Physical Unclonable Function from Disordered Silane-Based Self-Assembled Monolayers

As the quantity of the information increases, it is crucial to implement low-power operation devices. Here, we present physical unclonable function devices using two self-assembled monolayer (SAM) materials, octadecyl trichlorosilane (ODTS) and 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (PFOTES), which have different chain lengths, terminal functional groups, and dipoles. The surface was treated by UV-ozone before the SAM coating process to make it hydrophilic on a p-doped Si substrate. The current value at zero voltage bias was evaluated to utilize the electrical characteristics of the electrical characteristics of the different SAMs on the p-doped Si substrate without an external electric field. The current values of the device-to-device were dispersed based on a specific current. We performed atomic force microscope (AFM), Kelvin probe force microscopy (KPFM), Raman spectroscopy, X-ray photoelectron spectroscopy, contact angle, and ultraviolet-visible spectroscopy to analyze the mixed SAM structure and its electrical properties. We verified the current dispersion caused by dipole affection, not the physical accumulation of SAM materials through the AFM and KPFM patterns of Z-phase and potential on the device surface. Compared to the median value each security key, higher value is defined as the state '1' whereas lower value is defined as the state '0'. The uniqueness and security were evaluated by the 50~66 % of uniformity and 41.1~52.9 % of inter-HD.