Innovative low temperature plasma approach for deposition of alumina films

Abstract

Alumina films were deposited from a new plasma method using aluminum acetylacetonate (AAA) powder as precursor. The AAA was sputtered in argon and oxygen plasma mixtures. It was investigated the effect of the oxygen proportion (O 2 %) on the properties of the coatings. Deposition rate was derived from the layer height measured by profilometry. The elemental composition and molecular structure of the films were determined by Rutherford backscattering and infrared spectroscopies, respectively. Grazing incidence X-ray diffraction was used to investigate the microstructure of the films while hardness was determined by nanoindentation technique. Inspections on the surface morphology and on the film composition were conducted associating scanning electron microscopy and energy dispersive spectroscopy. Incorporation of oxygen affects the plasma kinetics and consequently the properties of the coatings. As moderated concentrations of oxygen (< 25%) are added, the structure is predominantly organic containing stoichiometric amorphous alumina. On the other hand, as high O 2 % (> 25%) are incorporated, the structure become rich in metallic aluminum with carbon rising at low proportions. The deposited layer is not homogeneous in thickness once the chemical composition of the precursor is changed by the action of the reactive oxygen plasma. Oxygen ablation on the film surface also contributes to the lack of homogeneity of the structure, especially as high oxygen proportions are imposed. Hardness data (0.5-2.0 GPa) corroborated the idea of an amorphous structure. Based on the results presented here it was possible to identify the oxygen concentration in the plasma atmosphere which mostly removed organics while preserving the stoichiometric alumina precipitation, subject of great relevance as one considers the reduction in the energy necessary for the creation of fully oxide coatings.

SiOxCyHz-TiO2 Nanocomposite Films Prepared by a Novel PECVD-Sputtering Process

“…With increasing O 2 %, there is an elevation in the concentration of particulate material present on the surface, which can be pointed out as the factor responsible for the roughness rise in Figure 3. The same effect has already been observed in the work of Darriba and collaborators 19 . The roughness of oxides, in general, decreases with the oxygen content due to the reduction in the deposition rate and the enhancement in exothermic processes taking place on film surface during the growth.…”

“…The process was carried out without cooling the electrodes. Under similar conditions to those used here and using the same system, temperatures lower than 60°C are reported in the driven electrode (target) 19 , but still lower values are expected for the grounded sample holder. The proportion of O 2 in the plasma was increased from 0 to 50% while that of Ar was decreased from 80 to 30% in order to keep the working pressure constant in all the experiments.…”

Bifunctional Catalyst NiFe–MgAl for Hydrogen Production from Chemical Looping Ethanol Reforming

“…The particle was found to dealloy again after 30 min, and lower intensities were obtained after an hour. In addition, the appearance of the bands positioned between 914 and 936 cm –1 in DRIFTS results with TOS corresponds to Al–OH bending vibrations of the catalyst. , According to the results, a graphical illustration of carbon species removal on the catalytic surface of NiFe–MgAl is depicted in Figure .…”

Films Deposited from Reactive Sputtering of Aluminum Acetylacetonate Under Low Energy Ion Bombardment

“…Considering the evidences of the benefits of ion bombardment utilization in obtaining alumina films by other methodologies 8,15 , the purpose of this work is to associate ion bombardment to the reactive sputtering method proposed by Battaglin et al 14 . The hypothesis to be verified is whether the synergy between the chemical routes of organic removal associated to the physical process of ion bombardment affects the properties of the resulting layers.…”

“…The system was pumped to reach the bottom pressure of 4.3 Pa. The plasma atmosphere was established by introducing 6.7 Pa of the oxygen (25%) and argon (75%) mixture, as optimized in earlier work 14 , and keeping the system total pressure at 11.0 Pa. Oxygen and argon flow ratios were of 3.75x10 -8 and 1.17x10 -7 m³/s (2.25 and 7.00 sccm), respectively.…”