Solution-processed zirconium acetylacetonate charge-trap layer for multi-bit nonvolatile thin-film memory transistors

The charge trap property of solution-processed zirconium acetylacetonate (ZAA) for solution-processed nonvolatile charge-trap memory (CTM) transistors is demonstrated. Increasing the annealing temperature of the ZAA from room temperature (RT) to 300°C in ambient, the carbon double bonds within the ZAA decreases. The RT-dried ZAA for the p-type organic-based CTM shows the widest threshold voltage shift (∆V_TH ≈ 80 V), four distinct V_THs for a multi-bit memory operation and retained memory currents for 10³ s with high memory on- and off-current ratio (I_M,ON/I_M,OFF ≈ 5Ⅹ10⁴). The n-type oxide-based CTM (Ox-CTM) also shows a ∆V_TH of 14 V and retained memory currents for 10³ s with I_M,ON/I_M,OFF ≈ 10⁴. The inability of the Ox-CTM to be electrically erasable is well explained with simulated electrical potential contour maps. It is deduced that, irrespective of the varied solution-processed semiconductor used, the RT-dried organic ZAA as CTL shows the best memory functionality in the fabricated CTMs. This implies that the high carbon double bonds in the low-temperature processed ZAA CTL are very useful for low-cost multi-bit CTMs in flexible electronics.