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For the first time ultrathin films of palladium oxide are set forth as the perspective materials for detecting oxidizing gases. PdO 1± x thin films were prepared by thermal oxidation of previously formed Pd layers. By RHEED and HRTEM investigations it has been established that homogenous polycrystalline PdO 1± x films (thickness was about 5 – 10 nm) with grain size ∼ 7 – 15 nm were formed on polished poly-Al 2 O 3 , SiO 2 /Si(100), optical quartz, and amorphous C/KCl substrates. At ozone detecting in air PdO 1± x films have shown high values of sensor response, signal stability, and reproducibility of sensor response. At fabrication of gas sensors usage of PdO 1± x ultrathin films has some advantages in comparison with other materials. Firstly, PdO 1± x films have shown high values of sensor response, signal stability, and reproducibility of sensor response. Secondly, the synthesis procedure of binary films PdO 1± x is rather simple and is compatible with planar processes of a microelectronic industry also. [ABSTRACT FROM AUTHOR]

Hierarchical thermal molecular motion was studied in thin films of polystyrene (PS). The segmental motion in the thin films was examined by dynamic mechanical analysis. Molecular motions with a relatively small scale in the thin films were discussed on the basis of the kinetics of photoinduced trans to cis isomerization for azobenzene probes tagged to PS. Apparent glass transition temperatures generally decreased with decreasing film thickness. Although relaxation temperatures of β and γ processes in the thin films would be comparable to those in the bulk, the photoisomerization reaction of azobenzene probes became faster with decreasing thickness. Finally, a model for hierarchical thermal molecular motions in thin films was proposed on the basis of the above-mentioned results. [ABSTRACT FROM AUTHOR]

This article presents an orientation study of polyethylene terephthlate (PET) ultrathin films during crystallization. The preferred orientation of the main-chain of PET molecule in ultrathin film on gold substrate was interrogated by comparing the transmission mode and RAIR spectrum. The orientation during crystallization of the PET ultrathin film was also investigated. The isothermal and non-isothermal kinetics of PET ultrathin films with different thickness were investigated. It was found that during isothermal crystallization the thinner PET film shows slower kinetic than the thicker film. Moreover, the obtained Avrami components decreased with the film thickness. As for the case of the non-isothermal crystallization, the cold-crystallization starting temperature shifted to lower temperature as film thickness increased. The orientation of PET ultrathin films was investigated by the combination of RAIR and IR transmission. It is concluded that the main-chain of PET molecule in ultrathin film is prone to alignment parallel to the gold substrate. During isothermal crystallization, the phenyl and C=O in molecule chain of PET tended to take orientation more parallel to the substrate. Moreover, the orientation also showed significant thickness dependence. This was consistent with thickness dependence of the crystallinity during isothermal crystallization.

• The electrical transport mechanism of non-percolated copper ultra thin films was studied. • Resistance behavior was measured during sample growth, aging in vacuum and oxidation in air. • During sample growth, the resistance decreases, and it was modeled by a tunnel transport model. • During aging, the resistance of copper and gold ultra thin increases in a similar way. • During the oxidation, the effect of a semi-conductor type mechanism affected the resistance. The electrical transport mechanism of non-percolated copper ultrathin films was studied. For this purpose, resistance behavior was measured during sample growth, aging in vacuum and oxidation in air, and contrasted with a model based on tunnel current and on film's morphology. In addition, the electrical characterization of chromium and gold ultrathin films was performed and compared with that obtained for copper. All films were grown on muscovite mica through thermal evaporation under high vacuum conditions. Electrical characterization throughout films' growth, aging and oxidation was performed in situ and in real time. Finally, to address the transport mechanism of non-percolated oxidized copper films, samples were put into a cryostat in which electrical resistance was measured changing the temperature between 35 and 300 K. It was found that the three materials present an almost constant resistance decay during growth. This resistance decrease was studied for copper films by fitting a tunnel transport model which considered islands' distance as a function of film thickness, indicating a resistance reduction given by coalescing islands. During aging, the resistance of copper and gold ultrathin films increases without reaching a saturation value after 30 min, with a behavior independent of the material or the initial resistance. The theoretical model applied to copper film resistance explains the increment by further formation of 3D structures, mainly conducted by atom diffusion on the substrate. Finally, a change in the resistance behavior is observed during the oxidation of copper ultrathin films, electrical transport is mediated by two mechanisms a semi-conductor type, resembling that of oxidized chromium layers, and a tunnel conduction type, observed in gold films. The first mechanism dominates when temperature is above 200 K, while tunneling is the main process for temperatures below 150 K. [ABSTRACT FROM AUTHOR]