Low-temperature sintering of in-plane self-assembled ZnO nanorods for solution-processed high-performance thin film transistors

ZnO is an attractive active semiconducting material for thin-film transistor (TFT) applications due to its high band gap, high mobility, ease of forming Ohmic contacts, and low toxicity. Here we present a process for solution fabrication of ZnO TFTs based on a simple, double-layer spin-coating process during which a dense layer of in-plane zinc oxide nanorods is deposited first, followed by coating of a chemical precursor solution and low-temperature annealing. First, a lower ZnO nanorod concentration can lead to the self-assembly of nanorods along the in-plane direction to form a relatively dense semiconductor layer. Then the chemical precursor solution sinters the nanorods and improves the contact between them. The n-channel TFTs exhibit high ON/OFF ratio of 10(5)-10(6), mobilities of similar to 1.2 cm(2) V-1 s(-1) and low threshold voltages of about -4 V with low hysteresis. We show that the quality of the semiconductor film and the minimum annealing temperature depends sensitively on the thickness and composition of the two layers.