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High-temperature chloride passivation (HTCP) was proposed to improve the crystalline quality and electrical properties of PbSe epitaxial films. The PL intensity of HTCP (111) PbSe epitaxial films exhibits a 14 times higher intensity than that of as-grown films, and a threefold increase in Hall mobility has been obtained after HTCP at 300 °C for 2 h. The improvement of optical and electrical properties is attributed to the high-temperature defect passivation induced by the HTCP process. The HTCP process of PbSe films was implemented in a CdSe/PbSe heterojunction PV detector, which exhibits a room temperature peak detectivity

Being a promising candidate infrared transparent and conductive coatings in the 1–12 μm, the practicality of CdSe:In was verified by building uncooled PbSe/CdSe photovoltaic detectors with 1.0 × 109 cm Hz1/2 W−1 under blackbody radiation.

Indium oxide has been demonstrated to be a suitable catalytic material for CO2 adsorption and activation, and in this study a phase-mixing strategy is used to improve its catalytic hydrogenation of...

TiO2 nanotubes (TNTs) have been extensively applied in many fields owing to their excellent porous structure and surface properties. Herein, a series of CuO-ZnO-CeO2/TNTs catalysts are synthesized through a deposition-precipitation method. The effects of TNTs content and support morphology on the catalyst physicochemical properties and catalytic performance are investigated. The incorporation of TNTs support into CuO-ZnO-CeO2 catalysts not only promotes CuO reducibility and improves the metallic Cu dispersion and specific surface area, but also enhances CO2 adsorption and increases the proportion of basic sites γ, thereby resulting in high CO2 conversion and CH3OH selectivity. It is also shown that CO2 conversion is positively correlated with the Cu specific surface area and that CH3OH selectivity is related to the proportion of basic sites γ. Due to the excellent reducibility, high metallic Cu surface area, superior CO2 adsorption and large proportion of basic sites γ, CuO-ZnO-CeO2/10 wt.% TNTs gives excellent catalytic performance and possesses a great potential as catalyst for methanol synthesis.

In this work, we introduce the growth of a new complex oxide lead oxy-chalcogenide (PbOxSe1–x) thin film using an oxygen plasma-assisted molecular beam epitaxy method. Freshly cleaved BaF2(111) wafers were used as the substrates for this growth study. Systematic characterization of X-ray diffraction peaks, Raman shifts, absorption spectra, scanning electron microscopic imaging, and Hall measurements were conducted to elucidate the structural, optical, and electric properties of the as-grown PbOxSe1–x thin films. Specifically, X-ray diffraction measurements revealed that PbOxSe1–x films maintained the same rock-salt crystal structure as the PbSe semiconductor, but a slight shift in the lattice parameter was observed. A blue shift in the optical absorption edge also suggests that the inclusion of oxygen atoms led to the formation of a ternary compound crystal structure. Furthermore, all PbOxSe1–x thin films were observed to be polycrystalline in nature and displayed preferred [100] orientated grains. Slight...

Device performance of organic–inorganic halide solar cells significantly depends on the quality of the perovskite absorber films, which is dominated by synthesis techniques. Here, we demonstrated a...

A mid-wave infrared (MWIR) uncooled PbSe-QDs/CdS p–n heterojunction photodiode has been fabricated using a wet-chemical synthesis route. This offers a low-cost alternative to traditional monocrystalline photodiodes relying on molecular beam epitaxy (MBE) technology. It was demonstrated that the post-annealing is critical to tailor the photoresponse wavelength and to improve the performance of photodiodes. After annealing at 673 K in air for 0.5 h, the ligand-free PbSe-QDs/CdS photodiode exhibits a MWIR spectral photoresponse with a cutoff wavelength of 4.2 μm at room temperature. Under zero-bias photovoltaic mode, the peak responsivity and specific detectivity at room temperature are 0.36 ± 0.04 A W−1 and (8.5 ± 1) ×108 cm Hz1/2 W−1, respectively. Temperature-dependent spectral response shows an abnormal intensity variation at temperatures lower than 200 K. This phenomenon is attributed to the band alignment transition from type II to type I, resulting from the positive temperature coefficient of PbSe. In addition, it was proved that In doped CdSe (CdSe:In) films could be used as a promising new candidate of infrared transparent conductive electrodes, paving the way for monolithic integration of uncooled low-cost MWIR photodiodes on Si readout circuitry.

Secondary aluminum dross (SAD) from aluminum industry is classified as a hazardous solid waste due to containing aluminum nitride (AlN). In this work, AlN was first used to reduce heavy metals by pyrometallurgy. The reduction rates for iron, chromium and nickel were up to 90%, 80% and 100%, respectively. However, the reduction from AlN and oxygen oxidization of AlN occurred simultaneously. AlN which formed solid solution with alumina could reduce heavy metals, while the rest was oxidized by oxygen. In addition, the reduction rates for iron and chromium could be increased with increasing CaF2 from 6.7 to 9.0 wt%. CaF2 could decreased viscosity of molten slag, which favored the ion migration, and then increased the reduction rates. After the reduction, glass ceramics were manufactured from the molten slags. The bending strength, microhardness and alkali resistance of the glass ceramics were up to 77 MPa, 1011 HV and 98.7%, respectively. According to XRD and SEM results, glass ceramics with CaAl2SiO6 crystal phase, crosslinked network structure grains and smaller pores exhibited better bending resistance. In addition, glass ceramics with CaAl2SiO6 crystal phase possessed the highest microhardness and alkali resistance. After this process, hazardous pickling sludge and SAD were totally recycled.

A series of Cu-Ni/CeO2-nanotube catalysts is prepared by an impregnation method for CO2 hydrogenation to CH3OH. Regular CeO2 nanotubes are perfectly formed with a tube diameter of about 30-50 nm and Cu-Ni alloy is well dispersed on CeO2 nanotube without nanotube morphology change. There is a synergistic effect between Ni and Cu, promoting the bimetallic Cu-Ni dispersion, reducibility, CO adsorption and hydrogenation. Additionally, a strong interaction is observed between Cu-Ni alloy and CeO2, and it contributes to partial reduction of Ce4+ to Ce3+ and formation of oxygen vacancies which adsorb and activate CO2. It is shown that both CO2 conversion and CH3OH space-time yield increase at first, reach their maximum values at a Ni/(Cu+Ni) ratio of 2/3, and then decrease with increasing the Ni/(Cu+Ni) ratio. The CeO2-nanotube supported CuNi2 catalyst gives CO2 conversion of 17.8% and CH3OH space-time yield of 18.1 mmol/(gcat∙h) after preliminary optimization. Furthermore, it exhibits an excellent catalytic per...

This paper provides a theoretical study and calculation of the specific detectivity-D* limit of photovoltaic (PV) mid-wave infrared (MWIR) PbSe n+-p junction detectors operating at both room temperature and TE-cooled temperature. For a typical PbSe p-type doping concentration of 2 × 1017 cm-3 and with high quantum efficiency, the D* limits of a photovoltaic PbSe n+-p junction detector are shown to be 2.8 × 1010 HZ1/2/W and 3.7 × 1010 HZ1/2/W at 300 K and 240 K, with cut-off wavelength of 4.5 μm and 5.0 μm, respectively. It is almost one magnitude higher than the current practical MWIR PV detector. Above 244 K, the detector is Johnson noise limited, and below 191 K the detector reaches background limited infrared photodetector (BLIP) D*. With optimization of carrier concentration, D* and BLIP temperature could be further increased.

In this paper we have presented a power conversion efficiency (PCE) enhanced Pb-chalcogenide/CdS quantum dots (QDs) solar cells with novel tandem absorption layers synthesized by using chemical bath deposition (CBD) method. The tandem absorption layer is assembled by orderly stacking PbS-QDs layer, PbS-QDiM layer and PbSe-QDiM layer. Compared to single layer PbS-QDs/CdS solar cells, the solar cell with double-tandem layers (PbS-QDiM/QDs) shows the highest short current density ( J sc ) of 47.5 mA/cm 2 due to smoothing of the photo-generated carrier transportation and enhancing the absorption in the visible region 530–800 nm. However, the decreased open circuit voltage (V oc ) of 0.14 eV results in a low power conversion efficiency (PCE) of 2.2%. The triple-tandem absorber (PbSe-QDiM/PbS-QDiM/QDs) enhances the spectra absorption both in the visible (500–800 nm) and near-infrared (1000–1700 nm) regions, resulting in a higher short current density ( J sc ) of 40 mA/cm 2 , while keeping a relatively large open circuit voltage (V oc ) of 0.28 eV. Through an architectural modification, an enhancement of power conversion efficiency (PCE) of 4.2% has been achieved.

Photoconductive thin films on the basis of PbSe have been used as functional materials for infrared (IR) detectors. High quality PbSe thin films were grown on glass substrates by chemical bath deposition (CBD) yielding a peak detectivity of 2.8 × 10 10 cm Hz 1/2 W −1 at room temperature. The photoconductive sensor function is established by a sensitization process by annealing PbSe films in oxygen and iodine rich atmospheres. By studying such sensitized PbSe layers we discovered that new, quaternary phases are formed at the top of the layered structure. We could show that after annealing the following layer structure had formed: a bottom layer of PbSe (1 μm) and a top layer of Pb-Se-O-I (400 nm), containing (i) a poly-crystalline and (ii) a nano-crystalline phase. The poly-crystalline phase was found to be a solid solution of Se and I and yielded an average Pb/I mole fraction ratio of 3.1 and Pb/Se of 3.9, respectively. It contained the largest iodine mole fraction of ∼20 at.% while the nano-crystalline phase yielded less iodine (

TiO 2 nanoparticles functionalized with Cu x S (Cu x S-TiO 2 , x = 1 or 2) photocatalysts were synthesized via a facile precipitation method at room temperature. The resulting products were well characterized by XRD, TEM, EDS, XRF, BET, XPS, UV–vis and PL. The performance of H 2 production by photocatalytic water decomposition for the Cu x S-TiO 2 nanocomposite was examined in methanol aqueous solution using a 300 W Xe lamp as light source. Results showed that the activities of the CuS and Cu 2 S dual-cocatalysts co-loaded samples exhibited highly efficient water splitting capabilities for H 2 evolution, and 5.62 mmol h −1 g −1 of H 2 production was achieved with the composition-optimized Cu x S-TiO 2 , which was more efficient than those of single cocatalyst deposited samples and TiO 2 alone. It is proposed that the co-deposition of CuS and Cu 2 S onto TiO 2 nanoparticle surface could efficiently extend light absorption toward visible light range, facilitate the separation of photoinduced charge carriers and consequently enhance the photocatalytic H 2 production activity. The present work not only shows the possibility for the simultaneous utilization of Cu x S mixtures as efficient cocatalysts and photosensitizers to significantly facilitate the photoactivity of H 2 evolution, but also offers a general, feasible strategy for constructing ternary hybrid photocatalysts with other multivalent non-noble metal compounds as cocatalysts for target applications in solar energy conversion.

Novel red phosphorus-CdS (P-CdS) composite photocatalysts were successfully prepared through a facile and fast precipitation method. The samples were then characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence emission spectroscopy (PL). The photocatalytic activity was evaluated by H2 generation in the aqueous solution containing Na2S/Na2SO3 as hole scavengers under visible light irradiation (λ ≥ 400 nm). The results show the optimal P molar ratio was 10 mol% and the corresponding H2 production rate reached 923 umol h−1 g−1, which is about 2.53 times higher than that of CdS sample. Meanwhile, the composite photocatalysts show favorable photostability. The enhanced photocatalytic activity can be attributed to the highly effective charge separation on P-CdS hybrids as confirmed by PL result. Also, a possible photocatalytic mechanism of the P-CdS composites is proposed and discussed in detail.

TiO2 nanotubes (TNTs) with nickel sulfide (NiS) co-catalyst were prepared by a simple solvothermal method and characterized by X-ray diffraction, transmission electron microscope, N2-physisorption, UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. Loading NiS nano-clusters can significantly enhance the photocatalytic H2 evolution performance of TNTs. The optimum NiS loading content was found to be 8 wt% and the corresponding hydrogen production rate is ca. 7486 µmol/h/g, being about 79 times higher than that of pure TNTs. This enhancement of photocatalytic H2 evolution was attributed to the synergistic effect between NiS and TNTs.

In this work, the study of the influences of lifetime, doping concentration and absorption layer thickness to resistant- area product (R0A) and quantum efficiency of Pb1-xSnxSe photovoltaic detector are presented. Three fundamental current mechanisms including diffusion, generation-recombination, and tunneling models are considered. Using optimal doping concentration and absorption layer thickness parameters, the calculated detectivity (D*) of Pb1-xSnxSe photovoltaic detector is over 1012 cm Hz1/2/W.

Mid-infrared photonic crystal enhanced lead-salt light emitters operating under continuous-wave mode at room temperature were investigated in this work. For the device, an active region consisting of 9 pairs of PbSe/Pb0.96Sr0.04Se quantum wells was grown by molecular beam epitaxy method on top of a Si(111) substrate which was initially dry-etched with a two-dimensional photonic crystal structure in a pattern of hexagonal holes. Because of the photonic crystal structure, an optical band gap between 3.49 and 3.58 µm was formed, which matched with the light emission spectrum of the quantum wells at room temperature. As a result, under optical pumping, using a near-infrared continuous-wave semiconductor laser, the device exhibited strong photonic crystal band-edge mode emissions and delivered over 26.5 times higher emission efficiency compared to the one without photonic crystal structure. The output power obtained was up to 7.68 mW (the corresponding power density was ~363 mW/cm2), and a maximum quantum efficiency reached to 1.2%. Such photonic crystal emitters can be used as promising light sources for novel miniaturized gas-sensing systems.

A new method of surface passivation of PbSe epitaxial layers by growing a thin epitaxial CaF2 layer is proposed. Improvement in photoluminescence (PL) intensity is observed when the PbSe layer is passivated. The minority carrier lifetime (?), measured by photo-current decay method corroborates PL measurements and shows a consistent, albeit not considerable, improvement in the lifetime of PbSe samples after surface passivation. The positive effect of surface passivation, especially at low heat-sink temperature, offered by a new passivating material is critically important for IV-VI material-based infrared detector and sensor applications.

PbSe thin film was grown on a patterned Si substrate with (1 1 1)-orientation by molecular-beam epitaxy (MBE). On the mesa, a low dislocation density of 9×105 cm−2 was confirmed by the etch-pits density (EPD) wet-etching technique. The photoluminescence (PL) intensity at room temperature from the low dislocation PbSe film was much higher than that from the PbSe film grown on the planar area, which further indicated the high-quality of PbSe thin film grown on patterned Si substrate.

The continual improvement of IV–VI materials grown by molecular beam epitaxy (MBE) is a key step in the development of IV–VI infrared semiconductor devices on silicon substrates. This study presents a novel surface-treatment method which is carried out during MBE growth of monocrystalline PbSe on Si(1 1 1)-oriented substrates. Details of the experimental procedures are described and supported by reflection high-energy electron diffraction (RHEED) patterns. The effect of the in-situ surface-treatment method is exhibited in the forms of improved electrical and morphological properties of PbSe thin films. Specially, the carrier mobility increases almost three-fold at 77 K and nearly two-fold at 300 K. The density of the growth pits undergoes almost three-fold reduction, whereas the density of the threading dislocations decreases around four-fold.

PbSe thin films grown on (111)-oriented Si substrates by molecular-beam epitaxy were annealed under an oxygen atmosphere with a variety of temperatures and times. The photoluminescence intensity from the sample annealed at 350°C for 2 h was increased by 400-fold with frontside pumping and increased by 40-fold with backside pumping, respectively, in comparison with the as-grown sample. Furthermore, the mobility was increased twofold after annealing. Such large photoluminescence increases and mobility improvements could be attributed to the surface passivation and the dislocation and defect passivation caused by oxygen diffusion and reaction with the PbSe film.

A lead salt mid-infrared laser sample grown by molecular-beam epitaxy (MBE) on a polished BaF2 (110) substrate is studied. For improving the laser performance at higher operating temperature, a method of substrate transfer from a BaF2 substrate to a copper heat sink is developed. The cleaved facet along the {100} plane, which is helpful for the formation of a Fabry-Perot resonant cavity on the laser sample, is observed. Pulsed photoluminescence measurements are conducted on the laser sample step by step during processing in order to trace the effect of each process step.

We present a detailed study on the surface morphologies and chemical composition of growth pits in lead selenide (PbSe) epilayers grown by molecular-beam epitaxy. Various growth pits were investigated by scanning electron microscopy and energy-dispersive x-ray analysis. The vast majority of growth pits within the PbSe epilayers contained either single or multiple PbSe microcrystals with a distinct cuboid shape. Based on the observed structures and morphologies of the PbSe microcrystals, the formation mechanism of the cuboid structures was considered to be (100) preferential crystal growth originating from PbSe polycrystalline seeds.

Fabrication of microrods from multi-quantum well (MQW) PbSe-PbSrSe structure grown in molecular beam epitaxy (MBE) followed by its morphological as well as optical characterizations are described. Pulsed PL intensity is increased by 64 times per unit surface area from a free-standing MQW microrod mounted on copper heat sink compared with the bulk sample. Enhancement in side emission power due to the higher optical confinement effect during pulsed photoluminescence (PL) from MQW semiconductor microtube inserted in hollow quartz optical fiber signifies that these microstructures are robust in nature and crucial contenders for portable mid-infrared optoelectronic devices to be used in the field of industrial trace-gas sensing.

Recent advancements in IV–VI growth techniques have led to a renewed interest in using Pb1−x Sn x Se for mid infrared (mid-IR) detector fabrication. There is now a greater need for an in-depth theoretical understanding of the potential competitiveness of these material systems with Hg1−x Cd x Te (MCT) especially in regards to material defects and device performance. Herein, we calculate the shielding effects of the dielectric constant by considering the scattering of electrons due to ionized impurities and small charged dislocations. The higher dielectric constant in IV–VI materials, nearly ten times greater than that of MCT, is shown to more effectively screen out the influence of impurities.

Micropillars were fabricated on multiple quantum-well structure of PbSe/PbSrSe grown on top of BaF"2 substrate in molecular beam epitaxy (MBE). The photoluminescence spectra from the pillar structure, having a diameter of 5@mm and inter-pillar distance of 8@mm, was studied at various temperature starting from 77 to 300K. There had been an approximately consistent red-shift of photoluminescence peak of ~3.62cm^-^1 for unit K change in ambient temperature. The prominent and repeatable emission from the micropillars at various temperatures signified high crystalline nature of the fabricated micro-objects. This type of micropillar structure is one of the magnificent contenders of future opto-electronic micro-features.

In this work, we are reporting fabrication of micro-rods based on epitaxially grown lead selenide (PbSe) on (111) oriented barium fluoride (BaF2). The micro-rods were formed by folding back action of PbSe and their dimension was determined by the initial layer thickness and etching parameters. The micro-rods scattered throughout the surface were measured to have diameters mainly in the range of ∼14–18 μm and lengths ∼40–300 μm. These robust micro-rods can be used for future research on semiconductor microstructures and mid infrared opto-electronic devices.

Numerical analysis of a CdS/PbSe room-temperature heterojunction photovoltaic detector is discussed as to provide guidelines for practical improvement, based on the previous experimental exploration [1]. In our experiment work, the polycrystalline CdS film was prepared in hydro-chemical method on top of the single crystalline PbSe grown by molecular beam epitaxy method. The preliminary results demonstrated a 5.48×108 Jones peak detectivity at λ=4.7μm under zero-bias. However, the influence of some material and device parameters such as carrier concentration, interface recombination velocity remains uncertain. These parameters affect the built-in electric field and the carriers’ transportation properties, and consequently could have detrimental effect on the device performance of the CdS/PbSe detector. In this work, therefore, the numerical analysis is performed based on these parameters. The simulation results suggest that the device performance can be improved at least 4 times by increasing CdS concentration for two orders of magnitudes, and the device performance will degrade severely if the interface recombination speed is over 104 cm/s.

PbSe thin film and PbSe/PbSrSe multiple quantum well (MQW) structures were successfully grown on (1 1 0) BaF2 substrates by molecular beam epitaxy. The average linewidth of the rocking curve from high-resolution X-ray diffraction measurements of the (2 2 0) reflection for the PbSe thin film was 60 arcsec, which indicates high crystalline quality. The dislocation density estimated from the rocking curve was 1×107 cm−2. Strong photoluminescence (PL) of the MQW structure at room temperature was observed. This PL signal was two times larger than those measured from a duplicate structure grown at the same time on a (1 1 1) BaF2 substrate. The energy bandgap of (1 1 0) PbSe follows the same temperature dependence as [1 0 0]- and [1 1 1]-orientated PbSe.

Flower-like bundles of ZnO nanosheets have been prepared by using preheating hydrothermal process without any surfactants. The flower-like bundles consist of many thin and uniform hexagonal-structured ZnO nanosheets, with a thickness of 50 nm. The selected area electronic diffraction (SAED) and high-resolution transmission electron microscope (HRTEM) images indicate that the ZnO nanosheets are single crystal in nature. The growth mechanism of the flower-like bundles of ZnO nanosheets is discussed based on the morphology evolution with growth times and reaction conditions. It is believed that the formation of flower-like bundles of ZnO nanosheets is related to the shielding effect of OH−ions and the self-assembly process, which is dominated by a preheating time. Room temperature photoluminescence spectra results show that the annealing atmosphere strongly affects the visible emission band, which is sensitive to intrinsic and surface defects, especially oxygen interstitials, in flower-like bundles of ZnO nanosheets.