Modification of work function of Ti by self-assembled monolayer molecules on Si O ₂ p-Si

A method was used to change the work function of Ti (φTi) using self-assembled monolayer (SAM) molecules of dipolar, aminopropyl triethoxy silane, a change attributed to the change in the electrical potential at the TiSAM interface. The SAM was deposited on Si O2 Si followed by Ti electrode evaporation to form a TiSAMSi O2 p-Si stack for capacitance-voltage (C-V) analyses. The binding of SAM on the Si O2 surface was confirmed using Fourier-transform infrared spectroscopy, and the surface coverage of SAM was determined by the change in the flat-band voltages VFB with deposition time. After 1 h of deposition time, an independence of the total capacitance Ctotal and VFB was indicative of saturated surface coverage of SAM on the Si O2 surface. A relationship between the fraction x (where 0<x<1 and x=1 correspond to a monolayer) of the Si O2 surface covered with SAM, at saturated surface coverage, and the dielectric permittivity of SAM (KSAM) was found to be x=0.15 KSAM +0.09; if KSAM is assumed to be 3, x is estimated to be 0.54. The φTi on the bare Si O2 surface as well as on the Si O2 surface covered with SAM at saturated surface coverage were determined from VFB versus total equivalent oxide thickness plots. The maximum change in φTi from TiSi O2 p-Si to TiSAMSi O2 p-Si configuration was found to be 0.2 V.