Effective negative capacitance has been postulated in ferroelectrics because there is a hysteresis in plots of polarization-electric field. Compelling experimental evidence of effective negative capacitance is presented here at room temperature in engineered devices, where it is stabilized by the presence of a paraelectric material. In future integrated circuits, the incorporation of such negative capacitance into MOSFET gate stacks would reduce the subthreshold slope, enabling low power operation and reduced self-heating.
Dynamic piezoresponse force microscopy: Spatially resolved probing of polarization dynamics in time and voltage domains J. Appl. Phys. 112, 052021 (2012) Co-sputtering yttrium into hafnium oxide thin films to produce ferroelectric properties Appl. Phys. Lett. 101, 082905 (2012) Safe and consistent method of spot-welding platinum thermocouple wires and foils for high temperature measurements Rev. Sci. Instrum. 83, 084901 (2012) Additional information on J. Appl. Phys.
The characteristics of polycrystalline BaTiO3 metal-insulator-metal capacitors, fabricated using pulsed laser deposition, are investigated from room temperature to 420 K. The capacitance–voltage characteristics show ferroelectric behaviour at room temperature, with a phase transition to paraelectric at higher temperature. However, the permittivity response shows paraelectric behaviour across all measured temperatures. So BaTiO3 exists here in a mixture of cubic and tetragonal phases. The BaTiO3 films have a columnar structure, with grain size increasing with film thickness due to their increasing height but not diameter. This correlates with an increase in remnant polarization. The results support a size driven phase transition in thin films of polycrystalline BaTiO3.
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