Maximum Doping Level Research Articles

In-situ prepared co exsolution nano catalyst for efficient hydrogen generation via ammonia decomposition

Active and durable catalytic material for ammonia (NH3) decomposition reaction is attracting attentions for utilization of NH3 as an innovative hydrogen carrier. In this study, diverse single metal and alloy nano catalysts are prepared via in-situ exsolution method and their NH3 decomposition properties are evaluated. Transition metal cations (Ni, Co, Fe ions) are doped into the La0.43Ca0.37MxNyTi1-(x+y)O3-δ (LCMNT) perovskite oxide structure and exsolved on its surface as supported nano particles under reduction condition. The maximum doping level and chemical composition of exsolution catalysts are investigated to optimize their NH3 decomposition activity. The exsolution catalyst demonstrates improved NH3 decomposition characteristics compared to conventionally prepared infiltration catalysts, indicating higher conversion efficiency and H2 production rate. The exsolved nano catalysts also exhibit great thermochemical stability against catalyst agglomeration or surface nitriding. The results obtained in this study suggest the potential utilization of exsolution catalysts for on-site production of H2 through NH3 decomposition catalysis.

Cu2+/Dy3+ dual doped calcium based Ca1-xCuxFe12-xDyxO19 hexaferrites: Microstructural and magnetic properties for magnetic applications

The structural and magnetic behaviour of hexaferrite can be significantly altered by varying the sintering temperature and cationic subtitutions. Therefore, using the sol–gel route, we have synthesized M−type Ca1-xCuxFe12-xDyxO19 (x = 0.0, 0.05, 0.10, 0.15, 0.20) hexaferrite nanoparticles in the present research work. The samples' microstructure, phase, and magnetic characteristics are examined concerning different doping concentrations using SEM, XRD, and VSM. The analysis indicates a minor percentage of Fe2O3 phases in all samples. The refined lattice variables ‘a’ and ‘c’ are initially enhanced by increasing the level of doping upto x = 0.15 and then decreases. Similarly, the average crystallite size shows an increase continuously. The remanence and saturation magnetization rise first as the doping level increases, then show a minor change for the maximum doping level. Like this, as the doping content is raised, the coercivity and magneto-crystalline anisotropy field increased first and then showed a minor decrease. The sample with the best magnetic properties is Ca0.85Cu0.15Fe11.85Dy0.15O19 with Ms = 35.738 emu/g, mB(µB) = 6.732B, Mr = 20.430 emu/g, Hc = 3.15 kOe, and Mr/Ms = 0.572. All samples were excellent candidates for use in magnetic devices due to their high Mr/Ms values. The effect of doping on the magnetic features of M−type hexa-ferrites has made them useful in numerous applications, such as high-performance self-biased circulators, magnetic filters, and storage devices.

Fabrication of rare earth dysprosium doped Ca-Cu (1:1) based Ca0.5Cu0.5Fe12–xDyxO19 ferrites for structural and magnetic investigations

Hexaferrites' magnetic and structural properties are highly sensitive to changes in sintering temperature and cationic replacements. We fabricated Ca0.5Cu0.5Fe12–xDyxO19 hexaferrites using the sol-gel technique. We examined the phase, microstructure and magnetic aspects of the samples with respect to varying doping of rare earth dysprosium. The results show the expansion in the lattice upon incorporation of dysprosium against iron. Morphological studies confirm the uniform distribution of particles with slightly longitudinal nanoflakes in one direction. Magnetic investigations show an increase in magnetic saturation (Ms) with increasing dysprosium incorporation till optimum level is achieved for 15% doping concentration, with negligible change for maximum doping level. Furthermore, coercivity (Hc) and magnetic moment (mB) in terms of Bohr’s magneton (μB) also show an increasing trend with dysprosium substitution levels. The maximum saturation magnetization of 33.355 emu/g is achieved with magnetic remanence of 18.290 emu/g, along with optimum magnetic moment of 6.249 μB. In addition to the traditional magnetic parameters, magnetic anisotropy parameters were explored for the deep insights into magnetic parameters. These outcomes suggest that improved magnetic properties of Ca0.5Cu0.5Fe12–xDyxO19 ferrites make it good substitute for storage devices, magnetic filters, and other magnetic applications.

Improving Reliability of Fan -Out Wafer Level Package Through Doping of Lead-Free Solder Balls

Embedded wafer level ball grid array (eWLB) or FO-WLP (Fan-out wafer-level packaging) is investigated as a package for MMICs (Monolithic Microwave Integrated Circuit) for automotive radar applications in the 77GHz range. Doping of Bi and/or Sb was applied to improve the resistance of lead-free SAC balls against thermal cycling stress. We have shown that by increasing the doping level the lifetime can be increased and determined the maximum doping level before extrinsic failure modes dominate. It is well-known from the literature that doping of Bi and/or Sb improves the resistance of lead-free SAC balls against thermal cycling stress. It was shown that lifetime of FC-BGA package can be multiplied using Bi and/or Sb doping. The lifetime gain is achieved by reduced creepage of the hardened balls caused by the doping. This reduced creepage increases the risk of causing other failures than ball cracks in the eWLB package or the PCB during thermal cycling stress. We have tested robustness of 7x8,5 mm^2 eWLB packages against thermal cycling stress T = -40 to 125 °C using SAC-balls with different Bi-doping content from 0% to 2,5% Bi concentration. As could be expected the solder ball fatigue mode is delayed more and more increasing the Bi content. We found other failure modes than solder ball fatigue emerging at doping around 1%. The fatigue modes are shifted towards cupper lines on PCB or into the package. Cu line cracks can be overcome by switching the PCB layout from NSMD (non solder-mask defined) to SMD (solder-mask defined) solder pads. In general there is a lifetime penalty when switching from NSMD to SMD, but by avoiding the Cu line cracks this lifetime loss is overcompensated using SMD pads for optimum performance. As input for simulations we have characterized the doped solder material using specimens produced in glass columns. We have also tested the components on PCBs with different top layer laminate with different CTE and elastic modulus to assess the influence of the PCB properties on the lifetime. It is a trend in automotive radar systems to use stiffer laminates which are cheaper but have negative influence on component lifetime. Solder ball shear tests were also carried out to characterize the influence of ball doping on other board-level reliability beyond thermal cycling performance. As expected ball shear force is increased with increased doping level. At increased shear-force the shearing is still done through the solder ball and does not lead to different shear-mode. Finally drop-tests were done to check influence of doping on board-level reliability performance other than thermal-cycling performance.

Thermoelectric and Structural Properties of Sputtered AZO Thin Films with Varying Al Doping Ratios

Nanomaterials can be game-changers in the arena of sustainable energy production because they may enable highly efficient thermoelectric energy conversion and harvesting. For this purpose, doped thin film oxides have been proven to be promising systems for achieving high thermoelectric performances. In this work, the design, realization, and experimental investigation of the thermoelectric properties exhibited by a set of five Al:ZnO thin films with thicknesses of 300 nm and Al doping levels ranging from 2 to 8 at.% are described. Using a multi-technique approach, the main structural and morphological features of the grown thin films are addressed, as well as the electrical and thermoelectrical transport properties. The results show that the samples exhibited a Seebeck coefficient absolute value in the range of 22–33 μV/K, assuming their maximum doping level was 8 at.%, while the samples’ resistivity was decreased below 2 × 10−3 Ohm·cm with a doping level of 3 at.%. The findings shine light on the perspectives of the applications of the metal ZnO thin film technology for thermoelectrics.

In-Situ EC-AFM Study of Electrochemical P-Doping of Polymeric Nickel(II) Complexes with Schiff base Ligands

Conductive electrochemically active metallopolymers are outstanding materials for energy storage and conversion, electrocatalysis, electroanalysis, and other applications. The hybrid inorganic–organic nature of these materials ensures their rich chemistry and offers wide opportunities for fine-tuning their functional properties. The electrochemical modulation of the nanomechanical properties of metallopolymers is rarely investigated, and the correlations between the structure, stiffness, and capacitive properties of these materials have not yet been reported. We use electrochemical atomic force microscopy (EC-AFM) to perform in-situ quantitative nanomechanical measurements of two Schiff base metallopolymers, poly[NiSalphen] and its derivative that contains two methoxy substituents in the bridging phenylene diimine unit poly[NiSalphen(CH3O)2], during their polarization in the electrolyte solution to the undoped and fully doped states. We also get insight into the electrochemical p-doping of these polymers using electrochemical quartz crystal microgravimetry (EQCM) coupled with cyclic voltammetry (CV). Combined findings for the structurally similar polymers with different interchain interactions led us to propose a correlation between Young’s modulus of the material, its maximum doping level, and ion and solvent fluxes in the polymer films upon electrochemical oxidation.

Defect Healing in Graphene via Rapid Thermal Annealing with Polymeric "Nanobandage".

Overcoming throughput challenges in current graphene defect healing processes, such as conventional thermal annealing, is crucial for realizing post-silicon device fabrication. Herein, a new time- and energy-efficient method for defect healing in graphene is reported, utilizing polymer-assisted rapid thermal annealing (RTA). In this method, a nitrogen-rich, polymeric "nanobandage" is coated directly onto graphene and processed via RTA at 800 °C for 15 s. During this process, the polymer matrix is cleanly degraded, while nitrogen released from the nanobandage can diffuse into graphene, forming nitrogen-doped healed graphene. To study the influence of pre-existing defects on graphene healing, lattice defects are purposefully introduced via electron beam irradiation and investigated by Raman microscopy. X-ray photoelectron spectroscopy reveals successful healing of graphene, observing a maximum doping level of 3 atomic nitrogen % in nanobandage-treated samples from a baseline of 0-1 atomic % in non-nanobandage treated samples. Electrical transport measurements further indicate that the nanobandage treatment recovers the conductivity of scanning electron microscope-treated defective graphene at ≈85%. The reported polymer-assisted RTA defect healing method shows promise for healing other 2D materials with other dopants by simply changing the chemistry of the polymeric nanobandage.

Effect of Cu Doping on Structure and Physical Properties in the Antiferromagnetic Dirac Semimetal CaMnBi2.

The newly discovered AMnBi2 (A = Ca, Sr, Ba, Eu, and Yb) materials composed of two-dimensional Bi square nets provide an excellent platform to investigate the effect of magnetism on topological band structures. Effectively tuning the magnetic interaction in AMnBi2 is of great importance to advance this issue. Here, we describe an effective route to tune the magnetism in Dirac semimetal CaMnBi2 through Cu doping. Structural analysis on CaMn1-xCuxBi2 single crystals indicates that Cu atoms occupy the Mn sites randomly, with the maximum doping level of 25%. After Cu doping, the Bi square net in charge of the Dirac band is still retained, but the Bi-Bi bond distance is markedly shortened. The antiferromagnetic interaction of CaMnBi2 is strongly weakened in the Cu-doped crystals, with the transition temperature decreased from 260 to 85 K. On the contrary, the ferromagnetic component that originated from the canted AFM is enhanced, suggesting that the spin canting in this system is tunable. In addition, the magnetoresistance is decreased upon Cu doping, probably due to the disorder in structure. Our work suggests that the CaMn1-xCuxBi2 (0 ≤ x ≤ 0.25) system can offer a suitable playground to address the interplay between magnetism and the topological state.

Influence of post-annealing, defect chemistry and high pressure on the magnetocaloric effect of non-stoichiometric La0.8-xK0.2Mn1+xO3 compounds

In view of the need to limit harmful emissions of chlorofluorocarbons into the atmosphere and sharp increase in life support areas that require cooling, the search for new magnetocaloric materials is very urgent at the present time. In this work, we suggest the ways for improving the magnetocaloric properties of the promising La0.8-xK0.2Mn1+xO3 (0 ≤ x ≤ 0.2) perovskites and compare the functional properties of nanocrystalline samples of about 40 nm with polycrystalline samples of about 1 μm. The structure, morphology, magnetic properties and magnetocaloric effect of these compounds were studied as a function of manganese doping level. The main crystalline phase of all samples is a rhombohedral R3‾c perovskite structure. The maximum doping level of excess manganese for preserving single-phase structure of the nanocrystalline La0.8-xK0.2Mn1+xO3 compounds is x = 0.10. As x increases the Curie temperature TC is increased slightly. The best composition with the highest entropy change ΔSMmax = −3.629 J/(kg⋅K) under 3 T at TC = 332 K is the La0.8-xK0.2Mn1+xO3 with x = 0.05. On the other hand, the La0.8-xK0.2Mn1+xO3 polycrystalline manganite with x = 0.10 exhibits the highest ΔSMmax = −4.176 J/(kg⋅K) under 3 T at TC = 274 K. Additionally, the effect of hydrostatic pressure P up to 1.4 GPa has been investigated for the La0.7K0.2Mn1.1O3 polycrystalline sample that leads to increasing TC to 287 K and reducing ΔSMmax to −3.145 J/(kg⋅K) under 3 T. The obtained results demonstrate the ways for controlling magnetocaloric properties of the La0.8-xK0.2Mn1+xO3 compounds under internal and external conditions.

Enabling Ga2O3’s neutron detection capability with boron doping and conversion layer

There is a growing necessity to develop revolutionary neutron detectors for nuclear energy, nuclear physics, medical physics, astrophysics, biological imaging, nonproliferation, and national security. The often-used Helium-3 (He-3) neutron detector is becoming increasingly difficult to obtain due to He-3 shortages. As an emerging oxide semiconductor material, Ga2O3 exhibits excellent physical properties. These physical merits enable Ga2O3’s potential as a high-performance semiconductor neutron detector for extreme condition applications. Here, two approaches are explored, i.e., applying an exterior conversion layer of boron-10 (B-10) on Ga2O3 and directly doping B-10 into Ga2O3 to demonstrate Ga2O3’s capability for neutron detection. Using Monte Carlo simulation, we show the distinct difference in neutron detection efficiency of Ga2O3 when applying direct doping of B-10 into Ga2O3 vs applying a uniform B-10 conversion layer on top of Ga2O3. Our results exhibit that the theoretically predicted maximum doping level of B-10 in Ga2O3 does not lead to the same detection efficiency as that of a simple B-10 conversion layer when detecting 480 keV gammas. Except for the most thermalized neutrons at 0.01 eV, direct doping simulations are not able to achieve comparable results to that of the conversion layer method.

Tunable superconductivity of epitaxial TiN films through oxygen doping

Titanium nitride (TiN) film is a remarkable material for a variety of applications ranging from superhard coating to superconducting quantum devices, which can be easily oxidized when it works in the atmosphere. However, the study of its oxidation effect on the crystal and electronic structures of epitaxial TiN films is rare as yet. Here, we coherently synthesize TiN epitaxial films on MgO single crystal substrates via reactive magnetron sputtering and, then, dope oxygen into these films via a controllable oxidation process. The crystal and electronic structures are characterized by high-resolution x-ray diffraction, x-ray photoelectron spectra, and Raman spectra. It is revealed that the crystal structure remains to be of the rocksalt type in these films even with heavy oxygen doping. The data of temperature-dependent electrical transport measurements indicate that the superconducting critical temperature (kinetic inductance) decreases (increases) from 4.6 K (0.672 pH/□) in the pristine TiN film to 3.4 K (1.13 pH/□) in the film with a maximum oxygen doping level. Our work provides a controllable way to tune the superconductivity of TiN films, which enables the flexibility to engineer the resultant performance of TiN-based superconducting quantum devices.

Preparation of poly(3,4-ethylenedioxythiophene) by vapor-phase polymerization at the interface between 3,4-ethylenedioxythiophene vapor and oxidant melt

Poly(3,4-ethylenedioxythiophene) (PEDOT) was fabricated via vapor-phase polymerization (VPP) of the monomer 3,4-ethylenedioxythiophene (EDOT) with FeCl3·6H2O melt as the oxidant at the EDOT vapor–FeCl3·6H2O melt interface. Highly doped VPP-PEDOT films were formed on the oxidant melt surfaces. The morphological changes and decrease in the doping level at the VPP-PEDOT film surface were attributed to slower oxidant transport up to the surface during VPP. The doping level of VPP-PEDOT was higher when the oxidant melt was used compared to when the oxidant thin film was employed, and the maximum doping level was twice of that obtained in our previous work.

Sonochemical assisted fabrication of 3D hierarchical porous carbon for high-performance symmetric supercapacitor.

A scalable fabrication of 3D hierarchical porous carbon structure (3D-HPC) has been achieved via a simple sonochemical route at different pyrolysis temperatures. It is worth noting that all the 3D-HPC samples possess oxygen-functional groups after activation by KOH and self-doped by nitrogen, which are beneficial to improving their surface wettability as well as increasing the electro-active surface area between the electrode and the surrounding electrolyte, consequently enhancing their electrochemical performance. Remarkably, the resulting carbon sample pyrolyzed at 850 °C (AC-850) possesses a maximum doping level of 2.75 at% and a high surface area of 1376.19 m2 g-1, which exhibits high electrochemical performance with high capacitance up to 269.19 F g-1 at a current density of 2 A g-1. Moreover remarkably, the AC-850-based symmetric supercapacitor delivers a high energy density of 21.4 Wh kg-1 at a power density of 531.2 W kg-1 with excellent rate performance and superior cycling stability (94.7% retention over 5000 cycles). The present approach is very suitable for large scale production of high-quality porous carbon materials at low cost, which can be used in different aspects, such as energy storage, gas storage, environmental remediation, and so on.

Anion-Dependent Doping and Charge Transport in Organic Electrochemical Transistors

We study the effects of different electrolyte anions on the mixed ionic/electronic transport properties of organic electrochemical transistors (OECTs) based on poly(3-hexylthiophene-2,5-diyl). We show that the transport properties depend on the anion present in the electrolyte, with greater source-drain currents resulting from the use of molecular anions such as hexafluorophosphate and trifluoromethanesulfonylimide than from the use of smaller atomic anions such as fluoride or chloride. Using spectroelectrochemistry, we show the maximum doping level that can be achieved in an aqueous environment is also anion-dependent. Furthermore, we find that the average electronic carrier mobility at a given doping level depends on the chemistry of the compensating counterion. We further investigate this dependence by electrochemical quartz crystal microbalance measurements, showing the solvation of the dopant anions within the polymer is drastically different depending on the choice of the anion. Surprisingly, we fin...

Electrical and optical evaluation of n-type doping in InxGa(1−x)P nanowires

To harvest the benefits of III–V nanowires in optoelectronic devices, the development of ternary materials with controlled doping is needed. In this work, we performed a systematic study of n-type dopant incorporation in dense InxGa(1−x)P nanowire arrays using tetraethyl tin (TESn) and hydrogen sulfide (H2S) as dopant precursors. The morphology, crystal structure and material composition of the nanowires were characterized by use of scanning electron microscopy, transmission electron microscopy and energy dispersive x-ray analysis. To investigate the electrical properties, the nanowires were broken off from the substrate and mechanically transferred to thermally oxidized silicon substrates, after which electron beam lithography and metal evaporation were used to define electrical contacts to selected nanowires. Electrical characterization, including four-probe resistivity and Hall effect, as well as back-gated field effect measurements, is combined with photoluminescence spectroscopy to achieve a comprehensive evaluation of the carrier concentration in the doped nanowires. We measure a carrier concentration of ∼1 × 1016 cm−3 in nominally intrinsic nanowires, and the maximum doping level achieved by use of TESn and H2S as dopant precursors using our parameters is measured to be ∼2 × 1018 cm−3, and ∼1 × 1019 cm−3, respectively (by Hall effect measurements). Hence, both TESn and H2S are suitable precursors for a wide range of n-doping levels in InxGa(1−x)P nanowires needed for optoelectronic devices, grown via the vapor–liquid–solid mode.

Enhancing the structural, optical and magnetic properties of Cu2O films deposited using a SILAR technique through Fe-doping

Undoped and Ferrous (Fe)-doped Cu2O thin films were deposited onto glass substrates using successive ionic layer adsorption and reaction method. The variation in the concentration of Fe has significant impact on the final film properties, Fe doping with 5 wt% exhibited major property improvements compared with undoped and Fe doped films. The structural, optical, morphological, magnetic properties and atomic force microscope of the films were systematically investigated. The X-ray diffraction analysis showed that all the films had good crystalline quality and the preferential orientation along (111) plane. Optical studies show that the transmittance and optical band-gap values are maximum (2.5 eV) for the Fe doping level of 5 wt%. The relative errors are calculated for crystallite size and optical energy band gap values. The photoluminescence study confirms the presence of various defects in the Cu2O matrix. The Fourier transform infrared results confirmed the presence of expected compounds in the samples. The field emission-scanning electron microscope images indicate that there is a gradual decrease in the grain-size with increase in the Fe doping level and a flower-like structure is obtained in the maximum doping level of Fe. The high resolution transition electron microscope reveals single-crystal nature. Magnetic measurements showed that undoped Cu2O films exhibit diamagnetic behavior and at the maximum (5 wt%) Fe doping level, the films behave as anti-ferromagnetic material. The atomic force microscope reveals that the smoothness of the film surface increases at the maximum doping of Fe concentration.

(Invited) Achieving Vertical Trench-Gate GaN MOSFETs via Process Optimization

The processing optimization necessary to achieve the GaN-based trench MOS device is reported. Devices of this type have been designed, fabricated and characterized. The operation of the device is based on the formation of a vertical inversion layer between the gate oxide and the p-type region. In the on-condition, this requirement is satisfied through the application of a positive voltage at the gate with respect to the source. Electrons are then accumulated at the vertical interfaces (only one shown) between the gate oxide and the p-type region. In this case, electrons flow from the source through the inversion layer on the side of the gate to the drift region onto the drain. The on-state losses are mainly determined by the resistance of the channel and the drift region. The former is controlled by the electron channel mobility while the latter by the doping level of the drift region. In the off-state (or blocking mode) the channel is removed and the p-n junction between the n- drift region and the p-type layer is reverse biased. The blocking voltage of the device is determined by the critical electric field of the drift region and its doping concentration. Furthermore, the doping level of the p-type region has to be selected based both on on-state and off-state requirements. In fact, the p-type doping value has an upper bound that is imposed by the fact that a suitable threshold voltage, between 3V and 5V, needs to be obtained. On the other hand, in off-state, at the nominal blocking voltage the p-type region must not be completely depleted in order to avoid punch-through. This imposed a lower bound on the p-type doping of the channel layer. In the same way, the n-type doping level of the drift region is bounded by the need of reasonable low on-state losses, that requires moderately high doping, and blocking voltage that impose a maximum doping level given a thickness of the drift region. To ensure a reliable operation of the device, it is critical to control the electric field value at the interface at the bottom of the gate trench at the interface with the drift region. In fact the shape of the gate trench has to be engineered to avoid high field region that may led to a local breakdown of the gate oxide. This can be avoided by a rounded trench profile and/or gate oxide shielding by additional p-type regions. Consideration of the above device with a blocking voltage of 5KV leads to the determination of the thickness and doping needed for both the p-type and n-type drift regions. The thickness and doping of the drift region have to be selected to maintain the maximum electric field below the critical field, which for GaN is ~3MV/cm. Allowing a maximum electric field of the order of 2MV/cm leads to the need of a drift region thickness of 50 m with a maximum doping of 2.5 x 1015 cm-3. Moreover, first design considerations show that to avoid punch through, the p-type region has to have a doping level of 5 x 1017 cm-3 and a thickness of 0.75 m. Devices designed with such a p-region are expected to have a threshold voltage of 4.8V. The GaN-MOS transistor properties of the inversion layers are of paramount importance for the proposed devices. Quantitative models of the carrier transport and breakdown properties of III-Nitrides-MOS inversion layer will be developed to address them. They will include a realistic description of the semiconductor/insulator interface. Alternative approaches such as the creation of vertical 2D electron channels will also be explored. The carrier transport and breakdown processes in high-voltage lateral and vertical devices will be an important aspect that we intend to address. We report on two major areas: dielectric characterization, and mask design for the next research phase. Detailed electrical characterization of GaN metal-oxide-semiconductor (MOS) capacitors with atomic layer deposited (ALD) ZrO2 high-k dielectrics from conventional tetrakis(dimethyl)amido-zirconium (TDMAZ) or novel zirconium tert-butoxide (ZTB) precursors has been ongoing. Characterization of ZTB-ZrO2 has been of particular interest after demonstration of record positive threshold voltage for an AlGaN/GaN high electron mobility transistor, indicative of negative charge in the oxide.

Comprehensive evaluation of dopant solubility, proton concentration, proton mobility and phase stability of lanthanum polyphosphate for conductivity improvement

Lanthanum polyphosphate (LaP3O9) is a candidate for the electrolytes in protonic ceramic fuel cells (PCFCs). In this work, the solubility of dopants (Ca, Sr, Ba and Pb), proton concentration, and proton mobility in LaP3O9 were evaluated to clarify the limiting factors for conductivity improvement. The maximum doping levels of Ca, Sr, Ba, and Pb in LaP3O9 synthesized by precipitation method were about 8, 14, 3, and 6 mol% respectively. Here doping level is defined as the concentration ratio of the dopant (M) to the host cation (La) site (M/(La + M)). The concentration ratio of protons to the dopant cations in doped LaP3O9, or hydration level, was almost independent of dopant species and as high as those in the perovskite-type oxides. The proton mobility in Sr-doped LaP3O9 was about twice those of Ca and Ba-doped LaP3O9, and it was ∼7 times that of Pb-doped LaP3O9. Remarkably, the highest conductivity of Sr-doped LaP3O9 precipitated from phosphoric acid solution was about one order of magnitude higher than that synthesized by solid state reaction, and comparable to that of Sr(Zr0.9Y0.1)O3-δ. This conductivity enhancement should be attributed to the increase in Sr-doping level, reduction of grain boundary density and c-axis orientation of grains by the precipitation method. Nevertheless, instability of LaP3O9 in humidified hydrogen atmosphere should be a problem for the practical applications.

Electrical properties of electrochemically doped organic semiconductors using light-emitting electrochemical cells

We present a study of the electrical properties of electrochemically doped conjugated polymers using polymeric light-emitting electrochemical cells (PLECs) and interpreting the results according to a phenomenological model (PM) which assumes that, above the device turn-on voltage, the bulk transport properties of the doped organic semiconductor are responsible for the main contribution to the whole device conductivity. To confirm the predictions of this model, the dependence of the conductivity of PLECs with different parameters is evaluated and compared with the behavior expected for a doped semiconducting polymeric material. The organic semiconductor doping level, the blend concentration of organic semiconducting molecules, the device thickness, the charge carrier mobility, and the temperature are the parameters varied to perform this analysis. We observed that the device conductivity is independent of the active layer thickness, weakly dependent on the temperature, but strongly dependent on the semiconductor doping level, on the semiconductor fraction in the blend, and on the intrinsic charge carrier mobility. These results were well described by the variable range hopping (VRH) model, which has been widely employed to describe the charge transport in doped semiconducting polymeric materials, confirming the prediction of the phenomenological model. The current analysis demonstrates that PLECs are a suitable system for studying, in situ, the electrochemical doping of semiconducting polymers, permitting the evaluation of material properties as, for instance, the density of electronic charge carriers (and, consequently, the ionic charge carrier concentration) necessary to achieve the maximum electrochemical doping level of the organic semiconductor.

Effect of size reduction on the magnetic and antibacterial properties of ZnO:Zr:Mn nanoparticles synthesized by a cost-effective chemical method

Zr and Zr + Mn doped ZnO nanopowders were synthesized using a simple soft chemical route keeping the Zr concentration in the precursor solution constant (3 at.%) and varying the Mn concentration (0, 1.5 and 9 at.%). From the X-ray diffraction studies, the crystallite size of ZnO:Zr nanopowder is found as 57 nm. The crystallite size decreases with the increase in the Mn doping level and attains a minimum of 23 nm at the maximum doping level examined in the present work (9 at.%). The Zr doped ZnO nanopowders found to have ferromagnetic property. The saturation magnetization increases with the increase in the Mn doping level and attains a maximum value at 7 at.% of Mn doping. The material shows superparamagnetic behavior at the doping level of 9 at.%. The antibacterial efficiency is found to be maximum at 9 at.% of Mn doping and at this doping level the grain size is minimum (20 nm) as evidenced from the SEM and TEM results.