R. Drese

Structural and optical properties of thin zirconium oxide films prepared by reactive direct current magnetron sputtering

Thin films of zirconium oxide have been deposited onto glass and Si(100) substrates at room temperature by reactive dc magnetron sputtering of a metallic Zr target in an argon–oxygen atmosphere. The films were characterized by Rutherford backscattering spectroscopy, x-ray diffraction, x-ray reflectometry, atomic force microscopy, and optical spectroscopy to investigate the variation of stoichiometry, structure, density, and optical properties upon increasing oxygen partial pressure. The Zr target shows a well-defined hysteresis upon varying the oxygen pressure as determined by quartz crystal microbalance measurements. Rutherford backscattering experiments reveal that the films are metallic with a small amount of oxygen incorporation at oxygen flows well below 2.7 sccm. Stoichiometric ZrO2 films, however, are formed above 2.8 sccm O2 flow (oxidic mode). Grazing angle incidence x-ray diffraction studies show that crystalline ZrO2 films with monoclinic structure grow in this oxygen flow regime. X-ray reflect...

Temperature stability of sputtered niobium-oxide films

The effect of annealing temperature on the structural and optical properties of sputtered niobium–oxide films has been investigated. The temperature dependence of structure, density, and optical constants has been studied by Rutherford backscattering, x-ray diffraction, x-ray reflection, optical spectroscopy, and variable angle spectroscopic ellipsometry techniques. Rutherford backscattering measurements show no variation in the stoichiometry of the films upon annealing of amorphous Nb2O5 films, while amorphous NbO is oxidized to Nb2O5. X-ray diffraction studies show that as-deposited films are amorphous and only crystallize at around 500 °C. X-ray reflectivity studies reveal a continuous increase of film density with increasing annealing temperature. Optical spectroscopy and spectroscopic ellipsometry confirm that the refractive index n and the band gap Eg increase upon increasing annealing temperature. The variation of the refractive index with density of the niobium–oxide films is observed to follow th...

Characterization of Niobium Oxide Films Prepared by Reactive DC Magnetron Sputtering

Niobium oxide films have been prepared on glass and Si(100) substrates by reactive dc magnetron sputtering of a metallic Nb target in an argon-oxygen atmosphere. The properties of the films as a function of oxygen partial pressure have been studied systematically by Rutherford backscattering spectroscopy, X-ray diffraction, X-ray reflectometry and optical spectroscopy. Rutherford backscattering studies show that the films are substoichiometric at lower oxygen flow while stoichiometric films can be formed above 7.5 sccm O 2 flow. Grazing incidence X-ray diffraction studies show that the films are amorphous. X-ray reflectometry was used to determine the sputter rate, density and surface roughness of the films. The films prepared at lower oxygen flow rates had a higher density than those prepared at higher oxygen flow rates. For appropriate oxygen flow rates fully transparent niobium oxide films can be grown with rates up to 0.5 nm/s for a constant cathode current of 900 mA. From optical spectroscopy measurements of reflectance and transmittance we have determined the optical constants such as the refractive index (n), extinction coefficient (k) and band gap (Eg) as well as the film thickness. For the fully transparent films prepared above 7.5 sccm O 2 flow rate a band gap of 3.5 to 3.6 eV is obtained. Optical spectroscopy measurements show that the refractive index of the films decreases upon increasing oxygen flow rate and this finding is related to a decrease of density upon increasing oxygen flow.

The STM view of the initial stages of polycrystalline Ag film formation

The growth of Ag thin films deposited at 300?K on amorphised Si surfaces under ultra high vacuum conditions is investigated by in situ scanning tunnelling microscopy. The analysis of film morphology as a function of film thickness together with additional annealing experiments allow a quite complete picture of the film formation processes to be obtained.

In situ stress measurements in zirconium and zirconium oxide films prepared by direct current sputtering

The evolution of stress during growth of thin zirconium and zirconium oxide films deposited from a metallic target using direct current magnetron sputtering has been analyzed in situ. The oxygen flow during the deposition was varied to obtain films with different stoichiometries ranging from metallic zirconium to fully stoichiometric zirconium oxide. The stresses in the metallic films depend strongly on the pressure during deposition. Films created at low pressure possess tensile stresses in the beginning of growth, which turn highly compressive with increasing film thickness. Films created at high pressures show only tensile stresses similar to evaporated metals of low mobility. The transition between metallic and oxidic zirconium films has been analyzed. The compressive stresses in the metallic film turn tensile once low amounts of oxygen are let into the chamber. This behavior is related to a structural change of the zirconium film, which was confirmed by x-ray analysis. Upon further increasing oxygen ...

Thermal Stability of Lead Oxide Films Prepared by Reactive DC Magnetron Sputtering

The thermal stability of different lead oxide films prepared by reactive dc magnetron sputtering from a Pb target has been investigated. The temperature dependence of composition as well as structural and optical properties have been studied by Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD) and variable-angle spectroscopic ellipsometry (VASE). Both XRD and RBS experiments confirm that different kinds of lead oxides are formed upon increasing the oxygen flow. Upon annealing at 500 °C, all samples form orthorhombic PbO. VASE studies show that the refractive index n and the band gap energy Eg increase with increasing annealing temperature. For films annealed at 500 °C, n is approximately 2.7 at 650 nm and a band gap energy of 2.8 eV is obtained, which corresponds to the value for bulk PbO. The stoichiometric changes observed by XRD on increasing the annealing temperature are discussed and supported by thermodynamics arguments.