Vacuum-UV (VUV) was utilized to develop previously studied structure-property relationships on the growth of organic semiconductors as a unique tool to controllably vary the prevailing surface energy of the dielectric over a wide range. Before fabricating organic field effect transistors (OFETs), the AlOx ODPA dielectric's physical and electrical properties were determined. AlOx dielectrics were grown via anodization of Al electrodes to yield 23 nm thick layers. The surface energy of the VUV-treated n-octadecylphosphonic acid (ODPA) surfaces were evaluated by measuring the contact angles of toluene and water on the surface. The Owens-Wendt-Kaelble equation was used to determine the surface Energy. All surface energy evaluations were performed using six replicates. The electrical characteristics of OFETs were measured in air and in the dark using a semiconductor parameter analyzer. For high surface energy substrates and thin dinaphtho[2,3- b :2',3'- f ]-thieno[3,2- b ]thiophene (DNTT) films, the resulting films were smoother, with the DNTT molecules effectively wetting the substrate. The early-stage growth resulted in surface topologies with low grain sizes and thus lower field-effect mobilities. Furthermore, VUV treatment also resulted in an increased density of fixed charges at the semiconductor?dielectric interface, contributing to the lower observed field-effect mobilities.
- organic field-effect transistors
- structure-property relationships
- thin films
ASJC Scopus subject areas
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering