A nanoscale Cu_2-xSe ultrathin film deposited via atomic layer deposition and its memristive effects

An ultrathin film of copper selenide 50 nm thick was deposited using a home-made atomic layer deposition apparatus. Synthesized copper pivalate and bis(triethylsilyl) selenide precursors were used. The deposition rate at 160 °C was 0.48 Å per atomic layer deposition cycle. The thickness was monitored by an in situ ellipsometer and further analyzed by an atomic force microscope. The composition and structure of the film were confirmed by x-ray photoelectron spectroscopy, Raman spectroscopy, and x-ray diffraction to be Cu_1.16Se. The fluorine-doped tin oxide/Cu_1.16Se/tungsten wire memristor was fabricated and its memristive effect was investigated. The non-linear I-V curve and spike-timing-dependent plasticity of our Cu_1.16Se memristor demonstrate that the short-term and long-term potentiation that occurs in a human brain can be mimicked by adjusting voltage-pulse intervals. A memristor is the electrical equivalent of a synapse. Our memristor has a 1 ms switching time, a 400 s retention time, R_off/on = 2, and reproducibility over 1000 cycles.