Fabrication of single crystal field-effect transistors with phenacene-type molecules and their excellent transistor characteristics

Abstract

Single crystal field-effect transistors (FETs) using [6]phenacene and [7]phenacene show p-channel FET characteristics. Field-effect mobilities, μs, as high as 5.6×10−1cm2V−1s−1 in a [6]phenacene single crystal FET with an SiO2 gate dielectric and 2.3cm2V−1s−1 in a [7]phenacene single crystal FET were recorded. In these FETs, 7,7,8,8-tetracyanoquinodimethane (TCNQ) was inserted between the Au source/drain electrodes and the single crystal to reduce hole-injection barrier heights. The μ reached 3.2cm2V−1s−1 in the [7]phenacene single crystal FET with a Ta2O5 gate dielectric, and a low absolute threshold voltage |VTH| (6.3V) was observed. Insertion of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) in the interface produced very a high μ value (4.7–6.7cm2V−1s−1) in the [7]phenacene single crystal FET, indicating that F4TCNQ was better for interface modification than TCNQ. A single crystal electric double-layer FET provided μ as high as 3.8×10−1cm2V−1s−1 and |VTH| as low as 2.3V. These results indicate that [6]phenacene and [7]phenacene are promising materials for future practical FET devices, and in addition we suggest that such devices might also provide a research tool to investigate a material’s potential as a superconductor and a possible new way to produce the superconducting state.