Koppole Kamakshi

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 25u2009nm 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 ≤50u2009nm and their mechanism is highlighted based on interface band offset and interface polarization coupling effect.

Ferroelectric phase transitions studies in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramics

The ferroelectric phase transitions in 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (BCZT 50/50) ceramics, fabricated by a solid state reaction, were studied by using X-Ray diffraction, Raman spectroscopy, and measuring electric polarization, dielectric permittivity and pyroelectric current. X-ray diffraction (XRD) confirms the coexistence of tetragonal (T) and rhombohedral (R) phases at room temperature. The temperature dependence of the Raman modes frequency reveals the existence of two phase transitions corresponding to the rhombohedral – tetragonal, and tetragonal - cubic close to 30 and 100xa0°C, respectively. The temperature dependence of electric polarization, pyroelectric current, and dielectric permittivity further supports the ferroelectric (tetragonal) to paraelectric (cubic) phase transition. Moreover, the dielectric permittivity reveals the diffuseness of the phase transition and is attributed to the compositional fluctuations of different polar micro-regions.

Resistive switching in ferroelectric lead-free 0.5Ba (Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 thin films

In this work, resistive switching in pulsed laser deposited ferroelectric lead-free 0.5Ba(Zr0.2Ti0.8)O3–0.5(Ba0.7Ca0.3)TiO3 (0.5BZT–0.5BCT) thin films was investigated. This study reveals that films grown at 5.5 J cm−2 have shown optimal ferroelectric and resistive switching response, which are attributed to high tetragonality, large grain size and less defect concentration. Au/0.5BZT–0.5BCT/Pt capacitors show the electroforming free resistive switching that is explained based on the polarization modulation of the Schottky-like barrier at the 0.5BZT–0.5BCT/Au interface. The polarization induced resistive switching is evidenced by its disappearance as the temperature increases to the Curie temperature. The capacitor based on film grown at 5.5 J cm−2 shows resistive switching characterized by high switching ratio of 106 at a low set/reset voltage ≈1 V, and by a stable memory window, which are highly required for memory applications.

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 PortuguesenFoundation for Science and Technology (FCT) under thenproject PTDC/FIS/098943/2008 and the strategic projectnPESTC/nFIS/UI0607/2011, and (ii) European COST ActionsnMP0901NanoTPnand MP0903NanoAlloy.nThe authors KKnand KCS are grateful for financial support through the FCTngrants SFRH/BPD/87215/2012 and SFRH/BPD/68489/2010nrespectively. The authors would also like to thank EngineernJose 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 (Tcu2009=u2009140u2009°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.

Surface Plasmon Resonance-Coupled Photoluminescence and Resistive Switching Behavior of Pulsed Laser-Deposited Ag:SiC Nanocermet Thin Films

In this study, Ag:SiC nanocermets were prepared via rapid thermal annealing (RTA) of pulsed laser-deposited SiC/Ag/SiC trilayers grown on Si substrate. Atomic force microscope images show that silver nanoparticles (Ag NPs) are formed after RTA, and the size of NPs increases with increasing Ag deposition time (tAg). Sharp dip observed in the reflectance spectra confirmed the existence of Ag surface plasmons (SPs). The infrared transmission spectra showed an intense and broad absorption band around 780–800xa0cm−1 that can be assigned to Si-C stretching vibration mode. Influence of tAg on the spectral characteristics of SP-enhanced photoluminescence (PL) and electrical properties of silicon carbide (SiC) films has been investigated. The maximum PL enhancement by 5.5 times for Ag:SiC nanocermets is achieved when tAgu2009≈u200950xa0s. This enhancement is due to the strong resonant coupling between SiC and the SP oscillations of the Ag NPs. Presence of Ag NPs in SiC also induces a forming-free resistive switching with switching ratio of 2u2009×u200910−2. The analysis of I–V curves demonstrates that the trap-controlled space-charge-limited conduction with filamentary model is the governing mechanism for the resistive switching in nanocerment thin films.

Substrate temperature effect on microstructure, optical and glucose sensing characteristics of pulsed laser deposited silver nanoparticles

This work reports the substrate temperature-influenced change in the structural, morphological, optical, and glucose sensing properties of silver (Ag) nanoparticles (NPs) deposited on p-type Si (100) wafers. AgNP films grown at temperatures ranging from RT to 600xa0°C clearly show a dependence of orientation texture and surface morphology on substrate temperature (Ts). As Ts increases from RT towards 600xa0°C, the preferred orientation of AgNP film changes from (111) to (200). The AgNPs size, that is Ts-dependent, reaches the maximum value at Tsxa0=xa0300xa0°C. This result is attributed to restructuring of AgNPs texture. Moreover, the AgNP shape also changes from ellipsoid to sphere as Ts increases from RT to 600xa0°C. Surface plasmon enhancement in photoluminescence intensity is observed with increase in Ts. It is found also that the AgNP film deposited at 300xa0°C has considerable reflectance reduction relative to the silicon substrate, in wavelength range of 300–800xa0nm and a progressive red shift of localized surface plasmon resonances caused by the adding of increasing quantities of glucose has been observed. As a proof of concept, we also demonstrate the capability of grown AgNP substrates for glucose detection based on surface enhanced Raman spectroscopy in physiological concentration range with short integration time 10xa0s, varying with Ts.

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 n(F.4-5(59-FRP)/2014(BSR))). The author A R Jayakrishnan acknowledges Central University of nTamil Nadu (CUTN) for the Ph.D fellowship.