Memristors Based on Many-Layer Non-Stoichiometric Germanosilicate Glass Films

Nonstoichiometric GeSixOy glass films and many-layer structures based on them were obtained by high-vacuum electron beam vapor deposition (EBVD). Using EBVD, the GeO2, SiO, SiO2, or Ge powders were co-evaporated and deposited onto a cold (100 degrees C) p(+)-Si(001) substrate with resistivity rho = 0.0016 +/- 0.0001 Ohm center dot cm. The as-deposited samples were studied by Fourier-transformed infrared spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. A transparent indium-tin-oxide (ITO) contact was deposited as the top electrode, and memristor metal-insulator-semiconductor (MIS) structures were fabricated. The current-voltage characteristics (I-V), as well as the resistive switching cycles of the MIS, have been studied. Reversible resistive switching (memristor effect) was observed for one-layer GeSi0.9O2.8, two-layer GeSi0.9O1.8/GeSi0.9O2.8 and GeSi0.9O1.8/SiO, and three-layer SiO2/a-Ge/GeSi0.9O2.8 MIS structures. For a one-layer MIS structure, the number of rewriting cycles reached several thousand, while the memory window (the ratio of currents in the ON and OFF states) remained at 1-2 orders of magnitude. Intermediate resistance states were observed in many-layer structures. These states may be promising for use in multi-bit memristors and for simulating neural networks. In the three-layer MIS structure, resistive switching took place quite smoothly, and hysteresis was observed in the I-V characteristics; such a structure can be used as an "analog" memristor.