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High quality (1 0 0) oriented thin films of (Y 0.9 Bi 0.1 )(Fe 0.5 Cr 0.5 )O 3 [YBFCO] were deposited on (1 0 0) LAO substrates with conducting LNO buffer layer as bottom electrode. YBFCO thin film was found to demonstrate interesting room temperature multiferroic properties where the origin of weak ferroelectricity could be mainly attributed to disordered transition metal ions of unlike spins, and magnetic behavior was ascribed to uncompensated weak ferromagnetism arises due to magnetic cluster state in disordered system. Dielectric anomaly near magnetization reversal temperature ( T irr ) revealed magnetodielectric effect in YBFCO film. In addition, leakage current behavior of the film was explained by trap-controlled space-charge-limited current conduction (SCLC) mechanism. [ABSTRACT FROM AUTHOR]

Highlights: [•] High quality thin film of multiferroic BiFeO3 on SrRuO3 is grown by RF Sputtering. [•] The Pt/BFO/SRO structure showed diode like behavior through I–V measurement. [•] Appreciable VOC and JSC were observed with illumination of white light. [•] The photoresponse at zero bias of BFO film showed rapid increase in photocurrent. [•] Application of BFO film for photosensitive capacitor is demonstrated. [ABSTRACT FROM AUTHOR]

Abstract: A novel multilevel resistive switching was observed in trilayer stacked geometry composed of graphene nano flakes sandwiched between polyvinylidene fluoride layers fabricated by spin coating method, which are expected to fulfill the need of high density data storage memories. External parameters such as current compliance and induced voltage pulse imposed on the devices provided an aid to tune the inherent resistance states. As fabricated devices exhibited multi level switching with stable resistance ratios between different resistance states having excellent data retention and endurance. Space charge limited conduction and Fowler–Nordheim (F–N) tunneling were found to be responsible for the switching mechanism. Graphene enriched with trapping sites provides the adequate environment for F–N tunneling process to occur, resulting in multi-bit resistance states. [Copyright &y& Elsevier]

The resistive switching phenomenon is attributed to local formation and rupture of conductive filaments (CF), however some aspects of the switching mechanism still need wider consensus. The origin of resistance contribution to low resistance state (LRS) and high resistance state (HRS) is although well known, the origin of capacitive contribution to the memory state of resistive random access memory device (RRAM) is ambiguous. Here we report impedance spectroscopic studies carried on Cu/TiO 2 /Pt devices to address the origin of resistive and capacitive contribution, where the effect of DC bias voltage, reset stop voltage and set compliance current on the impedance of RRAM memory states were investigated in detail. The studies revealed that the capacitive contribution was dominated by the surrounding TiO 2 bulk and contrary to existing knowledge, gap formed owing to ruptured CF has negligible role. These studies also reaffirmed the origin of the resistive contribution to the HRS and LRS state, which was dictated by the ruptured gap and connected CF, respectively. Results of this study may be significant towards improving the switching time and operating frequency performance of futuristic memory, RF switch and neuromorphic computing applications of RRAM devices. [ABSTRACT FROM AUTHOR]

Piezoelectric nanogenerators (PENG), which convert random mechanical energy into electrical energy, have attracted considerable attention due to their application potential in self-powered micro and nano electronics devices, wearable electronics, sensors etc. PENGs based on ZnO nanostructures are particularly important due to their low cost, flexibility and bio-compatibility. Flexible PENGs based on ZnO nanostructures dispersed in Polydimethylsiloxane (PDMS) in ITO/ZnO:PDMS/ITO device configuration were fabricated and characterized for vibration energy harvesting applications. Surfactant free ZnO nanostructures were grown using co-precipitation route and ZnO:PDMS nano-composite films with ZnO content varying in the range of 1.5–7.5 wt% were deposited on ITO/PET substrates for PENG fabrication. The maximum open circuit voltage and short circuit current of ~ 2.5 V and ~ 4 µA respectively were obtained in PENG fabricated with 6 wt% ZnO. The output characteristics were further enhanced to 5 V and 6 µA with flowing oxygen ambient annealing of ZnO nanostructures generating an instantaneous power density of ~9.55 µWcm−2. X-ray photoelectron spectroscopy studies confirmed reduction in oxygen vacancy and enhancement in oxygen interstitial concentrations on oxygen annealing which leads to the suppression of free carrier induced internal screening in ZnO nanostructures. This suppression of internal screening effect is the possible reason for the enhancement in output characteristics of ZnO:PDMS PENG fabricated with oxygen annealed ZnO nanostructures. The electrical energy generated by the ZnO:PDMS PENG was rectified and effectively stored in capacitors and used to power LEDs and LCD display. • ZnO nanostructures were grown by co-precipitation method with air and oxygen annealing. • ZnO:PDMS PENG with variable wt% of ZnO in PDMS were fabricated in ITO/ZnO:PDMS/ITO configuration. • The output performance of ZnO:PDMS PENG is improved significantly by annealing ZnO nanostructures in flowing oxygen ambient. • XPS established a correlation between the oxygen related point defects in ZnO and output characteristics of ZnO based PENG. • The output energy from ZnO:PDMS PENG was rectified and effectively stored in capacitor to flash LEDs and LCD display. [ABSTRACT FROM AUTHOR]

Abstract: We report valence and conduction band offset measurements in a pulsed laser deposited Ni0.07Zn0.93O/ZnO heterostructure using X-ray photoelectron spectroscopy, valence band spectroscopy and ultraviolet visible spectroscopy. Neglecting the strain effect, the valence band offset was estimated to be 0.32 eV and the conduction band offset comes out to be −0.23 eV. Ratio between conduction band and valence band offset is 0.72. Core level shifting due to Ni doping has also been explained. Magnetotransport study of Ni0.07Zn0.93O film reveals that the charge carriers might be spin polarized at the interface of the heterojunction. [Copyright &y& Elsevier]

Abstract: Lanthanum hexaboride films were grown on tungsten and rhenium tips and foils by pulsed laser deposition. The X-ray diffraction spectra of the PLD films on both the substrates show crystalline nature with average grain size . The field emission studies of pointed and foil specimens were performed in conventional and planar diode configurations, respectively, under ultra-high vacuum condition. An estimated current density of was drawn at the electric field of and from the coated tips of tungsten and rhenium, respectively. The Fowler–Nordheim plots were found to be linear showing metallic behavior of the emitters. The field enhancement factors were calculated from the slopes of the Fowler–Nordheim plots, indicating that the field emission is from nanoscale protrusions present on emitter surfaces. The emitters were operated for long time current stability (3h) studies. The post-field emission surface morphology of the emitters showed no significant erosion of films during 3h continuous operation. The observed behavior indicates that it is linked with the growth of films on W and Re. These results reveal that the films exhibit high resistance to ion bombardment and excellent structural stability and are more promising emitters for practical applications in field emission based devices. [Copyright &y& Elsevier]

The increasing demand of energy harvesting and wearable electronics applications requires the development of flexible and highly durable piezoelectric nanogenerators (PENG). In this work, We have fabricated flexible ZnO:PVDF based PENGs for vibrational energy harvesting and shoe insole pedometer application s. ZnO nanorods were grown by hydrothermal method and incorporated into PVDF matrixes in the concentration range of 5–15 wt%. These homogeneous ZnO:PVDF composite films were sandwiched between Al electrodes to realize flexible free standing PENGs. The open circuit voltage (Voc), short circuit current (Isc) and instantaneous power density of PENGs increased from ∼ 4 V, 0.4 µA and 1.6 µW/cm2 to ∼ 14.6 V, 0.6 µA and 21.3 µW/cm2 respectively when ZnO nanorods concentration in PVDF increased from 0 to 10 wt% and decreased with further increase in ZnO nanorods concentration. The enhancement in output characteristics of ZnO:PVDF PENG with increasing ZnO concentration was attributed to β-phase crystallization of PVDF, which was confirmed by XRD and FTIR measurements. The deterioration in output characteristics beyond 10 wt% of ZnO nanorods concentration was explained considering the variation of dielectric constant and remnant polarization. The rectified output of the PENGs was effectively stored in various commercially available capacitors and used to power LEDs and stopwatch displays. The PENG with 10 wt% ZnO concentration was used to develop shoe insole pedometer which was interfaced with android based mobile application via Bluetooth. The shoe insole pedometer was successfully tested for 5000 steps at different walking frequencies ranging from 0.5 Hz to 2 Hz in the speed range of ∼ 1.4 km/h to 5.5 km/h. This study not only gives an insight into the mechanism of ZnO:PVDF based PENGs but also opens up their potential in vibration energy harvesting and shoe insole pedometer applications. • ZnO:PVDF based flexible piezoelectric nanogenerators (PENGs) were fabricated with variable ZnO nanofiller concentrations. • The variation of output performance of ZnO:PVDF based PENGs was studied with ZnO nanofiller concentrations. • The PENGs were able to power capacitors, LEDs, and LCDs. • A pedometer device has been fabricated using the ZnO:PVDF based flexible PENG sensor. [ABSTRACT FROM AUTHOR]

Abstract: Lanthanum hexaboride (LaB6) films have been deposited on a zirconium foil by pulsed laser deposition method. The field emission studies of the LaB6 deposited film have been performed in the planar diode configuration under ultra high vacuum conditions. The Fowler–Nordheim plots were found to be linear in accordance with the quantum mechanical tunneling phenomenon. A typical field emission current of 7.02μA was drawn at an applied electric field of 2V/μm. The field enhancement factor is calculated to be 8913cm−1, indicating that the field emission is from nanoscale protrusions present on the emitter surface. The atomic force microscope (AFM) investigation of the surface clearly shows the conical shaped nanoprotrusions of few hundred nanometers with asperities of 20–40nm on its top. The emission current–time plot recorded at the pre-set value of emission current of 5μA over a period of more than 3h exhibits an initial increase and subsequent stabilization of the current. The results reveal that the LaB6/Zr field emitter obtained by the pulsed laser deposition (PLD) is a promising cathode material for practical applications in field emission-based devices. [Copyright &y& Elsevier]

Abstract: A novel highly transparent intrinsic zinc oxide (ZnO) thin films (without adding any dopants and annealing) were grown by pulsed laser deposition (PLD) technique using Johnson Matthey “specpure”- grade ZnO pellets. The effects of substrate temperatures on zinc oxide thin film growth, optical transmission, absorption, reflection and photoluminescence properties were studied. As well as the feasibility of developing high quality transparent oxide thin films was also studied simultaneously. The optical transmission window of such obtained films, i.e., T% (max)⩾95% is broader than those of other transparent conducting oxides such as indium tin oxide (ITO) and absolute rivals that of the most transparent conducting oxides (TCOs). Also as a novelty merit, we want to emphasize as a interesting, significant and novel physical effect that the average optical transmittance of ZnO thin films rivals that of the most transmittive TCO films reported to date for this conductivity level (of the order of 103 Ω−1 cm−1). Also this is the first time that we have applied these PLD prepared ZnO thin films to iso and hetero semiconductor–insulator–semiconductor (SIS) type solar cells as transparent conducting oxide (TCO) coatings. From optical studies, we know that the films were act as highly anti-reflective coatings. From photoluminescence study, we confirmed the purity and high electrical conductivity of the deposited thin films of ZnO. The optical parameter values for the films were calculated, tabulated and graphically emphasized. Supplementary studies on surface, electrical, structural and internal morphological properties of zinc oxide thin film growth correlated with optical transmission, absorption, reflection and photoluminescence properties gives added advantages to this work. We hope that surely these data should be helpful either as a scientific or technical basis in the semiconductor processing and technology. [Copyright &y& Elsevier]

Abstract: In this present work, the effects of various substrate temperatures and various substrates on Zinc Oxide (ZnO) thin film growth and on surface morphological properties were studied. To the best of our knowledge this is the first time that laser molecular beam epitaxy (L-MBE), i.e., pulsed laser deposited (PLD) zinc oxide (ZnO) thin films on semiconductor wafers have been applied to Semiconductor–Insulator–Semiconductor (SIS) type multi-junction solar cells, as wide band-gap transparent conducting oxide (TCO) front electrode window layers, compatible with current semiconductor processing techniques. As well as our main aim, the feasibility of developing highly nano-tectured thin films was also studied simultaneously. The surface morphological and film growth characteristics of ZnO thin films laser deposited on to various substrates like glass, Silicon (Si), Gallium Arsenide (GaAs) and Indium Phosphide (InP) at various substrate temperatures like room temperature, 200°C and 300°C using ZnO pallets as targets are very novel, intelligent and significant from reported so for. The deposition process was optimized. The micro- and nano-scale photo-graphs of Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) showed the improvements of crystalline and surface nature of ZnO thin films with respect to various substrate temperatures and substrates. Better surface architecture was observed for thin films deposited at 300°C than RT, 200°C and on InP than Si and GaAs. Increasing the substrate temperature leads the films to fine nano-structure world. The results were discussed in detail. Thus we have developed a novel nano-architecture to obtain high quality ZnO nano-crystalline semiconductor thin films of different nano-scale grain sizes on glass and Si, GaAs and InP semiconductor single crystal wafers by using different substrate temperatures and substrates as controlling tools as value in practical nano-robotic (machining) device fabrication efforts. [Copyright &y& Elsevier]

Intrinsic epitaxial zinc oxide (epi-ZnO) thin films were grown by laser-molecular beam epitaxy (L-MBE), i.e., pulsed laser deposition (PLD) technique using Johnson Matthey “specpure”-grade ZnO pellets. The effects of substrate temperatures on ZnO thin film growth, electrical conductivity (σ), mobility (μ) and carrier concentration (n) were studied. As well as the feasibility of developing high quality conducting oxide thin films was also studied simultaneously. The highest conductivity was found for optimized epi-ZnO thin films is σ=0.06×103 ohm-1 cm-1 (n-type) (which is almost at the edge of semiconductivity range), carrier density n=0.316×1019 cm-3 and mobility μ=98 cm2/V s. The electrical studies further confirmed the semiconductor characteristics of epi-n-ZnO thin films. The relationship between the optical and electrical properties were also graphically enumerated. The electrical parameter values for the films were calculated, graphically enumerated and tabulated. As a novelty point of view, we have concluded that without doping and annealing, we have obtained optimum electrical conductivity with high optical transparency (⩾95%) for as deposited ZnO thin films using PLD. Also, this is the first time that we have applied PLD made ZnO thin films to iso-, hetero-semiconductor–insulator–semiconductor (SIS) type solar cells as transparent conducting oxide (TCO) window layer. We hope that surely these data be helpful either as a scientific or technical basis in the semiconductor processing. [Copyright &y& Elsevier]

High quality epitaxial indium zinc oxide (heavily indium oxide doped) (epi-n-IZO) thin films were optimized by laser-molecular beam epitaxy (L-MBE) i.e., pulsed laser deposition (PLD) technique for fabricating novel iso- and hetero-semiconductor–insulator–semiconductor (SIS) type solar cells using Johnson Matthey “specpure”- grade 90% In2O3 mixed 10% ZnO (as commercial indium tin oxide (ITO) composition) pellets. The effects of substrate temperatures, substrates and heavy indium oxide incorporation on IZO thin film growth, opto-electronic properties with 〈1 0 0〉 silicon (Si), gallium arsenide (GaAs) and indium phosphide (InP) wafers were studied. As well as the feasibility of developing some novel models of iso- and hetero-SIS type solar cells using epi-IZO thin films as transparent conducting oxides (TCOs) and 〈1 0 0〉 oriented Si, GaAs and InP wafers as base substrates was also studied simultaneously. The optimized films were highly oriented, uniform, single crystalline approachment, nano-crystalline, anti-reflective (AR) and epitaxially lattice matched with 〈1 0 0〉 Si, GaAs and InP wafers without any buffer layers. The optical transmission T (max) ⩾ 95% is broader and absolute rivals that of other TCOs such as ITO. The highest conductivity observed is σ=0.47×103 Ω-1 cm-1 (n-type), carrier density n=0.168×1020 cm-3 and mobility μ=123 cm2/V s. From opto-electronic characterizations, the solar cell characteristics and feasibilities of fabricating respective epi-n-TCO/〈1 0 0〉 wafer SIS type solar cells were confirmed. Also, the essential parameters of these cells were calculated and tabulated. We hope that these data be helpful either as a scientific or technical basis in semiconductor processing. [Copyright &y& Elsevier]

We have optimised and deposited epitaxial indium zinc oxide (epi-IZO) (In2Zn2O5) thin films on 〈1 0 0〉 oriented Si, GaAs and InP by laser-molecular beam epitaxy (L-MBE) technique, i.e., pulsed laser deposition (PLD). Optimised growth conditions have been obtained for the deposition of high quality epi-IZO thin films. To our knowledge, this is the first time that the PLD deposited indium zinc oxide thin films on semiconductor wafers have been applied to semiconductor–insulator–semiconductor (SIS) iso- and hetero-type junction solar cell structures as wide band gap transparent conducting front electrode-window layers. We have carried out X-ray diffraction (XRD) and energy dispersive chemical analysis (EDAX) to determine the Structural and compositional properties of as-grown thin films. The crystalline quality of the obtained thin films is similar to that of the bulk single crystals. Increasing the deposition temperature leads the thin films to fine nano-structure nature. In the present work, the effects of various substrate temperatures, substrates and heavy indium oxide doping on indium zinc oxide thin film growth, structural and compositional properties were analysed. As well as our main aim, the feasibility of developing high quality transparent conducting oxide (TCO) thin films for opto-electronic devices was also studied simultaneously. Our novel achievement in this work is without any buffer layers, we have obtained good epitaxial lattice matching between the highly oriented IZO functional layers and the substrate materials suitable for III–V based high-speed opto-electronic and micro-electronic devices. [Copyright &y& Elsevier]

Highly textured zinc oxide (ZnO) thin films have been optimized and deposited by pulsed laser deposition (PLD), i.e., laser-molecular beam epitaxy technique on 〈100〉 Si, GaAs and InP wafers compatible with current semiconductor processing techniques. To our knowledge this is the first time that the PLD deposited zinc oxide thin films on semiconductor wafers have been applied to semiconductor–insulator–semiconductor type multi junction (homo and hetero) solar cell structures as wide band gap transparent conducting oxide (TCO) front electrode-emitter layers. In this present work, the effects of various substrate temperatures and substrates on ZnO thin film growth, structural and compositional properties were analyzed and the feasibility of developing high-quality TCO thin films for opto-electronic devices was also studied simultaneously. Increasing the deposition temperature leads the thin films to fine nano-structures. Our achievement in this work is elimination of any buffer layer like GaN and we have obtained good epitaxial lattice matching between the ZnO functional layers and the 〈100〉 substrates suitable for III–V-based high-speed opto- and micro-electronic devices. [Copyright &y& Elsevier]

Titanium dioxide (TiO2)-based gate insulators for MOSFETs are of current interest in VLSI technology due to the high permittivity (k) of TiO2. In this paper, we present a study of metal–TiO2–SiO2–Si (MTOS) capacitors with equivalent dielectric thickness (EDT) in the range of 36–130 A˚. Pulsed laser deposition (PLD) of TiO2 to realize this stacked dielectric is being reported for the first time. Interestingly, it has been observed that even though an additional TiO2 layer has been deposited, the capacitance of the MTOS structure actually increases or remains almost the same compared to the MOS device having the same SiO2 layer thickness. Secondary ion mass spectrometric (SIMS) analysis reveals that there is substantial penetration of titanium into the underlying SiO2 layer resulting in a reduction of EDT. In addition, the leakage current of the MTOS capacitor reduced by almost two orders of magnitude and the breakdown field strength nearly doubled after incorporating the TiO2 layer. Thus, PLD is shown to be a viable technique for controlled deposition of TiO2 to achieve lower EDT with smaller leakage current, the two most desirable parameters in present-day MOS devices. [Copyright &y& Elsevier]