Narrow Results

The effect of substrate temperature on the structural, optical and morphological properties of ZnO thin films has been investigated. ZnO thin films were deposited on quartz substrate for various temperatures ranging from room temperature to 250°C by pulsed laser deposition (PLD) technique. Nd:YAG laser (532 nm, 100 mJ, 6 ns, 10 Hz) with corresponding fluence of 6 J/cm² was employed for the ablation of ZnO target. Characterization of the thin films was carried out using X-ray diffraction (XRD), high resolution UV-visible spectrometer, atomic force microscope (AFM) and scanning electron microscope (SEM). From XRD analysis, the amorphous behaviors of films at room temperature and crystalline behavior along the preferred orientation of (002) is exhibited for higher substrate temperature. The transmittances of grown films increase with the increasing substrate temperature. The evaluated values of bandgap energies increase with increasing substrate temperature up to the range of 150°C and then monotonically decrease with the further increase in temperature. AFM and SEM analysis illustrates that the density and height of grains for deposited films increase significantly with increasing substrate temperature.

The effect of annealing temperature on sol–gel deposited ZnO thin films have been studied. The average crystallite size determined from XRD shows that the deposited films are nanocrystalline. FTIR confirms deposition of ZnO thin films. The transmittance of annealed ZnO thin films is greater than 80% in visible region with bandgap ranging from 3.25–3.19 eV. The films annealed at 450°C temperature shows lower resistivity value of 527.241 Ωm. The deposited nanocrystalline films are suitable for biosensing applications due to its higher surface area.

This work presents the influence of changing Ar:N₂ gas ratio on the growth and properties of InAlN films. InAlN films were deposited on $p$-type Si(111) substrates by using magnetron co-sputtering method in 6:12, 10:10, 12:8 and 12:6 Ar:N₂ mixtures at 300${}^{\circ }$C. The surface, structural, electrical and optical properties of the deposited films were evaluated at different Ar:N₂ ratios. The grain size and film thickness were increased by increasing the Ar flow with respect to N₂. Structural characterization by X-ray diffraction (XRD) revealed an improvement in the crystalline quality of the $c$-axis-oriented InAlN film by adjusting the Ar:N₂ ratio to 12:8, however no diffraction peak corresponding to InAlN was detected at 6:12 Ar:N₂ mixture. The surface roughness of InAlN film exhibited an increasing trend whereas the electrical resistivity of the film was decreased by increasing the Ar:N₂ ratio. The bandgap of InAlN film was calculated from the optical reflectance spectra and it was found to change by changing the Ar:N₂ gas ratio. The analysis of results from this work shows that the InAlN film with improved physical properties can be obtained through reactive magnetron co-sputtering method by adjusting the Ar:N₂mixture to 12:8.

In the present paper, the surface modification of low-density polyethylene (LDPE) polymer is done by plasma-etching to tune its surface structure, wettability and optical behavior to make it useful for technical applications. For this purpose, two gasses (N${}_2)$ and (O${}_2)$ are used as the discharge precursors in a home-built plasma reactor. The plasma-treated LDPE surface etch-rate (control other surface properties) is high at the beginning and slows down as the treatment time increases due to surface restructuring. The etched surfaces are analyzed by scanning electron microscopy (SEM), which indicate greater surface changes due to O₂ plasma compared to that of N₂. Also, the surface hardness is slightly low at the first treatment time and increases rapidly at higher exposure durations. Besides, the friction coefficient is significantly changed by plasma treatment, suggesting the formation of cohesive surface skin. The obtained X-ray diffraction (XRD) patterns show that the plasma-treated LDPE samples suffer disordering and structural changes which increase with raising the treatment duration. Surface restructuring is attributed to the combined effects of active species (from plasma) bombardments and surface oxidation. Also, the surface chemistry changes are evaluated using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy which reveals chain scission after N₂ plasma treatment. Whereas, the O₂ plasma-treated samples suffer surface oxidation and formation of polar groups which offer some surface oxidation coatings. Furthermore, the surface wettability has been determined by the sessile drop method and shows enhancement upon plasma treatment due to the combined influence of surface chemistry and morphology. Also, the surface free energy (SFE) and adhesion are found to increase with the plasma exposure time due to surface activation. The optical behavior of LDPE is studied using ultraviolet–visible (UV–Vis) spectrophotometer which indicates that the optical bandgap performance depends on the amorphous or crystalline nature of the polymer. Also, the conjugated carbon atoms were examined and correlated to the reduced bandgap. In conclusion, the studied home-built glow discharge plasma reactor could be utilized efficiently to tune polymer surface properties to be used in high technology applications.

It is critical to reduce the bandgap of a ferroelectric photovoltaic (FE-PV) material in order to get the optimal effect of FE-PV. The interface effect of PbO/PbTiO₃ (P/PT) is used in this work to lower the bandgap of PbTiO₃ via the addition of PbO. The bandgaps of (P/PT)_down and ${\text{(P/PT)}}_{\mathrm{\text{up}}1}$, which are two types of polarization structures, fall from 2.63 eV of pure PbTiO₃ to 2.07 eV and 2.08 eV, respectively. Densities of states are calculated for pure PbO, pure PbTiO₃, and P/PT to determine the reason of the bandgap drop. The results indicate that the PbO component of P/PT is critical for both the conduction band minimum (CBM) and valence band maximum (VBM) states. Calculations of the absorption coefficient indicate that P/PT absorbs more light over a wider range of wavelengths in the visible-light region than PbTiO₃.