| AVS 56th International Symposium & Exhibition | |
| Electronic Materials and Processing | Tuesday Sessions |
| Session EM-TuP |
| Session: | Electronic Materials and Processing Poster Session |
| Presenter: | J.E. Royer, University of California, San Diego |
| Authors: | J.E. Royer, University of California, San Diego S. Lee, University of California, San Diego C.N. Colesniuc, University of California, San Diego I.K. Schuller, University of California, San Diego W.C. Trogler, University of California, San Diego A.C. Kummel, University of California, San Diego |
| Correspondent: | Click to Email |
Understanding vapor interactions with organic thin films is key to application of organic thin films in chemical sensing. Ultra-thin organic thin film transistors (OTFTs) fabricated using only 4 monolayers (4ML) of metal phthalocyanines (MPc) are model devices for studying sensing physics since analyte adsorption is almost entirely restricted to the air/MPc interface since adsorption within the grain boundaries is minimal. Even in ultra-thin MPc OTFT heterostructures the films are sufficiently thin that gas adsorption occurs primarily from interfaces instead of grain boundaries. In an ideal ultra-thin heterostructure, gas adsorption should occur only at the interfaces thereby creating carrier traps which alter the conduction in the OTFT channel. This was directly investigated using MPc heterostructure OTFT s. The response to isophorone doses for metal free phthalocyanine (H2Pc) OTFTs and cobalt phthalocyanine (CoPc) OTFT s were compared to OTFT s fabricated with bilayer films (CoPc/H2Pc and H2Pc/CoPc). The sensitivity to isophorone is more than 5 times greater for H2Pc OTFTs than CoPc OTFTs, and the desorption kinetics fit a single exponential decay for H2Pc whereas a bi-exponential decay is required for CoPc. The heterostructure OTFT responses did not strongly correlate with the H2Pc or CoPc OTFTs which suggests a combination of surface doping and adsorption at the H2Pc/CoPc interface. This could lead to highly sensitive OTFT sensors based on multilayered MPc film structures.