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Fe-substituted NiO nanoparticles (Ni1−xFexO2) (x= 0.00, 0.03, 0.05, 0.07, and 0.09) were synthesised using ball-milling method followed by vacuum sintering and studied for their microstructural and magnetic properties. All the samples show a cubic structure with a crystallite size of 17–26 nm. Secondary phases related to Fe2O3 were identified from XRD, indicating that the observed ferromagnetism may be due to the dopants. The doping of Fe ions does not cause any significant variation in the crystal structure. The pure NiO nanoparticles were weak ferromagnetic in nature, and Fe-doped NiO nanoparticles exhibit room temperature ferromagnetism. The strength of magnetization increased from 0.57 to 0.94 emu/g with an increase of Fe concentration from 3 to 7 at.%, respectively. A high coercive field of 173 Oe was observed for the Ni1−xFexO2 nanoparticles at x= 0.09. The results and the process of development of ferromagnetism at room temperature in the Ni1−xFexO2 nanoparticles were presented and discussed in detail.

Nickel doped indium oxide thin films (In1−xNix)2O3 at x = 0.00, 0.03, 0.05 and 0.07 were deposited onto glass substrates by electron beam evaporation technique. The deposited thin films were subjected to annealing in air at 250 °C, 350 °C and 450 °C for 2 h using high temperature furnace. A set of films were vacuum annealed at 450 °C to study the role of oxygen on magnetic properties of the (In1−xNix)2O3 thin films. The thin films were subjected to different characterization techniques to study their structural, chemical, surface, optical and magnetic properties. All the synthesized air annealed and vacuum annealed films exhibit body centered cubic structure without any secondary phases. No significant change in the diffraction peak position, either to lower or higher diffraction angles has been observed. The band gap of the films decreased from 3.73 eV to 3.63 eV with increase of annealing temperature from 250 °C to 450 °C, in the presence of air. From a slight decrease in strength of magnetization to a complete disappearance of hysteresis loop has been observed in pure In2O3 thin films with increasing the annealing temperature from 250 °C to 450 °C, in the presence of air. The (In1−xNix)2O3 thin films annealed under vacuum follow a trend of enhancement in the strength of magnetization to increase in temperature from 250 °C to 450 °C. The hysteresis loop does not disappear at 450 °C in (In1−xNix)2O3 thin films, as observed in the case of pure In2O3 thin films.

High purity Iron oxide (α-Fe2O3) powder was grinded for 16 hours using mechanical milling and studied for its physical properties. The micro structures, crystallite size of the nanoparticles were examined using X-ray diffractrometer (XRD). From this it was found that the particles were in rhombohedral structure with average crystallite size of 39 nm. The optical absorbance and reflectance spectra were recorded using UV–Vis-NIR spectrophotometer in the wavelength range of 200 – 2500 nm. From this it was found that the optical band gap of the nanoparticles as 2.08 eV. The magnetic measurements were carried out using vibrating sample magnetometer at 100 K. From the magnetic studies it was found that the magnetic moment of the nanoparticles increased with increase of applied field and saturation was not observed even at high applied magnetic fields.

Chromium-doped tin oxide nano powders (Sn1-xCrxO2, x = 0.00, 0.03, 0.05 and 0.07) were prepared using simple low cost solid state reaction and followed by vacuum annealing at 900 oC and studied the effects of Cr dopant concentration on structural and magnetic properties. The X-ray diffraction (XRD) studies confirmed that all the diffracted peaks were polycrystalline rutile structure of SnO2 phase. FT-IR analysis gave additional supports of formation of O-Sn-O and Cr-Sn-O the system. Magnetic studies revealed that all the powder samples were ferromagnetic at room temperature. Further the saturation magnetization increased with increase of doping concentration.

Iron oxide (Fe2O3), Manganese oxide (MnO2) and Nickel oxide (NiO) nanopowder samples were prepared using mechanical grinding method and subjected to their structural and magnetic properties. Microstructures, crystallite size of the nanoparticles were studied using X-ray diffractometer (XRD). Magnetic measurements were carried out using vibrating sample magnetometer low temperature (100 K). From the magnetic studies, it was found that the magnetic moment increased with increase of applied field in iron oxide and saturation was not observed even at high magnetic fields. The magnetic studies of NiO revealed ferromagnetic behaviour whereas MnO2 undergoes paramagnetic behaviour.

The optimized concentration of oxygen vacant sites along with surface spin alignment in the nanoparticles can lead to the origin of ferromagnetism in them. So in this work, indium-tin-oxide was doped with iron by varying the concentration of Fe. Thus, cubic structured iron doped indium tin oxide nanoparticles were obtained with increasing crystallinity. Even the relative intensity ratio was found to be below 29% suggesting the optimization of amount of oxygen vacancies. Room temperature ferromagnetism was observed in case of Fe: ITO nanoparticles

An effort was made to develop semiconductor oxide-based room temperature dilute magnetic semiconductor (DMS) thin films based on wide band gap and transparent host lattice with transition metal substitution. The Sn $_{\mathrm {1}-x}$ Ni $_{x}\textit {O}_{\mathrm {2}}$ ( $x\,= \mathrm {0.00, 0.03, 0.05, 0.07, 0.10, and \,0.15}$ ) thin film samples were prepared on glass substrates by flash evaporation technique. All the samples were shown single phase crystalline rutile structure of host SnO $_{\mathrm {2}}$ with dominant (110) orientation. The Ni substitution promotes reduction of average crystallite size in SnO $_{\mathrm {2}}$ as evidenced from the reduction of crystallite size from 40 (SnO $_{\mathrm {2}}$ ) to 20 nm (Sn $_{\mathrm {0.85}}$ Ni $_{\mathrm {0.15}}\textit {O}_{\mathrm {2}}$ ). In the energy dispersive spectra as well as X-ray photoelectron spectra of all the samples show, the chemical compositions are close to stoichiometric with noticeable oxygen deficiency. The crystalline films were formed by coalescence of oval-shaped polycrystalline particles of 100 nm size as evidenced from the electron micrographs. The energy band gap of DMS films decreases from 4 (SnO $_{\mathrm {2}}$ ) to 3.8 eV (x $=$ 0.05) with increase of Ni content. The magnetic hysteresis loops of all the samples at room temperature show soft ferromagnetic nature except for SnO $_{\mathrm {2}}$ film. The SnO $_{\mathrm {2}}$ films show diamagnetic nature and it converts into ferromagnetic upon substitution of 3 % Sn $^{\mathrm {4+}}$ by Ni $^{\mathrm {2+}}$ . The robust intrinsic ferromagnetism (saturation magnetization, 21 emu/cm $^{\mathrm {3}}$ ). Further increase of Ni content weakens ferromagnetic strength due to Ni-O antiferromagnetic interactions among the nearest neighbour Ni ions via O $^{\mathrm {2-}}$ ions. The observed magnetic properties were best described by bound magnetic polarons model.

Iron doped tin oxide thin films (Sn1−xFexO2) at x = 0.00, 0.03, 0.05, 0.07,0.10 and 0.15 were prepared onto Corning 7059 substrates using flash evaporation technique and studied the effect of iron (Fe) doping concentration on structural, optical and magnetic properties of the prepared thin films. From the X-ray diffraction patterns, it was found that the Sn1−xFexO2 thin films were polycrystalline with tetragonal structure. The crystallite sizes of the films were calculated using Scherrer’s relation and found that it was about 25 nm. The chemical composition and oxidation states of the elements were found using energy dispersive analysis of X-rays and X-ray photoelectron spectroscopy. From this it was confirmed that the Fe was substituted Sn sites and is in Fe+3states. The optical band gap of the films decreased from 3.98 to 3.76 eV with increase of Fe doping concentration. The pure SnO2 thin films exhibited diamagnetism whereas Sn1−xFexO2 thin films exhibited ferromagnetism at room temperature. A magnetic (Ms), coercivity (Hci) and retentivity (Mr) were found to be 13.062 emu/cm3, 114.98 G, 7.487 × 10−6 emu/cm3, respectively Sn1−xFexO2 thin films at x = 0.07.

The (In1−xCrx)2O3 powders as well as thin films of x = 0.03, 0.05 and 0.07 were synthesized using a solid state reaction and an electron beam evaporation technique (on glass substrate), respectively. The influence of Cr doping concentration on structural, optical and magnetic properties of the In2O3 samples was systematically studied. The X-ray diffraction results confirmed that all the Cr doped In2O3 samples exist cubic structure of In2O3 without any secondary phases presence. The chemical composition analyses showed that all the Cr doped In2O3 compounds were nearly stoichiometric. The X-ray photoelectron spectroscopy analysis of the Cr doped In2O3 thin films showed an increase of oxygen vacancies with Cr concentration and the existence of Cr as Cr3+ state in the host In2O3 lattice. A small blue shift in the optical band gap was observed in the powder compounds, when the dopant concentration increased from x = 0.03 to x = 0.07. In thin films, the band gap found to increase from 3.63 to 3.74 eV, with an increase of Cr concentration. The magnetic measurements show that the undoped In2O3 bulk powder sample has the diamagnetic property at room temperature. And a trace of paramagnetism was observed in Cr doped In2O3 powders. However (In1−xCrx)2O3 thin films (x = 0.00, 0.03, 0.05 and 0.07) samples shows soft ferromagnetism. The observed ferromagnetism in thin films are attributed to oxygen vacancies created during film prepared in vacuum conditions. The ferromagnetic exchange interactions are established between metal cations via free electrons trapped in oxygen vacancies (F-centers).

Magnetic, magnetoresistivity and superconductivity studies were carried out on (In 1 − x Fe x ) 2 O 3 ( x = 0.00, 0.03, 0.05 and 0.07) thin films (2D structures) grown on glass substrate by electron beam evaporation technique at 350 °C. The films have an average size of 120 nm particles. All the samples shown soft ferromagnetic hysteresis loops at room temperature and saturation magnetization increased with iron dopant concentration. Observed magnetization could be best interpreted by F-center mediated magnetic exchange interaction in the samples. Temperature dependent resistivity of the sample ( x = 0.00 and 0.07) showed metallic behavior down to very low temperatures and superconductivity at 2 K for undoped In 2 O 3 whereas the In 1.86 Fe 0.14 O 3 sample shows superconductivity below 2 K in the absence of magnetic fields. The reduction in transition temperature was attributed to increase electrical disorder with iron doping. Both samples showed positive magnetoresistivity (MR) in superconducting state due to increase of resistivity resulting from breaking of superconducting Cooper pairs upon application of magnetic field. In addition, both the samples show feeble negative MR in normal electrical state. The observed MR in normal state is not due to spin polarized tunneling instead it is due to suppression of scattering of charge carrier by single occupied localized states.

Local-gate multilayer MoS2 phototransistors exhibit a photoresponsivity of up to 342.6 A W(-1) , which is higher by 3 orders of magnitude than that of global-gate multilayer MoS2 phototransistors. These simulations indicate that the gate underlap is critical for the enhancement of the photoresponsivity. These results suggest that high photoresponsivity can be achieved in indirect-bandgap multilayer MoS2 phototransistors by optimizing the optoelectronic design.

The In 2−xCu xO 3 (x = 0, 0.03, 0.05, and 0.07) thin films were deposited on a glass substrate under vacuum by electron beam evaporation technique. The influence of Cu concentration on the structural, chemical, and magnetic properties of In 2−xCu xO 3 was studied. The Cu concentration did not influence the host crystal structure; however, it does increase the oxygen vacancies and ferromagnetic strength in the In 2−xCu xO 3 system with Cu concentration. X-ray photoelectron spectroscopy revealed the dopant Cu has a Cu(II) state in the In 2O 3 host. The observed ferromagnetism in In 2−xCu xO 3 is similar to the higher oxidation semiconductors (Sn 1−xCu xO 2 and Ti 1−xCu xO 2) and is contrary to the lower oxidation semiconductor (Zn 1−xCu xO). Such a ferromagnetism is attributed to the intrinsic nature of the sample rather than any secondary magnetic phases existing in the films. The observed ferromagnetism in In 2−xCu xO 3 was attributed to the ferromagnetic exchange interaction between Cu 2+ ions via single free electron trapped oxygen vacancy. Increase in oxygen vacancies with Cu concentration leads to increase in such oxygen vacancy-mediated ferromagnetic pairs, resulting in increase in ferromagnetic strength with Cu concentration. However, if we increase Cu concentration above a critical level, Cu–O–Cu interaction leads to an antiferromagnetic nature.

Highlights: • Synthesis of Fe doped In{sub 2}O{sub 3} powders using a solid state reaction. • Characterization of the samples using XRD, UV–vis-NIR, FT-IR, and VSM. • All Fe doped In{sub 2}O{sub 3} powders exhibited the cubic structure of In{sub 2}O{sub 3}. • All the Fe doped In{sub 2}O{sub 3} samples exhibited room temperature ferromagnetism. - Abstract: Iron doped indium oxide dilute magnetic semiconductor (In{sub 1−x}Fe{sub x}){sub 2}O{sub 3} (x = 0.00, 0.03, 0.05, and 0.07) powders were synthesized by standard solid state reaction method followed by vacuum annealing. The effect of Fe concentration on structural, optical, and magnetic properties of the (In{sub 1−x}Fe{sub x}){sub 2}O{sub 3} powders have been systematically studied. X-ray diffraction patterns confirmed the polycrystalline cubic structure of all the samples. An optical band gap increases from 3.12 eV to 3.16 eV while Fe concentration varying from 0.03 to 0.07. Magnetic studies reveal that virgin/undoped In{sub 2}O{sub 3} is diamagnetic. However, all the Fe-doped In{sub 2}O{sub 3} samples are ferromagnetic. The saturation magnetization (M{sub s}) of ferromagnetic (In{sub 1−x}Fe{sub x}){sub 2}O{sub 3} (x = 0.03, 0.05, and 0.07) samples increases from 11.56 memu/g to 148.64 memu/g with x = 0.03–0.07. The observed ferromagnetism in these samples wasmore » attributed to magnetic nature of the dopant (Fe) as well as defects created in the samples during vacuum annealing.« less

Glasses in the (30 − x ) (NaPO 3 ) 6 + 30PbO + 40B 2 O 3 + x Gd 2 O 3 system with x = 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mol% have been prepared by the melt quenching method. The electron paramagnetic resonance (EPR) and FT-IR spectra of these glasses have been studied. The EPR spectra of sodium–lead borophosphate glasses at room temperature exhibit three prominent features with effective g -values of ≈5.99, 2.85 and 1.98 and weaker features at g ≈ 3.60 and 4.77. The EPR spectra of these glasses containing 1.0 mol% Gd 3+ ions have been studied at different temperatures (93–303 K). The spin concentration ( N ) participating in resonance for g ≈ 5.99 resonance signal has been calculated as a function of Gd content and temperature. It is observed that N increases with Gd content. A linear relationship is established between log N and 1/ T and the activation energy is calculated from the graph. The paramagnetic susceptibility ( χ ) is calculated from the EPR data at various temperatures and the Curie constant ( C ) and paramagnetic Curie temperature ( θ p ) have been evaluated from the 1/ χ versus T graph. The emission and excitation spectra are measured and it is found that the Gd 3+ ions doped glasses exhibit good UV-excited luminescence. The IR spectra of the borophosphate glasses reveal prominent IR absorption spectrum which is characterized by well-defined bands in the far- and mid-IR region. The IR results depict the presence of BO 3 , BO 4 , and PO 4 structural units. The theoretical values of optical basicity ( Λ th ) of the glasses have also been evaluated.

Polymer films of poly(vinylalcohol) (PVA) complexed with poly(ethyleneglycol) (PEG) with different dopant concentrations of Cu 2+ ions are prepared by solution casting technique. Improvement in the crystallinity of the samples is observed with the X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. Thermal transition and thermal degradation of the films with respect to copper concentration were studied by Differential Scanning Calorimetry (DSC) and thermo gravimetric analysis (TGA). The change in glass transition temperature ( Tg ) as a function of copper concentrations ( x = 1–5 mol%) has been attributed to branching and steric effects in PVA + PEG complexes. In TGA curves low thermal degradation in the samples has been observed with high copper content. The EPR spectra of all the polymer samples exhibit resonance signals characteristic of Cu 2+ ions. The spin-Hamiltonian parameter, indicate that the ground state of Cu 2+ ions is d x 2 - y 2 and the site symmetry around Cu 2+ ions is tetragonally distorted octahedral site. The spin concentration ( N ) participating in the resonance is measured as a function of temperature and it obeys Boltzmans law. The paramagnetic susceptibility ( χ ) is calculated from the EPR data at various temperatures and the Curie constant ( C ) is evaluated. The optical absorption spectrum exhibits a broad band at 784 nm which is assigned to the 2 B 1 g → 2 B 2 g transition.

Glasses with composition 10SrO:(30−x)ZnO:60B2O3:xMnO, 0≤x≤0.9 (all compositions in wt%) have been prepared and investigated by X-ray diffraction, EPR, Optical absorption and FT-IR spectroscopic techniques. The XRD pattern of all the glasses confirmed the formation of an amorphous structure. The EPR spectra of all glass samples exhibit resonance signals at g≈2.0 with a sextet of hyperfine lines. The spin concentration (N) and temperature dependence of EPR signals were studied for Mn2+ ions in strontium zinc borate glass samples. The zero-field splitting parameter D has been evaluated from the intensities of the allowed hyperfine lines. The paramagnetic susceptibility (χ) was calculated from EPR data at different temperatures and the Curie temperature (θp) was calculated from the 1/χ verses T graph. The optical absorption spectra exhibit a single broad band near 470 nm and this has been attributed to the spin-allowed 5Eg→5T2g transition of Mn3+ ions in octahedral symmetry. The theoretical optical basicity (Λth) of these glasses have also been evaluated. The FTIR studies show BO3 and BO4 structural units in strontium zinc borate glasses.

Electron paramagnetic resonance (EPR) and optical absorption spectral investigations have been carried out on Fe 3+ ions doped in sodium–lead borophosphate glasses. The EPR spectra exhibit resonance signals with effective g values at g ≈ 1.99, g ≈ 4.30 and g ≈ 8.40. The resonance signal at g ≈ 8.40 has been attributed to Fe 3+ ions in axial symmetry sites whereas the resonance at g ≈ 4.30 is due to rhombic symmetry site. The g ≈ 1.99 resonance is due to Fe 3+ ions coupled by exchange interaction in a distorted octahedral environment. The EPR spectra at different temperatures (93–303 K) have also been studied. The intensity of the resonance signals decreases with increase in temperature whereas linewidth is found to be independent of temperature. The paramagnetic susceptibility ( χ ) was calculated from the EPR data at various temperatures and the Curie constant ( C ) and paramagnetic Curie temperature ( θ p ) have been evaluated from the 1/ χ versus T graph. The optical absorption spectrum exhibits three bands characteristic of Fe 3+ ions in octahedral symmetry. The crystal field parameter (Dq) and the Racah interelectronic repulsion parameters ( B and C ) have also been evaluated and discussed. The optical band gap energy ( E opt ) and Urbach energy (Δ E ) are calculated from their ultra-violet absorption edges. Photoluminescence spectra show prominent blue emission peaks under near band edge UV excitation. The FT-IR spectrum shows that the glass system contains BO 3 , BO 4 and PO 4 structural units.

Electron paramagnetic resonance (EPR), optical absorption, and infrared spectral studies have been carried out on Mn2+ ions doped in poly(vinyl alcohol) (PVA) complexed with polyethylene glycol (PEG) films prepared by solution cast technique. The EPR spectra of 0.25 mol% Mn2+ ions doped polymer complex (PVA+PEG) at room temperature exhibit sextet hyperfine structure (hfs), centered at g ≈ 1.99. The spin–Hamiltonian parameter values indicate that the ground state of Mn2+ ion is d5 and the site symmetry around Mn2+ ions in tetragonally distorted octahedral site. The spin concentration participating in the resonance is measured as a function of temperature and it is observed that it obeys Boltzmann’s law. The paramagnetic susceptibility (χ) is calculated from the EPR data at various temperatures (93–333 K) and it obeys the Curie–Weiss law. The optical absorption spectra exhibits two bands which are assigned to 6A1g (S)→4A1g (G) or 4Eg (G) and 6A1g (S)→4T2g (G) transitions. The infrared spectrum exhibits few bands due to the presence of O–H, C–H, and C=C groups.

This letter presents a highly sensitive near-infrared (IR) $a$ -Si:H phototransistor for touch sensor applications. The narrow bandgap of $a$ -Si exhibits a wideband spectrum response from IR to ultraviolet region, where the IR bandpass filter layers allow the $a$ -Si:H phototransistor to respond to the selective IR light uninterrupted by visible light. The time-resolved photoresponse and transfer $I$ – $V$ characteristics for the near-IR $a$ -Si:H phototransistor as a function of power at 785-nm illumination allow the observation of fast photoresponse ( $\tau \sim 0.1$ ps), high external quantum efficiency (7.52), and high photoresponse. A prototype unit pixel structure for touch sensors composed of amorphous Si-based switching/amplification/near-IR phototransistors and a storage capacitor, is proposed and designed. The overall results suggest that the near-IR $a$ -Si:H phototransistor offers unique possibilities for user-friendly, low-cost, and large-area touch sensors, especially aimed at consumer applications and other areas of optoelectronics.

10 wt% SrO:30 wt% ZnO:60 wt% B 2 O 3 incorporated with different vanadyl concentrations were studied by means of electron paramagnetic resonance (EPR) and optical absorption techniques. The spin-Hamiltonian parameters ( g and A ), bonding parameters ( α 2 and β 2 ∗ 2 ) and Fermi contact interaction parameter K have been calculated. The values of spin-Hamiltonian parameters indicate that the VO 2+ ions in strontium zinc borate glasses were present in octahedral sites with tetragonal compression. The spin concentration ( N ) participating in resonance was calculated as a function of temperature (93–273 K) for strontium zinc borate glass sample containing 0.9 wt% of VO 2+ ions and the activation energy ( E a ) was calculated. From the EPR data, the paramagnetic susceptibility ( χ ) was calculated at various temperatures and the Curie constant ( C ) was evaluated from the 1/ χ – T graph. The optical absorption spectra of VO 2+ ions in these glasses show two bands corresponding to the transitions 2 B 2g → 2 B 1g and 2 B 2g → 2 E g in the order of decreasing energy respectively. The optical band gap energies ( E opt ) and Urbach energy (Δ E ) have been determined from their ultraviolet edges. The theoretical values of optical basicity ( Λ th ) of these glasses have also been evaluated.

Trivalent dysprosium (Dy3+) activated magnesium alluminate phosphors were synthesized by high temperature solid state reaction method. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FT-IR), photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting phosphors. The results show that the obtained MgAl2O4:Dy3+ phosphors have good crystallinity, spherical morphology with sizes ranged from 120 to 140 nm and strong blue emission under an excitation of 258 nm. The emission spectrum of this phosphor consists of two emission bands: blue band and yellow band, and the emission intensity of the former is stronger than that of the later. Luminescence quenching is explained and the corresponding luminescence mechanisms have been proposed.

This paper reports the results of MgAl2O4:Eu3+ red emitting phosphor which has been characterized by X-ray diffraction, FESEM, FT-IR and photoluminescence spectra. The ultraviolet excitation at 393 nm has been chosen because it has got maximum excitation intensity. These phosphors show different emissions of Eu3+ corresponding to 5D0 → 7FJ=0,1,2,3,4 transitions which lie in the wavelength range from 550 to 700 nm. One particular transition 5D0 → 7F2 which is centered at 615 nm has been known as a hypersensitive emission which obeys the selection rule of (ΔJ = 2) resulting in a strong and intense red emission. The lifetime, luminescence quenching has been discussed and the mechanism involved in the generation of red emission has also been explained.

A natural sample of clinochlore from the Longitudinal Valley area of northeastern Taiwan has been characterized by using the powder X-ray diffraction (XRD), differential thermal analysis and electron paramagnetic resonance (EPR) spectroscopic techniques. The lattice parameters of the monoclinic (IIb) clinochlore with the composition (Mg2.988 Al1.196 Fe1.6845 Mn0.026)5.8945 (Si2.559 Al1.441)4 O10 (OH)8 have been calculated from the powder XRD data and are found to be a = 5.347 A, b = 9.223 A, c = 14.250 A, β = 97.2° and Z = 2. The thermal behaviour of the sample showed the typical behaviour of clinochlore with a hydroxyl content of 12.5 wt%. The EPR spectrum at room temperature exhibits two resonance signals centred at g ≈ 2.0 and g ≈ 8.0. The signal at g ≈ 2.0 shows a six-line hyperfine structure which is a characteristic of Mn2+ ions in octahedral symmetry. The resonance signal at g ≈ 8.0 is a characteristic of Fe3+ ions. The EPR spectra have also been recorded at different temperatures (123–295 K). The population of spin levels (N) has been calculated for g ≈ 2.0 and g ≈ 8.0 resonance signals. It is observed that N increases with decreasing temperature. From EPR spectra, the spin-Hamiltonian parameters have been evaluated. The zero-field splitting parameter (D) is found to be temperature dependent. The peak-to-peak width of the g ≈ 8.0 resonance signal is found to increase with decrease in temperature.

This paper reports the emission analysis of green -emitting Tb 3+ -doped MgAl 2 O 4 phosphors. Uniformity of the phase of the Tb 3+ -doped MgAl 2 O 4 phosphor has been checked by X-ray diffraction (XRD) technique and show common bands existing in the results of Fourier transform infrared (FT-IR). This phosphor exhibits weak blue, orange emissions and a strong emission at λ exci =350 nm. The blue and green–orange emissions are ascribed to 5 D 3 → 7 F J and 5 D 4 → 7 F J (where J =3–6) transitions of Tb 3+ ions, respectively. These phosphors have shown a strong, more prominent green emission from 5 D 4 → 7 F 5 at 543 nm. The results have indicated that MgAl 2 O 4 :Tb 3+ could be a potential candidate as agreen-emitting powder phosphor.

ITO (In0.95Sn0.05)2O3 and Fe doped ITO (In0.90Sn0.05Fe0.05)2O3 nanoparticles were synthesized using standard solid state reaction and characterized by XRD, Raman and FT-IR studies, UV-Vis-NIR spectrophotometer and vibrating sample magnetometer for structural, optical and magnetic properties.The XRD patterns revealed the formation of nanocrystalline particles with cubic bixbyte crystal structure. The Raman spectra show that the nanoparticles are free of secondary crystalline phase.From FT-IR studies it was found that the bonds observed were due to In2O3 and no new peaks were found in FT-IR spectra. This clearly indicatesthat Fe ions are incorporate into the host In2O3 structure and does not alter the crystal structure of In2O3 host material. The undoped ITO nanoparticles exhibited room temperature ferromagnetism with clear hysteresis curve having coercive field of 683 G whereas the same ITO nanoparticles exhibited coercive field of 150 G at 100 K.

Electron paramagnetic resonance (EPR), optical, infrared and Raman spectral studies have been carried out on vanadyl ions doped in polyvinylalcohol (PVA) films. The spin-Hamiltonian parameters (g and A) and the molecular orbital coefficients ($\beta_2^{*2} $ and k) have been evaluated. The values of spin-Hamiltonian parameters confirm that the vanadyl ions are present in PVA films as $VO^{2+}$ molecular ions in an octahedral site with a tetragonal compression $(C_{4V})$. The temperature variation EPR studies reveal that the variation of number of spins with temperature is in accordance with Boltzmann law. It is interesting to observe that the variation of susceptibility with temperature obeys Curie–Weiss law. The FT-IR and FT-Raman spectrum exhibits few bands, which are attributed to O–H, C–H, CQC and C–O groups of stretching and bending vibrations. The optical absorption spectrum exhibits two bands, which are assigned to $^2B_{2g}\rightarrow ^2B_{1g}$ and $^2B_{2g}\rightarrow ^2E_g$ transitions in the decreasing order of energy.

Hexagonal molybdenum diselenide (MoSe2) multilayers were grown by chemical vapor deposition (CVD). A relatively high pressure (>760 Torr) was used during the CVD growth to achieve multilayers by creating multiple nuclei based on the two-dimensional crystal growth model. Our CVD-grown multilayer MoSe2 thin-film transistors (TFTs) show p-type-dominant ambipolar behaviors, which are attributed to the formation of Se vacancies generated at the decomposition temperature (650 °C) after the CVD growth for 10 min. Our MoSe2 TFT with a reasonably high field-effect mobility (10 cm2/V · s) exhibits a high photoresponsivity (93.7 A/W) and a fast photoresponse time (τrise ~ 0.4 s) under the illumination of light, which demonstrates the practical feasibility of multilayer MoSe2 TFTs for photodetector applications.

Large-area and highly crystalline CVD-grown multilayer MoSe2 films exhibit a well-defined crystal structure (2H phase) and large grains reaching several hundred micrometers. Multilayer MoSe2 transistors exhibit high mobility up to 121 cm(2) V(-1) s(-1) and excellent mechanical stability. These results suggest that high mobility materials will be indispensable for various future applications such as high-resolution displays and human-centric soft electronics.

Thin-film transistors (TFTs) based on multilayer molybdenum diselenide (MoSe2 ) synthesized by modified atmospheric pressure chemical vapor deposition (APCVD) exhibit outstanding photoresponsivity (103.1 A W-1 ), while it is generally believed that optical response of multilayer transition metal dichalcogenides (TMDs) is significantly limited due to their indirect bandgap and inefficient photoexcitation process. Here, the fundamental origin of such a high photoresponsivity in the synthesized multilayer MoSe2 TFTs is sought. A unique structural characteristic of the APCVD-grown MoSe2 is observed, in which interstitial Mo atoms exist between basal planes, unlike usual 2H phase TMDs. Density functional theory calculations and photoinduced transfer characteristics reveal that such interstitial Mo atoms form photoreactive electronic states in the bandgap. Models indicate that huge photoamplification is attributed to trapped holes in subgap states, resulting in a significant photovoltaic effect. In this study, the fundamental origin of high responsivity with synthetic MoSe2 phototransistors is identified, suggesting a novel route to high-performance, multifunctional 2D material devices for future wearable sensor applications.

Layered semiconductors with atomic thicknesses are becoming increasingly important as active elements in high-performance electronic devices owing to their high carrier mobilities, large surface-to-volume ratios, and rapid electrical responses to their surrounding environments. Here, we report the first implementation of a highly sensitive chemical-vapor-deposition-grown multilayer MoSe2 field-effect transistor (FET) in a NO2 gas sensor. This sensor exhibited ultra-high sensitivity (S = ca. 1,907 for NO2 at 300 ppm), real-time response, and rapid on–off switching. The high sensitivity of our MoSe2 gas sensor is attributed to changes in the gap states near the valence band induced by the NO2 gas absorbed in the MoSe2, which leads to a significant increase in hole current in the off-state regime. Device modeling and quantum transport simulations revealed that the variation of gap states with NO2 concentration is the key mechanism in a MoSe2 FET-based NO2 gas sensor. This comprehensive study, which addresses material growth, device fabrication, characterization, and device simulations, not only indicates the utility of MoSe2 FETs for high-performance chemical sensors, but also establishes a fundamental understanding of how surface chemistry influences carrier transport in layered semiconductor devices.

We used high-resolution Kelvin probe force microscopy (KPFM) to investigate the immobilization of a prostate specific antigen (PSA) antibody by measuring the surface potential (SP) on a MoS2 surface over an extensive concentration range (1 pg/ml–100 μg/ml). After PSA antibody immobilization, we demonstrated that the SP on the MoS2 surface characterized by KPFM strongly correlated to the electrical signal of a MoS2 bioFET. This demonstration can not only be used to optimize the immobilization conditions for captured molecules, but can also be applied as a diagnostic tool to complement the electrical detection of a MoS2 FET biosensor.

Various strategies and mechanisms have been suggested for investigating a Schottky contact behavior in molybdenum disulfide (MoS2) thin-film transistor (TFT), which are still in much debate and controversy. As one of promising breakthrough for transparent electronics with a high device performance, we have realized MoS2 TFTs with source/drain electrodes consisting of transparent bi-layers of a conducting oxide over a thin film of low work function metal. Intercalation of a low work function metal layer, such as aluminum, between MoS2 and transparent source/drain electrodes makes it possible to optimize the Schottky contact characteristics, resulting in about 24-fold and 3 orders of magnitude enhancement of the field-effect mobility and on-off current ratio, respectively, as well as transmittance of 87.4 % in the visible wavelength range.

This paper reports the results of MgAl2O4:Eu3+ red emitting phosphor which has been characterized by X-ray diffraction, FESEM, FT-IR and photoluminescence spectra. The ultraviolet excitation at 393 nm has been chosen because it has got maximum excitation intensity. These phosphors show different emissions of Eu3+ corresponding to 5D0 → 7FJ=0,1,2,3,4 transitions which lie in the wavelength range from 550 to 700 nm. One particular transition 5D0 → 7F2 which is centered at 615 nm has been known as a hypersensitive emission which obeys the selection rule of (ΔJ = 2) resulting in a strong and intense red emission. The lifetime, luminescence quenching has been discussed and the mechanism involved in the generation of red emission has also been explained.

Luminescent phosphors of Tm3+ & Er3+:Ca4GdO(BO3)3 have been prepared by a solid state reaction technique. For these two powder phosphors, XRD. SEM and FTIR have been carried out to understand their structural properties. Emission spectra and lifetimes of the prominent visible emission bands have been measured. For Tm3+:Ca4GdO(BO3)3 phosphor, a blue emission band of (1D2→3F4) at 452 nm with λexci = 356 nm and for Er3+:Ca4GdO(BO3)3 phosphor, an intense green emission band of (4S3/24I15/2) at 561 nm with λexci = 377 nm have been observed. Emission from these phosphors, have been explained in terms of relevant energy level schemes.

Electron paramagnetic resonance (EPR), optical absorption and FT-IR studies have been carried out on chromium ions incorporated in alkaline earth zinc borate glasses. The EPR spectra exhibit two resonance signals with effective g values at g ≈ 1.99 and ≈1.97. The resonance signal at g ≈ 1.99 is attributed to the contribution from both the exchange coupled Cr3+–Cr3+ ion pairs and the isolated Cr3+ ions and the resonance signal at g ≈ 1.97 is due to Cr5+ ions. The paramagnetic susceptibility (χ) was calculated from the EPR data at various (123–303 K) temperatures and the Curie temperature (θp) was calculated from the 1/χ–T graph. The optical absorption spectra exhibit three bands at ~360 nm, ~440 nm and a broad band at ~615 nm characteristic of Cr3+ ions in an octahedral symmetry. From the observed band positions, the crystal-field splitting parameter Dq and the Racah parameters (B and C) have been evaluated. From the ultraviolet edges, the optical band gap energies (Eopt) and Urbach energy (ΔE) are calculated. The theoretical optical basicity (Λth) of these glasses has also been evaluated. Chromium ions doped alkaline earth zinc borate glasses show BO3 and BO4 structural units in the FT-IR studies.