The present work reports synthesis, as well as a detailed and careful characterization of structural, magnetic, and dielectric properties of differently tempered undoped and doped CaCu3Ti4O12 (CCTO) ceramics. For this purpose, neutron and x-ray powder diffraction, SQUID measurements, and dielectric spectroscopy have been performed. Mn-, Fe-, and Ni-doped CCTO ceramics were investigated in great detail to document the influence of low-level doping with 3d metals on the antiferromagnetic structure and dielectric properties. In the light of possible magnetoelectric coupling in these doped ceramics, the dielectric measurements were also carried out in external magnetic fields up to 7 T, showing a minor but significant dependence of the dielectric constant on the applied magnetic field. Undoped CCTO is well-known for its colossal dielectric constant in a broad frequency and temperature range. With the present extended characterization of doped as well as undoped CCTO, we want to address the question why doping with only 1% Mn or 0.5% Fe decreases the room-temperature dielectric constant of CCTO by a factor of ~100 with a concomitant reduction of the conductivity, whereas 0.5% Ni doping changes the dielectric properties only slightly. In addition, diffraction experiments and magnetic investigations were undertaken to check for possible correlations of the magnitude of the colossal dielectric constants with structural details or with magnetic properties like the magnetic ordering, the Curie-Weiss temperatures, or the paramagnetic moment. It is revealed, that while the magnetic ordering temperature and the effective moment of all investigated CCTO ceramics are rather similar, there is a dramatic influence of doping and tempering time on the Curie-Weiss constant.
We have performed an angle-resolved photoemission study on untwinned PrBa$_2$Cu$_3$O$_7$, which has low resistivity but does not show superconductivity. We have observed a dispersive feature with a band maximum around ($π$/2,$π$/2), indicating that this band is derived from the undoped CuO$_2$ plane. We have observed another dispersive band exhibiting one-dimensional character, which we attribute to signals from the doped CuO$_3$ chain. The overall band dispersion of the one-dimensional band agrees with the prediction of $t-J$ model calculation with parameters relevant to cuprates except that …
A set of experiments was conducted to synthesize doped and undoped sodium tantalates with carbon and sulfur in energy efficient single-step hydrothermal process. Undoped sodium tantalate nanocubes were synthesized at 140$^\circ$C and doped one at 180$^\circ$C for 12 hours in rich alkaline atmosphere. The sizes of undoped, carbon-doped, and sulfur-doped sodium tantalate nanocubes were 38 nm, 45 nm, and 40 nm, respectively. The morphological, elemental, compositional, structural, thermal, and photophysical properties of as-synthesized doped and undoped sodium tantalate (NaTaO$_3$) were character…
We develop a model describing the electrochemical conversion of an organic semiconductor (specifically, the active material in a light-emitting electrochemical cell) from the undoped non-conducting state to the doped conducting state. The model takes into account both strongly concentration-dependent mobility and diffusion for the electronic charge carriers and the Nernst equation in the doped conducting regions. It is demonstrated that the experimentally observed doping front progression in light-emitting electrochemical cells can be accurately described with this model.
The effects of $n$-type carrier doping by Li intercalation on magnetism in undoped and Co-doped anatase TiO$_2$ are investigated. We have found that doped $n$-type carriers in TiO$_2$ are localized mainly at Ti sites near the intercalated Li. With increasing the intercalation, local spins are realized at Ti. In the case of Co-doped TiO$_2$, most of the added $n$-type carriers fill the Co 3$d$ bands and the rest are localized at Ti. Therefore, Co magnetic moment vanishes by Li intercalation to have a nonmagnetic ground state.
Electron spin resonance (ESR) spectra of Fe3+ and Mn2+ ions have been studied in the nominally pure and 0.05% Li-doped single crystals of CdWO4. The zero-field splitting parameters are determined with a high precision for both of the impurities. The result suggest that the Li-doping leads to the increase of the ionic charge of iron from 3+ to 4+ and of manganese, from 1+ to 2+.
The structure of the ferroelectric phase of undoped KTiOPO$_4$ and its solid solutions with zirconium and niobium is studied from first principles within the density functional theory. The second-order nonlinear susceptibility tensor and the spontaneous polarization of these materials are obtained. It is shown that an improvement in nonlinear optical properties of KTiOPO$_4$ upon its doping with Zr and Nb cannot be explained by a systematic change in the composition of crystals and is apparently associated with the occurrence of defects. Possible structures of such defects are discussed.
We present a rationalization of the Raman spectra of orthorhombic and rhombohedral, stoichiometric and doped, manganese perovskites. In particular we study RMnO3 (R= La, Pr, Nd, Tb, Ho, Er, Y and Ca) and the different phases of Ca or Sr doped RMnO3 compounds as well as cation deficient RMnO3. The spectra of manganites can be understood as combinations of two kinds of spectra corresponding to two structural configurations of MnO6 octahedra and independently of the average structure obtained by diffraction techniques. The main peaks of compounds with regular MnO6 octahedra, as CaMnO3, highly Ca …
Single crystals of LiCaAlF6 undoped and Eu, Na co-doped were studied by electron paramagnetic resonance, radioluminescence and thermally stimulated luminescence techniques applied in a correlated manner. The undoped samples exposed to X-ray irradiation exhibited two hole-like charge trapping centers creation, the molecular ions of the form: ClF- and F2^- - F2^- dimer. Their trap depths and frequency factors were determined as follows: Et1=1.7 eV and Et2=1.1. eV for trap depths and f ~ 10^13 s-1 for frequency factor, respectively. It was found that the europium preferable charge state is 2+ in …
The electronic properties of pure and As-doped Si nanowires with radii up to 9.53 nm are studied using large scale density functional theory (DFT) calculations. We show that, for the undoped nanowires, the DFT bandgap reduces with increasing diameter and converges to its bulk value, a trend in agreement with experimental data. Moreover, we show that the atoms closest to the surface of the nanowire contribute less to the states near the band edges, when compared with atoms close to the centre; this is shown to be due to differences in Si-Si atomic distances, as well as surface passivation effec…
We perform density functional calculations on one-dimensional zigzag edge graphene nano-ribbons (ZGNRs) of different widths, with and without edge doping including semi-local exchange-correlations. Our study reveals that, although the ground state of edge passivated (with hydrogen) ZGNRs prefers to be anti-ferromagnetic, the doping of both the edges with Boron atoms stabilizes the system in a ferromagnetic ground state. Both the local and semi-local exchange-correlations result in half-metallicity in edge passivated ZGNRs at a finite cross-ribbon electric field. However, the ZGNR with Boron ed…
Undoped and Mn-doped ZnS nanocrystals were produced by the microwave-assisted solvothermal method and characterized by X-ray diffraction, photoluminescence spectroscopy and scanning electron microscopy with energy-dispersive X-ray spectroscopy. All samples have the cubic zinc blende structure with the lattice parameter in the range of $a$ = 5.406-5.411 Å, and the average size of crystallites is in the range of 6-9 nm. These nanoparticles agglomerate and form large grains with an average size of up to 180 nm. The photoluminescence of the undoped ZnS sample shows a broad emission band located at…
Single-phase perovskite 5 at.% Mn-doped and undoped polycrystalline BaTiO3 thin films have been grown under different oxygen partial pressures by pulsed laser deposition on platinum-coated sapphire substrates. Ferroelectricity is only observed for the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. Compared to undoped BaTiO3, Mn-doped BaTiO3 reveals a low leakage current, increased dielectric loss, and a decreased dielectric constant. Ferromagnetism is seen on Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure and is attributed to …
For $β$-$\mathrm{Ga_2O_3}$ only little information exist concerning the thermal properties, especially the thermal conductivity $λ$. Here, the thermal conductivity is measured by applying the electrical 3$ω$-method on Czochralski-grown $β$-$\mathrm{Ga_2O_3}$ bulk crystals, which have a thickness of $200~\mathrm{μm}$ and $800~\mathrm{μm}$. At room temperature the thermal conductivity along the [100]-direction in Mg-doped electrical insulating and undoped semiconducting $β$-$\mathrm{Ga_2O_3}$ is confirmed as $13\pm 1~\mathrm{Wm^{-1}K^{-1}}$ for both crystals. The thermal conductivity increases f…
In this paper the magnetic behaviour of undoped and 15% F doped SmFeAsO (Sm-1111) and LaFeAsO (La-1111) samples is presented and discussed. Magnetization measurements are not a simple tool to use for the characterisation of the new family of Fe-based superconductors because magnetic impurities can be easily formed during the preparation procedure and may affect the magnetic signal. In spite of this problem bulk magnetization measurements, properly treated, may give very useful information. In the undoped samples we gathered the main aspects of the physical behavior of the 1111 phase, i.e. the …
Transparent and conductive ZnO:Ga thin films are prepared by laser molecular-beam epitaxy. Their electron properties were investigated by the temperature-dependent Hall-effect technique. The 300-K carrier concentration and mobility were about $n_s \sim 10^{16}$ cm$^{-3}$ and 440 cm$^{2}$/Vs, respectively. In the experimental `mobility vs concentration' curve, unusual phenomenon was observed, i.e., mobilities at $n_s \sim 5\times$ 10$^{18}$ cm$^{-3}$ are significantly smaller than those at higher densities above $\sim 10^{20}$ cm$^{-3}$. Several types of scattering centers including ionized don…
The semiconducting properties of regioregular poly(3-hexylthiophene) are characterized by impedance measurements, from 40 Hz to 100 MHz. X-ray diffraction shows the presence of both ordered and disordered regions. The analysis of impedance data by Nyquist plots show two semi-circular arcs, and its size is reduced by d.c. bias. Also, the carrier variation by light and chemical doping alters the shape and size of arcs. The fits to the data and equivalent circuits show considerable changes in the resistive, capacitive and constant-phase element parameters as the carrier density increases. The inc…
Relative $K$ x-ray intensities of $Mn$ in $Mn$, $MnO_{2}$, $LaMnO_{3}$ and $La_{0.7}B_{0.3}MnO_{3}$ ($B$ = $Ca$, $Sr$, and $Ce$) systems have been measured following excitation by 59.54 keV $γ$-rays from a 200 mCi $^{241}$Am point-source. The measured results for the compounds deviate significantly from the results of pure $Mn$. Comparison of the experimental data with the multiconfiguration Dirac-Fock (MCDF) effective atomic model calculations indicates reasonable agreement with the predictions of ionic model for the doped {manganites except} that the electron doped $La_{0.7}Ce_{0.3}MnO_{3}$ …
The magnetoresistivity and critical current density of well characterized Si-nanoparticle doped and undoped Cu-sheathed MgB$_{2}$ tapes have been measured at temperatures $T\geq 28$ K in magnetic fields $B\leq 0.9$ T. The irreversibility line $B_{irr}(T)$ for doped tape shows a stepwise variation with a kink around 0.3 T. Such $B_{irr}(T)$ variation is typical for high-temperature superconductors with columnar defects (a kink occurs near the matching field $% B_ϕ$) and is very different from a smooth $B_{irr}(T)$ variation in undoped MgB$_{2}$ samples. The microstructure studies of nanoparticl…
We have investigated the room temperature ferromagnetic order that develops in Al-substituted magnesium oxide, Mg(Al)O, nanoparticles with Al fractions of up to 5 at.%. All samples, including undoped MgO nanoparticles, exhibit room temperature ferromagnetism, with the saturation magnetization reaching a maximum of 0.023 emu/g at 2 at.% of Al. X-ray photoelectron spectroscopy identifies the presence of oxygen vacancies in both doped and undoped MgO nanoparticles, with the vacancy concentration increasing upon vacuum annealing of Mg(Al)O, resulting in two-fold enhancement of the saturation magne…
An original modification of the standard Pulse Laser Deposition (PLD) method for preparing both undoped and indium doped zinc oxide (ZnO:In) thin films at low substrate temperature is proposed. This preparation method does not demand any further post-deposition annealing treatment of the grown films. The developed method allows to grow thin films at low substrate temperature that prevents them from the considerable loss of their intrinsic electrical and optical properties. The influence of deposition parameters on the electrical and optical parameters of the undoped and the indium doped ZnO th…
We present a study on the crystallization process of undoped and Ta doped TiO2 amorphous thin films. In particular, the effect of ultra-fast annealing treatments in environments characterized by different oxygen concentrations is investigated via in-situ resistance measurements. The accurate examination of the key parameters involved in this process allows us to reduce the time needed to obtain highly conducting and transparent polycrystalline thin films (resistivity about $6 \times 10^{-4}$ Ωcm, mean transmittance in the visible range about $81\%$) to just 5 minutes (with respect to the 180 m…
We have systematically studied the transport properties of the La$_{2-x}$Y$_{x}$CuO$_{4}$(LYCO) films of T'-phase ($0.05\leq x \leq 0.30$). In this nominally "undoped" system, superconductivity was acquired in certain Y doping range ($0.10\leq x \leq 0.20$). Measurements of resistivity, Hall coefficients in normal states and resistive critical field ($H^ρ_{c2}$)in superconducting states of the T'-LYCO films show the similar behavior as the known Ce-doped n-type cuprate superconductors, indicating the intrinsic electron-doping nature. The charge carriers are induced by oxygen deficiency. Non-su…
The electronic excitation spectra of undoped, and potassium as well as calcium doped phenantrene-type hydrocarbons have been investigated using electron energy-loss spectroscopy (EELS) in transmission. In the undoped materials, the lowest energy excitations are excitons with a relatively high binding energy. These excitons also are rather localized as revealed by their vanishing dispersion. Upon doping, new low energy excitation features appear in the former gaps of the materials under investigation. In K$_3$picene and K$_3$chrysene they are characterized by a negative dispersion while in Ca$_…
A giant low-frequency, in-plane dielectric constant, eps~10^6, for epitaxial thin films of Ca(1-x)La(x)MnO(3) (x<=0.03) was observed over a broad temperature range, 4K <= T 300K. This phenomenon is attributed to an internal barrier-layer capacitor (IBLC) structure, with insulating boundaries between semiconducting grains. The room-temperature eps increases substantially with electron (La) doping. The measured values of eps exceed those of conventional two-phase IBLC materials based on (Ba,Sr)TiO(3) as well as recently discovered CaCu(3)Ti(4)O(12) and (Li,Ti) doped NiO.
Luttinger semimetals are three-dimensional electron systems with a parabolic band touching and an effective total spin $J=3/2$. In this paper, we present an analytical theory of dielectric screening of inversion-symmetric Luttinger semimetals with an arbitrary carrier density and conduction-valence effective mass asymmetry. Assuming a spherical approximation for the single-particle Luttinger Hamiltonian, we determine analytically the dielectric screening function in the random phase approximation for arbitrary values of the wave vector and frequency, the latter in the complex plane. We use thi…
Pyrochlore iridates have recently attracted growing interest in condensed matter physics because of their potential for realizing new topological states. In order to achieve such quantum states, it is essential to understand themagnetic properties of these compounds, as their electronic structures are strongly coupled with theirmagnetic ground states. In this work, we report a systematic study of the magnetic properties of pyrochlore Y2Ir2O7 and its hole-doped compounds by performing magnetic, electron spin resonance, electrical transport, and x-ray photoelectron spectroscopy (XPS) measurement…
Undoped and Mn doped ZnO samples with different percentage of Mn content (1 mol%, 2 mol% and 3mol%) were synthesized by a simple solvo-thermal method. We have studied the structural, chemical and optical properties of the samples by using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray (EDX) analysis, Fourier transform infrared (FTIR) spectroscopy and UV-VIS spectroscopy. The XRD spectra show that all the samples are hexagonal wurtzite structures. The lattice parameters calculated for the Mn doped ZnO from the XRD pattern were found to be slightly larger th…
Polycrystalline bulk samples of PrFe1-xMnxO3 (x=0.0, 0.1, 0.3, 0.5) were synthesized by solid state reaction method to understand their structural, optical and dielectric properties
In this paper, we report on the co-doping nitrogen and sulfur has been achieved in the TiO2 nanotube array films by treatment with thiourea and calcination under vacuum at 500 °C for 3 h. The samples were characterized by scanning electron microscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible diffuse reflectance spectroscopy. XPS spectra revealed that N might coexist in the forms of NTiO and NOTi, S was incorporated into the lattice of TiO2 through substituting oxygen atoms in the N + S co-doped TiO2 nanotube array films. XRD patterns indicated tha…
We report the growth by molecular beam epitaxy of highly resistive GdN, using intentional doping with magnesium. Mg-doped GdN layers with resistivities of 1000 Ω.cm and carrier concentrations of 10E16 cm-3 are obtained for films with Mg concentrations up to 5 x 10E19 atoms/cm3. X-ray diffraction rocking curves indicate that Mg-doped GdN films have crystalline quality very similar to undoped GdN films, showing that the Mg doping did not affect the structural properties of the films. A decrease of the Curie temperature with decreasing the electron density is observed, supporting a recently sugge…
EXAFS and confocal Raman microscopy have been used to study 50SnF2.(20-x)SnO.30P2O5.xEr2O3 (x=0, 0.1, 0.25) glasses. EXAFS data reveal an average coordination of Sn to O of 1.5 in both undoped glass and Er-doped glass samples. The first coordination sphere of Er in glasses doped with Er2O3 was found to have 9 F atom neighbours at an average bond length of 2.292+/-0.005 Å, indicating that Er preferentially bonds with F. Raman spectra clearly show the emergence of orthophosphate Q0 units on addition of Er2O3. The saturation of Er solubility is found to be between 0.25 and 0.5 mol$\%$ Er2O3. An i…
We have performed x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD) studies of the diluted ferromagnetic semiconductor Zn$_{1-\textit{x}}$Cr$_\textit{x}$Te doped with iodine (I) or nitrogen (N), corresponding to electron or hole doping, respectively. From the shape of the Cr $2p$ absorption peak in the XAS spectra, it was concluded that Cr ions in the undoped, I-doped and lightly N-doped samples are divalent (Cr$^{2+}$), while Cr$^{2+}$ and trivalent (Cr$^{3+}$) coexist in the heavily N-doped sample. This result indicates that the doped nitrogen atoms act as acce…
The phase diagram and low temperature properties of the doped manganites A1-xBxMnO3 are discussed for the concentrations x < 0.4. The transition from insulating antiferromagnetic to metallic ferromagnetic state at x_cr = 0.16 is treated by means of percolation theory. The unifying description of insulating and metallic states is presented. The undoped manganite is a band insulator consisting of ferromagnetic layers, which are coupled antiferromagnetically along the c direction with a low Neel temperature. The metallic phase can be described by the two-band Fermi liquid picture. The behavior of…
Relaxor ferroelectrics are complex materials with distinct properties different from classic ferroelectrics. Probing frequency depended dielectric susceptibility is its trait. Other empirical laws build on classic ferroelectrics are still applicable to relaxor ferroelectrics. Here we report an abnormal improved dielectric in La doped relaxor ferroelectric 0.4PNN-0.6PHT, which deviated from the consistent variation relationship with piezoelectric coefficient. A mesoscale mechanism is proposed to reveal the origin of the improved dielectric response in 0.4PNN-0.6PHT, where the polar nanoregions …
The state of art in the theoretical and experimental studies of transition metal doped oxides (dilute magnetic dielectrics) is reviewed. The available data show that the generic non-equilibrium state of oxide films doped with magnetic impurities may either favor ferromagnetism with high Curie temperature or result in highly inhomogeneous state without long-range magnetic order. In both case concomitant defects (vacancies, interstitial ions play crucial part.
The localized effect of impurities in single GaN nanowires in the sub-diffraction limit is reported using the study of lattice vibrational modes in the evanescent field of Au nanoparticle assisted tip enhanced Raman spectroscopy (TERS). GaN nanowires with the O impurity and the Mg dopants were grown by the chemical vapor deposition technique in the catalyst assisted vapor-liquid-solid process. Symmetry allowed Raman modes of wurtzite GaN are observed for undoped and doped nanowires. Unusually very strong intensity of the non-zone center zone boundary mode is observed for the TERS studies of bo…
The development of dielectric materials with colossal permittivity is important for the miniaturization of electronic devices and fabrication of high-density energy-storage devices. The electron-pinned defect-dipoles has been recently proposed to boost the permittivity of (Nb + In) co-doped TiO2 to 105. However, the follow-up studies suggest an extrinsic contribution to the colossal permittivity from thermally excited carriers. Herein, we demonstrate a marked enhancement in the permittivity of (Nb + In) co-doped TiO2 single crystals at sufficiently low temperatures such that the thermally exci…
We investigate the low-field relaxation of nuclear hyperpolarization in undoped and highly doped silicon microparticles at room temperature following removal from high field. For nominally undoped particles, two relaxation time scales are identified for ambient fields above 0.2 mT. The slower, T_1s, is roughly independent of ambient field; the faster, T_1f, decreases with increasing ambient field. A model in which nuclear spin relaxation occurs at the particle surface via a two-electron mechanism is shown to be in good agreement with the experimental data, particularly the field-independence o…
The effect of doping with Ti, Ta, SiC in complex with synthesis temperature on the amount and distribution of structural inhomogeneities in MgB2 matrix of high-pressuresynthesized-materials (2 GPa) which can influence pining: higher borides (MgB12) and oxygen-enriched Mg-B-O inclusions, was established and a mechanism of doping effect on jc increase different from the generally accepted was proposed. Near theoretically dense SiC-doped material exhibited jc= 1000000 A/sq. cm in 1T field and Hirr =8.5 T at 20 K. The highest jc in fields above 9, 6, and 4 T at 10, 20, and 25 K, respectively, was …
Single crystals of pure and Cd2+ doped potassium sulfate were grown from aqueous solutions by the slow evaporation technique. From nutrient solutions with a CdSO4 concentration of 4wt.% crystals containing 0.014wt.% dopant concentration could be obtained. The X-ray diffraction patterns of powdered crystals confirmed their crystal structures for both cases. Thermal analysis of pure crystals shows that the alpha-beta phase transformation peak around 580 deg C is superimposed with spurious effects, while for Cd2+ doped crystals this is not the case. The thermal hysteresis of the phase transition …
The spin states at the surface of epitaxial thin films of hematite, both undoped and doped with 1% Ti, Sn or Zn, respectively, were probed with x-ray magnetic linear dichroism (XMLD) spectroscopy. Morin transitions were observed for the undoped (T_M~200 K) and Sn-doped (T_M~300 K) cases, while Zn and Ti-doped samples were always in the high and low temperature phases, respectively. In contrast to what has been reported for bulk hematite doped with the tetravalent ions Sn4+ and Ti4+, for which T_M dramatically decreases, these dopants substantially increase T_M in thin films, far exceeding the …
In this manuscript, we report room temperature structural, microstructural, optical, dielectric, and magnetic properties of CuO and Cu0.995La0.005 ceramics, synthesized by solid-state reaction method. La doping in CuO leads to the evolution of compact and dense microstructure with reduced porosity. Due to noticeable differences in the ionic radii of, La doping creates vacancy defects which induce considerable strain in the CuO lattice resulting in a reduction in the lattice parameters and cell volume. However, both ceramics processes a similar monoclinic structure with the C2/c space group. De…
Manganites exhibit various types of electronic phenomena, and these electronic characteristics can be controlled by carrier doping. Herein, we report the dielectric and magnetic properties of electron-doped manganite Ca$_{1-x}$Sr$_x$Mn$_{0.85}$Sb$_{0.15}$O$_3$ ($x$ = 0, 0.1, 0.2, and 0.3). The temperature dependence of the real part of the dielectric constant exhibits a broad and large peak just below the kink temperature of magnetization and a sharp decrease at lower temperatures, accompanied by an anomaly of the imaginary part. Furthermore, isovalent Sr substitution enhances the temperature …
In this work, we report the combined effect of donor (Nd) and acceptor (Li) co-doping at the Zn-site of ZnO ceramics on structural, microstructural and dielectric properties. Combining experimental observations with DFT based theoretical study, we have shown that before experimental fabrication DFT based first principles study can be used as a good indication to have prior qualitative assessment of a dielectric medium. For implementing this objective various Li and Nd co-doped ZnO ceramics have been synthesized through the conventional solid-state reaction route. Quantitative XRD analysis reve…
Fundamental and harmonic magneto-dielectricity studied for varied perovskite systems-- Pb0.98Gd0.02(Mg1/3Nb2/3)0.995O3 (A-site co-doped PGMN magneto-relaxor), La0.95Ca0.05CoO3 (A-site doped spin-state LCCO), and La2NiMnO6 (double-perovskite LNMO multiglass) characterize intricately polarized phases. First-harmonic signal (ε2') of magnetically co-doped PGMN manifests finite polarization P(H) below 270K, corroborated by the measured remnant P-E traces. Second-harmonic (ε3') reveals the effect of random E-fields causing electrical vitreousity, latter indicated by the divergent timescale of the fu…
Bulk samples of $(Sn_{1-x}Sb_{x}O_{2-δ})$ with x = 0.00, 0.10, 0.20, 0.30 are synthesized by solid-state reaction route. Samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis spectroscopy. The x-ray diffraction patterns indicate that the gross structure/phase of $(Sn_{1-x}$ $Sb_{x}O_{2-δ})$ do not change with the substitution of antimony (Sb) up to x = 0.30. The surface morphological examination with SEM revealed the fact that the grain size in the antimony doped sample is larger than that of undoped …
The dynamics and internal structure of doping fronts in organic semiconductors are investigated theoretically using an extended drift-diffusion model for ions, electrons and holes. The model also involves the injection barriers for electrons and holes in the partially doped regions in the form of the Nernst equation, together with a strong dependence of the electron and hole mobility on concentrations. Closed expressions for the front velocities and the ion concentrations in the doped regions are obtained. The analytical theory is employed to describe the acceleration of the p- and n-fronts to…
Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents, were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD) technique. The Al2O3-BST films was demosnstrated to be a suitable systems to fabricate ferroelectric thin films with low dielectric loss and higher figure of merit for tunable microwave devices. Pure BST thin films were also fabricated for comparison purpose. The films' structure and morphology were analyzed by X-ray diffractiopn and scanning electron microscopy, respectively; nad showed that the surface roughness for the Al2O3-BST films increase…
