Title: Synthesis and characterizations of MPS or PANI heterojunctions doped with erbium

Abstract

P-type silicon was used for the formation of macroporous silicon (MPS) by electrochemical corrosion in HF:DMF solution, 1:9 in volume. The Schottky structure was obtained by depositing polyaniline (PANI); which was doped with different contents of erbium (Er) using cyclic voltammetry method, in millimolar order (mM). The structural analysis by scanning electron microscopy (SEM) showed that the pores are formed randomly throughout the porous region, with diameters ranging between 0.25 and 1.20 μm and length around 15 μm. The Spectrometry analysis X-rays by energy dispersion (EDS) reveals that the PANI was deposited along the pore walls, with a higher concentration in the regions closest to the surface. Rutherford backscattering spectrometry (RBS) shows that Er has been diffusing through the PANI layer, but with greater concentration at the superficial region. According to the Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) analysis, the presence of Er gave rise to the formation of additional functional groups besides that corresponding to polyaniline and silicon oxide phases. In samples doped with Er, both FTIR and Raman spectroscopy showed that Er creates additional functional groups that, according to X-ray diffraction (XRD), reduce the crystallinity of PANI and with that decrease the conductivity. The electrical characterization confirms not only the decrease in the conductivity of the PANI but also the decrease in the current that passes through the MPS/PANI junction. Those are associated with the increase of the SiO2 within the porous structure. This effect was partially recovered by the inclusion of Er, possibly due to its effect of reducing the width of the space charge region. The effect of Er present in the MPS/PANI interface through the modification of the work function or the increase of surface states.