K. C. Sekhar

Semiconductor layer thickness impact on optical and resistive switching behavior of pulsed laser deposited BaTiO3/ZnO heterostructures

This work reports the impact of ZnO layer thickness on optical and resistive switching behavior of BaTiO3/ZnO heterostructures grown by pulsed laser deposition. The interface polarization coupling becomes more efficient and causes a remarkable change in heterostructure properties with decrease in ZnO layer thickness. The heterostructure with ZnO thickness of 25 nm displays the enhanced resistive switching characteristics with switching ratio ≈106 and good stability in low and high resistance states. Moreover, the photoluminescence spectrum exhibits two additional blue emissions when ZnO thickness is ≤50 nm and their mechanism is highlighted based on interface band offset and interface polarization coupling effect.

Effect of Pt bottom electrode texture selection on the tetragonality and physical properties of Ba0.8Sr0.2TiO3 thin films produced by pulsed laser deposition

The effect of platinum (Pt) bottom electrode texture on the tetragonality, dielectric, ferroelectric, and polarization switching response of pulsed laser deposited Ba0.8Sr0.2TiO3 (BST) thin films has been studied. The x-ray diffraction and Raman analysis revealed the higher tetragonality of BST films when they were grown on higher (111) textured Pt layer. The properties like dielectric permittivity, polarization, switching time, and leakage currents were found to be correlated to tetragonality and orientation of the BST films. The polarization current was observed to be higher in BST films on Pt epitaxial layer and it exhibits exponential dependence on the electric field. The voltage-current measurements displayed Ohmic behavior of leakage current irrespective of Pt texture for low voltages (up to 1 V), whereas at higher voltages the conduction mechanism was found to be dependent on texture selection of bottom Pt electrode.

Tuning the surface plasmon resonance and surface-enhanced Raman scattering of pulsed laser deposited silver nanoparticle films by ambience and deposition temperature

This study has been partially funded by (i) the Portuguese Foundation for Science and Technology (FCT) under the project PTDC/FIS/098943/2008 and the strategic project PESTC/ FIS/UI0607/2011, and (ii) European COST Actions MP0901NanoTP and MP0903NanoAlloy. The authors KK and KCS are grateful for financial support through the FCT grants SFRH/BPD/87215/2012 and SFRH/BPD/68489/2010 respectively. The authors would also like to thank Engineer Jose Santos for technical support at the Thin Film Laboratory.

Enhanced resistive switching characteristics in Pt/BaTiO3/ITO structures through insertion of HfO2:Al2O3 (HAO) dielectric thin layer

An enhanced resistive switching (RS) effect is observed in Pt/BaTiO3(BTO)/ITO ferroelectric structures when a thin HfO2:Al2O3 (HAO) dielectric layer is inserted between Pt and BTO. The P-E hysteresis loops reveal the ferroelectric nature of both Pt/BTO/ITO and Pt/HAO/BTO/ITO structures. The relation between the RS and the polarization reversal is investigated at various temperatures in the Pt/HAO/BTO/ITO structure. It is found that the polarization reversal induces a barrier variation in the Pt/HAO/BTO interface and causes enhanced RS, which is suppressed at Curie temperature (Tc = 140 °C). Furthermore, the Pt/HAO/BTO/ITO structures show promising endurance characteristics, with a RS ratio >103 after 109 switching cycles, that make them potential candidates for resistive switching memory devices. By combining ferroelectric and dielectric layers this work provides an efficient way for developing highly efficient ferroelectric-based RS memory devices.

Oxygen partial pressure induced effects on the microstructure and the luminescence properties of pulsed laser deposited TiO2 thin films

In this work, the influence of oxygen partial pressure on structural, morphological, and optical properties of TiO2 thin films grown on fused quartz substrate at different oxygen partial pressure by pulsed laser deposition were examined. X-Ray diffraction (XRD) patterns show the formation of TiO2 anatase phase deposited at high oxygen pressure. Atomic Force Microscopy (AFM) reveals that surface roughness of the films increases with oxygen pressure. Variation of surface morphology of films with increasing oxygen partial pressure was studied by AFM. It is observed that energy band gap of the films increases from 3.27 eV to 3.52 eV with the increase of oxygen pressure and is attributed to the decrease of oxygen defects. TiO2 thin films exhibited blue emission under the excitation of 320 nm wavelength. De-convoluted photoluminescence (PL) peaks showed that defect states are responsible for visible emission in TiO2 thin films. The intensity of PL emission associated with oxygen vacancies decreases with increas...

Optical and electrical properties of sol-gel spin coated titanium dioxide thin films

This work was partially supported by UGC through the Start-up Grant (F.4-5(59-FRP)/2014(BSR))). The author A R Jayakrishnan acknowledges Central University of Tamil Nadu (CUTN) for the Ph.D fellowship.