Enhanced self-assembled monolayer treatment on polymeric gate dielectrics with ultraviolet/ozone assistance in organic thin film transistors

Poly-4-vinylphenol (PVP), cross-linked PVP and poly(methyl methacrylate) (PMMA) are employed as polymeric insulators and chemical vapor deposition (CVD) is utilized to form self-assembled monolayers on the polymeric insulators. With a hexamethyldisilazane monolayer on polymeric dielectrics, an ordered molecular orientation is formed with larger grains resulting in improved carrier mobilities, and low threshold voltages (V_T). Moreover, ultraviolet/ozone (UVO) treatment is used to enhance the alignment of HMDS monolayer on polymeric insulator surface and a time dependent effect is observed for UV/ozone treatment. For PVP and cross-linked PVP substrates, a short UVO exposure enhances the HMDS reaction on the polymer surface, and a long UVO exposure shows an adverse effect. On the other hand, PMMA is found to be more sensitive to UVO treatment and displayed performance degradation. These findings will be of value for solution processed insulators for printable electronic applications on flexible substrates.