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In this paper we report a set of experiments at the wafer level regarding field-effect transistors with a graphene monolayer channel transferred on the ferroelectric HfO2/Ge-HfO2/HfO2 three-layer structure. This kind of transistor has a switching ratio of 103 between on and off states due to the bandgap in graphene induced by the ferroelectric structure. Both top and back gates effectively control the carriers' charge flow in graphene. The transistor acts as a three-terminal memristor, termed a memtransistor, with applications in neuromorphic computation.

Trilayer memory capacitors of control HfOalt;subagt;2alt;/subagt;/ floating gate of Ge nanoparticles in HfOalt;subagt;2alt;/subagt; / tunnel HfOalt;subagt;2alt;/subagt; /Si substrate deposited by magnetron sputtering and subsequently annealed are investigated for the first time for applications in radiation dosimetry. a#13; In the floating gate (FG), amorphous Ge nanoparticles (NPs) are arranged in two rows inside the HfOalt;subagt;2alt;/subagt; matrix. The HfOalt;subagt;2alt;/subagt; matrix is formed of orthorhombic / tetragonal nanocrystals (NCs). The adjacent thin films to the FG are also formed of orthorhombic / tetragonal HfOalt;subagt;2alt;/subagt; NCs. This phase is formed during annealing, in samples with thick control HfOalt;subagt;2alt;/subagt;, in the presence of Ge, being induced by the stress. In the rest of the control oxide, HfOalt;subagt;2alt;/subagt; nanocrystals are monoclinic. Orthorhombic HfOalt;subagt;2alt;/subagt; has ferroelectric properties and therefore enhances the memory window produced by charge storage in Ge NPs to above 6 V. High sensitivity of 0.8 mV/Gy to ? particle irradiation from a alt;supagt;241alt;/supagt;Am source was measured by monitoring the flatband potential during radiation exposure after electrical writing of the memory.a#13

High performance trilayer memory capacitors with a floating gate of a single layer of Ge quantum dots (QDs) in HfO2 were fabricated using magnetron sputtering followed by rapid thermal annealing (RTA). The layer sequence of the capacitors is gate HfO 2/floating gate of single layer of Ge QDs in HfO 2/tunnel HfO 2/p-Si wafers. Both Ge and HfO2 are nanostructured by RTA at moderate temperatures of 600-700 °C. By nanostructuring at 600 °C, the formation of a single layer of well separated Ge QDs with diameters of 2-3 nm at a density of 4-5 × 1015 m-2 is achieved in the floating gate (intermediate layer). The Ge QDs inside the intermediate layer are arranged in a single layer and are separated from each other by HfO2 nanocrystals (NCs) about 8 nm in diameter with a tetragonal/orthorhombic structure. The Ge QDs in the single layer are located at the crossing of the HfO2 NCs boundaries. In the intermediate layer, besides Ge QDs, a part of the Ge atoms is segregated by RTA at the HfO2 NCs boundaries, while another part of the Ge atoms is present inside the HfO2 lattice stabilizing the tetragonal/orthorhombic structure. The fabricated capacitors show a memory window of 3.8 ± 0.5 V and a capacitance-time characteristic with 14% capacitance decay in the first 3000-4000 s followed by a very slow capacitance decrease extrapolated to 50% after 10 years. This high performance is mainly due to the floating gate of a single layer of well separated Ge QDs in HfO2, distanced from the Si substrate by the tunnel oxide layer with a precise thickness.