Searching of electronic system with functionality is the epitome of the material research and in this context; nanomaterials CuInSe2 and TiO2 are the promising stars whose possible applications in electronic devices are just endless. However, the fabrication of junction based device using these two materials is most tantalizing prospect in material science is still at its rudimentary stage. In this letter, we report our recognition of current rectification behavior of CuInSe2/TiO2 heterojunction, identical to the I-V characteristics of p-n junction diode and the impact of white light on it. The HOMO-LUMO band positions of hydrothermally derived CuInSe2 and TiO2 nanomaterials indicate that in thermal equilibrium a built-in-potential must arise across the junction. The current-rectification ratio of the configuration Al/CuInSe2/TiO2/ITO is improved from 560 to 627 at voltage +/- 2 V on white light illumination and this kind of behavior is certainly offering us an unprecedented way to realize the CuInSe2/TiO2 hetero-junction as photo-sensing p-n diode. The device performance is improved further by replacing TiO2 with HF treated TiO2.

With the increase in demand of electronic devices in the modern civilization, research in material science is being projected to grow in faster rate. In this facet, coordination polymer (CP) based electronic device is one of the promising candidates to the material researchers. Herein, two new Zn(II) and Cd(II) based one-dimensional (1D) CPs, denoted as [Zn(4-avp)2(5-nip)] & sdot; (solvent)x (1) and [Cd(4-avp)(5-nip)(CH3OH)] (2) have been synthesized using relatively less explored highly conjugated polycyclic aromatic hydrocarbon (PAH) based monodentate ligand, 4-[2-(9-anthryl)vinyl]pyridine (4-avp) and bidentate linker 5-nitroisophthalic acid (H25-nip). In this instance, the CP 1 creates 1D chain polymer, while CP 2 is made up with 1D ladder polymer. It is interesting to note that both the CPs exhibit semiconducting nature and generate metal-semiconductor (MS) junction Schottky barrier diodes (SBDs). However, Cd-based CP 2 shows higher charge transport as compared to Zn-CP 1, which could be due to stronger pi & sdot;& sdot;& sdot;pi contacts as well as larger size of Cd metal in CP 2. The experimental results are well corroborated with theoretical density of states (DOS) calculations. This work emphasizes the comparison of charge transport and Schottky barrier diode behavior of 1D coordination polymers (CPs) of Zn(II) and Cd(II) based on highly conjugated ligand 4-[2-(9-anthryl)vinyl]pyridine and their applications in the fabrication of semiconducting devices. However, Cd-CP with 1D ribbon chain exhibits better charge transport as compared to 1D linear chain Zn-CP. image

This study outlines the synthesis of copper sulfide (CuS) nanoparticles and their composites with carbon nanotubes (T-CuS) via a solvothermal reaction. X-ray diffraction techniques were employed to characterize the crystal structure of the synthesized materials. Thin films of both CuS and T-CuS were deposited using vacuum coating techniques to construct Schottky devices. Atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM) were utilized to examine the topography and surface morphology of the deposited films, enabling analysis of metal–semiconductor (MS) junction formation. The interfacial characteristics of MS junctions in Al/CuS and T-CuS/ITO designs were investigated using AC impedance spectroscopy (IS) over a frequency range of 40 Hz to 10 MHz. Bias-dependent impedance spectroscopy within a ± 1.0 V range was conducted to determine the equivalent circuit for the MS junction Schottky diodes (SDs). Parameters such as on/off ratio, series resistance, ideality factor, and barrier height of the fabricated diodes were derived from current–voltage (I–V) characteristics. Additionally, characteristics related to charge transport, including photosensitivity and conductivity, were calculated. The results indicate an enhanced performance of carbon nanotube-based Schottky devices, likely attributed to the strong interaction and synergy between CNTs and CuS nanoparticles.

Having ascertained the improvement of band gap and conductivity of the synthesized TiO2 after HF treatment under consideration, it occurred to us that the materials may perform as the better Schottky barrier diode. To verify our presumption, we studied the I-V characteristic of the device fabricated in a sandwich configuration of FTO/sample/Al. The comparative studies show better potentiality of the material in subject to study the qualitative and quantitative measures of the Schottky devices. The work is concluded by examined the various characteristic parameters related with performance of device that is fabricated with HF treated and untreated TiO2.

In this present work, copper (II) sulfide (CuS) nanoparticles (NPs) were synthesized via co-precipitation [CuS(copr)] and solvothermal [CuS(solv)] methods. The structural, optical, and electrical properties of these materials were analyzed and compared. It was observed that the particle size and crystallinity varied depending on the synthesis method employed. Further, two individual metal-semiconductor junction devices based on CuS(co-pr) and (CuS(solv) were fabricated. Then the current vs. voltage (I-V) measurements were performed. The comparative study of the electrical parameters like photo response, rectification ratio, barrier height and ideality factor were performed between the two synthesized CuS NPs based devices. Under no light condition, the rectification ratio for CuS(solv) increased by 28 % more than that of CuS(co-pr). The photo response for CuS (solv) also enhanced by 146 %. For a better understanding of junction and carrier transport properties space charge limited current (SCLC) theory is incorporated. The interfacial resistance of the devices was studied by Nyquist plots obtained from the impedance spectroscopy and were also fitted by equivalent circuit model and explained the mechanism of charge transport through the Schottky interface. The transit time and carrier mobility were improved for CuS(solv) than CuS(co-pr). Thus, the solvothermally synthesized CuS-based device could be assigned as it possesses lesser number of lattice defects, better crystallinity and larger particle size along with its better film properties leading to better performance.

In this study, we report the syntheses of two new coordination polymers (CPs) of Mn(II) and Co(II), [Mn(4-avp)(2)(adc)(H2O)](solvent)(x) (1) and [Co(4-avp)(2)(adc)(CH3OH)(2)] (2), respectively, using relatively less explored linear linker acetylenedicarboxylic acid (H(2)adc) and polyaromatic hydrocarbon (PAH)-based monodentate N-donor ligand 4-[2-(9-anthryl)vinyl]pyridine (4-avp). CP1 creates a two-dimensional (2D) structure in this instance, while CP2 is made up of a 1D chain polymer. It is of interest that CP1 and CP2 exhibit semiconducting behavior and behave as Schottky barrier diodes. However, CP1 exhibits higher conductivity and better Schottky diode formation when compared to CP2, which relates to the charge transportation through space via pipi interactions present in CP1. The experimental results are well validated by theoretical density functional theory (DFT) prediction based on band gap and density-of-state (DOS) calculations. It is noteworthy that fabrication of Mn/Co-based Schottky devices appears to be inadequate in the literature. Thus, this work showcases a new direction for the development of electronic device fabrication.

This letter reports the paramount fluorescence resonance energy transfer mechanism for photo induced charge transfer from P3HT to solvothermally derived CuInSe2. The HOMO (-4.85 eV) and LUMO (-3.38 eV) energy states of CuInSe2 (electrical conductivity = 1.1x 10(-7) Scm(-1)) are determined from cyclic voltammetry and optical study. This HOMO-LUMO position agrees to select P3HT polymer as possible donor of excitons. Steady-state luminescence study of composite (P3HT:CuInSe2) demonstrates possibility of successful charge transfer. Stern-Volmer analysis of absorption and emission spectroscopy ensures static energy quenching phenomena. The Forster distance (R-0) of critical energy transfer is estimated as 3.61 nm. The average distance between donor-acceptor (r(avg) = 4.71 nm) is<8 nm and within the range 0.5R(0) < r < 1.5R(0) (1.81 nm < r < 5.42 nm), which ensures energy transfer from P3HT to CuInSe2.

The critical current density (J(c)) of the body centered cubic (bcc) V0.6Ti0.4 alloy enhances significantly after the addition of rare earth Gd as the latter is immiscible in the matrix [S. Paul, et.al, IEEE Trans. Appl. Supercond. 31 , 5 (2021)]. Very low solubility of Gd in other bcc elements like Ta and Nb is also well known [Jr. KA Gschneidner in Prog Sci Technol Rare Earths, vol. 1, pp. 222-258, 1964 & M Neuberger, et.al in Handbook of Electronic Materials, Vol 4, 1972]. We use these facts to find the effect of adding 1 at.% Gd into the Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys on the superconducting properties e.g., the transition temperature (T-c), J(c) , flux pinning force density (F-p) and the microstructure. In spite of Gd being ferromagnetic, the T-c in these alloys change only marginally (increase by 0.3 K in Ta0.4Ti0.6 and decrease by 0.15 K in Nb0.6Ti0.4 after Gd addition. The J(c) (H = 1 T, T = 4 K) increases by 5 and 1.5 times respectively in the Gd containing Nb0.6Ti0.4 and Ta0.4Ti0.6 alloys, which is quite small as compared to the increase observed in the V0.6Ti0.4 (20 times) system. With Gd addition, the grain size reduces approximately by 65% and 10% respectively in Nb0.6Ti0.4 and Ta0.4Ti0.6. Our analysis indicates that grain boundaries are the major flux line pinning centres in these alloys and the role of Gd in increasing the J(c) depends on the effectiveness of Gd in reducing the grain size. The grain boundary density depends strongly on the distribution of Gd precipitates, which is quite different from each other for two alloy systems under study. Moreover, our results suggest that the addition of Gd to commercial Nb-Ti (Nb0.37Ti0.63) alloy is a new promising route for achieving higher J(c) values.

beta-V1-xTix alloy superconductors are considered to be promising materials for high magnetic field applications. So far, attempts to improve the critical current density (JC) of beta-V1-xTix alloys have shown limited success. Improving JC requires a controlled generation of defects. Similar to the V0.6Ti0.4-RE (RE = Gd, Y) alloys, RE = Ce, Dy and Nd are also immiscible in the V0.6Ti0.4 matrix. The superconducting transition temperature (TC), upper critical field (HC2), irreversibility field (HIrr), and JC increase with the RE addition. However, the tensile strength of V0.6Ti0.4-Gd alloy is observed to be significantly lower than that of V0.6Ti0.4 alloy. Cold-working is found to further improve the TC, HC2, HIrr, and JC of all the V0.6Ti0.4-RE alloys. Successive cold-working (with 50% reduction of thickness each time) and annealing (SCA) at 450 circle C for 5 hrs is found to significantly improve the HIrr, and JC of V0.6Ti0.4-RE (RE = Gd, Ce) alloys. The tensile strength is also found to increase to about 60-70% of the V0.6Ti0.4 alloy after the third annealing. It is observed that alpha ' and omega phases form at the defect sites at various stages of cold-working and annealing. JC(H = 0) and HIrr are about 840 Amm-2 and 7 T respectively for the ascast V0.6Ti0.4-RE alloys. Cold-working on the V0.6Ti0.4-RE alloys further improves the JC(H = 0) and HIrr to about 1250 Amm- 2 and 8.45 T respectively. SCA increases the JC(H = 0) and HIrr to about 4000 Amm- 2 (or more) and 9 T respectively, and the JC(7 T) to about 500 Amm- 2 in V0.6Ti0.4-RE alloy at 4 K. We present a detailed description of the defect structure in these alloys and its role in pinning the magnetic flux lines, thereby improving the overall JC.

We show here that yttrium is immiscible and precipitates with various sizes in the body centered cubic V0.6Ti0.4 alloy superconductor. The number and size of the precipitates are found to depend on the amount of yttrium added. Precipitates with various sizes up to 30 μm are found in the V0.6Ti0.4 alloy containing 5 at. % yttrium. The large amount of line disorders generated by the addition of yttrium in this alloy is found to be effective in pinning the magnetic flux lines. While the superconducting transition temperature increases with the increasing amount of yttrium in the V0.6Ti0.4 alloy, the critical current density is maximum for the alloy containing 2 at. % yttrium, where it is more than 7.5 times the parent alloy in fields higher than 1 T. We found that the effectiveness of each type of defect in pinning the flux lines is dependent on the temperature and the applied magnetic filed.

We report systematic field-cooled (FC) magnetisation of superconducting (V0.6Ti0.4)-Y alloys in the presence of applied magnetic fields up to 7 T. A paramagnetic response is clearly observed just below the superconducting transition temperature (T-c) in low fields ( <= 0.2 T). The lower T-c of the Y-rich precipitates, when compared to the bulk, is the origin of flux compression that leads to this paramagnetic response in low fields. It is also observed that the magnetisation obtained during the FC cooling cycle is lower than that of FC warming for the (V0.6Ti0.4)-Y alloys in fields higher than 0.02 T. Moreover, paramagnetic relaxation of the FC moment is also observed in this system. We infer that these features of the Y-containing alloys are related to the high-field paramagnetic Meissner effect (HFPME). Our analysis shows that the large difference in pinning strength of the different pinning centres, generated due to Y addition in the V0.6Ti0.4 alloys, is responsible for the HFPME. We find additional evidence of our claim in the form of an extension of the range of the temperature and magnetic fields over which the HFPME is observed, when the samples are subjected to cold work. The observation of the HFPME up to 7 T has not been reported until now in any low T-c superconductor, and only a very few high T-c superconductors show the HFPME upto such high fields.

The V-Ti alloys are promising materials as alternate to the commercial Nb-based superconductors for high current-high magnetic field applications. However, the critical current density (Jc) of these alloys are somewhat low due to their low grain-boundary density. We show here that grain refinement of the V-Ti alloys and enhancement of the Jc can be achieved by the addition of Gd into the system, which precipitates as clusters along the grain boundaries. Both the Jc and the pinning force density (FP) increase with the increasing Gd content up to 1 at. % Gd, where they are more than 20 times higher than those of the parent V 0.60 Ti 0.40 alloy. Introduction of Gd into the system also leads to ferromagnetic (FM) correlations, and the alloys containing more than 0.5 at. % Gd exhibit spontaneous magnetization. In spite of the FM correlations, the superconducting transition temperature increases slightly with Gd-addition.

β-Ag2Se is a promising material for room temperature thermoelectric applications and magneto-resistive sensors. However, no attention was paid earlier to the hysteresis in the temperature dependence of resistivity (ρ(T )). Here, we show that a broad hysteresis above 35 K is observed not only in ρ(T ), but also in other electronic properties such as Hall coefficient (RH(T )), Seebeck coefficient, thermal conductivity and ultraviolet photoelectron spectra (UPS). We also show that the hysteresis is not associated with a structural transition. The ρ(T ) and RH(T ) show that β-Ag2Se is semiconducting above 300 K, but metallicity is retained below 300 K. While electronic states are absent in the energy range from the Fermi level (EF ) to 0.4 eV below the EF at 300 K, a distinct Fermi edge is observed in the UPS at 15 K suggesting that the β-Ag2Se undergoes an electronic topological transition from a high temperature semiconducting state to a low temperature metallic state. Our study reveals that a constant and moderately high thermoelectric figure of merit (ZT ) in the range 300-395 K is observed due to the broad semiconductor to metal transition in β-Ag2Se.

We present here, the effect of microstructure on the magnetic, electrical and thermal properties of (V$_{0.60}$Ti$_{0.40}$)-Gd alloys. The gadolinium is found to be immiscible and precipitates with a size $<$1.2~$\mu$m in the (V$_{0.60}$Ti$_{0.40}$)-Gd alloys. These precipitates enhance the grain boundary density. The (V$_{0.60}$Ti$_{0.40}$)-Gd alloys become ferromagnetic below $T_{mc}$ = 295~K with an increase in the superconducting transition temperature ($T_{sc}$). Though the disorder increases with increasing Gd content, the electronic thermal conductivity ($\kappa_{e} (H = 0)$) reduces by at most 15\% which is in contrast with the 80\% decrease of the phononic thermal conductivity ($\kappa_{l} (H = 0)$). Our analysis suggests that the magnetic moments of Gd precipitates polarize the conduction electrons along and around the grain boundaries leading to increase in the mean free path of the electrons. The partial suppression of spin fluctuations in the (V$_{0.60}$Ti$_{0.40}$)-Gd alloy by the conduction electron polarization enhances the $T_{sc}$.

We report here, the systematic field-cooled (FC) magnetisation of superconducting (V_0.6Ti_0.4)-Y alloys in presence of applied magnetic fields upto 7 T. Paramagnetic response is clearly observed just below the superconducting transition temperature (T_c) in low fields (≤0.2 T). The lower T_c of the Y-rich precipitates as compared to the bulk, is the origin of flux compression and this leads to paramagnetic response. It is also observed that the magnetisation obtained during field cooled (FC) cooling cycle is lower than that of FC warming, for all the alloys in the field range 0.02-7 T. In addition, paramagnetic relaxation of FC moment is observed. We identify that these features of Y containing alloys are related to the high field paramagnetic Meissner effect (HFPME). Our analysis shows that the large difference in pinning strength of the different pinning centres generated due to Y addition to V_0.6Ti_0.4 alloy, is responsible for the observed effect. We provide further evidence to our claim in the form of extension of range in temperature and magnetic fields over which HFPME is observed when samples are subjected to cold work.

β-Ag2Se is a promising material for room temperature thermoelectric applications and magneto-resistive sensors. However, no attention was paid earlier to the hysteresis in the temperature dependence of resistivity [ρ(T)]. Here, we show that a broad hysteresis above 35 K is observed not only in ρ(T), but also in other electronic properties such as Hall coefficient [RH(T)], Seebeck coefficient, thermal conductivity, and ultraviolet photoelectron spectra (UPS). We also show that the hysteresis is not associated with a structural transition. The ρ(T) and RH(T) show that β-Ag2Se is semiconducting above 300 K, but metallicity is retained below 300 K. While electronic states are absent in the energy range from the Fermi level (EF) to 0.4 eV below the EF at 300 K, a distinct Fermi edge is observed in the UPS at 15 K suggesting that the β-Ag2Se undergoes an electronic topological transition from a high-temperature semiconducting state to a low-temperature metallic state. Our study reveals that a constant and moderately high thermoelectric figure of merit in the range 300–395 K is observed due to the broad semiconductor to metal transition in β-Ag2Se.

The morphological, transport and terahertz optical properties of DC magnetron sputtered granular molybdenum thin-films with nano-grains embedded in an amorphous matrix have been studied in the normal and superconducting states. The superconducting transition temperatures of these films are much higher than that of bulk molybdenum. The optical properties of these thin-films have been studied using terahertz time-domain spectroscopy. Their properties have been compared with the existing materials used for the development of radiation detectors. The resistivity of the films lies in >100 micro-Ohm-cm range which is ideal for making highly sensitive radiation detectors. The Hall measurements indicate the presence of holes as the dominant carriers with very small mean free path and mobility. In the normal state, the films are disordered bad metal but they have large superfluid density and stiffness in their superconducting state. The normal state and superconducting properties of the films are very promising for their use in cryogenic radiation detectors for microwave, terahertz, and far IR frequency ranges.

We present the results of resonant photoemission spectroscopy experiments on the Mo$_{1-x}$Re$_{x}$ alloy compositions spanning over two electronic topological transitions (ETT) at the critical concentrations $x_{C1}$ = 0.05 and $x_{C2}$ = 0.11. The photoelectrons show an additional resonance ($R3$) in the constant initial state (CIS) spectra of the alloys along with two resonances ($R1$ and $R2$) which are similar to those observed in molybdenum. All the resonances show Fano-like line shapes. The asymmetry parameter $q$ of the resonances $R1$ and $R3$ of the alloys is observed to be large and negative. Our analysis suggests that the origin of large negative q is associated with phonon assisted inter band scattering between the Mo-like states and the narrow band that appeared due to the ETT.

We report here the structural, electrical and magnetic properties of the annealed NbxZr1-xV2 alloys. We have observed that all the alloys formed mainly in a face centred cubic gamma-ZrV2 phase with small amount of beta-V phase. The addition of Nb to ZrV2 increases the superconducting critical temperature (T-C) from 8.4 K for x = 0 to 9.46 K for x = 0.2. It is also observed that the upper critical field (H-C2(0)) in the zero temperature limit increases from about 14T for x = 0 to 26.4 T for x = 0.2. Further increase in x results in the decrease of both T-C and H-C2(0). Moreover, the martensitic transformation observed in ZrV2 is absent in the Nb substituted alloys.