For HfO₂‐based films, which are mainly prepared by atomic layer deposition, the desired ferroelectric (FE) properties typically vanish while extending the thickness beyond a limit of about 50 nm. Herein, the successful fabrication of a 1 μm‐thick piezoelectric La:HfO₂ film is demonstrated using chemical solution deposition, paving the way toward sensor and actuator applications. After identifying the optimal La content, the film thickness is increased from 45 nm to 1 μm. Polarization and strain measurements evidence the persistence of the FE properties at all thicknesses and even a slight improvement due to a better orientation of the polar axis at higher thicknesses. Scanning electron microscopy and X‐ray reflectivity reveal a fine‐grained microstructure and a density of only 80% of the theoretical value, which seems to be a common issue of solution‐deposited HfO₂‐based films, based on the performed literature survey. Using tilt‐angle‐dependent X‐ray diffraction scans, homogeneous nucleation is found to be the likely root cause of the observed microstructure. It is suggested that this microstructure issue is key for the optimization of cycling stability of solution‐based films to exploit the full potential of the HfO₂ for cost‐efficient, thick piezoelectric films.

We present a study of the inkjet printing of tantalum-oxide-based dielectric structures on indium-tin-oxide-coated glass. Ta-Al-Si-alkoxide-based ink formulations with 2-methoxyethanol (2MOE) as the main solvent and a highly viscous glycerol (GLY) or 1,3-propanediol (PD) co-solvent exhibit the optimal values of viscosity and surface tension for piezoelectric inkjet printing, and show good jetting performance. However, the drying of the printed structures results in a pronounced “coffee-stain” effect. We relate this phenomenon to the much higher volatility of 2MOE than either of the viscous solvents and the dominant evaporation of the former immediately after the ink has been printed on the substrate. Consequently, the recirculating Marangoni solvent flow exists only at the onset of drying and ceases to exist once the 2MOE has completely evaporated from the drying feature. The combination of all three solvents appears to prolong the duration of the Marangoni flow, as suggested by differential scanning calorimetry, resulting in an improved uniformity of dried structures. By adjusting the solvent composition we could tailor the topology of deposits and print 45 nm-thick, flat and uniform capacitors with the performance (good dielectric properties of ε_r ∼ 15, tan(δ) ∼ 0.034 at 100 kHz and a low leakage current density of 2.4 × 10⁻⁷ A cm⁻² at 200 kV cm⁻¹) comparable to spin-coated films.