Solid State Phenomena Vol. 290

Abstract: The study is based on the use of NiO as an extended gate of field effect transistor (EGFET) using ITO/glass as a substrate for the sensitivity of pH sensor membrane. The NiO thin film was synthesis by wet and dry thermal oxidation method of Nickel metal thin film deposited by RF sputtering. The sensitivity of the NiO membrane was measured and comparatively analysed against the two different oxidation methods. Structural and morphological properties were investigated for both thin films. The sensitivities measurements of the two membranes were made as pH sensors. The results confirmed that NiO membrane grown by dry oxidation had much better sensitivity (87 μA/pH and 54 mV/pH) compared to wet oxidation membrane sample (52 μA/pH and 48 mV/pH).

Abstract: In this work, sol-gel spin coated of magnesium (Mg) doped gallium nitride (GaN) thin films grown on AlN sapphire substrate was reported. The structural, lattice vibrational, and electrical properties of the deposited films were investigated and compared. X-ray diffraction results show that the deposited films composed of wurtzite structure with preferred orientation of GaN(002). The Raman active phonon modes correspond to the E₂(high) and A₁(LO) at 568 cm^-1 and 733 cm^-1 phonon modes of the hexagonal GaN were observed, while a broad peak attributed to the Mg-related lattice vibrational mode was detected at 669 cm^-1. The Raman phonon modes were detected by using Raman spectroscopy. Hall effects results show that the resistivity, carrier concentration, and hall mobility of the Mg-doped GaN film was 0.1397 Ω cm, 1.77 × 10¹⁸ cm³, and 6.04 cm²/Vs, respectively. Besides, the characteristics of the ultraviolet (UV) photoresponse of the fabricated detector were investigated. The current-voltage characteristics of the Mg-doped GaN UV photodetector exhibits Schottky behaviour. The current-voltage measurements were carried out at room temperature with a computer-controlled integrated Source Meter (Keithley 2400). Lastly, the ideality factor and Schottky barrier heights were calculated using thermionic emission theory.

Abstract: Bismuth nanoparticles (BiNPs) are of interest in many applications such as imaging, antimicrobial agent, biosensors and electrochemical electrodes. However, synthesis of pure bismuth is difficult as bismuth tend to oxidise and form bismuth oxide that affects its properties. In this work, BiNPs were synthesised using hydrothermal method in an autoclave at 160°C. The effect of hydrazine (N₂H₄•H₂O) volume as reducing and capping agent was studied from 1.0-2.5ml with 3.6 Bi(NO₃)₃: 4.2 Polysodium 4-Styrene-Sulfonate: 50 H₂O (mass ratio). The produced BiNPs was used to modify indium tin oxide (ITO) substrates and tested as electrochemical heavy metal sensors to detect Pb and As. Pure BiNPs were successfully produced in all hydrazine volume. However, size and crystallinity of BiNPs were influenced by volume of hydrazine. Among these changeable compositions, the mass ratio of Bi(NO₃)₃ to N₂H₄•H₂O is the most important factor to form uniform size and shape of BiNPs. The addition of the reducing agent, N₂H₄•H₂O into the precursor solution promoted the subsequent reduction of Bi(III) and enabled the growth of BiNPs. Cyclic voltammetry (CV) in 0.002 mol/L of K₃Fe(CN)₆ electrolyte showed peak current responses obtained for BiNPs/ITO modified electrodes are larger than the bare ITO electrode, which were attributed to the fact that the electrochemical activities of ITO electrode increased by BiNPs surface modification. Stripping current responses of the Differential Pulse Anodic Stripping Voltammetry measurements were recorded for the determination of Pb(II) after a 300 seconds of deposition time at −1.2 V in 0.002 mol/L of acetate buffer solution with pH 4.5. Sensitivity response for the detection of Pb(II) was achieved in the range from 2.5 to 100 μg/L. The limit of detection (LOD) is 2.5 μg/L for Pb(II).

Abstract: This study involves synthesizing of nanostructured tin sulphide (SnS) thin film on a glass substrate by chemical bath deposition technique. SnS film was prepared using non-toxic trisodium citrate (TSC) as a complex agent. The structural and morphological characteristics of the film were characterized by using X-ray diffraction (XRD), optical field emission scanning electron microscopy (FESEM). The XRD pattern confirmed an orthorhombic structure. The FESEM image revealed nanoflakes of the as-prepared SnS thin film. Moreover, near-infrared (NIR) metal semiconductor metal photodetector, which exhibited good photoresponse characteristics under (750 nm) light illumination was fabricated. The photoresponse characteristics also were investigated at different illumination power densities. The photodetector revealed excellent reproducibility and stability characteristics.

Abstract: The effect of nanosized nickel ferrite (NiFe₂O₄) addition on (Tl_0.85Cr_0.15)Sr₂CaCu₂O_7-δ superconductors has been investigated. (Tl_0.85Cr_0.15)Sr₂CaCu₂O_7-δ high temperature superconductors was prepared via solid-state reaction method using high purity oxide powders. Nanosized NiFe₂O₄ was added to the compound at composition x = 0 - 0.003 wt.%. Samples were studied using scanning electron microscopy (SEM), X-ray diffraction method (XRD), electrical resistance versus temperature, transport critical current density J_c and AC susceptibility measurements. SEM micrographs showed close-packed microstructure with low porosity. XRD patterns showed a dominant phase of Tl-1212 with a minor phase of Tl-1201 for all samples. All of the samples displayed metallic normal state behavior before the onset transition temperature (T_c-onset) which was between 102 and 104 K. The transition temperature (T_cχ’) from AC susceptibility measurement also showed the similar results between 101 and 103 K. T_c-zero was slightly suppressed with the addition of nanosized NiFe₂O₄. The peak temperature T_p from the imaginary part of the susceptibility χ” was found between 77 - 91 K for all samples. The highest transport critical current density (J_c) at 77 K was shown by sample x = 0.001 wt.% at 2213 mAcm^-2. Nanosized NiFe₂O₄ has significantly enhanced the J_c of (Tl_0.85Cr_0.15)Sr₂CaCu₂O_7-δ superconductor.

Abstract: In this paper, solid state method was using to synthesize the of magnesium diboride (MgB₂) added in Bi _1.6Pb _0.4Sr₂Ca₂Cu₃O_δ(Bi-2223) superconductor from 0.00 to 0.10 wt.%. The effect on additions were investigated through X-ray Diffraction (XRD), resistance-temperature (R-T) measurement and Scanning Electron Microscope (SEM). From the XRD result, volume fraction of Bi-2223 showed the highest volume percentage was 76 % correspond to addition with MgB₂=0.02 wt.% and slightly decreased the percentage while increased the additions. From the R-T measurement, all samples showed the metallic behavior in the normal state. Morphology images showed that the grains were flaky plates and the size slightly increased. These results revealed that, additions of magnesium diboride change the microstructure and decrease the superconducting transition.

Abstract: The Tl_2-xTe_xBa₂CaCu₂O_8-δ (Tl-2212) high temperature superconductors with x = 0.0-0.5 have been prepared by the standard solid-state reaction method. The precursor powder were sintered at 900°C for 24 h with several grindings and heating. The powder were then pressed into pellets and heated at 910°C in oxygen flow for 4 min followed by furnace cooling. The electrical resistance versus temperature dependence measurements showed metallic normal state behavior for all samples. Substitution of Te at the Tl-site led to multi-phasic samples. The x = 0.4 sample showed the highestT_{c zero}= 98 K and T_conset= 111K. The Tl-2212 phase increased from 50% for x=0 up to 92% in the x= 0.4 sample.

Abstract: The effects of the multiforric BiFO₃ nanoparticles addition on the structure and superconducting properties of YBa₂Cu₃O_7–δ (Y123) with different concentrations were systematically investigated using X-ray diffraction (XRD), field emission scanning electron micrograph (FESEM), EDX and four point probe measurement. It was found that the added samples were predominant by Y-123 phase beside small amount of Y-211 and unreacted BiFeO3 secondary phases. Samples with less (wt.%) BFO added YBCO precursor powder preserved the orthorhombic structure similar to the pure YBCO, while samples with higher wt% addition show orthorhombic-to-tetragonal transition tendency. The samples became more porous and their grain size slightly decreased with addition of BiFeO₃. The addition of nanoBiFeO3 disturbed the grain growth of Y123, thus resulting in the degradation of superconducting properties of the samples. The superconducting transition temperature (Tc onset) of samples decreased from 92 K for x=0.0 to 44 K for x=10.0 wt. %, which could be attributable to oxygen vacancy disorder.

Abstract: The (Tl_1-xCr_x)Sr₂CaCu₂O₇ (Tl-1212) sample with nominal starting composition for x = 0.0, 0.2 and 0.3 were prepared by the solid-state reaction method. The samples were studied by powder x-ray diffraction method and electrical resistance versus temperature measurement. Excess conductivity analysis was carried out using the Aslamazov–Larkin (AL) theory, and the dimension of fluctuation-induced conductivity (λ) was determined. The Lawrence–Donaich (LD) theory was used to calculate the coherence length (ξ_c(0)), Josephson coupling (J), and γ = (ξ_ab(0)/ξ_c(0)) of the superconductive samples. Excess conductivity analysis showed that Cr substitution induced 2D-to-3D conductivity transition at the highest transition temperature (T_2D-3D) observed at x = 0.3. The calculations based on the Lawrence–Doniach model revealed that the shortest coherence length and weakest inter-plane coupling (J) occurred when x = 0.2. The sample with x = 0.2 and 0.3 showed the Tl-1212 as the major phase. The highest onset temperature of 110 K was observed in the x = 0.2 sample. Our result showed that the formal value of 2.3+ is more important than the Josephson interlayer coupling J in optimizing the transition temperature.

Abstract: In this study, Zinc Oxide (ZnO) microstructures were grown on porous silicon (PS) using chemical bath deposition (CBD) method by varying the growth time. The field emission scanning electron microscopy (FESEM) revealed the morphology and sized of ZnO. The X-ray diffraction (XRD) spectra indicate the high quality growth of ZnO on PS surface. Raman analyses revealed the peaks shift of E₂(High), characterized wurtzite lattice and indicates good crystallinity of ZnO.