Growth, Structural and Mechanical Characterization and Reliability of Chemical Vapor Deposited Co and Co₃O₄ Thin Films as Candidate Materials for Sensing Applications

Abstract

The adhesion and mechanical stability of thin film coatings on substrates is increasingly becoming a key issue in device reliability as magnetic and storage technology driven products demand smaller, thinner and more complex functional coatings. In the present study, chemical vapor deposited Co and Co3O4thin films on SiO2and Si substrates are produced, respectively. Chemical vapor deposition is the most widely used deposition technique which produces thin films well adherent to the substrate. Co and Co3O4thin films can be used in innovative applications such as magnetic sensors, data storage devices and protective layers. The produced thin films are characterized using nanoindentation technique and their nanomechanical properties (hardness and elastic modulus) are obtained. Finally, an evaluation of the reliability of each thin film (wear analysis) is performed using the hardness to elastic modulus ratio in correlation to the ratio of irreversible work to total work for a complete loading-unloading procedure.

Tribological characterization of chemical vapor deposited Co and Co 3 O 4 thin films for sensing reliability in engineering applications

“…The nanomechanical properties of the thin films, i.e. H and E, are presented elsewhere [7] and are in good agreement with similar measurements of the literature [8][9]. Cobalt thin film exhibit local changes (discontinuities), i.e.…”

“…Cobalt thin film exhibit local changes (discontinuities), i.e. changes in the slope, referred as pop-ins and elbows in the loading and in the unloading curve, respectively [7]. During the pop-in, the indenter tip penetrates in the sample without an increase in the applied load.…”

“…For lower loads than the load where the onset of plasticity occurs, reversibility of the indentations performed is observed. The pop-ins indicate a redistribution of material around the indentation site [7].…”

“…A high H/E ratio is related to a high elastic strain prior to the plastic deformation, while it has long been known that, in a tribo-contact event between rough surfaces, purely elastic contact is desired for wear reduction [7].…”

“…9, SPM images of the scratches for both thin films are presented (AFM images are presented elsewhere [13]). The Co 3 O 4 films were uniformly grain distributed with, however enlarged grains, probably due to high deposition temperature [7]. The mean surface roughness (RMS) deviation of the films deposited at 450 1C was of the order of 5.5 nm, with the mean height being around 17.5 nm.…”