Functionalization of a Fully Integrated Electrophotonic Silicon Circuit for Biotin Sensing.

Electrophotonic (EPh) circuits are novel systems where photons and electrons can be controlled simultaneously in the same integrated circuit, attaining the development of innovative sensors for different applications. In this work, we present a complementary metal-oxide-semiconductor (CMOS)-compatible EPh circuit for biotin sensing, in which a silicon-based light source is monolithically integrated. The device is composed of an integrated light source, a waveguide, and a p-n photodiode, which are all fabricated in the same chip. The functionalization of the waveguide's surface was investigated to biotinylate the EPh system for potential biosensing applications. The modified surfaces were characterized by AFM, optical microscopy, and Raman spectroscopy, as well as by photoluminescence measurements. The changes on the waveguide's surface due to functionalization and biotinylation translated into different photocurrent intensities detected in the photodiode, demonstrating the potential uses of the EPh circuit as a biosensor.

Silicon Conical Structures by Metal Assisted Chemical Etching.

A simple and inexpensive method to obtain Si conical structures is proposed. The method consists of a sequence of steps that include photolithography and metal assisted chemical etching (MACE) to create porous regions that are dissolved in a post-etching process. The proposed process takes advantage of the lateral etching obtained when using catalyst particles smaller than 40 nm for MACE. The final shape of the base of the structures is mainly given by the shape of the lithography mask used for the process. Conical structures ranging from units to hundreds of microns can be produced by this method. The advantage of the method is its simplicity, allowing the production of the structures in a basic chemical lab.