Solution-Processed Indium Oxide Transistors: Printing Two-Dimensional Metals UMN MRSEC Award DMR# 1420013 2017 Dan Frisbie & Chris Leighton (IRG-1), University of Minnesota Intellectual Merit Transistors, the building blocks of all computer technologies, are currently based on semi- conductors such as silicon, manufactured using energy-intensive processes. Materials that can be processed into electronic devices using cheaper and less energy-intensive methods are of high interest for a number of applications. In work recently performed in IRG-1, UMN MRSEC researchers have demonstrated landmark performance in transistors based on the widely studied transparent semiconductor indium oxide, fabricated via solution processing. Solution processing is a low temperature, low cost approach (in this case essentially a form of inkjet printing), but was shown here to be capable, in conjunction with cutting-edge electrolyte dielectrics, of voltage-induced metallic behavior at interfaces. This metallic conductivity is important, as it maximizes current output, improving device performance and applicability. This is work performed by former MRSEC student Wei Xie (in the Frisbie group), in collaboration with former student Xin Zhang (in the Leighton group). Solution processed transistors were made via inkjet printing, depositing In2O3 semiconductor layers, an ion gel dielectric, and a PEDOT:PSS top gate electrode. After thermal annealing in air at only 400 C high performance transistors were created, achieving almost 10^15 cm^-2 electron densities at a mobility of 11 cm^2V^-1s^-1 mobility. Critically, Hall effect measurements confirmed the electron densities, while temperature-dependent resistance measurements (see figure) verified a true 2D insulator-metal transition. Obtaining a voltage induced metallic state is important, as it maximized the “ON” current of such transistors, which is a key performance metric. The work was recently accepted for publication in Advanced Electronic Materials.