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The present work shows the improved humidity sensing characteristics of TiO2 nanoparticles in the form of a nanocomposite with multiwalled carbon nanotubes (MWCNTs) prepared by a hydration–dehydration method. The structural and morphological characterizations of TiO2–MWCNTs confirm the nanocomposite formation without any other impurities and with an improved surface area. The pure TiO2 and nanocomposite films are deposited on IDE coated flexible poly-ethylene terephthalate (PET) substrates by a drop casting method. The nanocomposite shows improved sensitivity (1246.2 MΩ/%RH) and an ultrafast response/recovery time (2 s/1 s) with a minimal hysteresis of 0.27%RH. Further, the flexible nanocomposite sensor is tested for human healthcare applications including respiratory monitoring, apnea like situations, and skin moisture detection. The sensor can distinguish different breath patterns like normal, fast, deep and apnea like situations significantly. Skin moisture detection can also be performed using the nanocomposite sensor in a non-invasive manner. Overall, this study represents an environmentally friendly, easy to fabricate, flexible TiO2–MWCNT nanocomposite based improved humidity sensor for application in human healthcare and wearable devices. [ABSTRACT FROM AUTHOR]

We study the structural and electronic properties of Fe doped (4-8 at. %) and undoped TiO2 thin films deposited by pulsed laser deposition on Si(111) substrate. The films grow in single phase anatase structure of TiO2 as revealed by x-ray diffraction and Raman spectroscopy measurements. The Fe doped films reveal room temperature magnetic hysteresis behavior. We have probed the electronic environment of Fe in TiO2 matrix and its coupling to the cations, using photoelectron spectroscopy measurements. Photoelectron spectroscopic studies reveal the ionic state of Fe in TiO2, precluding the formation of Fe metal clusters. Valence band spectra of these films suggest that it primarily consists of O-2p derived state, however, Fe derived state is also observed in Fe doped films. Resonance photoelectron spectroscopy studies indicate that Fe ions are hybridized with Ti3+ defect states. [ABSTRACT FROM AUTHOR]

The electronic structure of CeO2 thin film grown by pulsed laser deposition on Si (100) substrate has been investigated using resonance photoemission spectroscopy (RPES). X-ray photoemission study on the film suggests that Ce has 3+ and 4+ valence states. Valence band spectra of the film show a feature at 2.1 eV of binding energy and a broad band at higher binding energy due to O 2p derived state. RPES measurements performed in the Ce 4d→4f photoabsorption region show maximum intensity for 2.1 eV feature at photon energy of 122 eV confirming it to be due to Ce3+ (4f1) state. RPES measurements also show maximum intensity for binding energy position of 4.4 eV in the broad band at photon energy of 125 eV, suggesting it to be due to Ce4+ (4f0) state. Constant initial state (CIS) versus photon energy plots also confirm these findings and suggest that the broad band is admixture of O 2p and Ce 4f and 5d derived states. [ABSTRACT FROM AUTHOR]

The resonance photoemission spectroscopy (RPES) technique is employed to explain the electronic structure of the Ce[O.sub.2] thin film grown on Si (100) substrate by pulsed laser deposition technique. The valence band spectra of the film is shown to exhibit a binding energy of 2.1 eV.

We have studied the spin-dependent electron momentum density distribution in CoGaFeO ( x = 0.2, 0.3) at a low temperature (8 K) using magnetic Compton scattering technique. Further, the effect of Ga doping on the electronic structure is studied using X-ray photoemission spectroscopy (XPS). It is revealed that doping of Ga substitutes the Fe ions predominantly at tetrahedral (P) site, which promotes a gradual immigration of small amount of Co ions from tetrahedral to octahedral (Q) site. Total spin moment increases remarkably on increasing the doping concentration of nonmagnetic Ga ( x = 0 → 0.3) in the base cobalt ferrite. It is seen that major contribution to total spin moment mainly arises from Co ions while itinerant electrons show negative polarization. On Ga doping, spin moment at Fe site increases dramatically with a minor increment at Co site. The increased spin moment is attributed to the increased Q/P occupancy ratio of Fe as well as Co ions as determined using XPS measurements. In contrast, orbital moment does not show such deviations, suggesting that a small amount of Ga doping can enhance the magnetization significantly, without inducing any significant distortion to modify the spin-orbit coupling. [ABSTRACT FROM AUTHOR]

We have studied the electronic transport behaviour and band offset properties of the epitaxial TiO2-x (x = 0.05)/La0.7Sr0.3MnO3 hetero-structure. The bilayer shows non-linear I-V characteristics at different temperatures as well as negative magneto-resistance with the application of magnetic field. Valence band offset (VBO) was measured using photoelectron spectroscopy and consequently the conduction band offset (CBO) was determined. It is found that type-I alignment takes place at the interface. The value for CBO (1.1 eV) is much lower than VBO (2.3 eV), suggesting that transport is mainly dominated by electrons. Observed negative magneto-resistance in such bilayer is explained with the help of band structure of La0.7Sr0.3MnO3. [ABSTRACT FROM AUTHOR]

The electronic structure of epitaxial La0.7Sr0.3MnO3 thin film grown on LaAlO3 (001) substrate has been studied by resonant photoemission spectroscopy across Curie temperature (TC). Temperature dependent variations in the valence band structure divulge that beyond TC, Mn-O 2p hybridization is reduced. It is found that nature of the states in the lower binding energy range above TC would be rather due to Mn3+ ions, whereas below TC Mn3+ and Mn4+ contributes equally in the low binding energy region. At higher binding energy values, Mn4+ contribution is larger in the Mn-O hybridization at all temperatures. [ABSTRACT FROM AUTHOR]

Abstract: We have studied the influence of oxygen partial pressure (OPP; 250mTorr–1×10−5 Torr) and Fe doping (2 and 4at.%) on structural and electrical properties of TiO2 thin films on LaAlO3 substrates. X-ray photoelectron spectroscopy suggests that Fe is not in metal cluster form. It is found that the evolution of the three phases; anatase, rutile and brookite of TiO2 as well as the magneli phase (Ti n O2n−1) strongly depends on the OPP and Fe doping concentration. All the films grown at 250mTorr show insulating behavior, whereas films grown at 1×10−2 and 1×10−4 Torr reveal high temperature metallic to low temperature semiconducting transition. Interestingly, films deposited at 1×10−5 Torr reveal charge ordering, which is contributed to the magneli phase of TiO2. The present study suggests that functionality of TiO2 thin film based devices can be tuned by properly selecting the OPP and dopant concentration. [Copyright &y& Elsevier]

We have investigated the electronic and magnetic properties of the pulsed laser deposited epitaxial thin films of undoped and Fe doped (4 at. %) anatase TiO2-d by photoemission, magnetization measurements, and ab-initio band structure calculations. These films show room temperature magnetic ordering. It is observed that Fe ions hybridize with the oxygen vacancy induced Ti3+ defect states. Our study reveals the formation of local magnetic moment at Ti and Fe sites to be responsible for magnetic ordering. A finite density of states at the Fermi level in both undoped and Fe doped films is also observed, suggesting their degenerate semiconducting nature. [ABSTRACT FROM AUTHOR]

Spin momentum densities of ferromagnetic ZrFe 2 and Zr 0.8 Sc 0.2 Fe 2 have been measured using magnetic Compton scattering with 182.65 keV circularly polarized synchrotron radiations. Site specific spin moments, which are responsible for the formation of total spin moment, have been deduced from Compton line shapes. At room temperature, the computed spin moment of ZrFe 2 is found to be slightly higher than that of Sc doped ZrFe 2 which is in consensus with the magnetization data. To compare the experimental data, we have also computed magnetic Compton profiles (MCPs), total and partial spin projected density of states (DOS) and the site specific spin moments using spin-polarized relativistic Korringa-Kohn-Rostoker method. It is observed that the spin moment at Fe site is aligned antiparallel to that of Zr site in both ZrFe 2 and Zr 0.8 Sc 0.2 Fe 2 . The MCP results when compared with vibrating sample magnetometer based magnetization data, show a very small contribution of orbital moment in the formation of total magnetic moments in both the compounds. The DOS of ferromagnetic ground state of ZrFe 2 and Zr 0.8 Sc 0.2 Fe 2 are interpreted on the basis of a covalent magnetic model beyond the Stoner rigid band model. It appears that on alloying between a magnetic and a non-magnetic partner (with low valence), a polarization develops on the non-magnetic atom which is anti-parallel to that of the magnetic atom. [ABSTRACT FROM AUTHOR]

We have studied the structural, electronic and magnetic properties of pulsed laser deposited thin films of Ni 1− x Cr x Fe 2 O 4 ( x =0.02 and 0.05) on Si (111) and Si (100) substrates. The films reveal single phase, polycrystalline structure with larger grain size on Si (111) substrate than that on Si (100) substrate. Contrary to the expected inverse spinel structure, x-ray photoemission (XPS) studies reveal the mixed spinel structure. XPS results suggest that Ni and Fe ions exist in 2+ and 3+ states, respectively, and they exist in tetrahedral as well as octahedral sites. The deviation from the inverse spinel leads to modified magnetic properties. It is observed that saturation magnetization drastically drops compared to the expected saturation value for inverse spinel structure. Strain in the films and lattice distortion produced by the Cr doping also appear to influence the magnetic properties. [ABSTRACT FROM AUTHOR]

Structural and magnetic response of Ni 1-x Cr x Fe 2 O 4 (x = 0 and 0.05) are presented using X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and SQUID magnetometer. The single phase of both the compositions is confirmed using Rietveld refinement method. The absence of any impurity is further cinched using structural sensitive techniques, namely FTIR and Raman spectroscopy. Interestingly, a pinched shaped M − H behaviour is observed for the Cr doped ferrite. In addition, we have computed magnetic moment, Mulliken's population, density of states (DOS) and Compton profiles (CPs) for NiFe 2 O 4 using linear combination of atomic orbitals (LCAO) scheme with and without hybrid functional for exchange and correlation potentials. Further, theoretical CPs have been validated using isotropic CP measurement with 137Cs radio-isotope for NiFe 2 O 4. Among the considered exchange-correlation potentials within LCAO, the hybrid B3LYP scheme based momentum densities give better agreement with the experimental CP. Majority- and minority-spin DOS have confirmed the insulating nature of NiFe 2 O 4. Peculiarities of presently deduced MP data and magnetic moments are also discussed. Image 1 • Structural and magnetic response of NiFe 2 O 4 and Ni 0.95 Cr 0.05 Fe 2 O 4 using X-ray diffraction, Raman spectroscopy, FTIR spectroscopy and SQUID magnetometer. • Confirmation of impurity less single phase for both compositions by Rietveld refinement method, FTIR and Raman spectroscopy. • Computed magnetic moment, Mulliken's population, density of states (DOS) and Compton profile (CP) for NiFe 2 O 4 using LCAO with and without hybrid functional. • Validation of LCAO-B3LYP scheme for NiFe 2 O 4 using isotropic CP measurements with 137Cs radio-isotope and M-H measurements. • Analyzed spin dependent DOS and confirmation of wide band gap nature of NiFe 2 O 4 and projected use of LCAO approximations for deducing magnetic response. [ABSTRACT FROM AUTHOR]

We present the first-ever experimental Compton profile of Laves phase ZrFe 2 using indigenous 20 Ci 137 Cs Compton spectrometer. To annotate the experimental electron momentum density, we have calculated the theoretical Compton profiles using density functional theory (DFT) and hybridization of Hartree–Fock and DFT within linear combination of atomic orbitals (LCAO) method. The spin-polarized energy bands and density of states are computed using LCAO and full potential-linearized augmented plane wave methods. The revised Perdew-Burke-Ernzerhof functional (for solids) based theoretical profile gives a marginally better agreement with the experimental profile as compared to other approximations considered in the present work. The Fermi surface topology of ZrFe 2 is explained in terms of majority- and minority-spin energy bands. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sol–gel grown polycrystalline single phasic Zn1 − x Co x O system is synthesized. [•] X-ray Photoemission spectroscopy reveals that, Co-substitution results in the EF shift and chemical shift in ZnO. [•] Co-substitution induced electronic structure and valence band modifications in Zn1 − x Co x O (x =0, 0.5 and 0.15) samples. [•] Co 3d states around 3.4eV show resonance at ∼62eV and are hybridized with O 2p bonding states. [ABSTRACT FROM AUTHOR]

Highlights • Compared experimental MCP with those calculated using correct formula for isotropic Compton profiles. • Presented experimental MCPs of ZrFe 2 and Sc doped ZrFe 2. • Presented SPR-KKR based MCPs. [ABSTRACT FROM AUTHOR]

The present work shows the improved humidity sensing characteristics of TiO 2 nanoparticles in the form of a nanocomposite with multiwalled carbon nanotubes (MWCNTs) prepared by a hydration-dehydration method. The structural and morphological characterizations of TiO 2 -MWCNTs confirm the nanocomposite formation without any other impurities and with an improved surface area. The pure TiO 2 and nanocomposite films are deposited on IDE coated flexible poly-ethylene terephthalate (PET) substrates by a drop casting method. The nanocomposite shows improved sensitivity (1246.2 MΩ/%RH) and an ultrafast response/recovery time (2 s/1 s) with a minimal hysteresis of 0.27%RH. Further, the flexible nanocomposite sensor is tested for human healthcare applications including respiratory monitoring, apnea like situations, and skin moisture detection. The sensor can distinguish different breath patterns like normal, fast, deep and apnea like situations significantly. Skin moisture detection can also be performed using the nanocomposite sensor in a non-invasive manner. Overall, this study represents an environmentally friendly, easy to fabricate, flexible TiO 2 -MWCNT nanocomposite based improved humidity sensor for application in human healthcare and wearable devices.

We have investigated the effect of local magnetic moment on the electrical and magneto-transport properties of thin films of the degenerate semiconductor Ti(1-x)Fe(x)O(2-d) (x = 0,0.04). The electrical measurements of these films reveal high temperature metallic behavior and resistivity minima. The behavior below the resistivity minimum temperature is ascribed to Kondo like scattering. The coupling between the local moment and the charge carriers is reflected in the magnetoresistance measurements in these films. This work indicates competition between the magnetic ordering mechanism by J(RKKY) and the moment screening mechanism by J(Kondo). Accordingly the role of carrier density in achieving the magnetic ordering in such materials either by defect engineering or by transition metal doping is discussed.