A. S. Maan

Barrier height inhomogeneities induced anomaly in thermal sensitivity of Ni/4H-SiC Schottky diode temperature sensor

This paper presents the thermal sensitivity variation trend of Ni/4H-nSiC (0001) Schottky diode based temperature sensor, equipped with floating metal guard ring and oxide field plate as edge terminations in low current regime, i.e., ranging from 1 nA to 5 pA. Various measurements were carried out at temperatures ranging from 233 K to 473 K in steps of 20 K. An imperative outcome of the present study, which is in contrast with the theory, is that there exists an anomaly in the device thermal sensitivity behaviour after a range of current. The thermal sensitivity of the fabricated device, calculated from the slope of forward voltage versus temperature plot, was found to be varied from 3.11 mV/K at 1 nA to 3.32 mV/K at 5 pA with standard error of ±0.03 mV/K. A detailed analysis of I-V-T characteristics by taking into account all the possibilities for variation in the barrier height and the ideality factor with temperature emphasizes that there exist barrier height inhomogeneities at the metal–semiconductor ...

Structural and Physical Properties of Glasses

The structural and physical properties of xFe2O3-(40-x) B2O3-60V2O5 (0 ≤ x ≤ 20) glass system have been investigated. The samples were prepared by normal melt-quench technique. The structural changes were inferred by means of FTIR by monitoring the infrared (IR) spectra in the spectral range 600–4000 cm−1. The absence of boroxol ring (806 cm−1) in the present glass system suggested that these glasses consist of randomly connected BO3 and BO4 units. The conversion of BO3 to BO4 and VO5 to VO4 tetrahedra along with the formation of non-bridging oxygen’s (NBOs) attached to boron and vanadium takes place in the glasses under investigation. The density and molar volume of the present glass system were found to depend on Fe2O3 content. DC conductivity of the glass system has been determined in the temperature range 310–500 K. It was found that the general behavior of electrical conductivity was similar for all glass compositions and found to increase with increasing iron content. The parameters such as activation energy, average separation between transition metal ions (TMIs), polaron radius, and so forth have been calculated in adiabatic region and are found consistent with Mott’s model of phonon-assisted polaronic hopping.

Diameter dependent thermal sensitivity variation trend in Ni/4H-SiC Schottky diode temperature sensors

This report is on the diameter dependent thermal sensitivity variation trend of Ni/4H-nSiC Schottky barrier diode (SBD) temperature sensors. Scaled SBDs of 2, 1.6, and 1.2 mm in diameter were fabricated using standard photolithography process comprising a field plate and a guard ring as edge terminations on the same epitaxial wafer. Taking into consideration the heat loss and power consumption, the thermal sensitivities of the fabricated SBDs were measured in the current range from 1 μA to 50 pA. The temperature was varied from 273 to 473 K in step of 25 K. An authoritative consequence of the present study is the observed increase in thermal sensitivity with the diameter of the fabricated SBDs. An exhaustive investigation confirms that in all diodes, there exist nanosized patches, which assumed to have different barrier heights and hence ascertained to be the main cause of anomalies in thermal sensitivity variation with diode size. Taking into account the effective area of these patches, theoretically fit...

Physical, optical and structural properties of xNa2O−(50−x)Bi2O3−10ZnO−40B2O3 glasses

Glasses with composition xNa2O−(50−x)Bi2O3−10ZnO−40B2O3 with 0 ≤ x≤ 20 have been synthesized by conventional melt quench method. Density and molar volume decreases with increase in Na2O content. The optical absorption studies revealed that the cutoff wavelength decreases and optical band gap (Eopt) increases with increase in Na2O content and the present glass system shows indirect allowed transitions. The IR studies indicate that these glasses are made up of [BiO3] [BiO6], [BO3] and [BO4] basic structural units. Na2O acts a network modifier and modify the glass structure.

Effect of Annealing on Optical Properties of Glasses

The Melt-quench method is used to synthesize zinc fluoroborate glasses with compositions (, 5, 10, 15, and 20). Optical characterization was carried out to examine the variation of optical bandgap energy () and urbach energy () with respect to the concentration for the samples annealed at different temperatures (, and ). Annealing shows its effect on the samples with the variations in the values of and . These variations are explained on the basis of formation of different molecular species like units, boroxol rings, and the change in the number of nonbridging oxygen atoms.

Effect of Stepwise Replacement of LiF by Bi2O3 and of Annealing on Optical Properties of LiF⋅B2O3 Glasses

Bismuth fluoroborate glasses with compositions 𝑥Bi2O3⋅(40−𝑥)LiF⋅60B2O3(𝑥=0,5,10,15,and20) are synthesized by melt-quench method. Optical characterization was carried out to examine variation of optical band gap energy (𝐸𝑔) and Urbach energy (𝐸𝑈) with respect to the concentration. It reflects the effect of stepwise replacement of non-oxide and less polarizable LiF by an oxide and more polarizable (Bi2O3) group on the optical properties of the samples. The value of 𝐸𝑔 decreases with increase in concentration of Bi2O3. The samples were subjected to annealing at different temperatures (300°C, 350°C, and 400°C), and the effect of annealing on the optical properties of various samples was again studied. Annealing affects remarkably the values of 𝐸𝑔 and 𝐸𝑈 in the samples with 𝑥=0.

Effect of Stepwise Replacement of Non-Oxide to Oxide Group on Structural Properties of ·LiF· Glasses

Bismuth fluoroborate glasses with compositions xBi2O3·(40 − x)LiF·60 B2O3 (x = 0, 5, 10, 15, and 20) are synthesized by melt-quench method. XRD pattern is obtained for all the samples to confirm their amorphous nature. FTIR spectroscopy is carried out for the reported samples. It reflects the effect of replacement of a non-oxide group (LiF) with an oxide group (Bi2O3) in the glass network, due to the presence of the various absorption bands and their shifting with such replacement, assigning a role of network modifier to Bi2O3. Density and molar volume show an increase in their values with increase in Bi2O3 concentration. Theoretical optical basicity is calculated for the reported samples, which shows a decreasing trend with the increasing concentration of Bi2O3.

Structural, morphological, optical and photocatalytic investigation of Ag-doped TiO2

The pure and Ag-doped TiO2 nanoparticles were prepared by using Titanium isoproxide (TTIP), silver nitrate sodium hydroxide and sodium hydroxide. The calcined nanoparticles at 400°C were characterized by means of X-ray diffraction (XRD). XRD analyses reveal that the nanoparticles of various doping concentration were having anatase phase. The particle size was calculated by Scherrer formula and was found 11.08 nm for pure TiO2 and 8.86 nm for 6 mol % Ag doped TiO2. The morphology and nature of nanoparticles was analyzed by using scanning electron microscope (SEM), the optical absorption spectra of pure TiO2 and Ag-doped TiO2 nanoparticles showed that absorption edge increases towards longer wavelength from 390 nm (pure) to 450 nm (doped), also band gap energy calculated from Tauc’s plot decrease from 3.20eV to 2.92eV with increase in doing. The measurement of photocatalytic properties of pure TiO2 and Ag-doped TiO2 nanoparticles showed that Ag-doped TiO2 degrades MB dye more efficiently than pure TiO2.

Methanol assisted synthesis and characterization of tin oxide nanoparticles

Tin oxide nanoparticles (NPs) of size 12 nm, were synthesized at room temperature by the reaction of Sncl4.5H2O dissolved in Methanol via sol-gel method. The structural, optical and Photoluminescence (PL) properties of tin oxide nanoparticles have been studied by XRD, SEM, UV-Vis and Photoluminescence spectroscopic techniques. The X-ray diffraction measurement shows the tetragonal structure of the tin oxide nanoparticles. The average particle size of the sample was determined from the line broadening of (110) peak of XRD. The optical band gap of the sample was determined from UV-Visible spectrum and found 3.73 eV. The sample under study exhibits a strong emission at 384 nm in PL spectrum, which may be ascribed to the contribution of oxygen’s vacancies and defects in SnO2 nanoparticles.

Physical and electrical properties of copper oxide doped bismuth borate glasses

The role of CuO on the physical and electrical properties in x CuO.(25-x)Bi2O3.75B2O3;(5≤x≤20) glass system has been investigated. The glasses were prepared by normal melt quench technique. The density and molar volume of the glasses decreases with increase in CuO (mol %). The dc conductivity was measured in the temperature range 413-513 K. The conduction mechanism in these glasses was discussed in terms of small polaron hopping (SPH) theory proposed by Mott. The activation energy is found to decrease with increasing copper oxide content. The dc conductivity increases with increase in CuO content and ranging from 6.02×10−12 (Ωm)−1 to 1.096×10−10 (Ωm)−1 at 450K.