In-situ low temperature growth and orientation control in MOCVD PZT/RuO2 thin film heterostructures on SiO2/Si substrates

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Abstract
Pb(Zr0.5Ti0.5)O3/RuO2 (PZT/RuO2) thin film heterostructures with controlled PZT and RuO2 orientation were successfully grown in-situ on SiO2/(001)Si substrates at 525°C, using metal-organic chemical vapor deposition (MOCVD). XRD analysis revealed that the textured orientation of the PZT films is strongly dependent on the orientation of RuO2 bottom electrode layers. PZT layers grown on (101)-textured RuO2 exhibit a predominant (001) orientation, while those grown on (110)-textured RuO2 present a mixed (001)-(111)-(110) polycrystalline structure. Highly (110)-oriented RuO2 layers were grown using relatively high deposition temperatures and low rates (∼350°C and < 3 nm/min, respectively), while (101)-textured RuO2 layers were grown at slightly lower temperatures and higher deposition rates than those for (110) layers (i.e., ∼300°C and > 3 nm/min, respectively). The RuO2 layers exhibited resistivities of 34-40 μΩ-cm, average grain size of 65±15 nm, and surface roughness of 3-10 nm (rms), while the PZT layers were dense with average grain size of 150-250 nm. Ag/PZT (001)/RuO2(101) capacitors exhibited remanent polarization, saturation polarization, and coercive field of 49.7 μC/cm2, 82.5 μC/cm2, and 35.0 kv/cm, respectively, while the values for Ag/PZT (001-111-110)/RuO2 (110) capacitors were 21.5 μC/cm2, 35.4 μC/cm2, and 39.0 kv/cm, respectively.