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Abstract: La-doped BaTiO3 thin films with 200 nm thickness were fabricated by r.f. magnetron sputtering system onto Pt/Ti/SiO2/Si substrates. The effects of post-annealing and the amount of dopant on microstructure and electrical properties were studied. The X-ray diffraction (XRD) study reveals that, the film becomes crystallized when the annealing temperature is above 550 °C. In addition, all the films show tetragonal BaTiO3 crystal structure without any second phase or reaction phase formation after annealed at 750 °C. The X-ray photoelectron spectroscopy (XPS) results provide the evidence to support the existence of La2O3 with excess of BaTiO3 structure, when the dopant content reaches more than 1.4 at.%. The dielectric constant also increases with increasing annealing temperature and it may be due to the better crystallinity and larger grain sizes. The 0.1 La film annealed at 750 °C shows a high dielectric constant of 487 measured at 1 MHz. The doped film in the as-deposited condition yields a reduction of leakage current was also observed. [Copyright &y& Elsevier]

Tantalum nitride (TaN) and Hafnium nitride (HfN) coatings were deposited through magnetron sputtering at various Ar/N 2 inlet gas ratios and RF input power control, respectively. The nitrogen contents of the single layer nitride coatings decreased with the Ar/N 2 ratio and increased with the input powers. TaN coating could be fabricated with crystalline structure, c-TaN, with a preferred orientation (200), while the amorphous feature TaN, a-TaN, was deposited with low Ar/N 2 ratio and excess N content. For HfN, the similar HfN crystalline features with a preferred orientation (111) were observed for all conditions. The c-TaN and a-TaN layers were alternately stacked into nano-multilayer. The HfN multilayer was deposited with layers generated at 150 and 125 W. The c-TaN film exhibited superior mechanical strength, whereas the a-TaN coating had a better corrosion resistance. Combining crystalline and amorphous TaN layers to form a multilayer improved the mechanical behavior. The HfN films, both in single-layer and multi-layer form, exhibited columnar structure feature under various sputtering input powers. Although the multilayer feature for HfN coating by various power input modulation did not exhibit significant improvement for hardness, the scratch resistance was elevated. [ABSTRACT FROM AUTHOR]

Abstract: ZrYN coatings with various yttrium contents (0 to 15at.% in the targets) are deposited from zirconium yttrium composite targets using DC magnetron sputtering. The effect of varying amounts of yttrium addition on the microstructure and mechanical properties of ZrN coatings has been studied. The results reveal that yttrium atoms substitute zirconium atoms in Zr–N lattice forming the solid solution ZrYN coatings. The preferred orientation changes from (200) to (111) with yttrium addition, while the grain sizes are approximately the same. The indentation hardness of the ZrYN coatings first increases from 19.7GPa to 24.1GPa with increasing yttrium content up to 5at.% and is followed by a decrease to 20.9GPa with a further increase in yttrium content. Scratch test shows that yttrium addition has a beneficial effect on the adhesion of the ZrYN coatings with the critical load increasing from 2.8N for the ZrN coating to 7.6N for the ZrYN coating (yttrium content 10at.%). [Copyright &y& Elsevier]

Abstract: For the purpose of studying the inverse Hall–Petch effect in nanocrystalline hard coatings, nanocrystalline ZrN coatings have been fabricated using magnetron sputtering with grain sizes ranging from 45nm to 10nm by varying negative biases from 0V to 150V. The transition from the classical Hall–Petch effect to an inverse Hall–Petch effect in nanocrystalline ZrN coatings is observed at a grain size between 19.0nm and 14.2nm. The reality of the inverse Hall–Petch effect in the present study is validated by exclusion of other possible effects on hardness of nanocrystalline ZrN coatings, such as porosity, multiphase, chemical composition, texture, and residual stress. Furthermore, a concise model based on lattice dislocations piling up mechanism is proposed to illustrate the breakdown of the Hall–Petch effect and calculate the critical grain size. The predictions of the model fit well with experimental data in some nitride and carbide nanocrystalline coatings. Both experimental and theoretical results indicate that the inverse Hall–Petch effect is an essential property of nanocrystalline hard coatings as similar to nanocrystalline metals and alloys. [Copyright &y& Elsevier]

Abstract: Cu2O and two types of Cu2O–Ag–Cu2O (CAC) multilayered thin films were deposited on glass substrates using DC-magnetron sputtering. For CAC films, the mass thickness of Ag layer was controlled at 3nm. After deposition, some of these films were annealed using a rapid thermal annealing (RTA) system at 650°C, in order to create embedded Ag particles. AC films were used to study the clustering effect of Ag in Ar atmosphere, as well as for forming the 2nd type of CAC film by covering another Cu2O layer on the annealed AC structure. A UV–VIS–NIR photometer, a Hall measurement system, and a I–V measurement system were used to characterize the optical and electrical properties of these films with and without RTA. The results show that 2-dimensional Ag layer can transform into many individual particles due to its high surface tension at annealing temperature, no matter when the annealing was carried out. For CAC films, without annealing, the optical transmission and the resistivity are decreased with the inserted Ag layer. After annealing, both the transmission and resistivity are increased, possibly due to the clustering effect of Ag layer. Most importantly, it is found that the embedded Ag particles can increase the light absorption in the NIR–IR region, which can increase photo-induced current. [Copyright &y& Elsevier]