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Abstract: Pd-doped-SnO2 thin films were grown on Si (100) substrates using pulsed laser deposition at room temperature. Scanning electron microscopy and atomic force microscopy studies showed that the film morphologies are strongly related to two major parameters: first, high O2 background pressure, namely ≥10 Pa, induces the formation of nanoparticles by condensation in the gas phase; second, when the target–substrate distance d t–s is close to the plume length L p , considering an adiabatic expansion, textured thin films are obtained. Their morphologies depend therefore on the O2 pressure, since by increasing the pressure from 10 to 100 Pa the film morphology changes from a cracked structure to a well developed cauliflower-like-structure with a columnar growth. X-ray photoelectron spectroscopy, energy dispersive X-ray and grazing incidence X-ray diffraction were also employed to analyze, respectively, the chemical bonding state, the chemical composition and the structure in the deposited films. Sub-stoichiometric thin films are also synthesized with a Pd content of about 2.3 at.% under O2 background pressures higher than 10 Pa. [Copyright &y& Elsevier]

Abstract: Nanostructured tin oxide films were deposited on Si(100) substrates at room temperature using the PLAD method. Depositions were achieved by using a XeCl* laser, with a fluence of 10J/cm2 to ablate a SnO2 target either in vacuum or in an atmosphere containing a relatively low partial pressure (10−2 to 100Pa) of O2. A range of spectroscopic diffraction and real space imaging techniques, SEM, EDS, XRD, and XPS were used in order to characterize the surface morphology, structure, and composition of films. XPS results indicate that the film deposited in vacuum comprises a mixture of Sn, SnO and SnO2. In contrast, films deposited in oxygen comprise only SnO and SnO2. This indicates that the deposition of tin oxide films in relatively low partial pressures of O2 prevents the accumulation of unreacted tin metal within the resulting film. SEM studies reveal a sub-micron grain size structure, while XRD analyses indicate that the samples are crystalline, with no evidence for the presence of amorphous material. In this paper we discuss the significance and implications of these findings in terms of the optimization of tin oxide films for use in gas sensing devices and other technological applications. [Copyright &y& Elsevier]

The conventional configuration (substrate parallel and frontal to the target surface) of the pulsed laser ablation deposition technique has been modified for improving the film uniformity with acceptable deposition rates, leading to the ‘dynamic deposition configuration’. The novelty of this arrangement is the ability to place by computer-control the substrate synchronously in front of the plume axis compensating the plume deflection effect. The new geometrical configuration was used to deposit films of Ti, Al and Cu. All the deposited films exhibited both high thickness uniformity and remarkable deposition rates. Initial results of the experiments are explained and compared with the results obtained in the conventional configuration, in otherwise similar experimental conditions. [Copyright &y& Elsevier]

The growth of thin films by pulsed-laser deposition involves extremely complex physical processes. The study of different aspects of the basic mechanisms of the laser ablation is still in progress, with special emphasis on the modelling of the plume deflection effect and the structure formation on the irradiated surface. In this work, the initial stages of the laser ablation process have been investigated considering the surface roughness and the continuous morphological changes of the surface produced by laser irradiation. Assuming a thermal ablation model, a computational approach of the structure formation on the irradiated surface by finite elements using ansys® (6.1) has been developed. Complementary, different ablation experiments on silicon wafers using a XeCl excimer laser (308 nm) impinging at 45° with respect to the target were carried out. Scanning electron microscope analyses were performed to study the morphological changes of the Si surface. The validity of the model and the agreement of the numerical results are discussed. [Copyright &y& Elsevier]