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Recently, two-dimensional (2D) semiconductor-based broadband photodetectors have gained tremendous attention due to their immense potential applications in high-performance optoelectronic devices.

InGaN epilayers with different indium concentrations have been grown on 100-nm-thick AlN/n-Si(111) template using plasma assisted molecular beam epitaxy.

Metal dichalcogenide semiconductors have shown tremendous performance in various optoelectronic applications due to their excellent properties. However, low carrier mobility associated with the photoactive materials restricts its applications in highly responsive and ultrafast photodetectors. Here, to improve the device performance, SnSe2 has been incorporated with reduced graphene oxide (RGO) to form a SnSe2-RGO bulk heterojunction. SnSe2-RGO solution has been drop cast on a pulsed laser deposited MoS2 film to fabricate SnSe2-RGO/MoS2 hybrid structure. The built-in electric potential generated at the SnSe2-RGO/MoS2 interface facilitates the self-powered photodetection. Under IR illumination, the device exhibits excellent photoresponse with a responsivity of 13.75 A W-1 and a detectivity of 5.08 A� 1012 Jones at 0 V. The excellent performance of the device is attributed to high charge carrier mobility of RGO and a robust built-in electric field at the interface. Also, the device shows excellent photoresponse under visible light illumination. © 2021 American Chemical Society.

VO2 is a material with high potential for low-cost optoelectronic, switching and energy saving devices. This work presents the synthesis of smooth high-quality VO2(M1) thin films on quartz (VO2-Qu) and c-sapphire (VO2-Saph) substrates by two-step DC reactive sputtering with enhanced semiconductor-to-metal transition (SMT) and infrared (IR) photoresponse characteristics. Phase formation and purity were confirmed by XRD and Raman measurements. Morphological analysis by AFM and SEM revealed the nanosized nature of the films with a surface roughness of 37 ± 0.5 nm and 48 ± 1 nm for VO2-Qu and VO2-Saph thin films respectively. The VO2-Qu and VO2-Saph thin films exhibit thermally activated SMT temperature (TSMT) of 71 °C and 68 °C with resistance change of 4 and 5 orders of magnitude respectively. Infrared (λ = 1064 nm and 1550 nm) photoresponse characteristics of the low-cost photodetector fabricated based on the synthesized VO2(M1) films increase with a decrease in film roughness. The responsivity increases in the order VO2-Qu (14.02 mA W−1) > VO2-Saph (11.12 mA W−1) under an IR (λ = 1064 nm, 250 mW cm−2) laser at a bias voltage of 10 V. The higher energy (λ = 1064 nm) laser yields an enhanced photoresponse compared to the lower energy (λ = 1550 nm) laser owing to the efficient generation of charge carriers with a higher laser energy. This work provides a way for the large-scale synthesis of high-quality VO2(M1) thin films for various device applications.

Heterojunctions based on two-dimensional (2D)/three-dimensional (3D) semiconductors have become an integral component of next-generation optoelectronic devices. Here, we report the photodetection a...

The dielectric properties of TiNb2O7 (TNO) thin films are studied in Metal-Insulator-Metal configuration (Au/TiNb2O7/Pt) devices. The temperature dependence of the dielectric dispersion and the AC conductivity behavior is strongly dependent on TNO thin film thickness. Low thickness (∼236 nm) films shows considerably less variation with temperatures than their thicker counterparts (∼480 nm). These behaviors are explained on physical basis – nearly constant loss (NCL) and Jonscher's Universal Dielectric Response (UDR). The TNO thin films show large dielectric constant ( ∼ 59–73) and moderate dielectric loss (∼0.07–0.11). The AC conductivity values of the thin films lie in the range of about ( 10 − 8 to 10 − 9 ) at 10 kHz. The thicker films show DC conductivity values which are thermally activated with an activation energy of about 0.44 eV. This is slightly higher (about 0.1 eV) than ω p in Jonscher's UDR response and this discrepancy is explained on the basis of mixed ionic electronic conduction in TNO thin films. The possible role of growth morphology in the dielectric response is also briefly mentioned.

Iron-based polyanionic materials can be exploited to realize low cost, durable, and safe cathodes for both bulk and thin film sodium-ion batteries. Herein, we report pulsed laser deposited mixed ph...

By combining unique properties of ultrathin 2D materials with conventional 3D semiconductors, devices with enhanced functionalities can be realized. Here, we report a self-powered and ultrafast pho...

Optoelectronic properties of nonpolar a-plane GaN are superior along the [0002] azimuth direction compared to other azimuth directions. We have grown a-GaN on r-sapphire, and interdigitated electro...

We report synthesis, characterization and IR photoresponse properties of 150 ± 10 nm thick high quality VO2(M1) thin films synthesized by DC reactive sputtering. Phase formation was confirmed by X-ray diffraction and Raman spectroscopic measurements. Morphology and microstructure were analysed by atomic force microscope, scanning electron microscope and transmission electron microscope which revealed polycrystalline nature of nanosized films with root mean square (rms) roughness value of 8 ± 0.7 nm. Electrical measurements revealed 1st order transition of thin films with a change in resistance of more than two orders of magnitude and temperature coefficient of resistance, TCR of − 1.24% K−1 at 30 °C. The fabricated VO2(M1) IR photodetector exhibited excellent reproducible photoresponse properties when subjected to a 1064 nm laser under 250 mW cm−2 power density with a bias voltage of 5 V at the ambient conditions of temperature and pressure. The sensitivity, responsivity, external quantum efficiency and specific detectivity were observed to be 1775%, 40.09 mA W−1, 4.67% and 7.07 × 1011 Jones, respectively.

In the last few decades, there has been a phenomenal rise and evolution in the field of III–Nitride semiconductors for optoelectronic applications such as lasers, sensors and detectors. However, certain hurdles still remain in the path of designing high-performance photodetectors (PDs) based on III-Nitride semiconductors considering their device performance. Recently, a lot of progress has been achieved in devices based on the high quality epilayers grown by molecular beam epitaxy (MBE). Being an ultra-high vacuum environment based-technique, MBE has enabled the realization of high-quality and highly efficient PDs which have exhibited competitive figures of merit to that of the commercial PDs. Moreover, by combining the novel properties of 2D materials with MBE-grown III-Nitrides, devices with enhanced functionalities have been realized which would pave a way towards the next-generation photonics. In the current chapter, the basic concepts about photodetection have been presented in detail, followed by a discussion on the basic properties of the III-Nitride semiconductors, and the recent advancements in the field of MBE-grown III-Nitrides-based PDs, with an emphasis on their hybrid structures. Finally, an outlook has been provided highlighting the present shortcomings as well as the unresolved issues associated with the present-day devices in this emerging field of research.

From the past few decades, photodetectors (PDs) are being regarded as crucial components of many photonic devices which are being used in various important applications. However, the PDs based on the traditional bulk semiconductors still face a lot of challenges as far as the device performance is concerned. To overcome these limitations, a novel class of two-dimensional materials known as transition metal dichalcogenides (TMDCs) has shown great promise. The TMDCs-based PDs have been reported to exhibit competitive figures of merit to the state-of-the-art PDs, however, their production is still limited to laboratory scale due to limitations in the conventional fabrication methods. Compared to these traditional synthesis approaches, the technique of pulsed laser deposition (PLD) offers several merits. PLD is a physical vapor deposition approach, which is performed in an ultrahigh-vacuum environment. Therefore, the products are expected to be clean and free from contaminants. Most importantly, PLD enables actualization of large-area thin films, which can have a significant potential in the modern semiconductor industry. In the current chapter, the growth of TMDCs by PLD for applications in photodetection has been discussed, with a detailed analysis on the recent advancements in this area. The chapter will be concluded by providing an outlook and perspective on the strategies to overcome the shortcomings associated with the current devices.

We report on the hybrid ZnO/AlN/Si heterostructure-based ultraviolet (UV) photodetectors with infrared- and visible-blind characteristics. The heterostructure was formed by depositing ZnO thin films on Si (111) substrate by introducing an AlN as an intermediate layer. The ZnO film has been grown epitaxially on the underlying substrate with the improved crystallinity and excellent optical properties. The vertical transport properties of the ZnO/AlN/Si heterojunction under dark and light illumination demonstrate the intrinsic infrared- and visible-blind characteristics with excellent ultraviolet responsivity. The heterostructure exhibits a high UV responsivity of 14.5 A/W with UV-to-Infrared rejection ratio of nearly 4 orders of magnitude. The vertical electrical transport properties across the heterostructure are dominated by the holes in the reverse bias condition, whereas the transport of electrons in the forward bias is hindered at the ZnO/AlN interface due to an existence of huge conduction band offset between ZnO and AlN layers. The AlN intermediate layer acts as an electron blocking layer which allows the hole to transport across the heterostructure in the reverse bias condition.

Perovskite halide materials with their salient optoelectronic features such as high absorption coefficient, large charge carrier diffusion lengths and low carrier recombination, have revolutionised the field of photodetectors. In this paper we report the synthesis of CH3NH3PbBr3 quantum dots for visible wavelength photodetector applications. Quantum dots of size 2–4.5 nm were obtained. UV–Vis and photoluminescence spectroscopy revealed an optical band gap of 2.3 eV. An electrochemical band gap of 2.09 eV was obtained using cyclic voltammetry. CH3NH3PbBr3 quantum dots based visible wavelength photodetector device was fabricated. The time dependent photoresponse was found to be stable over several ON–OFF cycles of the lamp. We have achieved a responsivity, external quantum efficiency and specific detectivity of 6.11 A W−1, 1380.2% and 3.81 × 1012 Jones under AM 1.5 G, 1 sun illumination.

We report detailed structural, electrical transport and IR photoresponse properties of large area VO2(M1) thin films deposited by a simple cost-effective two-step technique. Phase purity was confirmed by XRD and Raman spectroscopy studies. The high quality of the films was further established by a phase change from low temperature monoclinic phase to high temperature tetragonal rutile phase at 68 °C from temperature dependent Raman studies. An optical band gap of 0.75 eV was estimated from UV-visible spectroscopy. FTIR studies showed 60% reflectance change at λ = 7.7 μm from low reflectivity at low temperature to high reflectivity at high temperature in a transition temperature of 68 °C. Electrical characterization showed a first order transition of the films with a resistance change of four orders of magnitude and TCR of −3.3% K−1 at 30 °C. Hall-effect measurements revealed the n-type nature of VO2 thin films with room temperature Hall mobility, μe of 0.097 cm2 V−1 s−1, conductivity, σ of 0.102 Ω−1 cm−1 and carrier concentration, ne = 5.36 × 1017 cm−3. In addition, we fabricated a high photoresponsive IR photodetector based on VO2(M1) thin films with excellent stability and reproducibility in ambient conditions using a low-cost method. The VO2(M1) photodetector exhibited high sensitivity, responsivity, quantum efficiency, detectivity and photoconductive gain of 5.18%, 1.54 mA W−1, 0.18%, 3.53 × 1010 jones and 9.99 × 103 respectively upon illumination with a 1064 nm laser at a power density of 200 mW cm−2 and 10 V bias voltage at room temperature.

Graphene based heat mirror (i.e., graphene/Cu/graphene multilayer coating) was designed and developed to achieve enhanced optical absorption with tunable spectral selectivity. The concept of a heat mirror and a high/low/high refractive index stack was used to develop the graphene/Cu/graphene absorber and the transition from high transmittance to high absorptance was realized on quartz substrates. The thickness of the Cu layer has an important role in creating the destructive interference, for achieving high absorptance and low emittance. The refractive index of the multilayer graphene transferred on Si substrate was studied using phase-modulated spectroscopic ellipsometry. An absorptance of 0.91 and emittance of 0.22 was achieved for the SiO2/graphene/Cu/graphene multilayer coating. For the first time, the feasibility of graphene/Cu/graphene multilayer coating for photothermal applications have been demonstrated.

Humidity monitoring has become extremely vital in various technological fields such as environment control, biomedical engineering, and so on. Therefore, a substantial interest lies in the development of fast and highly sensitive devices with high figures of merit. Self-powered and ultrasensitive humidity sensors based on SnS2 nanofilms of different film thicknesses have been demonstrated in this work. The sensing behavior has been investigated in the relative humidity (RH) range of 2–99%. The observed results reveal a remarkable response and ultrafast detection even with zero applied bias (self-powered mode), with response and recovery times of ~ 10 and ~ 0.7 s, respectively. The self-powered behavior has been attributed to the inhomogeneities and the asymmetry in the contact electrodes. The highest sensitivity of ~ 5.64 × 106% can be achieved at an applied bias of 5 V. This approach of fabricating such highly responsive, self-powered and ultrafast sensors with simple device architectures will be useful for designing futuristic sensing devices.

While band gap and absorption coefficients are intrinsic properties of a material and determine its spectral range, response time is mainly controlled by the architecture of the device and electron/hole mobility. Further, 2D-layered materials such as transition metal dichalogenides (TMDCs) possess inherent and intriguing properties such as a layer-dependent band gap and are envisaged as alternative materials to replace conventional silicon (Si) and indium gallium arsenide (InGaAs) infrared photodetectors. The most researched 2D material is graphene with a response time between 50 and 100 ps and a responsivity of 4 A/W, response times fall short by 3–6 orders of magnitude compared to graphene, commercial Si, and InGaAs photodiodes. Slow response times limit their application in devices requiring high frequency. Here, we highlight some of the recent developments made with visible and near-infrared photodetectors based on two dimensional SnSe2 and MoS2 materials and their performance with the main emphasis on the role played by the mobility of the constituency semiconductors to response/recovery times associated with the hetero-structures.

We report the synthesis of vanadium oxide thin films by the pulsed laser deposition under different parameter conditions on $$\hbox {Si/SiO}_2$$ substrates using $$\hbox {V}_2\hbox {O}_5$$ target. The objective of the present work was to achieve smooth $$\hbox {VO}_2$$ thin film in a single step. Synergistic effect of the deposition parameters on the phase of vanadium oxides is studied by a series of experiments designed using Taguchi analysis. Conditions for depositing different oxides of vanadium like $$\hbox {VO}_2$$, $$\hbox {V}_2\hbox {O}_3$$, $$\hbox {V}_3\hbox {O}_5$$ and a new phase, $$\hbox {V}_7\hbox {O}_{16}$$ was established. The range of parameters varied were: gas pressure: $$10^{-3}$$–5 $$\times$$ $$10^{-2}$$ mbar; temperature: 500–700 $$^\circ$$C; target-substrate distance: 30–40 mm and laser energy: 100–200 mJ. $$\hbox {VO}_2$$ film with surface roughness of 3.68 nm having a semiconductor-to-metal transition (SMT) at 72 $$^\circ$$C with 2–3 orders of resistance change was achieved. Taguchi model was statistically analyzed to determine the suitable condition as well as effect of deposition parameters to obtain phase pure $$\hbox {VO}_2$$ thin film. The optimum condition for deposition was found to be: gas pressure: 5 $$\times$$ $$10^{-2}$$ mbar; temperature: 600 $$^\circ$$C; distance: 35 mm, and laser energy: 200 mJ after analyzing using Taguchi model.

Water dissociation, in general, requires external stimuli such as light energy or electricity. Here, we present a stimuli-free water dissociation using mesoporous SnO2-based hydroelectric cell that can directly be exploited to generate electric power for portable applications. The device configuration is almost identical to metal-air batteries but follows altogether a different reaction pathway. The mesoporous SnO2-based hydroelectric cell dissociates water molecule into hydroxyl ions (OH-) and hydronium ion without any stimuli, transports hydronium ions to the opposite end, and simultaneously acts as the separator. The OH- react with Al electrode to release the electrons, whereas hydronium ions get reduced at the Ag electrode to produce a potential difference as high as similar to 1000 +/- 20 mV between the electrodes that is stable over 3500 hours. The device also shows its potential toward electric power generation from atmospheric moisture with the help of CuO layer that acts as moisture pump.

To realize all-solid-state thin-film microbatteries, robust anode candidates play a key role. SrLi2Ti6O14 forms one such Ti-based anode with ideal combination of electrochemical performance and operational safety. In the current work, SrLi2Ti6O14 anode thin-films were deposited on stainless steel substrates by pulsed laser deposition technique. X-ray diffraction confirmed the crystallinity and phase-purity of these films with preferred orientation. They were found to have uniform thickness with homogeneous morphology as revealed by scanning electron and atomic force microscopy. These as-deposited thin-film anodes exhibited active electrochemical behavior, delivering a reversible capacity over 160 mAh.g−1 without any carbon or conductive additives. Involving a Ti4+/Ti3+ redox activity around 1.4 V lying in the safe operational window of organic electrolytes, the SrLi2Ti6O14 thin film forms a promising anode candidate for Li-ion micro-batteries.

Sodium-ion thin-film micro-batteries form a niche sector of energy storage devices. Sodium titanate, Na2Ti6O13 (NTO) thin films were deposited by pulsed laser deposition (PLD) using solid-state synthesized polycrystalline Na2Ti6O13 compound. The phase-purity and crystallinity of NTO in bulk and thin-film forms were confirmed by Rietveld refinement. Electron microscopy and atomic force microscopy revealed the formation of uniform ∼100 nm thin film with roughness of ∼4 nm consisting of homogeneous nanoscale grains. These PLD-deposited NTO thin-films, when tested in Na-half cell architecture, delivered a near theoretical reversible capacity close to 42 mA h g−1 involving Ti4+/Ti3+ redox activity along with good cycling stability and rate kinetics. Na2Ti6O13 can work as an efficient and safe anode in designing sodium-ion thin-film micro-batteries.

Organic–inorganic hybrid perovskite materials are considered as promising candidates for emerging thin-film photodetectors. In this work, we discuss the application of the CH3NH3PbI3 thin films by pulsed laser deposition for photodetection applications. With this method, we obtained good perovskite film coverage on fluorine-doped tin oxide-coated substrates and observed wel- developed grains. The films showed no sign of degradation over several months of testing. We investigated the surface morphology and surface roughness of the films by field emission scanning electron microscopy and atomic force microscopy. The optical response of the films was studied using ultraviolet–visible and photoluminescence spectroscopy. We carried out a study on the solar and infrared photodetection of CH3NH3PbI3 thin films. The values of the responsivity, sensitivity, external quantum efficiency and specific detectivity under 1 sun illumination and 0.7 V bias were 105.4 A/W, 1.9, 2.38 × 104% and 1.5 × 1012 Jones, respectively.

We report on the surprising observation of negative photoconductivity (NPC) in GaN nanorods (NRs) by bandgap and super bandgap excitations. A metal-semiconductor-metal (MSM) type of device configuration using Ni/Au as an electrode at both ends, has been used to study the NPC phenomenon. On exposing the device to the light sources with 363 nm (bandgap excitation) and 250 nm (super bandgap excitation) wavelengths, NPC with a drop of approximately 50 and 60% was observed, respectively. To explain this phenomenon, a model of trapping of photogenerated electrons by the trap states is proposed. Interestingly, a significant drop in the illumination current is observed at low values of power density (up to 3 μW/mm2) of the incident light. It has been interpreted that on increasing the power density, the density of trapped electrons starts approaching the density of available trap states. The de-trapping process is observed to be very slow as the illumination current reached the dark current value in nearly 2 h after switching off the incident light. The observation of NPC and saturation of trap states with high intensity of incident light are also validated by Kelvin Probe Force Microscopy (KPFM) characterization performed in the dark and on illumination with varying intensity of the incident light. Furthermore, on increasing the temperature from room temperature (RT) to 300 °C, the NPC was found to reduce to almost zero, which indicates the de-trapping of trapped electrons on increasing the temperature.

Conventional photodetectors (PDs) generally exhibit a unipolar photoresponse within their responsive spectral range. Different from the traditional PDs, we report here a broadband PD based on the MoS2/GaN/Si heterojunction that shows a unique phenomenon of wavelength selectivity through photocurrent polarity inversion. Overall, the device can differentiate the photons of the ultraviolet (UV)/visible region from that of the near infrared (NIR) region. This polarity inversion is explained with the help of the band diagram and the wavelength dependent photothermoelectric (PTE) effect in MoS2. The vertical transport characteristics of the MoS2/GaN/Si device exhibit a high spectral response in a broad range of wavelengths (300–1100 nm) in a self-biased mode. The maximum response of the device is found to be 23.81 A/W at a wavelength of 995 nm. Our results demonstrate a route for the development of PDs without filter that possess a lot of potential for the futuristic photonic devices.

Smart multifunctional materials such as vanadium dioxide (VO2), which exhibit a reversible semiconductor-to-metal transition (SMT), provide a new route toward engineering high speed switchable devices. Here, we present a detailed report on the modulation in the electrical properties of VO2/Si heterostructures by application of an external electrical field across VO2 thin films. Single-phase VO2 thin films have been deposited on an Si(111) substrate using the pulsed laser deposition technique. The electrical transport behavior across the VO2/Si heterostructure has been studied in the temperature range of 35–105 °C, and a reversible SMT can be seen at 68 and 63 °C for heating and cooling cycles, respectively. The temperature-dependent resistance of the device shows a hysteresis loop around the transition temperature of the VO2 thin film. In addition, the device shows a significant change in junction current when an external bias is applied on the VO2 thin film, and this phenomenon has been utilized to study the switching behavior of the device. Such behavior is due to the change in interfacial barrier height because of the bias dependent tilting of electronic energy bands of the VO2 thin film. Our results offer novel opportunities to externally control the electrical transport of vertical heterostructures and can be beneficial for extending the notion of electrical field modulation in electrical switches and sensors.

Ga and In co-doped ZnO (GIZO) thin films were grown by pulsed laser deposition for use as a transparent conducting oxide (TCO) in Cu2SnS3 (CTS) based photodetectors. The structural and optical properties were studied. The GIZO thin films were found exhibiting low resistivity of less than 10−3 Ω cm, and a high transparency of 97% both in visible and IR region. The performances of CTS photodetector with GIZO and with ZnO buffer assisted GIZO (ZnO/GIZO) as TCO layers were compared. The CTS photodetector with ZnO/GIZO as TCO was found to be exhibiting a higher photoresponse with responsivity, external quantum efficiency and specific detectivity of 552.3 A W−1, 1247.3% and 3.9 × 1012 Jones respectively. ZnO/GIZO could serve as an effective replacement for the commonly used TCO, indium tin oxide, which is expensive and non-earth abundant.

Studies have been carried out on the enhancement of responsivity and detectivity of the ZnO thin-films-based ultraviolet photodetectors by introducing an AlN buffer layer on silicon substrate. The ZnO film grown with AlN buffer layer established an epitaxial relation with the substrate and was found to show improved crystallinity with excellent optical properties. A strong and narrow photoluminescence emission was observed on the ZnO film grown with buffer layer, while a defect related broad emission was dominated on the film without buffer layer. The photodetectors showed a higher responsivity ( $R_{\lambda }$ ) of ${1.03} \times {10}^{{{{4}}}}$ A/W with a specific detectivity ( $D^{\ast }$ ) of ${5.21} \times {10}^{{{{12}}}}~ \text {cm}\cdot \text {Hz}^{{{{1/2}\cdot }}}\text {W}^{{{\text {-1}}}}$ at an applied bias of 3 V due to their excellent crystal quality.

Despite of the progress, graphene based photodetectors still suffer from very low responsivity. Tunable optical properties and ease of preparation of has made reduced graphene oxide (RGO) a promising substitute material for graphene in many optoelectronic applications. We have studied solvothermal reduction of graphene oxide in ethylene glycol and photodetection properties of as made RGO based devices. In near infrared region a responsivity value as high as 0.78 A W−1 with an external quantum efficiency of 62% has been achieved at a bias of only 0.5 V. Corresponding values in ultraviolet region are 0.27 A W−1 and 102%. Few layer nature and increased reduction can increase absorption efficiency of RGO. Defects in graphene sheets in RGO create mid-gap states band (MGB). MGB can generate gain in photocurrent by preventing quick recombination of photogenerated charge carriers. Increased absorption and longer carrier lifetime enhances the performance of RGO based devices. Also a linear variation of photocurrent in RGO with temperature indicates its potential as temperature sensor.

We, herein, report an eco-friendly low temperature route for the gram-scale synthesis of copper indium selenide nanoparticles. We have also shown the possibility of using CuInSe₂ nanoparticles in infrared photodetection by maneuvering the photoconductive property. We rationalize the long-lived trap states to be the cause for the observed photoconductive gain. It is worth noting that the photoresponse time of the device was found to be faster than 0.1 s.

We report the synthesis of Cu(2)SnS(3) nanostructures using solvothermal technique and the study of its visible and infrared (IR) photoresponse under different illumination intensities. The CTS nano-crystals were found to have tetragonal crystal structure using X-ray Diffraction (XRD). Both flower and sphere shaped structures of around 1.5 μm were obtained as seen using scanning electron microscopy (SEM). Transmission electron microscopy (TEM) was used to study the crystalline nature as well as the different planes present in the crystal. The band gap of the obtained crystals was found to be 1.4 eV using optical studies. The visible photocurrent increased from 0.25 μA at dark to 0.42 μA at 1.05 suns and 1 V applied bias. The sensitivity increased from 1.25 at 0.88 suns to 1.68 at 1.05 suns. The IR photocurrent increased from 0.13 μA at dark to 0.66 μA at 477.7 mWcm(−2). The device exhibited an increase in the sensitivity, responsivity, external quantum efficiency and specific detectivity from 1.23, 0.10 mA/W, 0.016% and 5.02 × 10(8) Jones respectively at 127.4 mWcm(−2 ) to 4.95, 0.46 mA/W, 0.071% and 2.22×10(9) Jones respectively at 477.7 mWcm(−2). The time response of the photocurrent was measured over different ON-OFF cycles and the cyclic stability of the device was verified.

Cu2SnS3 quantum dots in the size range of 2.7 nm to 3.6 nm were synthesized using a solution based heat up method. The structural, optical and electrical properties were studied using X-ray diffraction, transmission electron microscopy, UV-Vis spectroscopy, X-ray photoelectron spectroscopy and cyclic voltammetry. In this paper we report, the infrared photo detection of Cu2SnS3 quantum dots. The responsivity, external quantum efficiency and specific detectivity were measured for the infrared lamp under different applied biases and for different illumination intensities of the 1550 nm and 1064 nm lasers. The responsivity, external quantum efficiency and specific detectivity exhibited high values of 1.76 A W−1, 272.53% and 2.79 × 1011 Jones at −0.5 V applied bias, under infrared lamp illumination intensity of 0.48 W cm−2.

Pulsed laser deposited TiNb 2 O 7 thin films are demonstrated as anode materials in rechargeable Li-ion micro-batteries. The monoclinic and chemically pure TiNb 2 O 7 films in different morphologies were successfully deposited at 750 °C. The single phase formation was confirmed by grazing incident X-ray diffraction, micro-Raman spectroscopy, high resolution transmission electron microscopy, field emission scanning electron microscopy and X-ray photoelectron spectroscopy. The oxygen partial pressure during the deposition significantly influenced the properties of TiNb 2 O 7 films. The TiNb 2 O 7 thin films exhibited excellent stability with fast kinetics reversible reaction. The TiNb 2 O 7 films showed initial discharge specific capacity of 176, 143 μAh μm −1 cm −2 at 30, 50 μA cm −2 current densities respectively with 92% coulombic efficiency in a non-aqueous electrolyte consisting of Li + ions. The high discharge specific capacity of TiNb 2 O 7 thin films may be attributed to nanometer grain size with high roughness which offers high surface area for Li-diffusion during charge and discharge process.

We report a MoS