Domain Wall Movement in Undoped Ferroelectric HfO2: A Rayleigh Analysis

The discovery offerroelectricity in doped HfO2 in 2011gave rise to quite a stir in the scientific world that persists upto this day. The complementary metal oxide semiconductor compatibility,as well as good scalability, enables versatile applications rangingfrom ferroelectric field effect transistors to ferroelectric tunneljunctions and neuromorphic devices. Stabilizing the metastable polarorthorhombic phase with space group Pca2(1)-phase, which is responsible for the ferroelectricity in HfO2, is still challenging. We demonstrate for the first timea sputter deposition of undoped ferroelectric HfO2 on superconductingNbN electrodes, with a remanent polarization of 6.4 & mu;C/cm(2). Grazing incident X-ray diffraction on the layer structure,dynamic hysteresis measurements, and electron energy loss spectroscopyon fabricated devices indicate a HfO2 layer with low oxygendeficiency. Furthermore, no evidence of interdiffusion of oxygen ornitrogen at the interfaces is found. A sudden "wake-up"for the transition from the dielectric state to the ferroelectricstate as well as no classical fatigue effect for the degradation ofthe ferroelectric performance are observed. These analyses are extendedby an investigation of Rayleigh behavior using impedance spectroscopy.In that way, the domain wall flexibility is quantified and classifiedwithin different regimes of the various domain wall motions.