Growth of (111)-oriented Pb(Zr,Ti)O3 layers on nanocrystalline RuO2 electrodes using the sol-gel technique

The influence of the RuO2 bottom electrode microstructure on the texture and ferroelectric properties of sol-gel PZT in RuO2/PZT/RuO2/Pt capacitors is discussed, For high growth temperatures, RuO2 has a columnar microstructure and a mixed (100)/(110) texture, attributed to epitaxial growth on Pt(111) and TiO2 (110) grains of the preannealed Pt/Ti layer. The mixed orientation of RuO2 resulted in a mixed PZT texture and slanted ferroelectric hysteresis characteristic. As the RuO2 growth temperature was reduced, the microstructure of the RuO2 layer turned to fine-grained equiaxed, with a grain size of approximately 10 nm, and PZT developed a sharp (111) texture (I-111/I-100> 100) resulting in a rectangular hysteresis characteristic and a remanent polarization >30 muC/cm(2). The emergence of a strong (111) fiber texture in PZT on fine-grained RuO2 shed new light on the orientation selection mechanisms in sol-gel-prepared PZT layers. Possible applications of this phenomenon for high-density ferroelectric memories with a stacked layout are briefly discussed.