Silicon Nanostructuring Using SF6/O2 Downstram Plasma Etching: Morphological, Optical and Sensing Properties

Saker Saloum,Samer Abo Shaker,Mohammad Ali Zrir,Bachar Alkhaled

doi:10.1590/1980-5373-mr-2017-1082

Saker Saloum, Samer Abo Shaker + Show 2 more

Open Access

https://doi.org/10.1590/1980-5373-mr-2017-1082

Copy DOI

Journal: Materials Research	Publication Date: Jul 10, 2018
Citations: 15	License type: cc-by

Affiliation: Atomic Energy Commission of Syria

Abstract

Silicon (Si) nanostructures were prepared in the downstream of radiofrequency SF6/O2 mixture plasma generated in 13.56 MHz hollow cathode discharge system. Depending on the oxygen percentage in the mixture, the obtained Si nanostructures were characterized for their different properties: etching rate, morphology, optical reflectance, photoluminescence, spectral response and humidity sensing. It is found that the etching rate exhibits a maximum value when the O2 ratio reaches 5%. An interesting defect-induced violet luminescence is reported from the Si nanostructures, whose intensity depends on their density. The obtained Si nanostructures have shown to induce a spectral response (SR) enhancement, in comparison with a smooth Si substrate, of about 100 times at 1100 nm wavelength. A very short response time (1 sec) to the humidity was measured for 5% O2 in the SF6/O2 plasma mixture, which was found to be well-correlated with the porosity of the Si nanostructures.

Highlights

The so-called 'Black Silicon' (b-Si) describes nano or micro textured silicon surfaces,[4] it can be produced by Si surface etching using plasma technique, which is compatible with the silicon fabrication technology.[4,5,6,7,8]
The technological motivation behind our present work is to investigate, besides the light anti-reflection property, other potential applications of the Si nanostructures using the maskless SF6/O2 plasma etching, such as light emitting, photo-sensing and humidity sensing
It is more probably related to the formation of the SiOxFy passivation layer, whose thickness increases with the oxygen content in the discharge.[9]

Summary

Introduction

Silicon (Si) nanostructures have a broad, emerging application spectrum ranging from optics and optoelectronics over chemical and biological sensing to photovoltaics.[1,2,3] The so-called 'Black Silicon' (b-Si) describes nano or micro textured silicon surfaces,[4] it can be produced by Si surface etching using plasma technique, which is compatible with the silicon fabrication technology.[4,5,6,7,8] Plasma is a versatile and environmentally friendly technique which uses gases as reactants to modify materials surface. Gas discharges environments have active species such as ions, free radicals, electrons, molecular fragments and photons that are simultaneously generated and can induce surface modification of different materials. Etching is well-known as a consequence of plasma surface activation that results in morphological changes. SF6/O2 plasma mixture, providing the highly reactive etchant fluorine atoms, is widely used for silicon surface nanostructuring,[9,10,11,12,13,14] where the resulted Si nanostructures exhibited remarkable enhanced antireflective surface and light trapping efficiency, which is of great importance for photovoltaic applications to enhance the light absorption in Si solar cells.[10,11,13]

Methods

Results

Conclusion