Study of black silicon obtained by cryogenic plasma etching: approach to achieve the hot spot of a thermoelectric energy harvester

Abstract

In this paper, we study the enhanced absorption properties of micro/nano structured silicon surface under incident electromagnetic illumination and its capacity to convert light into heat. We simulate the optical reflectance of three-dimensional micro/nano silicon cones of different dimensions and under different electric field incident angles (źi). According to the favorable simulation results, we fabricate black silicon with conical microstructures that exhibits excellent anti-reflectivity behavior. Plasma etching under cryogenic temperatures is used for this purpose in an inductively coupled plasma-reactive ion etching reactor. The reflectance of the black silicon is measured to be approximately 1 % in the optical wavelength range, by using an integrating sphere coupled to a calibrated spectrometer. Furthermore, a device integrating a resistance temperature detector in a black silicon area is developed in order to investigate its efficiency as a photo-thermal converter.