The memory effect and retention characteristics of a Ge nanocrystal (NC) floating gate memory structure consisting of Hf-aluminate (HfAlO) tunnelling and control oxides have been investigated by means of high-frequency capacitance–voltage (C–V) and capacitance–time (C–t) measurements. The trilayer structure (HfAlO/Ge-NC/HfAlO) on Si was fabricated by pulsed-laser deposition at a relatively low temperature. A high-resolution transmission electron microscopy study revealed that the Ge nanocrystals are about 5 nm in diameter and are well distributed within the amorphous HfAlO matrix. The memory effect was revealed by the counter-clockwise hysteresis loop in the C–V curves and a high storage charge density of about 1 × 1013 cm−2 and a large flat-band voltage shift of 3.6 V have been achieved. An 8% decay in capacitance after 104 s in the C–t measurement suggests a promising retention property of Ge NC charge storage. The effects of size/density of the Ge NC, the tunnelling and control oxide layer thicknesses and their growth oxygen partial pressure to the charge storage and charge retention characteristics have been studied.

The memory effects of gold (Au) nanocrystal (NC) non-volatile memory structures consisting of polyvinylpyrrolidone (PVP) K-30 polymer tunneling and control layers are investigated. The trilayer structure (PV P/Au-NCs + PV P/PV P) on p-type Si substrate was fabricated by spin coating, and transmission electron microscopy study reveals that the average size of the Au-NCs formed is about 5 nm in diameter. Capacitance-voltage (C-V) measurement on the memory structure shows a counter-clockwise hysteresis loop with a significant flat band voltage shift, revealing a memory effect of the Au-NCs with a charge density of up to 1 x 10(12) cm(-2) and a flat band voltage shift of 2.0 V. A unique feature of the double loop in the C-V curves suggests double barriers during electron tunneling. The I-V hysteresis is also characterized, and a switching mechanism of resistive change is discussed.