2011 11th IEEE International Conference on Nanotechnology
DOI: 10.1109/nano.2011.6144602
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This work claims that VO2, of interest currently for its metal-insulator phase transition properties, is also a ferroelectric material. Using a VO2 film sandwiched between two silicon dioxide layers, memory transistor structures with substantial and useful properties have been fabricated. Threshold voltage shifts are opposite of charge trapping phenomena and consistent with ferroelectric polarization switching phenomena. Hysteresis memory window of ∼1 V is obtained in −4 to 4 V gate voltage cycling. We argue that the effects observed are due to the ferroelectricity of VO2. Its remnant polarization of ∼0.53 µC/cm2 and coercive field of ∼450 kV/cm are extracted from the saturation behavior of threshold voltage shift. Similar to other ferroelectric memory structures, depolarization effects are observed. The state of memory devices decays gradually and retention times of approximately 15 minutes are obtained at room temperature. These ferroelectric properties do not vanish above metal-insulator phase transition temperature.