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ZnO thin films were processed by radio frequency magnetron sputtering at room temperature on p-Si/SiO2 substrates under pure argon (Ar:O2 = 100:0 vol.%) and argon–oxygen mixture (Ar:O2 = 99:1 vol.%) gas environment. Morphological, optical and electrical characteristics of the ZnO films are reported, and they show a clear relationship with the gas mixture employed for the sputtering process. Scanning Electron Microscopy revealed the formation of grains of 15.3 and 19.9 nm average sizes and thicknesses of 59 nm and 82 nm for films growth in pure argon and argon–oxygen, respectively. Photoluminescence measurements at room temperature showed the violet emission band (centered at 3 eV) which was only detected in the ZnO film grown under pure argon. From thermally stimulated conductivity measurements two traps with 0.27 and 0.14 eV activation energies were identified for films grown in pure argon and argon–oxygen mixture, respectively. The trap at 0.27 eV is associated with a level located below the conduction band edge and it is supported by the PL band centered at 3 eV. Both types of ZnO films were used as the active channel layer in thin film transistors with thermal SiO2 as gate dielectric. Field effect mobility, threshold voltage and current ratio were improved in the devices with ZnO channel deposited with the argon–oxygen mixture (99% Ar/1% O2 vol.). Threshold voltage decreased from 25 V to 15 V, field effect mobility and current ratio increased from 0.8 to 2.4 cm2/Vs and from 102 to 106, in that order.

ZnO films were processed by radiofrequency (RF) magnetron sputtering under argon gas environment at room temperature, varying the RF power (90 W, 100 W, 150 W, and 200 W), on p-Si/SiO2 substrates. Structural, morphological, and electrical characteristics of the ZnO films were determined using several experimental techniques, and they showed a clear relationship with the RF power. All the ZnO films exhibited a hexagonal wurtzite polycrystalline structure with (002) preferred orientation. Atomic force microscopy (AFM) revealed the formation of grains or clusters as a result of the accumulation of nanoparticles, and the grain size increased with increasing power. An ascending trend of the root-mean-square surface roughness of the films with increasing power was also observed. ZnO film thickness and refractive index were determined by spectroscopy ellipsometry. In agreement with AFM results, the observed increase of refractive index from 2.15 to 2.44 was the result of improved film compactness on increasing the deposition power. The electrical resistivity ranged from 3.5 × 103 Ω-cm for ZnO film deposited at 200 W to 5 × 107 Ω-cm for that deposited at 100 W. The sputtered ZnO films were employed as the active channel layer in thin-film transistors, and the impact of the deposition power on device performance was studied. As the power was increased, the field-effect mobility increased from ~0.1 cm2/V s to 4.2 cm2/V s, the threshold voltage decreased from 33.5 V to 10.7 V, and the I on/I off ratio decreased from 106 to 102.

Lead zirconate titanate, Pb(Zr 0.53 ,Ti 0.47 )O 3 or PZT, thin films and integrated cantilevers have been fabricated for energy harvesting applications. The PZT films were deposited on PECVD SiO 2 /Si substrates with a sol–gel derived ZrO 2 buffer layer. It is found that lead content in the starting solution and ramp rate during film crystallization are critical to achieving large-grained films on the ZrO 2 surface. The electrical properties of the PZT films were measured using metal–ferroelectric–metal and inter-digital electrode structures, and revealed substantial improvement in film properties by controlling the process conditions. Functional cantilevers are demonstrated using the optimized films with output of 1.4 V peak-to-peak at 1 kHz and 2.5 g.