Single‐Crystal Statistical Field‐Effect Transistors

Abstract

highly specialized ink-jet printer that can print 1 μm dots with excellent alignment; [ 10 ] however, to contact single crystals that are randomly oriented would require too complex mapping and aligning methods. This complexity, in fi nding a suitable method to use single crystals in a simple fabrication process, is probably part of the reason that there is very little synthetic effort devoted to fi nding better crystal-forming molecular structures, not to mention their implementation in devices through a printing process.Here, we propose to arrive at highperformance materials by making the crystal-forming molecules relevant through the use of a dedicated transistor architecture that is designed to accommodate the features of the crystal-forming organic materials. In ref. [ 11 ] the authors developed a method for contacting nanowires that is based on forming highly dense and aligned nanowires such that the deposition of the contacts did not need to be aligned to a single nanowire. However, aligning the nanowires was a must and to capture nanowires between source and drain electrodes it was required to maintain few microns resolution, which was achieved through photolithography. Here we report a transistor architecture where the fabrication of the source and drain contacts and the contacting of the crystals are implemented separately. This introduces another degree of freedom in the device design which can be used to easily accommodate organic crystals in an FET structure. After discussing the new transistor structure and its mode of operation we demonstrate its high performance. We fi rst demonstrate a P-type transistor having a 100 μm channel length which is based on multiple, primarily isolated and randomly oriented, single crystals having the size of ≈10 μm. We fi nd that the transistors' effective mobility is at least 50% of that found for a single crystal. We then move to showing the generality of the structure by demonstrating also N-type and varying crystallites morphologies. Results and Discussion The Statistical FETThe concept of the statistical FET (SFET) structure is shown in Figure 1 a-c, which also illustrates the specifi c implementation process adapted here. Figure 1 a shows a top view of the gate and gate dielectric onto which many crystallites were deposited at a number density such that they form a discontinuous polycrystalline layer.

Wafer‐Scale Growth of Aligned C60 Single Crystals via Solution‐Phase Epitaxy for High‐Performance Transistors

“…In this way, the trap carrier density of the 1D C 60 crystal array is estimated to be as low as 3.31 × 10 −9 C cm −2 , which is 7-136 times lower than that of the C 60 crystals prepared by previously reported methods (Figure 4f and Table S1, Supporting Information). [11][12][13][14]20,[46][47][48][49][50][51][52] The excellent device performance of the OFET device could be attributed to the high crystal quality of 1D C 60 single crystal and the optimized device structure with good electrical contacts. Next, the performance uniformity of 55 C 60 crystal array-based devices on the same substrate was investigated.…”

“…Fullerene (C 60 ) and its derivatives with outstanding optoelectronic properties are identified to be promising materials to construct high-performance electronic and photonic devices, such as solar cells, [1][2][3] superconductors, [4,5] ferromagnets, [6] photodetectors, [7][8][9] tunnel transistors, [10] and organic field-effect transistors (OFETs), [11][12][13][14] owing to their highly conjugated molecular structures, [15] high electron-accepting, [16,17] and 3D electrontransporting properties. [18] Though most of the current applications rely on the use of C 60 thin films, further improvement of the device performance is hindered by the intrinsic problems in the polycrystalline thin-film systems, such as abundant grain boundaries as well as a large number of defects.…”

Key factors affecting contact resistance in coplanar organic thin-film transistors

“…A general-purpose 2D finite-element simulator (ATLAS, Silvaco) was employed for a physical and numerical investigation into OTFTs. This simulation tool performs selfconsistent calculation of solutions to coupled Poisson's and drift-diffusion equation over a user-defined 2D discrete mesh [14][15][16][17][18]. The Schottky model for metal electrodes is included to dictate contact effects in OTFTs.…”

Nanostructured Graphene: An Active Component in Optoelectronic Devices

“…In this case, the overall charge transport is limited by inter-domain transport, and graphene blended into a film can effectively solve this problem by forming highly conductive inter-domain pathways. Previously reported statistical transistors where metallic islands passivate disconnected crystals or FETs with a carbon-nanotube/polymer hybrid channel showed similar benefits from enhanced connectivity or percolation [ 51 , 52 ]. However, it is important to note that, especially for transistor applications, care has to be taken not to make the entire channel too metallic (i.e., on-off ratio compromised).…”