA layers upon functionalization. Successful
attachment of each bio/organic layer was confirmed by X-ray photoelectron spectroscopy (XPS) and fluorescence
microscopy. Fluorescence microscopy also demonstrated that there was an undesirable non-specific binding of the SA
protein as well as a control protein, bovine serum albumin (BSA), to the APTES-coated Si NWs. However, inhibition of
BSA binding and enhancement of SA binding were achieved following the biotinylation step. The biofunctionalized Si
NWs show potential as label-free biosensing platforms for the specific and selective detection of biomolecules.