Papers by j pundareekam goud
Nanomaterials
The contamination of water by organic substances poses a significant global challenge. To address... more The contamination of water by organic substances poses a significant global challenge. To address these pressing environmental and energy concerns, this study emphasizes the importance of developing effective photocatalysts powered by sunlight. In this research, we achieved the successful synthesis of a novel photocatalyst comprised of polymeric carbon nitride (CN) nanosheets embedded with Co3O4 material, denoted as CN-CO. The synthesis process involved subjecting the mixture to 500 °C for 10 h in a muffle furnace. Structural and morphological analyses confirmed the formation of CN-CO nanostructures, which exhibited remarkable enhancements in photocatalytic activity for the removal of methylene blue (MB) pollutants under replicated sunlight. After 90 min of exposure, the degradation rate reached an impressive 98.9%, surpassing the degradation rates of 62.3% for pure CN and 89.32% for pure Co3O4 during the same time period. This significant improvement can be attributed to the except...
Materials Science in Semiconductor Processing
Journal of Materials Science: Materials in Electronics
Journal of Materials Science: Materials in Electronics, 2022
We report an athermal laser annealing technique to fabricate a high-density array of gold nanopar... more We report an athermal laser annealing technique to fabricate a high-density array of gold nanoparticles on the surface of hafnium oxide thin films without altering the phase of HfO2. Au (~ 5 nm) films deposited on amorphous HfO2 (~ 10 nm) are subjected to laser annealing by using an Excimer laser (248 nm) to produce Au nanoparticles. It is important to note that the usual thermal methods would change the phase of the HfO2. It is observed that the size of the spherical Au nanoparticles decreases and their surface density increases as the number of laser pulses increases. These Au nanoparticles has induced a significant enhancement in the Raman signature of the standard R6G dye. Further, Metal–Oxide–Semiconductor capacitors were fabricated by depositing another layer of HfO2 followed by metal contacts on the surface of these nanoparticles. The leakage current conduction through the gate oxide with and without embedded nanoparticles has been studied using the Poole–Frenkel and Fowler–Nordheim tunneling mechanisms by examining the leakage current–voltage characteristics. PF tunneling is found to be prominent in these MOS structures with Au nanoparticles, which is attributed to the possible charge trapping by the embedded Au nanoparticles. The capacitance–voltage (C–V) characteristics show a significant broadening in the hysteresis loop indicating the improvement in the storage capacity of these MOS capacitors.
arXiv: Applied Physics, 2018
This report presents a robust composite resonator known as the high overtone bulk acoustic wave r... more This report presents a robust composite resonator known as the high overtone bulk acoustic wave resonator (HBAR) for demonstrating experimentally the ability of the resonator to tune the envelope of the spectrum by applying dc bias. The reported HBAR exhibits exceptionally high-quality factor in the frequency range of 700 MHz to 3 GHz and high effective coupling coefficient over the broad range of microwave frequencies. The HBAR is based on thin Ba0.5Sr0.5TiO3 film sandwiched between two electrodes forming a transducer, supported by a thick sapphire substrate which is a low acoustic loss material. The resonator works on the principle of induced piezoelectricity due to the applied dc bias. The minima of the envelope changes from 1.16 GHz with S11 of -3.51 dB at 100 kV/cm bias to 1.90 GHz with S11 of -42.23 dB at 700 kV/cm bias, giving a relative tunability of the envelope to be around 64%. The spacing of the parallel resonance frequency (SPRF) for different bias voltages are also pre...
arXiv: Applied Physics, 2018
This report presents the realization and characterization of a robust composite resonator i.e. hi... more This report presents the realization and characterization of a robust composite resonator i.e. high overtone bulk acoustic wave resonator (HBAR) and the changes happening to the resonance peaks once it undergoes mass loading which has got the potential for application in material characterization, communication system and sensing. Mass loading effect on a HBAR based on BaxSr1-xTiO3 (BST) have been demonstrated by coating photoresist of various thicknesses and characterization of resonance modes present in the frequency spectrum of the resonator. Upon investigation, HBAR proves to be one of the most promising and robust systems for gravimetric sensing. Burning effect in the resonances occurs and it shifts significantly according to the amount of mass loaded (increasing thickness of the photoresist coated) on the resonator system. Some of the most important parameters like effective coupling coefficient, spacing of parallel resonance frequency (SPRF) and quality factor of the resonato...
Journal of Materials Science: Materials in Electronics, 2021
Herein, we have investigated the optical and microwave dielectric properties of Bi0.5Na0.5TiO3 (B... more Herein, we have investigated the optical and microwave dielectric properties of Bi0.5Na0.5TiO3 (BNT) thin films grown under different oxygen pressure (PO2) using pulsed laser deposition (PLD) technique. The X-ray diffraction measurements confirms the single phase of BNT along with secondary phase and further reduction in secondary phase and increase in BNT phase with PO2, signifies the close relation between the crystal structure and oxygen content. The shift of Raman-active TO1, TO2 and TO3 modes towards higher wavelengths and increase in mode intensity with PO2 indicating the films degree of crystallinity. The local roughness (αloc) of all films obtained as 0.85, and the interface width () and lateral correlation length (ξ) of films varies with PO2. Also, the films exhibit the increase in refractive index and reduction in optical bandgap of due to improvement in crystallinity and reduction in the oxygen vacancies. The microwave dielectric properties show a strong PO2 depends with higher dielectric constant (εr = 336) with lower loss (tanδ = 0.0093) at 5 GHz which show the potential applications in high frequency devices.
2022 IEEE International Conference on Emerging Electronics (ICEE)
Journal of The Korean Ceramic Society, Apr 18, 2023
2016 Joint IEEE International Symposium on the Applications of Ferroelectrics, European Conference on Application of Polar Dielectrics, and Piezoelectric Force Microscopy Workshop (ISAF/ECAPD/PFM), 2016
DC bias field dependent high overtone resonances are observed in a metal insulator metal (MIM) st... more DC bias field dependent high overtone resonances are observed in a metal insulator metal (MIM) structure based on Ba0.5Sr0.5TiO3 (BST) thin films on a sapphire substrate. The microwave measurement shows the bias dependent nature of the device, wherein without any bias it acts like a MIM capacitor but upon biasing resonant peaks start appearing in its frequency spectra, which is typical of a response given by a high overtone bulk acoustic wave resonator (HBAR). Acoustic velocity of the sapphire substrate is calculated to be 11440 m/s and the HBAR exhibits a high quality factor of 4370 around 1.39 GHz.
Sintering is an important factor that affects the microstructure development in ceramics. In this... more Sintering is an important factor that affects the microstructure development in ceramics. In this work, Bi and Li co-substituted Strontium Titanate (ST) ceramics samples sintered at different temperatures are prepared and analyzed by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). XRD was used to detect phase structure of the sintered samples and SEM was used for microstructure analysis. Dielectric properties of Bi and Li co-substituted SrTiO3 samples were measured using Agilent 4294A Impedance analyzer in the frequency range 40 Hz to 5 MHz at room temperature. The result reveals that the dielectric constant of Bi and Li co-substituted SrTiO3 ceramics increases with increasing sintering temperature up to 1250°C and then decreases beyond that. The highest value of dielectric constant obtained is 860 at 1KHz frequency and lowest dielectric loss observed is 0.04 at the same frequency for samples sintered at 1250°C. Also the grain size increases with increase of sinterin...
Advanced Electronic Materials, 2021
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 2021
This article describes the characterization and analysis of the effects an additional polymer lay... more This article describes the characterization and analysis of the effects an additional polymer layer has on a high-overtone bulk acoustic wave resonator based on Ba0.5Sr0.5TiO3 (BSTO) thin film by studying its spectral information. From both the simulation (numerical model) and experimental results of the resonator with and without coating, significant difference of both cases is evident in the spacing of the parallel resonance frequencies (SPRFs), effective coupling coefficient ( ${k}_{\text {eff}}^{{2}}$ ), and quality factor distribution of the resonator. The acoustic velocity of the coated material (SU-8) is calculated from the new periodicity introduced in the SPRF distribution. The SPRF distribution of the SU-8-coated resonator decreases overall as expected due to the additional layer introduced but sharply increases in regions defined by the thickness and acoustic velocity of the SU-8 layer. The mechanical loss of the added layer has significant effect on the parameters of the resonator. The study reveals that this method of characterization can be used to approximate the mechanical loss of materials such as polymers or polymer composites. The simulation with finite-element method agrees with the experimental result.
IEEE Microwave and Wireless Components Letters, 2021
<jats:p>A ferroelectric metal insulator metal (MIM) varactor structure incorporating a floa... more <jats:p>A ferroelectric metal insulator metal (MIM) varactor structure incorporating a floating metal and coplanar waveguide (CPW) has been introduced here. The work of the proposed varactor is based on the field-dependent material properties of (Ba,Sr)TiO3 (BST) thin film. A capacitance tunability of 44% has been achieved for the bias voltage of 0 V to 10 V over a frequency range of 1 GHz to 3 GHz. The proposed varactor structure yields a compact area, high capacitance density, and reduced mask process (2 masks)</jats:p>
Applied Physics Letters, 2017
This letter reports the use of the resonant spectrum method to characterize a high overtone bulk ... more This letter reports the use of the resonant spectrum method to characterize a high overtone bulk acoustic wave resonator (HBAR) which has a thin film ferroelectric BaSrTiO3 (BSTO) active layer on a YAG substrate. The HBAR works on the principle of electric field induced piezoelectricity of the thin film ferroelectric BSTO and exhibits switching functionality. From the parallel and series resonant frequencies of each of the multiple peaks in the frequency spectrum of the HBAR, the distribution of spacing of parallel resonance frequency and the distribution of effective coupling coefficient are studied and parameters like acoustic wave velocity, electromechanical coupling coefficient, elastic constant, and density for the thin film are determined. The influence of dc bias voltages on the distribution of the effective coupling coefficient and the electromechanical coupling coefficient is also reported. This letter also establishes the relationship between the relative tunability of the device capacitance and...
Journal of Materials Science: Materials in Electronics, 2016
Amorphous and crystalline Na 0.5 Bi 0.5 TiO 3 (NBT) thin films were deposited at different substr... more Amorphous and crystalline Na 0.5 Bi 0.5 TiO 3 (NBT) thin films were deposited at different substrate temperatures on fused silica by plused laser deposition method. The phase and microstructure of the deposited films were investigated by XRD and FE-SEM respectively. The noticeable difference is observed in the Raman and optical spectra of amorphous and crystalline films. To grasp further insight, the dispersion data of the refractive index is fitted with the single oscillator model. The oscillator strength and oscillator energy are computed. The refractive index of NBT thin films decrease with increase in wavelength and approach a constant value in long wavelength limit while extinction coefficient increase with increase in wavelength. In Raman spectra of amorphous materials, many Raman peaks coalesce and form very broad spectral bands, whereas the polycrystalline material shows distinct band.
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Papers by j pundareekam goud