Low Leakage Current Density Research Articles

Tunable optical and electrical properties of thermal and plasma-enhanced atomic layer deposited Si-rich SixTi1−xO2 thin films

Ternary dielectrics with varying composition formed by alloying two binary oxides can enable tunable optical and electrical properties for advanced technological applications. Atomic layer deposition (ALD) gives precise control over ternary dielectric composition through the ability to finely tune the precursor pulsing ratio. This work presents ALD development of Si-rich SixTi1−xO2 dielectrics with varying composition (x), along with spectroscopic and electrical characterization of their properties. Stoichiometry of the SixTi1−xO2 films was determined using X-ray photoelectron spectroscopy. Their composition-dependent refractive index, energy bandgap, and reflectance show promise for diverse optical applications ranging from anti-reflective coatings in photovoltaics to optical waveguides. This work also reports a first comparative study of SixTi1−xO2 films prepared by thermal (T-) and plasma-enhanced (PE-) ALD with varying Si composition and deposition temperatures. Deposition rates of 0.67–0.92 Å/cycle were obtained for SixTi1−xO2 films with x = 0.5–0.91 deposited using PE-ALD at 250 °C, which were higher than that of T-ALD at 200 °C (0.42–0.05 Å/cycle). PE-ALD also exhibited a high deposition rate of 0.81 Å/cycle for SixTi1−xO2 film with x = 0.91 at a low growth temperature of 150 °C. The PE-ALD Si-rich silica–titania films show substantially lower (100×) leakage current densities than the thermally deposited films, along with higher breakdown fields for decreasing deposition temperature. A dielectric constant as low as ∼5 was achieved for PE-ALD SixTi1−xO2 films with high Si (x = 0.91) content.

Enhancement of electrical properties of solution-processed oxide thin film transistors using ZrO2 gate dielectrics deposited by an oxygen-doped solution

Solution deposition of high-quality dielectric films is one of the big challenges in achieving excellent electrical performance of bi-layer solution-processed metal oxide (MO) thin film transistors (TFTs). Using an oxygen-doped precursor solution (ODS), we successfully deposited high-quality zirconium oxide (ZrO2) dielectric films by a solution process. The ODS-ZrO2 films show low leakage current density (10−7 A cm−2 at 2 MV cm−1), high breakdown electric field (7.0 MV cm−1) and high permittivity (19.5). Consequently, solution-processed indium oxide (In2O3) TFTs with ODS-ZrO2 film as the gate dielectric show excellent electrical performance, for example high carrier mobility up to 62.02 cm2 V s−1, a large on/off drain current ratio of 3.0 × 106, a small subthreshold swing of 0.14 V and excellent bias stress stability. Our work demonstrates the critical role of the dielectric film in the electrical performance of MO-TFTs. More importantly, we reveal that high dielectric constant (κ) dielectric film deposited with ODS should be an effective way to significantly increase the electrical properties of MO-TFTs for future low-cost, high-performance applications.

Ultraviolet Light-Densified Oxide-Organic Self-Assembled Dielectrics: Processing Thin-Film Transistors at Room Temperature.

Low-temperature, solution-processable, high-capacitance, and low-leakage gate dielectrics are of great interest for unconventional electronics. Here, we report a near room temperature ultraviolet densification (UVD) methodology for realizing high-performance organic-inorganic zirconia self-assembled nanodielectrics (UVD-ZrSANDs). These UVD-ZrSAND multilayers are grown from solution in ambient, densified by UV radiation, and characterized by X-ray reflectivity, atomic force microscopy, X-ray photoelectron spectroscopy, and capacitance measurements. The resulting UVD-ZrSAND films exhibit large capacitances of >700 nF/cm2 and low leakage current densities of <10-7 A/cm2, which rival or exceed those synthesized by traditional thermal methods. Both the p-type organic semiconductor pentacene and the n-type metal oxide semiconductor In2O3 were used to investigate UVD-ZrSANDs as the gate dielectric in thin-film transistors, affording mobilities of 0.58 and 26.21 cm2/(V s), respectively, at a low gate voltage of 2 V. These results represent a significant advance in fabricating ultra-thin high-performance dielectrics near room temperature and should facilitate their integration into diverse electronic technologies.

Ferroelectric and nano-mechanical properties of the chemical solution deposited lead-free BCZT films

Lead-free ferroelectric BCZT ((Ba0.85Ca0.15)(Ti0.9Zr0.1)O3) films with thickness ~ 750 nm were deposited on Si/SiO2/TiO2/Pt (100) substrates using polyvinyl pyrrolidone modified chemical solution. BCZT films crystallized at 800 °C showed better electrical and mechanical properties as compared to the films crystallized at 700 °C. The BCZT films crystallized at 800 °C exhibited maximum polarization of 58 µC/cm2 and energy storage density of 27.53 J/cm3. Furthermore, these films displayed extremely low dielectric loss and leakage current densities. The dielectric loss varied from 0.005 to 0.026 in measured frequency range: 3 kHz to 500 kHz. Hardness and elastic modulus values calculated from nanoindentaion measurements of the 700 °C annealed film were 5.2 ± 0.3 GPa and 87.3 ± 2.6 GPa respectively. The same for the 800 °C annealed film were 3.9 ± 1.02 GPa and 227 ± 28 GPa respectively. The higher values of elastic modulus of the 800 °C annealed film could be correlated to the microstructure of the film.

An Energy and Power Dense Aqueous Zinc-Ion Hybrid Supercapacitor with Low Leakage Current and Long Cycle Life

Imparting high energy density to already power dense capacitor leads to hybrid supercapacitor (SC), which is most sought after in automobile, heavy-duty electronics application, and internet of things. The hybrid SCs with lithium or sodium ion chemistry demand organic electrolytes for their operation, which is environmental unfriendly and poses fire-hazard. As an alternative, here we report a low cost and highly safe energetic hybrid SC based on zinc-ion chemistry operated in 3 M ZnSO4 with high surface area (1018 ± 4 m2 g−1) hierarchical porous carbon cathode material derived from the Tamarindusindica seeds (ACTS-800), a bio-source. The hybrid SC demonstrates a maximum energy density of 127 (± 3) Wh kg−1 (254 μWh cm−2) at 0.1 A g−1 and power density of 7920 (± 24) W kg−1 (15.84 mW cm−2) at 10 A g−1. Besides having excellent power/energy density values, ∼ 100% capacity retention over 5000 galvanostatic charge/discharge cycles was observed. The most interesting feature of this SC is its low open-circuit voltage decay (34% in 60 h) and low leakage current density (11 mA g−1), which allows it to hold charge for longer duration qualifying it as one of the best aqueous SC known in the literature.

Enhanced electrical properties by optimizing sintering temperature and dwell time in BiFe0.96Zn0.02Ti0.02O3 ceramics

In this paper, effects of sintering temperature (T s) and dwell time (t d) on crystalline structure, microstructure and electrical properties (dielectric and ferroelectric) of BiFe0.96 Zn0.02Ti0.02O3 (BFZTO) ceramics synthesized by sol-gel method were investigated. The crystalline structure of BFZTO ceramics remained unchanged with different sintering conditions. The microstructure of BFZTO ceramics have an evident modification by changing sintering temperature and dwell time. With increasing T s or t d, grains of samples become larger. Because of the differences of sintering pross, The large grains and low porosity led to the alignment of the dipole, the low coercive field (E c of ca. 12 kv/cm), low leakage current density (10−1 μA/cm) and good remnant polarization (P r of ca. 1.2 μC/cm2) were achieved in BFZTO ceramics at T s = 800 °C, t d = 1 h. While the excessive T s or t d resulted in lower number of defect complexes, which had significant influence on ferroelectric properties. The work reported herein demonstrated that the porosity, grain size and the presence of defect complexes have a big part in determining ferroelectric properties of BFZTO ceramics.

Nanocluster-Based Ultralow-Temperature Driven Oxide Gate Dielectrics for High-Performance Organic Electronic Devices.

The development of novel dielectric materials with reliable dielectric properties and low-temperature processibility is crucial to manufacturing flexible and high-performance organic thin-film transistors (OTFTs) for next-generation roll-to-roll organic electronics. Here, we investigate the solution-based fabrication of high-k aluminum oxide (Al2O3) thin films for high-performance OTFTs. Nanocluster-based Al2O3 films fabricated by highly energetic photochemical activation, which allows low-temperature processing, are compared to the conventional nitrate-based Al2O3 films. A wide array of spectroscopic and surface analyses show that ultralow-temperature photochemical activation (<60 °C) induces the decomposition of chemical impurities and causes the densification of the metal-oxide film, resulting in a highly dense high-k Al2O3 dielectric layer from Al-13 nanocluster-based solutions. The fabricated nanocluster-based Al2O3 films exhibit a low leakage current density (<10−7 A/cm2) at 2 MV/cm and high dielectric breakdown strength (>6 MV/cm). Using this dielectric layer, precisely aligned microrod-shaped 2,7-dioctyl[1]benzothieno [3,2-b][1] benzothiophene (C8-BTBT) single-crystal OTFTs were fabricated via solvent vapor annealing and photochemical patterning of the sacrificial layer.

(Invited) Germanium-Tin Based Nano-Electronic and Photonic Devices

1. Introduction Germanium-Tin (Ge1-x Sn x ) alloy has many attractive properties that make it promising for many applications in nano-electronic and photonic devices and systems. GeSn has both higher hole and electron mobilities than Ge and Si to possibly enable scaling of the supply voltage for future high performance field-effect transistors (FETs). In addition, the tunable bandgap of GeSn by changing Sn compositions helps to extend the photo detection range beyond what can be achieved by Ge, covering wavelength larger than 1.55 µm.In this paper, we discuss the research and development of utilizing GeSn for various applications in nano-electronic and photonic devices. This includes multi-gate GeSn p-channel FETs (pFETs) on GeSn-on-insulator (GeSnOI) substrates, realization of ultra-low contact resistivity by incorporation Sn into Ge for the metal/GeSn S/D contact, and GeSn photodetectors for applications at 2 µm wavelength range. 2. GeSn pFinFETs with Sub-10 nm Fin Width on GeSnOI Substrates Large-area GeSnOI substrates were fabricated using direct wafer bonding (DWB) and layer transfer techniques at a 200 mm wafer scale [1]. This GeSnOI substrate, together with the multi-gate architecture, enabled the realization of high performance Ge1-x Sn x p-FETs with ultra-scaled channel length down to 50 nm [2]. An optimized try etch process was developed to fabricate GeSn FinFETs with fin width less than 10 nm. Excellent electrical characteristics were achieved with subthreshold swing of 63 mV/decade, intrinsic transconductance of 900 µS/µm at VDS of -0.5 V, and high-field effective mobility of 275 cm2/V·s. 3. Metal/ GeSn p-type Contact with Ultra-low Contact Resistivity. GeSn has a smaller hole Schottky barrier and a hole effective mass (mh ) as compared to Ge. These advantages make GeSn attractive for low-resistance p-type contacts. In-situ Ga doping was introduced during the epitaxial growth of GeSn using molecular-beam epitaxy (MBE) and more than 50% reduction of specific contact resistivity ρc has been observed by incorporation of 5% Sn into Ge [3]. Further optimization of GeSn doping process by surface segregation or cold implantation reduces ρc of Ti/p+-GeSn to sub-10-9 Ω-cm2 regime [4]. The ultra-low ρc of Ti/p+-GeSn is retained after anneal at 420 oC for 1 hour, showing adequate thermal stability for BEOL process in current CMOS technology [5]. 4. GeSn Photo-detectors for Applications at 2 µm Wavelength Range High-speed photo detection was demonstrated beyond traditional telecommunication bands and reaching at 2 μm band, realized by GeSn/Ge multiple-quantum-well (MQW) photodiode on Si substrate [6]. GeSn/Ge MQW structure was employed to increase the critical thickness (hc ) of epitaxial GeSn on Ge virtual substrate. A decent responsivity of 15 mA/W was obtained at 2 μm. A low leakage current density of 44 mA/cm2 was achieved at reverse bias of 1 V, which is among the lowest reported values for all GeSn photodiodes. A 3-dB bandwidth (f 3-dB) larger than 10 GHz was experimentally demonstrated directly at 2 μm. Acknowledgment We would like to acknowledge the funding support from Singapore Ministry of Education Tier 2 grants (R-MOE2018-T2-1-137 and MOE2018-T2-2-154).[1] D. Lei et al., Appl. Phys. Lett., 109, 022106, 2016.[2] D. Lei et al., VLSI Symposia, 2018, 197-198.[3] Y. Wu et al., J. Appl. Phys., 122, 224503, 2017.[4] Y. Wu et al., VLSI Symposia, 2018, 77-78.[5] Y. Wu et al., IEEE Electron Device Lett., 40, 1575-1578, 2019.[6] S. Xu et al., IEDM, 2018, 544-547.

A Low-Temperature Solution-Process High-k Dielectric for High-Performance Flexible Organic Field-Effect Transistors

Applying high-k dielectrics can effectively reduce the operating voltage of OFETs to a few volts, thus significantly miniaturizing the dynamic power consumption of OFETs. Aluminum oxide is known as a promising dielectric material for its high permittivity (k=6–9). In this work, a simple, low-cost, low-temperature (only 85 °C) solution process is used to prepare amorphous AlOx dielectric thin films for high-performance flexible OFET applications. The AlOx thin film was spin-coated and then solidified using deep ultraviolet irradiation without high-temperature annealing. The as-deposited AlOx thin film has a root mean square surface roughness of 0.47 nm and maintains a very low leakage current density of 8×10−9 A/cm2 at 3.5 MV/cm and high dielectric constant of about 8.3 (at 1 kHz). The complete OFET based on this dielectric can operate at a 3 V gate bias with saturation mobility of 1.8 cm2/Vs, and steep sub-threshold swing of 110 mV/dec. Our work demonstrated a low-temperature solution process to fabricate a high-k metal oxide dielectric for low-power OFET applications.

Improved electrical properties of sputtering Pb1.10(Zr0.52,Ti0.48)O3/Pb1.25(Zr0.52,Ti0.48)O3 multilayer thin films

Multilayer PZT thin films composed of Pb1.10(Zr0.52,Ti0.48)O3 and Pb1.25(Zr0.52,Ti0.48)O3 films were deposited on Pt(111)/Ti/SiO2/Si(100) substrate coated by Pb1.10(Zr0.52,Ti0.48)O3 buffer layer using RF magnetron sputtering. The effect of variation of layer numbers of Pb1.10(Zr0.52,Ti0.48)O3 and Pb1.25(Zr0.52,Ti0.48)O3 thin films in multilayer PZT films was investigated. X-ray diffraction (XRD) analysis indicates all PZT films possess pure perovskite phase and (111) preferred orientation. For multilayer thin films, dense perovskite microstructures without obvious defects were observed using scanning electron microscope (SEM). Optimal dielectric properties with a er of 1092 and a tanδ of 0.04 at 1 kHz were obtained in the PZT film with the maximum layer numbers (8-layer film, namely L-8). Well-saturated P–E was observed in L-8 film by a standard ferroelectric test system (Pr = 26.1 µC/cm2, Ec = 60.1 kV/cm). Moreover, a Lower leakage current density (J = 5.49 × 10−6 A/cm2 at 117 kV) was achieved in sample L-8.

Charge trap layer enabled positive tunable Vfb in β -Ga2O3 gate stacks for enhancement mode transistors

β-Ga2O3 based enhancement mode transistor designs are critical for the realization of low loss, high efficiency next generation power devices with rudimentary driving circuits. A large positive flatband voltage (Vfb) of 10.6 V in β-Ga2O3 metal-oxide-semiconductor capacitors, with the ability to fine-tune it between 3.5 V and 10.6 V, using a polycrystalline AlN charge trap layer has been demonstrated. This can enable enhancement mode operation over a wide doping range. An excellent Vfb retention of ∼97% for 104 s at 55 °C was exhibited by the gate stacks after charge trapping, hence reducing the requirement of frequent charge injection cycles. In addition, low gate leakage current density (Jg) for high negative gate voltages (Vg ∼−60 V) indicates the potential of this gate stack to enable superior breakdown characteristics in enhancement mode transistors.

Solid cross linked-poly(ethylene oxide) electrolyte gate dielectrics for organic thin-film transistors

Solid polymer electrolyte gate dielectric based on cross-linked poly(ethylene oxide) (CPEO) was developed and employed for organic thin-film transistors (OTFTs). Mechanical stability, high areal capacitance, and amorphous morphology of CPEO were achieved via the use of polyhedral oligomeric silsesquioxane (POSS) as cross-linker, dissolved ion [EMIM][TFSI] as electrolyte, and PEO with low molecular weight as polymer matrix, respectively. The resulting solid polymer electrolyte showed excellent insulating properties with low leakage current density (1.8×10−7Acm−2 at 1V) and high capacitance per area (∼ 1μFcm−2 at 100Hz). Furthermore, dielectric properties of the developed polymer electrolytes including ionic conductivity as well as segmental relaxation time were investigated. The polyelectrolyte dielectric was employed for bottom-gate/top-contact organic thin-film transistors and the resulting devices showed decent electrical performance with a carrier mobility of 0.12 (±0.03)cm2V−1s−1 and a current on/off ratio of 103 at low operating voltage of 5V.

Growth and electrical properties of high‐Curie point rhombohedral Mn‐Pb(In1/2Nb1/2)O3‐Pb(Mg1/3Nb2/3)O3‐PbTiO3 thin films

AbstractHigh‐quality ternary relaxor ferroelectric (100)‐oriented Mn‐doped 0.36Pb(In1/2Nb1/2)O3‐0.36Pb(Mg1/3Nb2/3)O3‐0.28PbTiO3 (Mn‐PIMNT) thin films were grown on SrRuO3‐buffered SrTiO3 single‐crystal substrate in a wide deposition temperature range of 550‐620°C using the pulsed laser deposition method. The phase structure, ferroelectric, dielectric, piezoelectric properties, and nanoscale domain evolution were studied. Under the deposition temperature of 620°C, the ferroelectric hysteresis loops and current‐voltage curves showed that the film owned significantly enhanced remnant ferroelectric polarization of 34.5 μC/cm2 and low leakage current density of 2.7 × 10−10 A/cm2. Moreover fingerprint‐type nanosized domain patterns with polydomain structures and well‐defined macroscopic piezoelectric properties with a high normalized strain constant of 40 pm/V was obtained. Under in situ DC electric field, the domain evolution was investigated and 180° domain reversal was observed through piezoelectric force microscope. These global electrical properties make the current Mn‐PIMNT thin films very promising in piezoelectric MEMS applications.

Deposition-temperature dependence of structure, ferroelectric property and conduction mechanism of BCZT epitaxial films

Ba0·85Ca0·15Zr0·1Ti0·9O3 (BCZT) epitaxial films were successfully deposited on (001) Nb-doped SrTiO3 substrate, and the effects of deposition temperatures on the structure, ferroelectric property, and conduction mechanism were studied. The results of XRD and AFM verified the well epitaxial structure with smooth surfaces of the deposited BCZT epitaxial films. BCZT epitaxial films deposited at 650 °C exhibited the best ferroelectric property (2Pr = 22.91 μC/cm2, 2EC = 1702.11 kV/cm) and relatively low leakage current density (7.91 × 103 A/cm2). The conduction mechanism of BCZT films corresponds to the space-charge-limited current (SCLC) mechanism and the Fowler-Nordheim (F–N) tunneling mechanism in the low and high electric field range, respectively.

NrGO Floating Gate/SiOXNY Tunneling Layer Stack for Nonvolatile Flash Memory Applications

This paper presents an ultra–thin silicon oxynitride (SiOXNY, 4 nm) tunneling layer, nitrogen functionalized reduced graphene oxide (NrGO, 3–5 layer) floating gate (FG) and poly (methyl methacrylate) (PMMA, 60 nm) blocking layers based Al/PMMA/NrGO/SiOXNY/p–Si/Au, non–volatile flash memory (NVFM) structures. The ultra–thin SiOXNYhelps in improving the interface with Si, resulting in lower gate leakage current density and considerable enhanced retention characteristics. The nitrogen engineered GO followed by reduction to NrGO under UV illumination attributes to the modification of the physiochemical properties, hence beneficial for non-volatile memory applications. The uniform, stress free and low temperature processing advocates the potential of PMMA as blocking layer for improved memory characteristics. The electrical characterizations on the fabricated Al/PMMA/NrGO/SiOXNY/p–Si/Au gate stack demonstrates a memory window ( ${\delta }\text{W}$ ) of ~1.25 V @ ± 3 V and ~2.6 V @ ± 5 V, low gate leakage current density (J) ~10 nA/cm2@ −1 V, retention $\sim 3 \times 10^{11}$ sec (> 10 years with extrapolation) and endurance of more than 100 cycles.

Surface polished of bulk methylammonium lead tribromide single crystal

Organic-inorganic halide perovskite materials have been demonstrated with wide applications in optoelectronics and ionization radiation detection. For bulk as-grown crystals, the existence of surface cracks and defects can significantly increase charges recombination and reduce the performance of the device. Herein, we polished the crystal surfaces with both mechanical and chemical mechanical methods at room temperature. After been chemical-mechanical polished, the crystal surface with root mean square roughness about 0.5 nm was obtained. Optical transmission and photoluminescence spectra indicate that chemical mechanical polishing technology can effectively reduce the density of crystal surface defects. The achieved low leakage current density on the surface and bulk crystal is 0.05 nA mm−2 and 0.07 nA mm−2, respectively. Furthermore, the current-voltage curve under visible photons and X-ray photons reveals that surface polishing treatment can suppress the charges recombination and increase the charges transportation.

Toward ultraviolet solution processed ZrOx/IZO transistors with top-gate and dual-gate operation: Selection of solvents, precursors, stabilizers, and additive elements

Low-temperature processed oxide thin-film transistors (TFTs) have been developed by the process of solution-processed metal oxide films using deep ultraviolet (UV) irradiation, although they still suffer from relatively poor electrical performance and severe electrical and chemical instability. This UV coating solution essentially involves chemical damage from acidic or basic precursor ligands; therefore, the top-gate and dual-gate TFTs suffer structurally inherent chemical damage, which limits the freedom of process design. An engineering concept solution using the four functional components of solvent, precursor, stabilizer, and additive was suggested for UV solution coating of high-k zirconium oxide (ZrOx). Here the proposed solvent, stabilizer, precursor, and additive include polar-aprotic N,N-methylformamide, zirconium acetylacetonate, ethanolamine, and oleic acid for polar-aprotic solution, effective photolysis, complete precursor dissolution, and high densification, respectively. The ultrathin ZrOx (15 nm) revealed a low leakage current density of <10−11 mA/cm2 at 1 MV/cm, good breakdown voltage, and a constant capacitance of approximately 260 nF/cm2 at 1 MHz. Similar transfer characteristics of both the bottom and top gates, and a field-effect mobility of 24 cm2/V, without degradation of subthreshold swing and threshold voltage values in the dual-gate, were involved in the chemically durable process and the dense coating conditions of ZrOx, regardless of the IZO and ZrOx stacking sequence.

A 1.86-kV double-layered NiO/ β -Ga2O3 vertical p–n heterojunction diode

In this Letter, high-performance vertical NiO/β-Ga2O3 p–n heterojunction diodes without any electric field managements were reported. The devices show a low leakage current density and a high rectification ratio over 1010 (at ±3 V) even operated at temperature of 400 K, indicating their excellent thermal stability and operation capability at high temperature. Given a type-II band alignment of NiO/β-Ga2O3, carrier transport is dominated by the interface recombination at forward bias, while the defect-mediated variable range hopping conduction is identified upon strong reverse electric field. By using the double-layer design of NiO with a reduced hole concentration of 5.1 × 1017 cm−3, the diode demonstrates an improved breakdown voltage (Vb) of 1.86 kV and a specific on-resistance (Ron,sp) of 10.6 mΩ cm2, whose power figure of merit (Vb2/Ron,sp) has reached 0.33 GW/cm2. The high breakdown voltage and low leakage current are outperforming other reported Ga2O3 based p–n heterojunctions and Schottky barrier diodes without field plate and edge termination structures. TCAD simulation indicates that the improved Vb is mainly attributed to the suppression of electric field crowding due to the decreased hole concentration in NiO. Such bipolar heterojunction is expected to be an alternative to increase the breakdown characteristics of β-Ga2O3 power devices.

Low leakage current density and improved dielectric behavior of BiFexO3 nano-ceramics

BiFexO3 (x = 0.8, 1.0, 1.2) sample were prepared using citrate precursor method sintered at 600 °C. The X-ray diffraction (XRD) patterns confirmed the rhombohedral structure of BiFexO3 samples. The average crystallite size was found to about 50 nm. Higher value of tensile strain was observed for the samples with the excess and deficiency of iron contents in Williamson- Hall plots. Surface morphology of these isostructural materials were studied using Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). Average particle size estimated from TEM for the sample BiFe1.2O3 is found to be about 55 nm. FTIR studies reported two strong peaks at 444 cm−1 and 544 cm−1 supporting the formation of pervoskite structure. The value of leakage current density of BiFe1.2O3 is reduced by two orders of magnitude (∼1.34 × 10−10A/cm2) which may be ascribed to the suppression of oxygen and Bi vacancies. Dielectric measurements of these samples were greatly affected by the excess and deficiency of Fe content in BFO. BiFe1.2O3 samples were found to have higher value of dielectric constant ∼315 at 1 kHz.

Synthesis and characterization of rare-earth ion-based double perovskite: Gd2CoMnO6

The double perovskite gadolinium cobalt manganate (Gd2CoMnO6) ceramic material was prepared via mixed oxide route. The preliminary X-ray structural study reveals that the material was found in monoclinic structure. We have found the small voids with almost uniform distribution of grains from the microstructural analysis. Analysis of the dielectric and electrical data, collected in a wide range of frequency range (1 kHz–1 MHz) and temperature (25–500 °C), has provided many interesting results. We have discussed frequency dependence dielectric parameter by Maxwell–Wagner model. We found that the room temperature dielectric constant at 1 kHz frequency is 300 and tangent loss is nearly equal to 2. A dielectric anomaly (ferroelectric–paraelectric phase transition) was found in the temperature dependence of dielectric study. The study of diffuse phase transition exhibits the existence of relaxation process in the compound. In the Nyquist plots, both grain and grain boundary effects are observed which is characterized by (RQC) and (RQC)(RC) circuits. As the resistance decreases with increase of temperature, the material shows the semiconductor behavior. The existence of non-Debye type of relaxation mechanism in the material is confirmed by the depression angle. The frequency dependence of electric conductivity has been studied using the Jonscher’s power law, in which the frequency exponent n (< 1) signifies the translational motion with involvement of an intuitive hopping of charge carriers. The leakage current and conduction mechanism follow the space charge-limited conduction phenomenon. The low leakage current density may be suitable for high-temperature applications.