Influence of Dopant Nature on Biological Properties of ZnO Thin-Film Coatings on Ti Alloy Substrate

Effect of Al Incorporation on the Structural and Optical Properties of Sol-Gel AZO Thin Films

ZnO and Al-doped ZnO (AZO) thin films were prepared using the sol-gel method and deposited on a Silicon (Si(100)) substrate using the dipping technique. The structure, morphology, thickness, optical constants in the spectral range 300-1700 nm, bandgap (E_g) and photoluminescence (PL) properties of the films were analyzed using X-ray diffractometry (XRD), X-ray fluorescence (XRF), atomic force microscopy (AFM), scanning electron microscopy (SEM), spectroscopic ellipsometry (SE), Raman analysis and PL spectroscopy. The results of the structure and morphology analyses showed that the thin films are polycrystalline with a hexagonal wurtzite structure, as well as continuous and homogeneous. The PL background and broader peaks observable in the Raman spectra of the AZO film and the slight increase in the optical band gap of the AZO thin film, compared to undoped ZnO, highlight the effect of defects introduced into the ZnO lattice and an increase in the charge carrier density in the AZO film. The PL emission spectra of the AZO thin film showed a strong UV line corresponding to near-band-edge ZnO emission along with weak green and red emission bands due to deep-level defects, attributed to the oxygen-occupied zinc vacancies (O_Zn lattice defects).

Structural and optical characteristics determined by the sputtering deposition conditions of oxide thin films

The influence of film thickness on the structural and optical properties of silicon dioxide (SiO2) and zinc oxide (ZnO) thin films deposited by radio frequency magnetron sputtering on quartz substrates was investigated. The deposition conditions were optimized to achieve stoichiometric thin films. The orientation of crystallites, structure, and composition were investigated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), while the surface topography of the samples was analyzed using scanning electron microscopy (SEM). The optical characteristics were measured for samples with the same composition but obtained with different deposition parameters, such as increasing thickness. The optical constants (i.e., the refractive index n, the extinction coefficient k, and the absorption coefficient α) of the SiO2 and ZnO oxide films were determined from the transmission spectra recorded in the range of 190-2500 nm by using the Swanepoel method, while the energy bandgap was calculated from the absorption spectra. The influence of thickness on the structural and optical properties of the oxide films was investigated. Good optical quality and performance were noticed, which makes these thin films worthy of integration into metamaterial structures.

Antimicrobial Properties of Samarium Doped Hydroxyapatite Suspensions and Coatings

Post-implant infections are a major health problem, and it is well-known that treating them with conventional drugs is accompanied by many disadvantages. The development of new biomaterials with enhanced antimicrobial properties are of major interest for the scientific world. The aim of this study was to synthesize and characterize hydroxyapatite doped with Samarium (Ca10−xSmx(PO4)6(OH)2, xSm = 0.05, 5Sm-HAp) suspensions, pellets and coatings. The 5Sm-HAp coatings on Si substrates were obtained by rf magnetron sputtering technique. The different techniques such as ultrasound measurements, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Glow Discharge Optical Emission Spectroscopy (GDOES), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were used to examine the obtained coatings. The results showed that the doped Sm ions entered the structure of hydroxyapatite successfully and Sm ions was uniformly doped onto the surface of the support. The depth profile curves of Ca, P, O, H, Ce and Si elements exhibit their presence from a surface to substrate interface as function of sputtering time. XPS analysis indicated as calcium-phosphate structures enriched in Sm3+ ions. Furthermore, the antimicrobial properties of the 5Sm-HAp suspensions, targets and coatings were assessed against Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Candida albicans ATCC 10231. The results of the antimicrobial assays highlighted that that the samples presented a strong antimicrobial activity against the tested microbial strains. The results showed that the coatings after 48 h of incubation inhibited the growth of all tested microbial strains under the value of 0.6 Log CFU/mL. This study shows that the 5Sm-HAp samples are good candidates for the development of new antimicrobial agents.