Effect of etching parameters on the electrochemical response of silicon nanowires

Silicon nanowires combine a high electrical conductivity with low thermal conductivity due to the small cross section offering a good template for sensing. Silicon p-type (100) substrate was used in this work to present a comparative study from a morphological point of view as well as for the electrical properties of silicon nanowires (SiNWs) etched by Ag-assisted chemical method in one-step and two-step process. The comparison between both techniques for SiNWs samples' elaborated with Metal-Assisted Chemical Technique (MACE) was investigated by Scanning Electron Microscopy images that clearly show the presence of nanowires and the existence of porous silicon structure especially by Transmission Electron Microscopy technique. Several particles on the SiNWs surface such as oxygen and hydrogen elements were identified by Fourier-Transformed Infrared Spectroscopy measurements. The results indicate that the MACE's steps influence the nucleation and motility of Ag particles, which leads to a different length and density structure within the nanowires. These parameters influence the electrochemical properties of the surface that was studied using electrochemical measurements. Impedance analysis revealed that the charge transfer resistance decreases with the length of the SiNWs dissimilar to the capacitance based on the cyclic voltammetry analysis. In this paper, we studied the electrochemical parameters which indicate that two-step MACE procedure presents a resistance nearly the half of the value of SiNWs produced using one-step MACE technique; as for the capacitance, it increases by 28.5%. We can notice that SiNWs produced using two-step MACE show better results for biosensing application. For that reason, we decide to functionalize the two-step MACE SiNWs to prove the ease of the surface modification. Deposition of nickel nanoparticles was analysed manifesting a good amelioration of the resistance with a factor of 2.5.