Carrier transport mechanisms of multilevel nonvolatile memory devices with a floating gate consisting of hybrid organic/inorganic nanocomposites

Nonvolatile memory devices based on a poly(4-vinylphenol) (PVP) layer containing Cu2ZnSnS4 (CZTS) nanoparticles were fabricated by using a simple spin-coating method. An energy dispersive spectrum revealed that the CZTS nanoparticles were Cu poor and Zn rich. Transmission electron microscopy images showed that the CZTS nanoparticles were randomly distributed in the PVP layer. Capacitance-voltage (C-V) curves for Al/CZTS nanoparticles embedded in PVP layer/p-Si devices at 1 MHz showed a hysteresis with flat-band voltage (V-fb) shifts, which resulted from the existence of CZTS nanoparticles acting as trap sites in the memory devices. The magnitudes of the V-fb corresponding to the memory window shifts between 1.0 and 2.5 V, as determined from the C-V data at 1 MHz, were dependent on the voltages applied to the memory device, indicative of multilevel characteristics for the memory effect. The operating mechanisms of the writing and the erasing processes for Al/CZTS nanoparticles embedded in PVP layer/p-Si devices are described on the basis of the C-V results and the energy-band diagrams. (C) 2014 Elsevier B.V. All rights reserved.