Thin Film Sequential Circuits: Flip-Flops and a Counter Based on p-SnO and n-InGaZnO

Oxide semiconductors have emerged as ideal candidate materials for flexible electronics and circuits. However, complementary flip-flops, which are the essential building blocks in sequential circuits, based on all-oxide thin-film transistors (TFTs) have not yet been demonstrated. Here, we employed n-type indium gallium zinc oxide and p-type tin monoxide to achieve J-K flip-flop (JK-FF) and D-type edge-triggered FF (D-FF). The operation properties of the JK-FF and D-FF were characterised both statically and dynamically. The output signals of the D-FF show great robustness. The D-FF shows very short propagation delay times of 17 and 40 μs from “0” to “1” and from “1” to “0”, respectively. Based on the D-FFs, a two-bit counter with 90 transistors was designed and fabricated successfully, acting as either up-counter or down-counter. To the best of our knowledge, this counter has the highest integration among the reported thin-film complementary sequential circuits based on all-oxide transistors to date.