High mobility solution-processible organic semiconductor: Copper tetrabenzoporphyrin

In this study, two device architectures were employed to pursue better device performance: (1) recessed-electrode geometry and (2) Ta₂O₅/SiO₂ bi-layer gate dielectric. Surface uniformity is critical for tetrabenzoporphyrin precursor (CuT-CP). To enhance the uniformity, recessed-electrode geometry was employed. The substrate was a highly doped n-type silicon wafer with 160 nm thick grown oxide on top, and a thin layer of CYTOP® was applied to protect the gate dielectric from contamination. After patterning with photolithography, the samples were exposed to oxygen plasma and followed by a SiO₂ etch. Devices with a Ta₂O₅/SiO₂ bi-layer gate dielectric were fabricated to lower the operating voltage. The substrate was a highly doped n-type silicon wafer with two gate insulators, Ta₂O₅ and SiO₂, deposited on top by electron-beam deposition and Plasma Enhanced Chemical Vapor Deposition (PECVD), respectively. A 2.5 nm titanium adhesion layer and a 35 nm gold electrode were pattered with photolithography and deposited with e-beam evaporator. In comparison, samples with standard gold electrodes and SiO₂ gate dielectric were fabricated in a parallel process.