IMF2017

Recently, one-dimensional nanostructures of functional materials have been attracted much attention from the viewpoint of practical applications and as well as for studying their basic physics. Among nanowires (NWs) of various materials, NWs including ferroelectrics can be used as capacitors and transistors in very high density non-volatile memories, and as piezoelectric transducers in vibration energy harvesters. We have developed fabrication technique of ferroelectric NWs/nanotubes using ZnO NWs as a template via MOCVD. In this study, we report introduction of HfO₂-based ferroelectrics, which is more suitable for nanowire capacitors than conventional perovskite typed ferroelectrics because of its excellent ferroelectric properties in thin films below 10nm, into NW capacitors and their electrical properties. ZnO NW templates were grown on Pt-covered SiO₂/Si substrate by MOCVD using Zn(C₂H₅)₂ and O₂ as the precursor and oxidizing gas, respectively. Amorpous (Hf,Zr)O₂ layer was prepared on ZnO NW template at 200 ^oC by MOCVD, and crystallized to ferroelectric orthorhombic phase by high temperature annealing at 800 ^oC and 60-300 s in N₂. Finally, (Hf,Zr)O₂/ZnO NWs are covered with ZnO top layer by MOCVD at low temperature of 300 ^oC. ZnO/(Hf,Zr)O₂/ZnO Multi-shell structure was clearly confirmed by back scattering electron microscopy which can contrast a difference in atomic numbers. XRD analysis revealed that (Hf,Zr)O₂ was successfully crystallized to orthorhombic phase which can show ferroelectricity after annealing. In the conference, ZnO/(Hf,Zr)O₂/ZnO NW capacitors will be discussed.