Impact of the oxide layer on the electrical properties of silicon nanowires fabricated by metal‐assisted chemical etching

Abstract

Silicon nanowires (SiNWs) have been obtained by metal‐assisted chemical etching (MACE) method from a monocrystalline Si substrate (100). The SiNWs were fabricated by etching the entire thickness of the silicon wafer, obtaining an extraordinary density of monocrystalline long SiNWs with lengths up to 300 microns and diameters ranging from 100 to 500 nm. Once fabricated, SiNWs were dispersed in ethanol. The structure, chemical composition, and surface morphology of the resulting SiNWs were characterized by field emission scanning electron microscopy, transmission electron microscopy, and energy‐dispersive X‐ray spectroscopy. Through these techniques, it was observed that the crystalline core of the nanowires was surrounded by an amorphous layer, which is thicker in the bigger SiNWs. By the chemical analysis of this amorphous layer it was determined that its composition is mainly silicon oxide. To measure the SiNWs electrical properties, single nanowire devices were fabricated aligning nanowires by AC dielectrophoresis between pre‐patterned electrodes. The I–V characteristics of SiNWs were obtained by this method. It was observed that the surface oxide layer produced during the MACE process strongly influences on the electrical conductivity of the SiNWs, producing larger currents in the thinnest nanowires than in the thickest ones, a counter intuitive result that can contribute to the optimization of the MACE process for industrial applications.