1:30 PM - 3:30 PM
▲ [17p-PA06-10] Ferroelectric polarization switching of hafnium zirconium oxide thin-film device investigated by second harmonic generation spectroscopy II
Keywords:Hafnium zirconium oxide, second harmonic generation, Fixed polarization
The research on HfO2-based ferroelectric thin films is getting more attention for having various advantages such as large remanent polarization and coercive field, thinner physical thickness compared to conventional ferroelectric films, and Si-based CMOS compatibility. The ferroelectricity is typically obtained in HfO2 thin films with a thickness of less than 20 nm and doped with various elements such as zirconium and yttrium.
we investigated the relationship between SHG traces with respect to the applied pulse voltages and polarization-voltage (P-V) hysteresis loops for Zr-doped HfO2 (Hf-1-xZrxO2 [x~0.5]; HZO) junctions.The fabricated 200 µm ´ 200 µm junctions consist of HZO ferroelectric layers (20 nm) and indium-tin-oxide top and bottom electrodes (30 nm), which show a remanent polarization of 8.8 mCcm-2 and a coercive voltage of 4.5 V. Figure 1 (left side) shows the change in the square root of SHG (400 nm) light intensity (ISHG) with respect to the applied pulse voltages using an 800nm femtosecond laser. ISHG is proportional to the square of the P value, meaning that in an ideal case, the SHG trace shows a butterfly curve. However, the observed SHG traces showed hysteresis loops similar in form to P-V hysteresis loops. This result can be explained in terms of the presence of unidirectional and voltage-independent fixed polarization (Pfix) (for example, surface and interface polarizations) which is greater than the remnant polarization of HZO (PHZOr). Figure 1 (right side, schematic) shows the change in the total polarization of the junction for Pfix> PHZOr.
we investigated the relationship between SHG traces with respect to the applied pulse voltages and polarization-voltage (P-V) hysteresis loops for Zr-doped HfO2 (Hf-1-xZrxO2 [x~0.5]; HZO) junctions.The fabricated 200 µm ´ 200 µm junctions consist of HZO ferroelectric layers (20 nm) and indium-tin-oxide top and bottom electrodes (30 nm), which show a remanent polarization of 8.8 mCcm-2 and a coercive voltage of 4.5 V. Figure 1 (left side) shows the change in the square root of SHG (400 nm) light intensity (ISHG) with respect to the applied pulse voltages using an 800nm femtosecond laser. ISHG is proportional to the square of the P value, meaning that in an ideal case, the SHG trace shows a butterfly curve. However, the observed SHG traces showed hysteresis loops similar in form to P-V hysteresis loops. This result can be explained in terms of the presence of unidirectional and voltage-independent fixed polarization (Pfix) (for example, surface and interface polarizations) which is greater than the remnant polarization of HZO (PHZOr). Figure 1 (right side, schematic) shows the change in the total polarization of the junction for Pfix> PHZOr.