G. Kiriakidis

Surface characteristics of In and Zn oxides by atomic force microscopy

Indium and zinc oxide (InO/sub x/, ZnO) thin films with different thickness were prepared by dc magnetron sputtering onto silicon substrates. Structural investigations carried out by atomic force microscopy (AFM) shown a strong correlation between surface topology and growth parameters. Grain radius (GR) and roughness (RMS) were found to be dependent on film thickness and deposition parameters. The results revealed a linear variation of both GR and RMS as a function of thickness, pressure, substrate temperature, and growth rate. All measurements were made at room temperature using AFM-tapping mode.

Ultra sensitive low temperature metal oxide gas sensors

InO/sub x/ films, in the thickness range of 10-725 nm, were grown by dc magnetron sputtering. Their structural, electrical, and O/sub 3/ and NO/sub 2/ sensing properties were analyzed at various temperatures. Structural investigations carried out by XRD and AFM showed a strong correlation between crystallinity, surface topology and gas sensitivity. Moreover, the electrical conductivity exhibited a change of over six orders of magnitude during the processes of photoreduction and oxidation. The films have shown sensitivities towards O/sub 3/ of <50 ppb and NO/sub 2/ of <100 ppb, at temperatures from RT to 100/spl deg/C.

Mechanical Properties and Deformation Behavior of ZnO Thin Films under Illumination

As a wide band gap semiconductor with a large exciton binding energy (60 meV), zinc oxide (ZnO) has many existing and promising future applications. The main objective of this work was to study the mechanical properties and deformation behavior of undoped ZnO thin films grown by direct current magnetron sputtering technique in the light of their possible application on SPM cantilevers. Nanoindentation techniques and scratch tests were carried out in order to investigate mechanical properties of a ZnO thickness series deposited under the same sputtering conditions. Nanoindentation measurements were also applied on specific ZnO/Si and ZnO/glass structures in darkness and under illumination utilizing a low power mercury lamp with the aim of understanding the impact of the UV irradiation on the mechanical properties of the ZnO layer.

Study of thermochromic VO 2 material as thermal switch for power lines

Thin thermochromic VO2 films grown by RF magnetron sputtering on various substrates (SnO2/glass, glass, Si) and with different deposition parameters, were studied in order to find the optimum conditions to produce thin film coatings with good thermochromic and thermoelectric characteristics as required for power line protection / switching applications. Regarding the electrical/electronic applications of metal to insulator transition materials they may include thermal switches, thermal sensors, energy dissipation, circuit protection etc. In particular, applications currently under consideration include electrical power systems such as cooling systems in high voltage and high power equipment, integration of thermal switches and sensors in power electronic systems and elements, intelligent current protection systems such as thermal triggered fuses and circuit breakers. In addition, their involvement in industry is also considered as such in control systems for industrial electrical heating systems and elements. In this study the influence of the different substrates on the thermochromic properties of VO2 films and their correlation to applications as thermal switches was attempted. Properly tuning the growth parameters, to obtain thermochromic VO2 films under optimum conditions was made including depositions on glass, SnO2-coated glass and Si substrates.

The Effect Of Au Nanoclusters In Tin OxIDe Film Gas Sensors

G. A. Mousdisa, M. Kompitsasa, I. Fasakia, M. Sucheab, G. Kiriakidisb aNHRF-National Hellenic Research Foundation, Theoretical and Physical Chemistry Institute-TPCI, 48 Vass. Constantinou Ave., Athens 11635, Greece b IESL-FORTH and University of Crete a) Chemistry Dept. and b) Physics Dept. Greece The effect of Au nanoparticles in SnO2 was investigated for gas sensor applications. The films were prepared by the sol-gel method. HAuCl4 in different concentrations was added to a tin alkoxide solution, the mixture was hydrolyzed and spin coated on borosilicate glass substrate. The samples were thermally treated to remove the organics. The change of the electrical conductivity was used to detect H2. The response of SnO2 and SnO2 Au to H2 was investigated at different temperatures and concentrations. In situ preparation of Au nanoparticles in SnO2 matrix Preparation of SnO2 films doped with Au nanoparticles

Surface characteristics and tribology study of metal oxide thin films

Abstract Microcrystalline high quality undoped ZnO thin films were deposited on Si(100) and Corning 1737F glass substrates by a dc magnetron sputtering system. Surface and mechanical properties of ZnO thin films deposited under different deposition conditions (thickness, deposition rate and plasma composition) were investigated. Atomic force microscopy, nanoindentation techniques and scratch tests have been carried out. The lateral grain radius was between 50 and 160 nm. Surface roughness was found to vary from 1·3 to 10·3. In order to measure the real hardness of ZnO thin films grown on Si(100) and glass Continuous Stiffness Measurement technique was used. The hardness was found to be between 11 and 13 GPa for the polycrystalline ZnO almost five times larger than for the corresponding single crystalline material, while scratch tests verified a film structure, thickness, and surface morphology dependency on the mechanical properties for these metal oxide thin films.