Investigation of deposition temperature effect on spatial patterns of MgF2 thin films.

In this work, the atomic force microscopy (AFM) technique was used to characterize 3D MgF2 thin film surfaces through advanced analysis involving morphological, fractal, multifractal, succolarity, lacunarity and surface entropy (SE) parameters, consistent with ISO 25178-2: 2012. Samples were synthesized by electron beam deposition, grown in three different temperatures. Three different temperatures of 25°C (laboratory temperature), 150 and 300°C were chosen. The temperature of 300°C is usually the highest temperature that can be deposited with the electron beam evaporation coating system. The substrates were made of glass (diameter 16 mm, thickness 3 mm), and the samples were prepared at a pressure of 5 × 10-5  Torr. The statistical results from the AFM images indicate that topographic asperities decrease with increasing deposition temperature, showing a decrease in roughness values. Regardless of the deposition temperature, all surfaces have a self-similar behavior, presenting a very linear PSD distribution, and, according to our results, the sample deposited at 300° had the highest spatial complexity. On the other hand, surface percolation is increasing when temperature increases, indicating that its low roughness and high spatial complexity play an important role on the formation of their most percolating surface microtexture. Our results demonstrate that the lower deposition temperature promoted the formation of less discontinuous height distributions in the MgF2 films.

Morphological and multifractal properties of Cr thin films deposited onto different substrates.

In this study, the morphological properties and micro-roughness of chromium thin film prepared by thermal evaporation technique and confirmed via EDS analysis are examined on different substrates of BK7, Silicon (Si), and glass using atomic force microscope analysis (AFM). Analysis of amplitude parameters, Minkowski functionals, and films' spatial microtexture extracted from AFM analysis showed the difference between glass substrate and the other two (BK7 and Si) substrates for the growth of chromium thin films. In addition, we observed robust signatures of multifractality of the Cr thin films deposited on all substrates we studied. Moreover, we highlight that the Glass substrates displayed the strongest multifractality indicating that such samples present space filling properties distributed over more spatial scales than the samples of BK7 and Si.

Corrosion resistance and surface microstructure of Mg3 N2 /SS thin films by plasma focus instrument.

Utilizing a plasma focus (PF) instrument, magnesium nitride (Mg3 N2 ) thin films were synthesized on stainless steel substrates. Twenty five optimum focus shots at 8 cm distance from the anode tip were used to deposit the films at different angular positions regarded to the anode axis. Scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) analyses were performed to assess the surface morphology and structural characteristics of Mg3 N2 films. Based on AFM images, these films were studied to understand the effect of angular position variation on their surfaces through morphological and fractal parameters. By increasing the angle, we verify that the grain size decreased from 130(0) nm to 75(5) nm and also the mean quadratic surface roughness of the films reduced in its average values from (28.97 ± 3.24) nm to (23.10 ± 1.34) nm. Power spectrum density analysis indicated that films become more self-affine at larger angles. Furthermore, the corrosion behavior of the films was investigated through a potentiodynamic polarization test in H2 SO4 solution. It was found that the ion energy and flux, varying with the angular positions from the anode tip, directly affected the nanostructured roughness and surface morphology of the samples. The electrochemical studies of films show that the uncoated sample presented the lowest corrosion resistance. The highest corrosion resistance was obtained for the sample deposited with 25 optimum shots and at 0° angular position reaching a reduction in the corrosion current density of almost 800 times compared to the pure stainless steel-304 substrate. HIGHLIGHTS: Mg3 N2 /SS films have been deposited at different angles by plasma focus (PF) instruments. The effect of angular position on the surface microtexture, morphological parameters, and corrosion features of the films was studied. The RBS measurement and X-ray diffraction are utilized to identify the crystalline phases and thickness of films.

Surface dynamics, fractal features, and micromorphology analysis of kefir biofilms.

We introduce a study of image analysis of kefir biofilms associated with Acai extract prepared by fermentation of fresh kefir grains natural. Atomic force microscopy data were studied, aiming to understand how the concentration of acai berry (Euterpe oleracea Mart.) influences the surface morphology as well as the texture complexity, evaluated by the fractal dimension. The results showed that the superficial morphology was affected by the increase of Acai concentration in the biofilms, as well as the fractal dimension. It has also been observed that the surface of the biofilm presented saturation when concentration changes from 40 to 60 ml. On the other hand, it was observed that the intermediate sample produced with 20 ml of acai berry seems to be the best point for biofilms production that can serve as a skin dressing since other studies related to mechanical properties and in vitro and in vivo tests can confirm this applicability. Thus, the characterization of the surface morphology of kefir biofilms by the evaluation of surface statistical parameters and fractal geometry may provide promising results regarding the applicability of these films. RESEARCH HIGHLIGHTS: We characterized the structural complexity of the 3-D surface of the kefir biofilms associated with açaí extract. The 3-D surface analysis of the samples was performed using an atomic force microscope operating in contact mode. We determined the stereometric and fractal dimension of the analyzed samples.