Nanopatterning of Octadecyltrichlorosilane (OTS) Self-Assembled Monolayers By Probe-based Lithography: Extending the Range of Substrates

Surface functionalization of oxides plays a fundamental role in nanotechnology, from microelectronics to photovoltaics [1,2]. Local oxidation by scanning probe is a powerful tool to fabricate chemical patterns at the nanometer scale, enabling the hierarchical assembly of complex structures [3,4]. Notwithstanding the paramount interest in the tailored functionalization of various kinds of oxide materials, most of the literature about probe-based electrooxidation lithography has so far focused on Si wafer substrates. The potential of titanium dioxide (TiO2) and surface-passivated aluminum (Al/AlOx) to serve as substrates for electrooxidative nanolithography is here demonstrated. The results obtained on TiO2 and Al/AlOx are compared with reference commercial substrates, such as surface-passivated silicon (Si/SiOx) and indium tin oxide (ITO). The conditions for the functionalization of the different substrate materials with n-octadecyltrichlorosilane (OTS) monolayers are reported. Next to the structural study of the formed monolayers by contact angle goniometry, Fourier Transform Infrared (FTIR) spectroscopy and Scanning Force Microscopy (SFM), the different oxidation processes on bare and OTS-functionalized substrates were studied by lateral force imaging and scanning Kelvin probe microscopy. Chemical activation was also confirmed by metallization processes.