Zinc oxide (ZnO) thin films are deposited by plasma‐enhanced atomic layer deposition (PE‐ALD). This deposition method allows depositing stoichiometric and highly resistive ZnO films at room temperature. Despite such important requirements for piezoelectricity being met, not much is known in literature about the piezoelectric properties of ZnO thin films (1.8 nA) and charge (>80 pC) compared with films deposited on glass (>0.3 nA and >30 pC) due to bending effects of the substrate when mechanically excited. Furthermore, increasing the substrate temperature, during deposition, enhances the growth along the (002) crystallographic orientation, which further strengthens the generated piezoelectric current signal for mechanical excitations along the ZnO film's c‐axis.

The ability to grow inorganic thin films with highly controllable structural and optical properties at low substrate temperature enables the manufacturing of functional devices on thermo-sensitive substrates without the need of material postprocessing. In this study, the authors report on the growth of zinc oxide films by direct plasma-enhanced atomic layer deposition at near room temperature. Diethyl zinc and oxygen plasma were used as the precursor and coreactant, respectively. The process was optimized with respect to the precursor and coreactant dosing as well as to the purging times, which ultimately resulted in saturated atomic layer deposition growth. The so-obtained films exhibit a polycrystalline pattern with a (100) texture and low amount of incorporated carbon. Furthermore, the possibility to tune crystallite size, refractive index, and bandgap of the films by adapting the plasma radio-frequency power is demonstrated.

ZnO thin films and nanostructures are applied in various devices due to their interesting optical and electrical properties. Atomic layer deposition (ALD) of ZnO offers unique advantages such as precise thickness control, uniformity, and conformality. Using reactive plasma species as the co‐reactant (PE‐ALD) allows further enhancement of the material characteristics and tunable properties. The substrate temperature has been reported to be the most influential parameter in this technique, as it affects the growth per cycle (GPC) and material properties. However, an investigation on how the film properties are linked to the GPC is lacking in the literature. Herein, the temperature dependence of several material properties is found closely related to the GPC. The preferential crystal orientation switches from (100) to (002) up to the constant region of the GPC versus temperature, the so‐called ALD window. Refractive index and mass density show different slopes in temperature regions outside and within the ALD window. Excitonic absorption is only found for films prepared within the ALD window, and the resistivity drops rapidly above the ALD window. Following these results, more insights can be gained on the ALD growth (especially the role of the ALD window) and ideal temperature ranges for specific applications.

Vapor phase infiltration (VPI) of ZnO into the elastomeric polymer polyisoprene creates an organic-inorganic hybrid material. Inorganic loading and hybrid structure depend upon the initial polymer free volume and the extent of polymer oxidation.

Direct plasma enhanced-atomic layer deposition (PE-ALD) is adopted for the growth of ZnO on c-Si with native oxide at room temperature. The initial stages of growth both in terms of thickness evolution and crystallization onset are followed ex-situ by a combination of spectroscopic ellipsometry and X-ray based techniques (diffraction, reflectivity, and fluorescence). Differently from the growth mode usually reported for thermal ALD ZnO (i.e., substrate-inhibited island growth), the effect of plasma surface activation resulted in a substrate-enhanced island growth. A transient region of accelerated island formation was found within the first 2 nm of deposition, resulting in the growth of amorphous ZnO as witnessed with grazing incidence X-ray diffraction. After the islands coalesced and a continuous layer formed, the first crystallites were found to grow, starting the layer-by-layer growth mode. High-temperature ALD ZnO layers were also investigated in terms of crystallization onset, showing that layers are amorphous up to a thickness of 3 nm, irrespective of the deposition temperature and growth orientation.