C. Besleaga

Physical properties of AlxIn1−xN thin film alloys sputtered at low temperature

In this paper, we report on the structural, optical, and electrical properties of a wide compositional range of AlxIn1−xN thin layers deposited on glass and polyethylene terephthalate substrates. AlxIn1−xN layers of controlled composition were obtained by a simple reactive magnetron co-sputtering protocol, using a single aluminium target with indium insets, by varying the Al/In target surface area ratio, and the composition of the deposition atmosphere. The relevant physical properties were investigated and discussed. It is shown that the texture of the thin films is dependent on the cation ratio, while the bowing parameters of lattice constants and band gap values are larger than those of epitaxial layers.

Combinatorial MAPLE deposition of antimicrobial orthopedic maps fabricated from chitosan and biomimetic apatite powders

Chitosan/biomimetic apatite thin films were grown in mild conditions of temperature and pressure by Combinatorial Matrix-Assisted Pulsed Laser Evaporation on Ti, Si or glass substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. A KrF* excimer (λ=248nm, τFWHM=25ns) laser source was used in all experiments. The nature and surface composition of deposited materials and the spatial distribution of constituents were studied by SEM, EDS, AFM, GIXRD, FTIR, micro-Raman, and XPS. The antimicrobial efficiency of the chitosan/biomimetic apatite layers against Staphylococcus aureus and Escherichia coli strains was interrogated by viable cell count assay. The obtained thin films were XRD amorphous and exhibited a morphology characteristic to the laser deposited structures composed of nanometric round shaped grains. The surface roughness has progressively increased with chitosan concentration. FTIR, EDS and XPS analyses indicated that the composition of the BmAp-CHT C-MAPLE composite films gradually modified from pure apatite to chitosan. The bioevaluation tests indicated that S. aureus biofilm is more susceptible to the action of chitosan-rich areas of the films, whilst the E. coli biofilm proved more sensible to areas containing less chitosan. The best compromise should therefore go, in our opinion, to zones with intermediate-to-high chitosan concentration which can assure a large spectrum of antimicrobial protection concomitantly with a significant enhancement of osseointegration, favored by the presence of biomimetic hydroxyapatite.

InN Based Water Condensation Sensors on Glass and Flexible Plastic Substrates

In this paper, we report the realization and characterization of a condensation sensor based on indium nitride (InN) layers deposited by magnetron sputtering on glass and flexible plastic substrates, having fast response and using potentially low cost fabrication technology. The InN devices work as open gate thin film sensitive transistors. Condensed water droplets, formed on the open gate region of the sensors, deplete the electron accumulation layer on the surface of InN film, thus decreasing the current of the sensor. The current increases back to its initial value when water droplets evaporate from the exposed InN film surface. The response time is as low as 2 s.

Mechanical, Corrosion and Biological Properties of Room-Temperature Sputtered Aluminum Nitride Films with Dissimilar Nanostructure

Aluminum Nitride (AlN) has been long time being regarded as highly interesting material for developing sensing applications (including biosensors and implantable sensors). AlN, due to its appealing electronic properties, is envisaged lately to serve as a multi-functional biosensing platform. Although generally exploited for its intrinsic piezoelectricity, its surface morphology and mechanical performance (elastic modulus, hardness, wear, scratch and tensile resistance to delamination, adherence to the substrate), corrosion resistance and cytocompatibility are also essential features for high performance sustainable biosensor devices. However, information about AlN suitability for such applications is rather scarce or at best scattered and incomplete. Here, we aim to deliver a comprehensive evaluation of the morpho-structural, compositional, mechanical, electrochemical and biological properties of reactive radio-frequency magnetron sputtered AlN nanostructured thin films with various degrees of c-axis texturing, deposited at a low temperature (~50 °C) on Si (100) substrates. The inter-conditionality elicited between the base pressure level attained in the reactor chamber and crystalline quality of AlN films is highlighted. The potential suitability of nanostructured AlN (in form of thin films) for the realization of various type of sensors (with emphasis on bio-sensors) is thoroughly probed, thus unveiling its advantages and limitations, as well as suggesting paths to safely exploit the remarkable prospects of this type of materials.

The Influence of Magnetron Sputtering Conditions on the Physical Properties of (00l) Oriented Nanostructured ZnO Thin Films

Smooth, transparent and highly oriented nanostructured ZnO films were synthesized by RF‐magnetron sputtering onto Si(100) substrates. A mild‐pressed zinc oxide powder target was used for all depositions. The sputtering parameters were varied in order to obtain structures with good adherence and crystallinity. The depositions were carried out in inert argon atmosphere at four sputtering pressures (0.2 Pa, 0.25 Pa, 0.3 Pa and 0.45 Pa). ZnO films were deposited at 150 °C. The films were characterized from structural (XRD) and morphological (AFM) point of view. The influence of each sputtering parameter on the morphological and structural properties is discussed.