Solution-processed ZnO Single Nanoparticle Transistor Using Water-based Dispersions
K. Wolff, U. Hilleringmann
University of Paderborn, DE
Keywords: ZnO nanoparticles, Schottky barrier, FET
Abstract:The integration of printable transistors is an issue of recent work. Different proposals base on ZnO nanoparticle inks, which have to undergo a post-deposition annealing in order to improve the film quality and burn away organic residuals. Therefore, a solution-processed field effect transistor with ZnO nanoparticles (np-ZnO) is presented, which were deposited by spin-coating of water-based dispersions. The highest temperature used in presence of the semiconductor was 200°C. This qualifies the process for flexible substrates (e.g. plastic foils) in general. The single nanoparticle transistor’s active region consists of several nanoparticles connected in parallel (fig. 1). Electrical characterisation revealed n-type FET behaviour. As can be seen in figure 2, the np-ZnO transistor undergoes a saturation. Because the nanoparticle transistor is a S/D Schottky barrier FET, charge carriers can overcome the junction barriers. The transfer I-V-curve (fig. 3) can be modelled by the basic equations for FETs, which leads to simple extraction of the device parameters. Complete I-V-measurements revealed the subthreshold swing of 290 mV/dec, the on/off current ratio of 5 _ 10^3, the threshold voltage of -0.13V and the carrier mobility of 0.05cm^2/Vs, which is the highest mobility of low temperature processed np-ZnO FETs reported to date.