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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.

The broad application of lead selenide (PbSe)-based uncooled midinfrared (MIR) detectors has been hindered by the nonuniformity of wafer-level films prepared by the conventional chemical bath deposition (CBD) method. Herein, using a vapor phase deposition (VPD) approach, we demonstrate the deposition of 3 in. wafer-scale uniform PbSe thin films with thicknesses of up to 1.5 μm. To trigger the MIR response, the as-grown films were sensitized at an elevated temperature in an oxygen-iodine atmosphere. We discovered that the key to spark off the MIR response of the PbSe detector originated from the self-assembled rodlike microstructures in the thin films, which can be controlled by the I

The low performance of middle infrared (MIR) PbSe detectors fabricated from vapor phase deposition (VPD) technology restricts the rapid development of VPD technology and detector commercialization. A modified VPD process was proposed to duplicate the microstructural features of high-performance CBD-PbSe detectors for a breakthrough in the VPD technology. A peak detectivity D* of 1.6 × 1010 cm Hz1/2 W−1 at 298 K was achieved under the optimized sensitization, approaching the best performance of CBD-PbSe detectors. Through the contrasting various microstructures obtained from diverse methods, the nanoparticle self-assembly structure in VPD-PbSe oriented rod-like crystals is an important factor for the IR sensitivity. The microstructural evolution demonstrated that there is a large space to grow for VPD-PbSe detectivity D* via eliminating the voids formed in the iodine-sensitization process. The increased performance indicates that the modified VPD technology can provide technical support for the manufacturing of the megapixel uncooled lead-salt FPA imager and accelerate its industrialization.

PbSe films deposited by chemical bath deposition (CBD) technology were sensitized in various atmospheres to distinguish the role of iodine and oxygen in the sensitization process. No infrared (IR) photo response was observed in samples sensitized in pure oxygen, showing the O element cannot trigger the infrared response of PbSe. However, a high detectivity of 1 × 1010 was achieved in the sample sensitized in a N2/I2 atmosphere, which demonstrates iodine is a key element for inducing an IR response. The role of iodine was analyzed from the morphological evolution, phase composition transformation and resistance change during the sensitization process. The XRD and FESEM results show a PbI2 3D network forming around the PbSe grains in the sensitization process, playing the role of photo-generated electron transporting channels, which is key to inducing the IR response of PbSe detectors. The 3D network conducting model can explain well the charge separation mechanism of PbSe IR photoconductive detection.

PbSe films deposited by chemical bath deposition (CBD) technology were sensitized in various atmospheres to distinguish the role of iodine and oxygen in the sensitization process. No infrared (IR) photo response was observed in samples sensitized in pure oxygen, showing the O element cannot trigger the infrared response of PbSe. However, a high detectivity of 1 × 10

Employing atomic-scale simulations, the response of a high-angle grain boundary (GB), the soft/hard GB, against external loading was systematically investigated. Under tensile loading close to the hard orientation, strain-induced dynamic recrystallization was observed to initiate through direct soft-to-hard grain reorientation, which was triggered by stress mismatch, inhibited by surface tension from the soft-hard GB, and proceeded by interface ledges. Such grain reorientation corresponds with expansion and contraction of the hard grain along and perpendicular to the loading direction, respectively, accompanied by local atomic shuffling, providing relatively large normal strain of 8.3% with activation energy of 0.04 eV per atom. Tensile strain and residual dislocations on the hard/soft GB facilitate the initiation of dynamic recrystallization by lowering the energy barrier and the critical stress for grain reorientation, respectively.

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.

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 (

Axially (c-axis)-oriented ZnO thick films with a ∼8.1 μm thickness were fabricated on ZnO seed layer coated substrates by using a filtered preheated hydrothermal solution. The thick films composed of single-crystal ZnO microrods with various diameters were formed by coalescing each nanorod together along their side surfaces. From the X-ray diffraction result a biaxial stress exists was found to exist in the as-grown thick films, and the stress gradually increased with increasing annealing temperatures from 200 to 550 °C due to a degradation in the crystalline quality. The biaxial stress is responsible for the red-shift of the optical band gap of the ZnO thick films. Photoluminescence and Hall results revealed that the optical and the electrical properties of the thick films were degenerated after high-temperature annealing (> 200 °C), which was due to the introduction of point defects, such as oxygen interstitials and zinc vacancies.

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.

In this report, upstanding and nanoporous hexagonal TiO2 nanosheet arrays were achieved via using kassite [CaTi2O4(OH)2] as an intermediate. The process developed involved a TiO2 nanorod-derived synthesis of upstanding hexagonal kassite nanosheet arrays and a transformation of the kassite to TiO2. To the best of our knowledge, this is the first successful attempt to grow ordered hexagonal kassite nanosheet arrays. The as-obtained kassite nanosheets showed a single-crystalline nature with their c-axis parallel to the substrate. A stepwise study of the growth of the interesting hexagonal kassite nanosheet arrays was demonstrated. Upon hydrothermal treatment with diluted HNO3 aqueous solution, the single-crystalline hexagonal kassite got converted to nanoporous rutile TiO2, with shape preservation. The approach described in this study provides a novel method for the synthesis of kassite and TiO2 nanosheet arrays and are ready for a variety of applications such as in catalytic or optoelectronic fields.

The porous nanotubes were successfully fabricated by coating a porous layer on the walls of the TiO2 nanotubes. This method was proved available for effectively increasing the specific surface area of the nanotubes. The DSSCs based on such porous nanotubes has a higher conversion efficiency than that of the DSSCs using common TiO2 nanotubes. This could be explained by the enhanced loading of dye molecules on porous TiO2 nanotubes, which resulted in the improvement of short-circuit current. The light to electric energy conversion efficiency of the DSSCs applying porous TiO2 nanotubes is about 1.79% nearly two times higher than that of the DSSCs based on normal TiO2 nanotubes.

Volmer―Weber-type ZnO nanorods (VW ZnO NRs) were fabricated by using a hybrid method combined with RF sputtering and hydrotherma) methods. The structural and optical properties of VW ZnO NRs were investigated by using synchrotron X-ray diffraction (XRD), micro-Raman spectroscopy, photoluminescence (PL) spectroscopy and X-ray photo-electron spectroscopy (XPS). it was found that VW ZnO NRs showed wurtzite structure and were verticaDy standing on a substrate with a compressive stress from the substrate that can be reduced by annealing. in the micro-Raman study, a forbidden E 1 (LO) mode in a bulk ZnO was observed in VW ZnO NRs due to the many edges in NR structures. It was also confirmed that VW ZnO NRs have a wurtzite structure by observing E 2 Iow and E 2 high peaks. In the PL spectra, VW ZnO NRs showed a broad emission in the visible range, especially yellow emission, with a weak UV emission. The UV emission was monotonously enhanced on increasing the annealing temperature. The yellow emission was enhanced in the annealed sample at 200 C due to an evaporation ofhydroxy) groups (OH )on the surface of VW ZnO NRs.

A single-crystalline twinned ZnO nanostructure with a 2-dimensional leaf-like morphology (nanoleaves) was synthesized using a facile hydrothermal strategy. The ZnO nanoleaves had 2-fold symmetric branches, which were identified by the existence of an inversion domain boundary (IDB) along the [2110] growth direction of the ribbon-like stems with both side surfaces of the stems terminated with a chemically active Zn-(0001) plane. A proposed growth mechanism suggested that the formation of IDB and the leaf-like shape are related to the dissolution of seed particles on the substrate surfaces and an OH- shielding effect in solution, respectively. Optical measurements revealed visible emission, suggesting the possession of defects in the as-grown and annealed ZnO nanoleaves. In addition, various ZnO nanostructures were synthesized by simply controlling the fabrication conditions.

Ultralong ZnO nanorod arrays with a length of 10 microm were synthesized using a preheated hydrothermal-solution precursor, and their optical and electrical properties were studied using photoluminescence (PL) spectra and field effect transistors (FETs). The PL spectra showed ultraviolet, orange, and red emissions and had different temperature dependences with increasing temperature. The high-resolution photoluminescence spectra showed that the ultraviolet (UV) emission had different origins within different temperature ranges. The parameters describing the temperature dependence of the peak position shift, intensity, and full width at half maximum were evaluated using different models. After the fabrication of individual nanorod FETs, the ultralong ZnO NRs showed a clear n-type gate modulation with a typical electron concentration of 10(17) cm(-3) and a typical electron mobility of 35.7 cm2/V x s.

ZnO nanowires (NWs), grown by hydrothermal and vapor phase transport (VPT) methods, were employed as the channel layers to fabricate single nanowire Field Effect Transistors (NWFETs) with a p+-silicon as the bottom gate. The FET employing hydrothermal grown ZnO NWs shows n-type depletion mode with a field mobility of 18.27 cm2/V⋅s, an on/off ratio of 106, and a threshold voltage of -48.5 V. In comparison, the device using VPT grown NWs operates in n-type depletion mode with a field effect mobility of 36.94 cm2/V⋅s, a drain current on/off ratio of 105, and a threshold voltage of -14 V. The reason for the difference of threshold voltage and the mobility by two methods was discussed in this paper.

A simple, rapid and eco-friendly method has been introduced to prepare suboxide Cu(x)O(x = 8, 64) nanocrystals on multiwall carbon nanotube (MWCNT) composites. The structural characterization by using high-resolution transmission electron microscopy and X-ray diffraction methods indicates that Cu(x)O(x = 8, 64) can be uniformly grown on the sidewalls of carbon nanotube under direct copper deposition at room temperature. Our results suggest that the growth method of nano-Cu(x)O (x = 8, 64) crystals could be used to synthesize other nano-metal suboxides, such as M(x)O [M=metal; x = 1, 2, 4, 8 and 64]

Nanocrystalline CuSCN films were deposited from the room-temperature (20–25 °C) aqueous solutions by the successive ionic layer adsorption and reaction (SILAR) method. The substrate rinsing procedure in SILAR was modified to realize the deposition of CuSCN at reasonable rate. The S2O32− (chelating reagent)–Cu2+ molar ratio in the precursor was increased from 1:1 to 3:1, to stabilize the precursor and improve the film quality. Effects of the [SCN−/Cu2+] molar ratio on the crystallinity, the morphology and optical properties were examined. Obtained CuSCN film deposited at the optimal condition exhibits obvious crystallinity, high purity, dense and uniform morphology with the crystallite size of 20–30 nm, optical transmittance of 50–70% at 400–800 nm, and band gap of 3.94 eV. The higher S2O32−–Cu2+ molar ratios can prevent the formation of precipitations in the precursor and the by-products (Cu(SCN)2 and Cu3(SO4)2(OH)2 · xH2O) in the film. The optimal SCN−–Cu2+ molar ratio of 4:1 has been found, at which the film exhibits better crystallinity, smaller crystallite size, and denser film structure.

Porous TiO2 thin films obtained from sol–gel self-organize approach were firstly used as masks to control the growth of ZnO nanorod arrays by aqueous solution method. The effect of TiO2 pore size on the density of ZnO nanorod arrays was investigated by atomic force microscopy and field emission scanning electron microscope. The results show that the density of ZnO nanorod arrays obviously decreases after using porous TiO2 masks, and increases with increasing the TiO2 pore size. Additionally, the existence of TiO2 mask can also effectively prolong the wet-chemical etching time of TiO2 nanotube arrays manufactured from ZnO nanorod templates assisted sol–gel method, to completely remove the ZnO nanorod templates and to avoid collapsing of TiO2 nanotube arrays from the substrates.

ZnO-SDS hybrid thin films were grown on ITO glass using the potentiostatic electrodeposition route from aqueous zinc nitrate solution containing surfactant sodium dodecyle sulfanate (SDS). The electrochemical process of the hybrid films was analyzed by comparing the cyclic voltammetric curve and current–time curve with those of pure ZnO film. Results showed that the addition of a small amount of SDS could decrease the deposition current density, and inhibit the growth of ZnO crystals significantly. The hybrid films electrodeposited at −0.9 V for 30 min exhibited smooth and platelet-like morphology, with the film thickness of about 110 nm. The well-defined ZnO-SDS lamellar structures could be clearly observed, with two interlayer spaces of 35.1 and 30.9 A, respectively. Optical analysis showed that the hybrid films had good optical quality, and exhibited the fundamental absorption edge of ZnO at 380 nm.

Ordered porous TiO2 films, including TiO2 nanotube arrays, are fabricated by a sol-gel dip-coating approach via ZnO nanorod templates obtained from aqueous solution approach. The results indicate that the morphologies of ordered porous TiO2 films have been great affected by the sol-gel dip-coating cycle number. Open-ended TiO2 nanotube arrays can be obtained in optimum dip-coating cycle numbers. The TiO2 nanotubes with the inner diameter matching well with the diameters of ZnO nanorods, are well assembled and separate each other. When the cycle number is less than this optimum value, no intact porous TiO2 film can be obtained. As the cycle number is larger than this optimum value, an ordered porous TiO2 film with many throughout holes is formed. The evolutive mechanism of ordered porous TiO2 films is proposed.

Compact and transparent ZnO films were deposited on the ITO/glass substrates from zinc nitrate aqueous solution by the two-step electrodeposition technique. While the first potentiostatic step was used to produce ZnO seed layer, the ZnO film growth has been done galvanostatically. Effects of the potentiostatic parameters on the crystal structure, morphology and optical properties of ZnO films were investigated. Results show that ZnO films with highly c-axis preferred orientation can been obtained when the potentiostatic deposition at −1.2 V for 15 s has been applied. Such an observation might be attributed to the etching process of ITO substrate in the diluted HCl solution. The film exhibits smooth and compact morphology, high transmittance in the visible band (>80%) and sharp absorption edge (at ∼370 nm). The analysis on the growth mechanism indicates that the short potentiostatic process prior to the film growth can produce ZnO seed layer and substitute the initial nucleation process in the conventional one-step galvanostatic deposition, thus increasing the nucleation density and preventing the formation of loose structures.

The morphology of ZnO submicron crystals formed in a weak alkaline environment (pH value less than 11.0) was systematically studied for the first time. ZnO submicron particles with different morphologies (flowers, rod, and wire) were synthesized from an aqueous solution by adopting ethylenediamine as the source of hydroxyl group, hexamethylenetetramine (HMT) as the additive, and potassium chloride (KCl) as the background electrolyte. The effects of primary experimental parameters such as HMT and KCl addition, precursor concentration, and reaction temperature on the microstructure, crystallinity of the resultant particles, and their distribution on substrate are discussed in this paper. In the flowerlike structure, the particle size is more controlled by the precursor concentration, and the microstructure is modulated by increasing the concentration of HMT and the reaction temperature. The introduction of ZnO seed layer on substrate promotes even distribution of ZnO flowers. High concentration KCl electrolyte inhibits formation of the flowerlike structure and promotes the growth of submicron ZnO crystals in rod or wire shape. Mechanism studies indicate that the degree of supersaturation of Zn(OH)2 and the adsorption of organic/inorganic species on the surface of ZnO are the prime factors influencing the nucleation, growth rate, and eventual morphology.

A novel solution method was developed for the deposition of transparent ZnO film from aqueous solution, integrating the ultrasonic irradiation with the stepwise chemical deposition at relatively high temperature (>100 °C). Obtained ZnO films exhibited high crystallinity, highly preferential orientation along the c-axis, smooth and compact morphology, and high transmittance in the visible band (>80%). The deposition temperature and ultrasonic irradiation were found to have significant influence on the phase purity, crystallinity, grain size, and morphology of ZnO films. While the lower temperature (120 °C) was inefficient to eliminate the intermediate phase of Zn(OH)2, the higher deposition temperature and ultrasonic irradiation were found powerful to improve the crystalline degree and the quality of film. Mechanism analysis indicated that the rapid water evaporation in the precursor layer and the rapid decomposition of zinc–ammonia complex during the high-temperature deposition process were indispensable for the growth of high-quality ZnO films.

The influence of annealing effects in CuInSe 2 ternary films prepared by successive ionic layer absorption and reaction method has been investigated. The films have firstly been deposited on glass substrates at room temperature and then heat-treated under Ar atmosphere at various annealing temperatures. CuInSe 2 films were characterized using X-ray diffraction (XRD), scanning electron microscopy, X-ray photoelectron spectra, optical absorption spectrum and Hall system. XRD results showed that the proper post-annealing process can lead to a complete formation of chalcopyrite structure CuInSe 2 with high degree of preferred orientation towards (112) reflection. After annealing process, the composition of annealed films was close to the standard stoichiometry and O, Cl impurities decreased. The direct band gap increased from 0.94 to 0.98 eV and resistivity showed a big decrease with the increase of annealing temperature.

A novel stepwise method was developed for the deposition of ZnO nanorod array (NRA) from the simple inorganic aqueous solution. Different from the traditional one-pot synthesis route, merely a thin liquid precursor layer adsorbed on the substrate instead of the bulk solution underwent the reaction at elevated temperature in a typical deposition cycle. Sparse and vertically grown wurtzite ZnO NRA was deposited on seed layer-free glass substrate after 20 cycles (in typically 20 min). Each individual ZnO rod possessed the well-defined hexagonal facet, the side length of about 150 nm, the aspect ratio of 2:3, and the small size dispersity. Also the overall ZnO NRA exhibited high ultraviolet photoluminescence and weak blue emission, indicating its good optical properties. Mechanism analysis indicated that, the decrease of the supersaturation degree in solution after the climax in the reaction period of each deposition cycle is the root cause of the sparse nucleation and the vertical growth of ZnO nanorods. The work has opened up a novel stepwise approach toward high quality ZnO NRA, being valuable for extending the synthetic methods of semiconductor nanostructures in mild solutions.

High density TiO 2 nanotube film with hexagonal shape and narrow size distribution was fabricated by templating ZnO nanorod array film and sol–gel process. Well-aligned ZnO nanorod array films obtained by aqueous solution method were used as template to synthesize ZnO/TiO 2 core–shell structure through sol–gel process. Subsequently, TiO 2 nanotube array films survived by removing the ZnO nanorod cores using wet-chemical etching. Polycrystalline anatase TiO 2 nanotube films were ∼ 1.5 μm long and ∼ 100 nm in inter diameter with a wall thickness of ∼ 10 nm.

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.

Ion layer gas reaction (ILGAR) method for CuInS 2 films was developed by using ethanol as solvent. The influences of [Cu] / [In] ratio in ethanol solution on structural, chemical, topographical, optical and electrical properties of CuInS 2 thin films were investigated. X-ray diffraction and X-ray photoelectron spectroscopy results showed that all CuInS 2 thin films derived from different [Cu] / [In] ratios were sphalerite with preferred orientation (112). Scanning electron microscopy revealed that the microstructure and the growth rate of the films depended on the relative amounts of copper in the solution. When [Cu] / [In] ratio was 1.50 growth rate of the film was about 30 nm/cycle and the film was uniform, compact and good in adhesion to the substrates. The absorption coefficients of CuInS 2 films estimated from transmittance spectra were more than 10 4 cm − 1 , and the films behaved with p-type conductivity. The band gap E g changed from 1.30 to 1.40 eV and the dark resistivity decreased from 3.1 to 0.04 Ω cm with increase of [Cu] / [In] ratio.

Polystyrene spheres (PS) were synthesized by an emulsifier-free emulsion polymerization technique and the PS colloidal crystal templates were assembled orderly on clean glass substrates by dip-drawing method from emulsion of PS. Porous ZnO thin films were prepared by filling the ZnO sol into the spaces among the close-packed PS templates and then annealing to remove the PS templates. The effects of ZnO precursor sol concentration and dipping time in sol on the porous structure of the thin films were studied. The results showed an ordered ZnO porous thin film with designed pore size that depended on the sol concentration and PS size could be obtained. And the shrinkage of pore diameter was about 30–43%. X-ray diffraction (XRD) spectra indicated the thin film was wurtzite structure. The transmittance spectrum showed that optical transmittance decreased with the decrease of wavelength, but kept above 80% optical transmittances beyond the wavelength of 550 nm. Optical band gap of the porous ZnO thin film (fired at 500 °C) was 3.22 eV.

CuInS 2 ternary films were prepared by a soft solution processing, i.e. successive ionic layer absorption and reaction (SILAR) method. The films were deposited on glass substrates at room temperature and heat-treated under Ar atmosphere at 500 °C for 1 h. CuCl 2 and InCl 3 mixed solutions with different ionic ratios ([Cu]/[In]) were used as cation precursor and Na 2 S as the anion precursor. The effect of the [Cu]/[In] ratio in precursor solution on the structural, chemical stoichiometry, topographical, optical and electrical properties of CuInS 2 thin films was investigated. XPS results demonstrated that stoichiometric CuInS 2 film can be obtained by adjusting [Cu]/[In] ratios in solution. Chalcopyrite structure of the film was confirmed by XRD analysis. The near stoichiometric CuInS 2 film has the optical band gap E g of 1.45 and resistivity decreased with increase of [Cu]/[In] ratios.

Porous ZnO plate crystal thin films were electrodeposited from an aqueous solution containing 0.5 M zinc nitrate as electrolyte with pH = 5 ± 0.1. Polystyrene spheres (PS) template was used as pore-forming assistant. The deposition was carried out with an applied potential − 0.8 V and − 0.9 V and bath temperature was 70 °C. The influence of potential on microstructure of porous plate crystal was observed by SEM. X-ray diffraction (XRD) spectra showed that the thin film was wurtzite structure. And the transmittance spectrum indicated that transmissivity was low in 300–900 nm and approximately linear decreasing with the decrease of wavelength. Additionally, the formation process of porous plate crystal was also discussed.

Ordered ZnO porous thin films were fabricated by cooperative assembly method using polystyrene sphere (PS) and ultrafine ZnO particles, in which ultrafine ZnO particles were directly assembled in the voids of PS while the template was being assembled by capillary forces. The influence of experimental parameters, such as evaporation temperature, ZnO concentration and the concentration ratio of PS/ZnO on morphology of the porous structure was mainly studied. The results showed that an ordered porous structure could be obtained by this method. X-ray diffraction (XRD) spectra indicated the porous ZnO thin film was wurtzite structure. The transmissivity decreased with the decrease of wavelength, but still kept above 80% beyond the wavelength of 550 nm. Optical band gap of the ZnO thin film was 3.13 eV.