Molecular Modification of CNT Junctions

Carbon nanotube networks (CNNs) are increasingly finding applications as thin film transistors (TFTs), integrated circuits, and display drivers on flexible, transparent substrates. This is attributed to the higher carrier mobility of CNNs as compared to amorphous silicon and organic TFTs [1,2]. However, high electrical [3-5] and thermal [6,7] resistances at individual nanotube junctions (NJs) limit the performance of CNN devices. The resistances of the junctions are no less than an order of magnitude higher than those of individual carbon nanotubes (CNTs). This causes high power dissipation at the NJs. In the end this causes degradation of the overall device performance and reliability [3,4]. Previous studies have shown how molecular modification of CNT junctions can reduce the sheet resistance of conducting and transparent CNN electrodes. [refs to Vikar and Bao]. However, to our knowledge, the effects of molecular modification of CNT junctions on device performance remain unreported.In this study, we present a novel method to improve CNN TFT performance, through the application of 0-dimensional (0D) molecules, e.g. C60 fullerenes and CdSe quantum dots, onto the surface of the CNN device. These materials can be applied through spin-coating, dip-coating, or spray coating. We find the absorbance spectra of the 0D materials correlate with their HOMO-LUMO gap and concentration of these molecules in solution. Our preliminary data also suggest preferential attachment of these nanoparticles to NJs, eliminating the need for lithography to selectively deposit 0D materials at NJs. Our results suggests these molecules may act as a nanosolder or nanoglue at the NJs, modifying their electrical and thermal resistances for improved device performance.[1] D. Sun, et al., Nat. Nanotechnol. 6, 156 (2011); [2] Q. Cao, et al., Nature 454, 495 (2008); [3] P. Nirmalraj, et al., Nano Lett. 9, 3890 (2009); [4] M. Stadermann, et al., Phys. Rev. B: Condens. Matter Mater. Phys. 69, 201402 (2004); [5] A. Kyrylyuk, et al., Nat. Nanotechnol. 6, 364 (2011); [6] R. Prasher, et al., Phys. Rev. Lett. 102, 105901 (2009); [7] J. Yang, et al., Appl. Phys. Lett. 96, 023109 (2010).