Polymer ferroelectric field-effect memory device with SnO channel layer exhibits record hole mobility

Abstract

Here we report for the first time a hybrid p-channel polymer ferroelectric field-effect transistor memory device with record mobility. The memory device, fabricated at 200°C on both plastic polyimide and glass substrates, uses ferroelectric polymer P(VDF-TrFE) as the gate dielectric and transparent p-type oxide (SnO) as the active channel layer. A record mobility of 3.3 cm(2)V(-1)s(-1), large memory window (∼16 V), low read voltages (∼-1 V), and excellent retention characteristics up to 5000 sec have been achieved. The mobility achieved in our devices is over 10 times higher than previously reported polymer ferroelectric field-effect transistor memory with p-type channel. This demonstration opens the door for the development of non-volatile memory devices based on dual channel for emerging transparent and flexible electronic devices.

Figure 1. Conceptual design of the devices.

(a), polyimide substrate; (b), glass substrate: the following layers make up the device stack (from bottom to top): substrate, 200 nm Si₃N₄ layer, 30 nm SnO active layer, 10 nm Ti/40 nm Au source and drain contacts, 300 nm P(VDF-TrFE) ferroelectric layer and 80 nm Al top gate; (c), optical transmission characteristics of the glass substrate, SnO/glass, and P(VDF-TrFE)/glass, and (d), TEM image showing cross section of the SnO/P(VDF-TrFE) interface, and optical profilometer scan (inset) showing the major parts of the device.

Figure 2. FeFET static characteristics.

Output characteristics from V_GS = 0 V to −15 V at −3 V steps of (a), glass substrate; (b), flexible substrate; Transfer characteristics at V_DS = −1 V of (c), rigid device; (d), flexible device.

Figure 3. Materials Characterization.

(a), XRD pattern of SnO thin films. The lines at the bottom show the diffraction patterns of tetragonal SnO (JCPDS card No. 06-0395) and tetragonal Sn (JCPDS card No. 04-0673); (b), GIXRD pattern of P(VDF-TrFE) layer showing the dominat reflection corresponds to the ferroelectric β phase; (c), AFM image of the SnO surface. The SnO films show very smooth surfaces with a root mean square roughness of ∼1.8 nm; (d), AFM image of the P(VDF-TrFE) surface morphology, with an average grain size of ∼160 nm.

Figure 4. Retention characteristics.

(a), rigid device; (b), flexible device. The ON/OFF states were produced at gate voltages of −30/+30 V with a 1 sec pulse and the retention was measured at zero gate bias condition.