High conductance bottom-contact pentacene thin-film transistors with gold-nickel adhesion layers

Abstract

Bottom-contact pentacene thin-film transistors (TFTs) with different electrode types have been fabricated to investigate influence of the adhesion layers and surface modification on the transistor characteristics. Gold-nickel alloy or Ti was used for the adhesion layer; the drain/source electrodes were modified with pentafluorobenzenethiol (PFBT) or nonmodified. The TFTs with AuNi layers and PFBT-modified electrodes exhibit channel-length independent saturation mobility. The electrode-type TFT with a channel length of 2.2 μm has a saturation mobility of 0.73 cm2/V s and a transconductance of 229 μS/mm. The high performance is attributed to the low contact resistance of 408 Ω cm.

High‐Mobility Organic Transistors with Wet‐Etch‐Patterned Top Electrodes: A Novel Patterning Method for Fine‐Pitch Integration of Organic Devices

“…At applied V G of below ‐8 V, the normalized contact resistances R c W for both devices are estimated to be ∼200 Ωcm, which is almost the minimum value reported for top‐contact OFET devices . Since the HOMO levels of pentacene, C 10 ‐DNTT, and C 10 ‐DNBDT are estimated to be 5.0 eV, 5.5 eV, and 5.6 eV, and work function of deposited gold films are reported as around 4.7–5.0 eV, the injection barriers between C 10 ‐DNTT/gold, and C 10 ‐DNBDT/gold would have the height of around 0.5 eV. The reason of the low contact resistance is rather attributed to the cleanness of the interfaces between organic semiconductors and metal electrodes.…”

“…However, a major concern for the bottom‐contact OFETs with a polycrystalline semiconductor film relates to the molecular disorder occurring in the vicinity of the metal electrodes . To overcome this problem, electrode surface modifications on gold films by thiol‐based self‐assembled monolayers or UV/O 3 treatment are effective to reduce the contact resistance, however, these devices suffer from irreproducibility and poor long‐term reliability due to chemical instability of most Au‐thiolate SAMs …”

Solvent-Free Toner Printing of Organic Semiconductor Layer in Flexible Thin-Film Transistors

“…The Au contact electrodes were thermally evaporated using a shadow mask, and the channel length and width were 20 µm and 3.5 mm, respectively. The Au contact electrodes were chemically treated with pentafluorobenzenethiol to reduce the contact resistance [40][41][42][43][44]. This substrate is called the base film in this work.…”

High Current-Gain Cutoff Frequencies above 10 MHz in n-Channel C60 and p-Channel Pentacene Thin-Film Transistors

“…We achieved high mobility C 60 and pentacene TFTs with micron-order channel length adopting AuNi adhesion layers and surface modification of drain/source electrodes. 18,19) High frequency operation is expected in the TFTs with high mobility and short channel length. In actual, we realized high current-gain cutoff-frequency of 20 MHz in a C 60 TFT.…”