The thickness measurement of the deposited Ba1-xCaxTiO3 thin films was performed by the Fizeau fringes method. The thickness of the deposited Ba1-xCaxTiO3 thin films are measured in the range from 407 to 429 nm. The surface topography of Ba1-xCaxTiO3 thin films is analyzed by using AFM. AFM images indicated two and three-dimensional views of the topography of the surface of Ba1-xCaxTiO3 thin films. The surface roughness of Ba1-xCaxTiO3 thin film at x=0 is 86 nm and increases drastically from 86 to 187 nm. RMS roughness values of the deposited Ba1-xCaxTiO3 thin films increased for thicker samples due to the increase of successive grains oriented in different directions within the substrate normal with the doping concentration of Ca.
From the UV visible spectroscopy measurements, the transparency of the deposited thin films was measured with the wavelength range of 190-1000 nm. It is seen that all the films synthesized at Ts (350 ºC) are transparent. The BaxCa1-xTiO3 thin films exhibited transparency about 47% with 2 at.% Ca doping concentration. The refractive index (η) of Ba1-xCaxTiO3 thin film is increased with Ca doping concentration up to 2 at.% and then it drastically decreased at 8 at.% of Ca doping concentrations. The values of η are varied in the range of 1.5 to 2.6 for the deposited films. The value of the extinction coefficient (k) for doping material is given a higher value compared to the Ba1-xCaxTiO3 thin films at x=0.
From the values of optical conductivity of the deposited thin films it has been shown that the optical conductivity is increased exponentially with increasing photon energy in the visible region. The direct band gap value is 3.90 eV for Ba1-xCaxTiO3 thin films at x = 0 and the band gap value increases up to 3.98 eV with Ca doping concentration from 2 to 4 at.% and after that the band gap value decreases to 3.80 eV with Ca doping concentration from 4 to 8 at.%.
Electrical measurement was performed to study of electrical properties of Ba1-xCaxTiO3
thin films. The electrical measurements of Ba1-xCaxTiO3 thin films were performed by using four point probe method in the range of 300 ~ 475 K. It is found that I-V characteristics graphs are almost linear and the electrical conduction is ohmic in nature in the range of 0-65 V at room temperature. The current density of Ba1-xCaxTiO3 thin films is more up to 8 at.% than Ba1-xCaxTiO3 thin films at x = 0.
From the electrical resistivity measurement data, it is shown that the lowest electrical resistivity is found for Ba1-xCaxTiO3 thin films at x = 0. The electrical resistivity for Ba1-xCaxTiO3 thin films at x=0 is about 4.98×103 Ωm. It is also observed that the electrical resistivity is increased with the values from 4.98×103 to 11.95×103 Ωm with increasing from 0 to 4 at.% Ca doping concentration. After that, the electrical resistivity is decreasing for 4 to 8 at.% Ca concentration with the values from 11.95×103 to 7.54×103 Ωm. It is also observed that the activation energy, E1 in the low temperature region varies from 0.41 to 0.38 eV and in the high temperature region, E2 varies from 0.28 to 0.26 eV. The values of E2 is slightly lower than that of E1.
5.2 Conclusions
In this present study, the results obtained from surface, structural, optical, and electrical characteristics of Ba1-xCaxTiO3 thin films. Structural, morphological, optical, and electrical measurements were performed to assess the mechanism of formation of Ba1-xCaxTiO3 thin films with various behaviors and their correlation with the biological responses. Because of their remarkable physical and structural properties, the incorporation of Ca doping materials has an impact in crystalline matrices of Ba1-xCaxTiO3 thin films materials and can be considered a powerful tool to design hybrid materials for biomedical hard and soft tissue engineering applications. This behavior is attributed to the highly reactive surface area of nanomaterials as compared with micro or macro particles, thus enhancing the close chemical interaction with biological systems.
The thickness and roughness of the surface coatings of Ba1-xCaxTiO3 thin films could increase nonlinearly with an increase in the concentrations of the dopant Ca.
Different optical behaviors of Ba1-xCaxTiO3 thin films are studied which are optically active. Optical conductivity increases and optical band gap decreased with the increase of Ca doping concentrations in BTO thin film. Similarly, the optical property can be used in the characterization and early detection of bonelike apatite formation on the surface of alkaline-treated titanium implants which are optically active. Electrical resistivity of the Ba1-xCaxTiO3 thin films decreased with the increase of doping concentrations of Ca. Like this feature, the bio-electrical potential stimulates the activity of the Ca2+ pathway in
Ba1-xCaxTiO3 composite that enhances the rapid regeneration of damaged tissue and cell growth in the biological systems.
Finally, it can be concluded from the above analysis that the chemical grafting of Ca molecules as a dopant onto the surface of BTO biomaterials could be an excellent potential candidate for the restoration of hard tissues like skin, bone, heart, cartilage, tendons, and other soft tissue engineering. These Ba1-xCaxTiO3 thin films are also applicable in thermistor, heat sensor and various optoelectronic applications.
5.3 Suggestions for Future Work
It is possible to investigate different characteristics of Ba1-xCaxTiO3 thin films by using different characterization methods. More investigations about the thin films are needed to explain different characteristics elaborately, which will help to find out the suitable applications of Ba1-xCaxTiO3 thin films in other suitable fields of applications. For further understanding about these Ba1-xCaxTiO3 materials, the following study may be carried out:
To study the composition analysis by X-ray Photoelectron Spectroscopy.