Built-in electric field (BIEF)-induced charge transfer in planar and bulk junctions has significantly improved electrochemical performance in current and advanced energy storage devices such as lithium, sodium, and aluminum batteries. In this study, fuel cells with different junctions based on semiconductor membranes were designed in thin-film planar, bulk planar, and bulk heterojunction (BHJ) configurations to investigate the BIEF effects on their electrochemical performance. These semiconductor membrane fuel cells were constructed with p-type LiCoO2 and n-type SnO2 sandwiched between Ni0.8Co0.15Al0.05LiO2 (NCAL) electrode semiconductors. At 600 degrees C, the fuel cells with bulk heterojunction (BHJ), bulk planar p-n junction, and thin-film planar p-n junction deliver remarkable peak power densities of 0.82, 0.61, and 0.28 W/cm2 in H2/air operation, respectively. The band structures were determined and the charge transport properties and device operation were investigated. Our results show that the semiconductor membrane-based devices are a good alternative to replace the conventional electrolyte membrane fuel cells for the next generation of fuel-to-electricity conversion technology.

From the viewpoint of high- (room-) temperature operation of donor-based single-electron transistors, we make a comparative study of nano-scale silicon-on-insulator transistors with phosphorus-doped channels for two dopant-concentration regimes: N D ≈ 1 × 10 18 and 2 × 10 20 cm −3 . We experimentally show that the high- N D devices can provide room-temperature single-electron tunneling operation owing to a large tunnel-barrier height, while operation temperature is limited to about 100 K for the low- N D devices. Numerical simulations of random donor-atom distributions indicate that donor clustering plays a dominant role in the formation of quantum dots, and suggests that clusters comprising of more-than-three donors are responsible for room-temperature operation.

As an extension of the continuous miniaturization trend for Si transistors, single-electron effects related to dopants in the nanoscale transistor channels have been recently considered for low-power and fundamental applications. Research on dopant-based single-electron tunneling (SET) functionality extends from single-donor quantum dots (QDs) to multiple-donor QDs. Different from using complex techniques for doping, we show that a simpler, uniform doping technique at high-concentration of nanoscale silicon-on-insulator (SOI) transistors can offer the statistical conditions for the formation of isolated multiple-donor clusters that allow SET functionality, even at room temperature.

LiCoO2 thin film cathodes have been well established in Li-ion rechargeable batteries, however, its useful capacity hardly exceeds 50% of the theoretical value. Irreversible structural changes will occur upon exchange of Li ions i.e. > 0.5 per unit formula limit, during intercalation/deintercalation reactions. Reportedly, lattice doping phenomenon has noticed an improvement in cyclability of LiCoO2. In this work, the influence of Zr doping on microstructural and electrochemical properties of RF magnetron sputtered LiCoO2 thin film cathodes have been presented. A series of LiZr(x)Co(1- x)O(2)( )thin films have been deposited on Au/Ti/SiO2/Si (100) substrates using a Zr-LiCoO2 mosaic target. All the films were deposited at optimized processing conditions. XRD and Raman spectroscopy measurements confirmed the hexagonal layered structure with R (3) over barm symmetry for Zr doped LiCoO2 film cathodes. The AFM reveals the estimated average grain size is around 50 nm. The cyclic voltammetry studies for these cathodes exhibit narrow potential peak separation of 24 mV and resulting highest diffusion coefficient ((D) over bar (Li)) of about 1.8 x 10(-11) cm(2)s(-1), respectively. These films exhibited a highest initial discharge capacity of 64.4 mu A h cm(-2) mu m(-1) with a capacity retention of 98.5% even after 25 cycles. In non-aqueous region, the cell exhibited an initial discharge capacity of about 65 mu A h cm(-2)mu m(-1) with good cycling stability even after 80 cycles, and is observed to be the more promising cathode candidate than the pristine LiCoO2 films.

Garnet Li7La3Zr2O12 nanoparticles with 1 mass% Al were prepared via a solid-state route at 750 °C within 3 h. A model cell sandwiched by Li and LiCoO2 exhibited initial discharge capacity of 64 μA h cm−2 μm−1, being 93% of LiCoO2 theoretical value.

We present a novel approach to the solid-state synthesis of garnet-type cubic Li7La3Zr2O12 (c-LLZO) nanostructured particles with 1.0 mass% Al at 750 C within 3 h. In contrast to conventional solid-state processes, a highly reactive precursor was prepared in two steps: (i) by homogenizing the stoichiometric mixture without Li, and (ii) subsequent addition of Li in the form of an ethanolic solution of lithium acetate. The actual composition determined by ICP analysis was Li6.61La3Zr2Al0.13O11.98. Sintering these nanoparticles at 1100 C for 3 h in air after cold isostatic pressing brought a dense ceramic pellet with a relative density of 90.5%. The corresponding ionic conductivity with Au electrodes was 1.6 10 4 S cm 1 at room temperature. To study its electrochemical behavior as an electrolyte, a model cell of Li//(1 M LiPF6 + c-LLZO)//LiCoO2 configuration was constructed. Cyclic voltammetry of the cell delivered one set of redox couple with narrow voltage separation (15 mV) with a Li diffusion coefficient at room temperature of about 2 10 11 cm s 1 at the interface between LiCoO2 and 1 M LiPF6 + c-LLZO. The cell received an average discharge capacity of 64.4, 60.3, 56.1, 51.9 and 46.9 mA h cm 2 mm 1 at discharge rates 0.5C, 1C, 2C, 4C and 6C, respectively. The cell exhibited complete oxidation and reduction reactions with an average initial discharge capacity of about 64 mA h cm 2 mm , which is 92.7% of LiCoO2 theoretical value. These observations indicate the applicability of the present c-LLZO as an electrolyte for a solid-state Li-ion battery.

LiTi y Co 1-y O2 (y = 0, 0.02, 0.05, 0.1) thin films were deposited on metalized Si substrates using RF magnetron sputtering technique. The films were deposited at a substrate temperature of 250 °C with subsequent annealing at 600 °C for 3 h in controlled oxygen environment. The films exhibited predominant (003), (101), and (104) orientations representing single-phase hexagonal structure with R \( \overline{3} \) m space group. Two well-defined Raman peaks observed at 489 and 598 cm−1 corresponding to E g and A1g modes confirm the hexagonal layered structure. The grain size and grain distribution were observed using atomic force microscopy. The cyclic voltammetry studies on Pt//LiTi y Co1-y O2 film cathodes in aqueous region exhibited perfect redox peaks at expected potentials. The Pt//LiTi0.02Co0.98O2 film cathode exhibited better discharge capacity of about 65 μA h cm−2 μm−1 with good cycling stability compared to pure Pt//LiCoO2. The electrochemical impedance analysis revealed a lower charge transfer resistance in Ti doped LiCoO2 film cathode, resulting better discharge capacity.

Thin films of pure and molybdenum (Mo)-doped tungsten trioxide (WO3) were deposited on indium tin oxide (ITO)-coated glass and Corning glass substrates by RF magnetron sputtering technique. The effect of Mo doping on the structural, morphological, optical and electrochromic properties of WO3 films was studied systematically. The energy dispersive X-ray analysis (EDAX) revealed that the films consist of molybdenum concentrations from 0 to 2 at.%. X-ray diffraction (XRD) studies indicated that with the increase of Mo concentration the structural phase transformation takes place from polycrystalline to amorphous phase. The crystallite size of the films decreased from 24 to 12 nm with increase of doping concentration of Mo in WO3. Scanning electron microscope (SEM) analysis revealed that Mo dopant led to significant changes in the surface morphology of the films. The electrochemical and electrochromic performance of the pure and Mo-doped WO3 were studied. The WO3 films formed with 1.3 at.% Mo dopant concentration exhibited high optical modulation of 44.3 % and coloration efficiency of 42.5 cm(2)/C.

Lithium transition metal oxides such as LiMO 2 (where M= Co, Ni, Mn etc.) are commonly used cathode material for micro-battery applications. Am ong these, LiCoO 2 is one of the most promising cathode materials because of its high energy density, high discharge capacity and good reversibility during th e oxidation and reduction process. In the present investigatio n, the influence of Ti doping on the structural and electrical properties of LiCoO 2 thin films were studied. Ti doped LiCoO 2 thin films were deposited by rf-sputtering at moderate substrate temperature of 523K with subsequent annealing at 923K. The structural analysis was carried out using X-ray diffraction (XRD) and atomic force microscopy (AFM). Electrical and dielectric propert ies of deposited films were studied at different temperatu res over a frequency range of 1Hz - 1MHz. The electrical conductivity of the films was observed to be increa sed with increasing temperature. The dielectric pro perties were analyzed in the framework of complex dielectric permittivity and complex electric modulus formali sms. The complex permittivity as a function of frequency and temperature was investigated. Keywords: Structural analysis, AC impedance analysis, rf spu ttered Ti doped, LiCoO 2 thin films.

Lithium iron phosphate (LiFePO 4 ) cathode material has been prepared by hydrothermal synthesis. The XRD spectrum exhibited different characteristic peaks along with (311) predominant orientation corresponding to orthorhombic crystal structure with Pnma space group. Electric and dielectric properties were studied over a frequency range of 1 Hz–1 MHz at different temperatures. The conductivity was found to be increased with increasing temperature following Arrhenius relation with an estimated activation energy of 0.44 eV. The dielectric properties were analyzed in the framework of complex dielectric permittivity and complex electric modulus formalisms. The complex permittivity as a function of frequency and temperature was investigated. Several important parameters, such as activation energy, ionic hopping frequency, carrier concentration, ionic mobility, and diffusion coefficient, etc., were determined. The electrochemical characteristics of LiFePO 4 are examined in aqueous region. It exhibited a good reversible cyclic voltammogram on sweeping the potential upward and downward with discharge capacity of 140 mAh/g.

Influence of Si substrate texturing on growth, microstuctural and electrochemical properties of lithium cobalt oxide (LiCoO2) cathode films was investigated. A batch of rf magnetron sputtered LiCoO2 films were prepared on both Au/Ti/SiO2/(polished) Si and AulTi/SiO2/(textured) Si substrates and the film properties were studied, systematically. As-grown films on polished Si substrates were exhibited partially ordered rock-salt structure with a very poor electrochemical performance. However, the as-grown films on textured Si substrates exhibited relatively predominant (0 0 3) orientation with R 3 m symmetry and exhibited an initial discharge capacity of 57.5 mu Ahcm(-2) mu m(-1) with an appreciable capacity fade rate of 0.07%, even after 50 cycles. Electrochemical performance of these films was in close comparison with the annealed (650 degrees C) LiCoO2 films of Au/Ti/SiO2/(polished) Si substrates. The experimental observations were thoroughly demonstrated and suggested that the as-grown LiCoO2 films on textured Si substrates can be useful for all types of 2D solid state Li-Lion microbattery applications. (C) 2013 Elsevier B.V. All rights reserved.

LiMn2O4 thin films are deposited on gold coated polyimide flexible substrates using RF magnetron sputtering technique maintained at a moderate substrate temperature of 300℃. The films exhibited characteristic peaks with predominant (111) orientation representing cubic spinel structure of Fd3m symmetry with an evaluated lattice parameter of 8.199 ?. The surface topography of films exhibited pyramidal shaped grains oriented vertical to the substrate surface with root mean square surface roughness of 90 nm. The Pt/LiMn2O4 electrochemical cell in aqueous region exhibited two step de-insertion and insertion kinetics of Li ion during oxidation and reduction reaction with an initial discharge capacity of 36 μAh?cm_2?μm_1.

Polycrystalline HT-LiCoO2 films were successfully synthesized by rf magnetron sputtering. The films were characterized by the studying their phase, structure, and morphology using ex-situ measurements of X-ray diffractometry (XRD), Raman Spectroscopy, Atomic force micrometry (AFM). Electrochemical performance evaluation indicated that the as grown LiCoO2 films The anodic electrochemical performances of the films have been evaluated by cyclic voltammetry (CV) at a scan rate of 0.5 mV/s and by galvanostatic cycling, with lithium metal as the counter and the reference electrode, and cycled in the range of 3.0 - 4.2 V at a current density of 50 mu A/cm(2). The films show a discharge capacity at the 20th cycle of 58 mu Ah cm(-2)mu m(-1) which exhibited excellent capacity retention with a small capacity fade.

Lithium transition metal oxides have received considerable attention in recent years as high voltage positive electrode materials in the fabrication of all solid state microbatteries. Among various lithium-based cathode materials, LiMn2O4 is one of the most promising cathode materials as it offers high energy density, high cell voltage, low cost, and low toxicity over the other electrode materials. Thin films of LiMn2O4 were prepared by radio frequency magnetron sputtering on gold-coated silicon substrates under various substrate temperatures ranging from 373 to 673 K in a partial pressure of 3 × 10−3 mbar with rf power 100 Watts. In the present investigation, the influence of substrate temperature on the growth and microstructural properties was studied. The films deposited at a substrate temperature less than 473 K was found to be X-ray amorphous. The initial crystallization has been observed at a substrate temperature of 523 K. The X-ray diffraction patterns of the films deposited in the substrate temperature range 523–673 K exhibited predominant (111) orientation representing cubic spinel structure with Fd3m symmetry. The grain size was found to be increased with the increase of substrate temperature as evidenced from SEM studies. However, additional impurity phases like Mn3O4 were observed for the films deposited at higher substrate temperatures (>673 K) because of re-evaporation of Li+ ions in the films. The electrochemical (EC) studies were carried for the films deposited at Ts = 673 K in aqueous media in the potential window of 0.0–1.2 V exhibited better electrochemical performance suggesting that the films are well suited as binder free thin film cathode material for commercially viable Li-ion secondary batteries.