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Two-dimensional (2D) materials exhibit many unique optical and electronic properties that are highly desirable for application in optoelectronics. Here, we report the study of photodetector based on 2D Bi2O2Te grown on n-Si substrate. The 2D Bi2O2Te material was transformed from sputtered Bi2Te3 ultrathin film after rapid annealing at 400 ℃ for 10 min in air atmosphere. The photodetector was capable of detecting a broad wavelength from 210 nm to 2.4 μm with excellent responsivity of up to 3x105 and 2x104 AW-1, and detectivity of 4x1015 and 2x1014 Jones at deep ultraviolet (UV) and short-wave infrared (SWIR) under weak light illumination, respectively. The effectiveness of 2D materials in weak light detection was investigated by analysis of the photocurrent density contribution. Importantly, the facile growth process with low annealing temperature would allow direct large-scale integration of the 2D Bi2O2Te materials with complementary metal-oxide–semiconductor (CMOS) technology.

Ability to mass produce graphene at low cost is of paramount importance in bringing graphene based technologies into market. Here we report a facile liquid-phase catalytic growth of graphene suitable for mass production. Iodine tincture is used to catalyze graphene quantum dots to form graphene films at room temperature. Such method has many advantages, such as environment friendly, high yield, low cost and wide choice of substrates. Furthermore, bandgap of the graphene films is tunable by post-annealing. A photodetector based on the graphene films was developed and could response to a broad wavelength between 365 and 1200 nm. It exhibited detectivity and responsivity of up to 1.1x1013 cmHz1/2W-1 and 81.3 mAW-1 respectively. Hence, the graphene films demonstrated significant applications in the field of optoelectronics. Interestingly, surface of the graphene film prepared by this method has wrinkles that can also be explored for energy storage applications.

Two-dimensional (2D) materials exhibit many unique optical and electronic properties that are highly desirable for application in optoelectronics. Here, we report the study of a photodetector based on 2D Bi2O2Te grown on an n-Si substrate. The 2D Bi2O2Te material was transformed from a sputtered Bi2Te3 ultrathin film after rapid annealing at 400 °C for 10 min under an air atmosphere. The photodetector was capable of detecting a broad wavelength ranging from 210 nm to 2.4 μm with an excellent responsivity of up to 3 × 105 and 2 × 104 AW−1 and a detectivity of 4 × 1015 and 2 × 1014 Jones for deep ultraviolet (UV) and short-wave infrared (SWIR) under weak light illumination, respectively. The effectiveness of 2D materials in weak light detection was investigated by the analysis of the photocurrent density contribution. Importantly, the facile growth process at low annealing temperatures would allow the direct large-scale integration of 2D Bi2O2Te materials with the complementary metal–oxide–semiconductor (CMOS) technology.

SnOx thin films with tunable optical bandgap were prepared using RF magnetron sputtering. The bandgap was adjustable between 2.16 and 3.96 eV depending on oxygen partial pressure during deposition and heat treatment. The structure and properties of the SnOx films were studied. The optical absorption of the SnOx films covered multiple ultraviolet bands, such as UVA, UVB and UVC. A photodetector based on the annealed SnOx film exhibited a detectivity of 1 × 1011 Jones (under 365 nm UV light) at room temperature, which demonstrates the important potential application of SnOx films for UV detection.

Ultraviolet (UV) photodetector has attracted extensive interests due to its wide-ranging applications from defense technology to optical communications. The use of wide bandgap metal oxide semiconductor materials is of great interest in the development of UV photodetector due to their unique electronic and optical properties. In this work, deep UV photodetector based on NiO/β-Ga2O3 heterojunction was developed and investigated. The β-Ga2O3 layer was prepared by magnetron sputtering and exhibited selective orientation along the family of ($$ \overline{2} $$2¯ 01) crystal plane after annealing. The photodetector demonstrated good performance with a high responsivity (R) of 27.43 AW−1 under a 245-nm illumination (27 μWcm−2) and the maximum detectivity (D*) of 3.14 × 1012 cmHz1/2 W−1, which was attributed to the p-NiO/n-β-Ga2O3 heterojunction.

Additional file 1: Figure S1. XRD patterns of the NiO film deposited on quartz substrate before and after annealing (blue line and red line). Figure S2. TEM and HRTEM images of the NiO film after annealing. Figure S3. (a) UV-Vis absorption spectra of the NiO film before and after annealing (blue line and red line), the inset is the picture of the prepared film. (b) Plots of [α (hν)]2 versus photon energy. Figure S4. AFM images of the NiO film after annealing. Figure S5. The ohmic contact of Al-β-Ga2O3-Al.

Ultraviolet (UV) photodetector has attracted extensive interests due to its wide-ranging applications from defense technology to optical communications. The use of wide bandgap metal oxide semiconductor materials is of great interest in the development of UV photodetector due to their unique electronic and optical properties. In this work, deep UV photodetector based on NiO/β-Ga2O3 heterojunction was developed and investigated. The β-Ga2O3 layer was prepared by magnetron sputtering and exhibited selective orientation along the family of (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{2} $$\end{document}2¯ 01) crystal plane after annealing. The photodetector demonstrated good performance with a high responsivity (R) of 27.43 AW−1 under a 245-nm illumination (27 μWcm−2) and the maximum detectivity (D*) of 3.14 × 1012 cmHz1/2 W−1, which was attributed to the p-NiO/n-β-Ga2O3 heterojunction.

Sulphur-doped graphene quantum dots (S-GQDs) were prepared in this work by a novel and facile method using the co-combustion (T-X-J method) of a liquid mixture of paraffin oil and carbon disulphide (CS2). Ultra-high performance (R: 307 A W−1; D*: 1.5 × 1014 Jones) ultraviolet photodetectors based on S-GQDs were fabricated under ambient conditions, shedding light on the fabrication of graphene based high-performance optoelectronic devices.

Solution processable high-performance, large-area, low-cost infrared organic photodetectors (OPDs) have been receiving more and more attention for their important applications both in scientific and technological fields. The search for a simple method to upgrade device performance for OPDs becomes increasingly important. Here, the performance of an OPD in the near-infrared (NIR) region is tremendously improved by doping iodine into the device's active layer (P3HT:PCBM:I2), 2.7 wt% iodine doping may increase the absorption by 31.3% for the active film and result in a ∼11 000-fold increase in responsivity for the detector. A high detectivity (D*) of ∼1.6 × 1012 cm Hz1/2 W−1, a good specific responsivity (R) of ∼80 A W−1 and a large EQE (external quantum efficiency) of 120% are achieved under illumination (λ = 850 nm) at room temperature. Systematic characterizations reveal that iodine-doping can introduce acceptor states in the energy band gap for the polymer layer, and thus increase the harvesting to long wavelength photons. A small dose of iodine doping can significantly induce improvement in device performance. This work demonstrates a simple but feasible method to enhance an NIR optoelectronics device.

Ultraviolet (UV) photodetectors are important optoelectronic devices. The development of a high-performance UV detector, however, has been impeded by lack of stable p-type wide gap semiconductors. Herein, an extremely high UV response for a ZnO nanorods/phenanthrene (Phen) photovoltaic detector has been realized, utilizing phenanthrene as a p-type wide gap organic semiconductor; a detectivity (D*) as high as ∼9.0 × 1013 cm Hz1/2 W−1 has been reached, showing significant potential for optoelectronic applications.

γ′-Fe 4 N thin films with good soft magnetic properties were successfully prepared on single crystal Si(1 0 0) and GaAs(1 0 0) substrates with Fe buffer layer by facing target magnetron sputtering. The microstructure and magnetic properties of the samples at low temperature were investigated. Both structural and magnetic properties of the films were shown to be influenced by the substrate. Specifically, the film deposited on the GaAs exhibited a strong preferred orientation along the (1 0 0) plane, while the film deposited on Si exhibited higher saturation magnetization ( Ms ) and lower coercivity ( Hc ). The results suggest that the coercivity is probably related to the intrinsic stress and that Ms increases whereas Hc decreases with decreasing lattice mismatch. The Mr / Ms ratio decreased with decreasing temperature due to the effect of the thermal disturbance on the magnetization. Both films had a single easy magnetized direction parallel to the substrate plane.

Influence of nitrogen fractions[Nf¼N2/(N2þAr2)] on the structural and magnetic properties of Mn3NiNx thin films prepared on quartz substrates using magnetron sputtering have been studied. The N/Ni ratio increased (N/Ni¼0.3–1.1) while the peak (200) shifted to lower angles with increasing Nf. It revealed that there was significant variation in the preferred orientation and Neel temperature (TN) for the films with increasing Nf. Strong indication for a frozen state is found, determined from the difference between field-cooled and zero-field-cooled magnetizations. The ac susceptibility measurements show a peak position shifting as a function of the driving frequency f and magnetization value does not saturate in the field range. These findings consistently demonstrate that Mn3NiNx thin films exhibit a spin-glass state at low temperature.

Functionalized graphene quantum dot (GQD) based materials play an important role in the development of high-performance, low-cost, large-area optoelectronic devices. The progress, however, is impeded by the poor understanding of the physical mechanism for GQDs in these devices. In this paper, chlorine doped GQD (Cl-GQD) based photovoltaic photodetectors have been fabricated using a solution process, and it was found that the presence of Cl-GQDs can significantly enhance the performance of the device. The improved performance of Cl-GQD based devices has been investigated by systematically studying the structural, morphological, optical, electrical, electrochemical and photoelectrical properties. The important photovoltaic detectors parameters such as the saturation current densities (J0), barrier heights (Φb), built-in potentials (Vbi), carrier concentrations (N) and depletion layer widths (Wd) have been calculated and discussed by studying the I–V and C–V characteristics under different illuminations. The frequency dependent capacitance and conductance have also been discussed. The results provide guidance for developing high-performance graphene based optoelectronic devices.

Graphene has received intensive attention in recent years because of the special physical and chemical properties. However, up to now graphene has not been widely used in optoelectronic fields yet, which is mainly caused by its semimetal properties. Therefore, changing its properties from semimetal to semiconductor is becoming a focal point. Recently, aiming at tuning the energy band of graphene, we have carried out systematic studies on the preparations of graphene based materials and devices, the CVD growth techniques of monolayer and double layer graphenes have been developed, the large-area doped graphene films have been fabricated to tune the structure-related optical and electrical properties. A novel graphene oxide (GO) preparation method namely “Tang-Lau method” has been invented, the graphene quantum dots growths by microwave assisted hydrothermal method and “Soft-Template method” have been developed, the Cl, S and K doped graphene quantum dots preparations by hydrothermal methods have also been invented. Systematic investigations have been carried out for the effect of preparation parameters on the properties of graphene based materials, the effects of size, doping elements on the energy level of graphene based materials have been explored and discussed. Based on the semiconducting graphene based materials, some novel room temperature photodetectors covering detection wavebands from UV, Vis and NIR have been designed and fabricated.

Hot deformation characteristic of superaustenitic stainless steel 254SMO has been studied by isothermal compression testing in the temperature range of 950–1,200 °C and strain rate range of 0.01–10 s−1. The activation energy of 496 kJ/mol was calculated by a hyperbolic-sine type equation over the entire range of strain rates and temperatures. In order to obtain optimum hot working conditions, processing maps consisting of power dissipation map and instability map were constructed at different strains. The power dissipation map exhibits two domains with relatively high efficiencies of power dissipation. The first domain occurs in the temperature range of 990–1,070 °C and the strain rate range of 0.01–0.1 s−1. Microstructure observation in this domain indicates the partial dynamic recrystallization (DRX) accompanied with precipitation of tetragonal sigma phase. The second domain occurs in the temperature range of 1,140–1,200 °C and the strain rate range of 0.01–1 s−1 with a peak efficiency of power dissipation of 39%, and in this domain, the microstructure observation reveals the full DRX. The instability map shows that flow instability occurs at the temperatures below 1,140 °C and the strain rates above 0.1 s−1.

The hot deformation behavior of superaustenitic stainless steel S32654 was studied in the temperature range of 950–1200 °C and strain rate range of 0.001–10 s −1 employing hot compression tests. The results show that peak stress increases with decreasing of temperature and increasing of strain rate. The apparent activation energy of this alloy is about 469 kJ/mol. The processing maps for hot working were developed on the basis of flow stress data and the dynamic materials model. It is found that the features of the maps obtained in the strain range of 0.2–1.0 are fundamentally similar, indicating that the strain does not have a significant influence on processing map. The maps exhibited two domains. The first domain occurs in the strain rate range of 0.01–0.4 s −1 and temperature range of 1030–1150 °C with a peak efficiency of about 49%, which is considered as the optimum window for hot working. The microstructure observations of the specimens deformed in this domain showed the full dynamic recrystallization (DRX) structure with finer and more homogeneous grain sizes. The second domain occurs at the temperatures higher than 1160 °C and strain rates lower than 0.1 s −1 with a peak efficiency of about 41%, the microstructure observations in this domain also indicated the typical DRX structure accompanied with grain growth. A instability domain occurs at temperatures below 1175 °C and strain rate above 0.1 s −1 .

Tin sulfide quantum dots (SnS2 QDs) are n-type wide band gap semiconductor. They exhibit a high optical absorption coefficient and strong photoconductive property in the ultraviolet and visible regions. Therefore, they have been found to have many potential applications, such as gas sensors, resistors, photodetectors, photocatalysts, and solar cells. However, the existing preparation methods for SnS2 QDs are complicated and require a high temperature and high pressure environments; hence they are unsuitable for large-scale industrial production. An effective method for the preparation of monodispersed SnS2 QDs at normal temperature and pressure will be discussed in this paper. The method is facile, green, and low-cost. In this work, the structure, morphology, optical, electrical, and photoelectric properties of SnS2 QDs are studied. The synthesized SnS2 QDs are homogeneous in size and exhibit good photoelectric performance. A photoelectric detector based on the SnS2 QDs is fabricated and its J–V and C–V characteristics are also studied. The detector responds under λ = 365 nm light irradiation and reverse bias voltage. Its detectivity approximately stabilizes at 1011 Jones at room temperature. These results show the possible use of SnS2 QDs in photodetectors.

Graphene quantum dots (GQDs) possess unique photoelectronic properties ascribed to quantum confinement and edge effects, which have evoked important development and wide application in the optoelectronic field. Doping GQDs with heteroatoms can further modulate the energy band structure and thus produce unexpected properties. Herein, we obtained fluorine-doped GQDs (F-GQDs) by adopting an effective preparation technique, which includes the treatment of the as-prepared reaction precursor, fluorinated carbon fibers, with ultrasonic liquid phase exfoliation. The proposed method is simple, handy, and low-cost, opening up an alternate approach to prepare F-GQDs. Through multiple characterization techniques, the effective incorporation of fluorine in GQDs was confirmed, and the as-prepared F-GQDs exhibit excellent photoelectrical properties and good ultraviolet absorption performances. Accordingly, we have fabricated a vertical photovoltaic UV detector based on F-GQDs. The unoptimized device has an exceptionally...

Graphene has attracted much attention at various research fields due to its unique optical, electronic and mechanical properties. Up to now, graphene has not been widely used in optoelectronic fields due to the lack of large-area uniform doped graphene (n-doped and p-doped) with smooth surface. Therefore, it is rather desired to develop some effective doping methods to extend graphene to optoelectronics. Here we developed a novel doping method to prepare large-area (> centimeter scale) uniform doped graphene film with a nanoscale roughness(RMS roughness ∼1.4 nm), the method (nano-metal film doping method) is simple but effective. Using this method electron doping (electron-injection) may be easily realized by the simple thermal deposition of Ag nano-film on a transferred CVD graphene. The doping effectiveness has been proved by Raman spectroscopy and spectroscopic ellipsometry. Importantly, our method sheds light on some potential applications of graphene in optoelectronic devices such as photodetectors, LEDs, phototransistors, solar cells, lasers etc.

Ultraviolet (UV) photodetector is a kind of important optoelectronic device which can be widely used in scientific and engineering fields including astronomical research, environmental monitoring, forest-fire prevention, medical analysis, and missile approach warning etc. The development of UV detector is hindered by the acquirement of stable p-type materials, which makes it difficult to realize large array, low-power consumption UV focal plane array (FPA) detector. Here, we provide a novel structure (Al/Poly(9,9-di-n-octylfuorenyl-2,7-diyl)(PFO)/ZnO/ITO) to demonstrate the UV photovoltaic (PV) response. A rather smooth surface (RMS roughness: 0.28 nm) may be reached by solution process, which sheds light on the development of large-array, light-weight and low-cost UV FPA detectors.

UV photodetector is a kind of important optoelectronic devices that has vital applications in both scientific and engineering fields. The development of UV photodetectors has been impeded because of lacking stable p-type wide-gap semiconductor which is crucial for high-performance, low-cost, large-array UV photovoltaic detector. In this paper, we report a novel UV photovoltaic detector fabricated using 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as a sole photoactive material. The highest detectivity (D*) reaches 9.02 × 1011 cm Hz1/2 W−1 at −1 V bias voltage at room temperature under 365 nm illumination for the un-optimized BCP based detector (without using pre-amplifier), which is the highest value for the sole UV organic photoactive material based photovoltaic detector. The optical, electrical, and photovoltaic properties, including the UV absorption, photoluminescence (PL) emission, PL excitation, I-V, C-V, and photoresponse, have been systematically investigated to disclose the internal mechan...

Graphene quantum dots (GQDs) are becoming one of the hottest advanced functional materials because of the opening of the bandgap due to quantum confinement effect, which shows unique optical and electrical properties. The chlorine doped GQDs (Cl-GQDs) have been fabricated by chemical exfoliation of HCl treated carbon fibers (CFs), which were prepared from degreasing cotton through an annealing process at 1000 °C for 30 min. Raman study shows that both G and 2D peaks of GQDs may be redshifted (softened) by chlorine doping, leading to an n-type doping. The first vertical (Cl)-GQDs based photovoltaic detectors have been demonstrated, both the light absorbing and electron-accepting roles for (Cl)-GQDs in photodetection have been found, resulting in an exceptionally big ratio of photocurrent to dark current as high as ∼105 at room temperature using a 405 nm laser irradiation under the reverse bias voltage. The study expands the application of (Cl)-GQDs to the important optoelectronic detection devices.

Cadmium sulfide quantum dots (CdS QDs) are widely used in solar cells, light emitting diodes, photocatalysis, and biological imaging because of their unique optical and electrical properties. However, there are some drawbacks in existing preparation techniques for CdS QDs, such as protection of inert gas, lengthy reaction time, high reaction temperature, poor crystallinity, and non-uniform particle size distribution. In this study, we prepared CdS QDs by liquid phase synthesis under ambient room temperature and atmospheric pressure using sodium alkyl sulfonate, CdCl2, and Na2S as capping agent, cadmium, and sulfur sources respectively. This technique offers facile preparation, efficient reaction, low-cost, and controllable particle size. The as-prepared CdS QDs exhibited good crystallinity, excellent monodispersity, and uniform particle size. The responsivity of CdS QDs-based photodetector is greater than , which makes them suitable for use as ultra-violet (UV) detectors.