The Origin of Low Contact Resistance in Monolayer Organic Field‐Effect Transistors with van der Waals Electrodes

Abstract

been shown to be promising in other different applications, including organic logic circuits, memory devices, various sensors, medical applications, and display drivers. [1][2][3][4][6][7][8][9][10][11] Solution processing approaches for the growth of high-quality organic thin films of up to a wafer-scale size have been reported by several groups. [3,12] However, to fully utilize the advantages of highly crystalline organic semiconductors, large-area deposition is not enough; availability of ultrathin films, or even films with the thickness of down to a single molecular layer, is also very important for reducing the access contact resistance. This is necessary for maintaining the high-speed operation (especially in the staggered top-contact/bottom-gate OFETs), while further shrinking the device size dictated by the overall circuit miniaturization. Recently, we have successfully demonstrated a sub-thermionic subthreshold swing and a high-current-density operation of OFETs based on monolayers of a p-type organic semiconductor, 2,9-didecyldinaphtho[2,3-b:2',3'-f]thieno [3,2-b]thiophene (C 10 -DNTT), used as the active layer. [13,14] In addition, the impactful studies on the monolayer molecular crystals (MMCs) have been conducted broadly. The excellent optical properties of MMCs enable the highperformance optoelectronics. [15,16] Sensitive to the external stimuli owing to the ultrathin feature, the MMCs provide promising candidate for sensor application. [9,17] Meanwhile, the ultrathin smooth surfaces of MMCs allow the high-quality p-n junction and logic circuits. [18,19] In this communication, we investigate the origin of the low contact resistance observed

Ultrahigh On‐Current Density of Organic Field‐Effect Transistors Facilitated by Molecular Monolayer Crystals

“…[13][14][15] To date, the majority of reported contact resistance of OFETs, both in staggered or coplanar structures, are in the range from 100 to 10 000 Ω cm. [12,13,16,17] Recently, through precisely controlling the deposition of the OSC layers and employing charge injection interlayers, Borchert et al and Yamamura et al have improved the charge injection of OFETs by demonstrating contact resistance of only 29 and 47 Ω cm, respectively. [18,19] Other than striving for lower contact resistance, previous work by McCulloch et al, [20] Choi et al, [21] and Waldrip et al [16] have also pointed out the importance of contact resistance in OFETs and the potential risks of miscalculated carrier mobility.…”

High-speed hybrid complementary ring oscillators based on solution-processed organic and amorphous metal oxide semiconductors

“…The p-channel TFT exhibited µ lin and µ sat , I off , and I on /I off ratio of 4.4 and 1.1 cm 2 V −1 s −1 , 10 −13 A, and 10 8 , respectively, while the corresponding values for the n-channel TFT were 1.6 and 1.9 cm 2 V −1 s −1 , 10 −13 A, and 10 9 respectively. Note that, for the p-channel TFT, µ sat value was smaller than µ lin due to an early saturation phenomenon, which has been recently observed in the short-channel, single-crystal OSC-based TFTs and could be attributed to velocity saturation effect, thermal damage during depositing Au and/or the interface diode effect 49,50 .…”

Van der Waals Assembled Solution‐Processed Organic Monolayer Single‐Crystal Transistor for Electrocardiograph Sensing

“…[11] By further reducing the thickness of monolayer, access resistance could be minimized, which is one of the prerequisites of contact idealization for organic field-effect transistors (OFETs). [6,[12][13][14] However, it is important to note that the meniscus-guided solution shearing method is very sensitive to the dielectric and substrate surface properties, thus most of the devices are reported on the smooth SiO 2 substrate. [15][16][17] As a result, effective large-area transfer methods favor scaling up the mass production or commercialization of the OFETs are highly desired by the community.…”