Single wavelength interferometric sensing is based on reflectivity increases caused by specific binding between biomolecules. It is label-free and can be a portable and potentially inexpensive platform with sensitivity better than surface plasmon resonance. We have implemented the method using a thermally grown oxide on silicon that has been augmented with layer-by-layer deposition of polyelectrolytes to adjust the effective oxide thickness for near-perfect destructive interference prior to target exposure. The microscopic topology of surface can be mapped over centimeter dimensions with height changes smaller than an Angstrom detected. We demonstrate the efficacy of the platform with standard biotin-streptavidin binding chemistry. Reflectivity changes larger than a factor a 10 are observed upon functionalizing the augmented oxide surface with 3 Angstroms of biotin and larger than a factor of 100 for binding less than 3 nm of streptavidin. These are corresponding to the detection amount of ~ 25 femtomoles/mm².