Porous Silicon for Enhanced Detectors

The very large surface area to volume ratio, and tunable thermal and optical properties provides a unique and adaptable material to push the performance of next generation sensors, MEMS devices, and optical components. In FY2015 we will continue to characterize the thermal properties of porous silicon and use this data to build a low thermal conductivity support structure for a prototype bolometer detector. This will provide a basis for higher performance and higher fill-factor detector arrays for future NASA missions In addition, we will explore the optical properties of the etched porous silicon layers to construct a multilayer infrared filter which has general applicability for Mid-IR and Terahertz instruments.

   In FY2015, we will move forward with proof-of-concept devices that will show the feasibility of exploiting porous silicon for its thermal and optical properties. Porous Silicon is formed by an electrochemical etch of a silicon surface in a solution of a hydrofluoric-acid-based electrolyte.    The etching process turns the crystalline solid into one with a network of nano-capillaries creating nanopores of varying surface to volume ratio depending on the selected conditions. The porosity of the silicon may be varied over a wide range.

We have two cross cutting goals for the coming year.   First, we will build a simple support structure for a single pixel bolometer prototype that incorporates porous silicon with high critical temperature pixels. The electrical routing between the pixel and the support will be done with high resolution gold patterning.  We will  also continue to explore the multilayers of porous silicon and silicon structures.  We will begin rigorous characterization to study how well the thickness and refractive index can be controlled.