Crystal Growth Orientation Research Articles

Design and Synthesis of Carbazole‐Cyclopentathiophene Alternating Copolymers for Inhibiting Phase Separation of Cs0.15FA0.85PbI3

AbstractTo inhibit phase separation of CsxFA1−xPbI3 perovskite into optically inactive δ‐CsPbI3 and δ‐FAPbI3 under high humidity and light conditions, herein two polymers, poly[3‐methyl‐6‐(2‐methylspiro[cyclopenta[1,2‐b:5,4‐b′]dithiophene‐4,2′‐[1,3]dithiolan]‐6‐yl)‐9‐octyl‐9H‐carbazole] (TM3) and poly[3‐methyl‐6‐(2‐methylspiro[cyclopenta[1,2‐b:5,4‐b′]dithiophene‐4,2′‐[1,3]dioxolan]‐6‐yl)‐9‐octyl‐9H‐carbazole] (TM4), are designed and synthesized to dope the Cs0.15FA0.85PbI3 perovskite film for perovskite solar cells (PSCs). The results of X‐ray photoelectron spectroscopy and nuclear magnetic resonance confirm the existence of coordination and hydrogen bonds between the polymer and Cs0.15FA0.85PbI3 perovskite. Ion migration in the perovskite film is thus markedly suppressed by the TM doping, as verified by the electrical poling measurement. Benefiting from these interactions, the TM doping is able to inhibit phase separation of Cs0.15FA0.85PbI3 markedly at a relative humidity of 55–65% and under light. Furthermore, the TM doping has other positive effects such as enhancing perovskite crystallinity, improving crystal growth orientation, reducing trap density, increasing hole extraction, and suppressing charge recombination. Consequently, the TM3‐ and TM4‐doped PSCs achieve a power conversion efficiency of 21.96% and 20.01%, respectively, against 17.82% for the undoped PSC. The humidity, environmental, illumination, and thermal stabilities of unencapsulated devices are also improved significantly by the TM3‐ and TM4‐doping, respectively. By comparison, TM3 with the S substitution shows abetter effect than TM4 with the O substation on photovoltaic performance and device stability.

Recent Progress of Polarization‐Sensitive Perovskite Photodetectors

AbstractPolarization‐sensitive photodetectors are gaining numerous attention since polarization detection is important in geological remote sensing, atmospheric monitoring, military recon, and medical examination. Among various reported photoactive materials for photodetectors, metal halide perovskites have outstanding advantages such as tunable band gaps, excellent optoelectronic properties, and easy fabrication. Moreover, the characteristics of crystal structure anisotropy and controllable growth orientation of perovskite crystals endow the perovskite photodetector with the ability to identify light polarization states. This review outlines the recent research progress of perovskite photodetectors on polarization‐sensitive detection. Firstly, key device parameters of polarization‐sensitive detection are introduced. Then, the recent progress of polarization‐sensitive perovskite detectors in the field of linear and circular polarization is reviewed according to the different principles of polarization response. Finally, the challenges of polarization‐sensitive perovskite photodetector are discussed.

Effect of extrusion on the crystallinity, viscosity, damage starch, and thermal properties of corn flour, masa, and tortilla

Nixtamalized products are very appreciated in México and the world; however, the traditional nixtamalization process (TNP) is highly polluting. Extrusion nixtamalization process (ENP) is an alternative method; however, much research reported high starch damage by ENP that affects the rheology, crystallinity, and general quality of nixtamalized products. This work studies the structural changes of cornstarch exposed to ENP under controlled conditions to produce corn flour, masa, and tortilla. The results of ENP and TNP showed significant differences (p<0.05) for corn flour and masa with higher damage starch in extruded products, but they did not show significant differences (p<0.05) in tortillas. The X-ray diffraction patterns of the native starch granules were modified into an amorphous state when tortillas were produced, also similar preferential crystal growth at the final product: tortilla was observed for both processes ENP and TNP. In addition, the viscosity was similar in the tortillas from ENP and TNP respectively. ENP in proposed conditions is an effective, and non-contaminant technology to produce tortillas with similar characteristic to TNP in the crystallinity, damaged starch, and viscosity.

Structural, Gas Sensing and Dielectric Properties of HoXFe1-X FeO3 Perovskite Compound

Environmental pollutions and resources depletion motivates scientific research to innovate technologies for sustainable productive systems. To develop gas sensing substance with optimized performance a perovskite compound of HoxFe1-x FeO3 (where x= 0, 0.01, 0.03 and 0.05) were prepared by standard solid state reaction technique. The crystal structure was studied by XRD, which confirmed the formation of polycrystalline orthorhombic structure with space group Pbnm type perovskite. The preferred crystal growth of the main peak was (211). The structural parameters were also calculated and it was found that the lattice constants and particle size increased with the Ho doping ratio. The electrical properties were studied using the Hall effect, studied using the Hall effect, where the Hall coefficient, D.C conductivity (from 2.24E-06 (Ω-1.cm-1) at x=0) to 2.67E. -06 (Ω-1.cm-1) at x=0.05), mobility) 7.26 (cm2 / V.sec) at x=0 and decreased to 5.97 (cm2 / V .sec) at x=0.05 (and the concentration of charge carriers (2.14 E13 cm-3 at x=0 ) to 2.79E. 13 cm-3 at x=0.05 ) were calculated. The charge carrier concentration increased and charge mobility decreased with Ho addition. The Hall coefficient results revealed an n-type conduction mechanism. The dielectric constant ε r (in its real and imaginary parts) decreased with the increase in frequency of the applied electric field. tan δ and the AC conductivity were also calculated, and It was found that with the raise in the doping rate, the values of AC conductivity increase while tan δ decreases.

Self-Assembled Nano-Filamentous Zeolite Catalyst to Realize Efficient One-Step Ethanol Synthesis.

The non-petroleum synthesis route of ethanol from syngas (H2 +CO) with methyl acetate (MA) as the core intermediate product has been confirmed as an excellent industrialization route for high purity ethanol production. However, as the central part of this tandem-catalysis path, the carbonylation of dimethyl ether (DME) to MA is limited by the undesirable catalytic activity and stability of zeolite catalysts. Herein, a facile inhibitor-assisted strategy was developed for constructing self-assembled nano-Mordenite (nano-MOR) zeolites without using any expensive or complex template. A nano-filamentous MOR zeolite with only 70 nm crystal diameter was successfully synthesized by selectively controlling the crystal growth orientation with a specific inhibitor. The catalytic performance of self-assembled nano-MOR catalysts was remarkably outstanding in DME carbonylation reaction. The highest Space-Time Yield (STY) of MA was achieved over Nanofilament MOR (NF-MOR), which was significantly improved comparing with that of the traditional Ellipsoid-MOR (ES-MOR) [3780 mmol/(kg ⋅ h) vs. 1368 mmol/(kg ⋅ h)]. One-step ethanol synthesis was realized by combining the MOR catalyst and an innovative self-reduced Cu-ZnO/SiO2 (CZ/SiO2 ) catalyst in a rationally designed dual-bed catalysis system. Adopting the tailor-made NF-MOR&CZ/SiO2 combination, it obtained the highest STY of ethanol, about 4 times of the conventional ES-MOR&CZ combination [1800 mmol/(kg ⋅ h) vs. 476 mmol/(kg ⋅ h)]. The present self-assembled nano-MOR zeolites synthetic strategy opens a new way for the fabrication of high-performance zeolites for practical industrial applications in catalytic conversions of one-carbon (C1) small molecules to high value-added chemicals.

Crystallographic Variability in Additive Manufacturing

The crystallographic textures produced during additive manufacturing can be understood, predicted, and manipulated by varying the grain nucleation and growth processes. The resultant textures are primarily dictated by the melt pool geometry, which defines the local thermal gradient and thus the preferred crystal growth directions, as well as the scan strategy, which controls the propagation of grain orientations into subsequent layers. This texture can be diluted through heterogeneous nucleation of new grain orientations, which can occur through a variety of mechanisms. This ability to control the texture during additive manufacturing can enable the location-specific control of properties as a function of position in the build.

Alkyl Diamine-Induced (100)-Preferred Crystal Orientation for Efficient Pb–Sn Perovskite Solar Cells

The narrow band gap lead–tin (Pb–Sn) perovskite is a promising light absorption layer for highly efficient perovskite solar cells (PSCs), particularly for tandem applications. However, its random crystal orientation dramatically limits its power conversion efficiency (PCE). Here, a propane diamine bromide (PDABr) additive is developed to effectively modulate the Pb–Sn perovskite to grow along the (100)-preferred orientation. It is found that the PDA cations naturally anchor onto the colloidal perovskite nucleus to serve as a surface template to modulate the perovskite crystal to grow preferentially along its (100) orientation, while the bromide ions aid in increasing the grain size, resulting in a densely packed film with significantly reduced density of grain boundaries. As a result, the PDABr-based film exhibits increased carrier mobility and reduced defect density. With these merits, the PDABr-based Pb–Sn PSCs demonstrated an impressive PCE of 20.41%, which is much higher than that of the control device (16.23%). This work provides a general approach to realize the preferred crystal growth for Pb–Sn perovskite films to attain high optoelectronic performance.

Strain-dependent magnetism and anomalous Hall effect in noncollinear antiferromagnetic Mn3Pt films

The exploration of Berry curvature physics and the related non-trivial magnetic transport of two-dimensional kagome spin-lattice structure of Mn atoms in noncollinear antiferromagnetic materials, has received widespread attention in recent years. Current research is mainly focused on the hexagonal chiral antiferromagnets such as Mn3Sn. However, there are few researches about face-centered cubic (fcc) noncollinear antiferromagnetism. In this work, the influence of strain on the magnetic properties and the anomalous Hall effect (AHE) of the fcc noncollinear antiferromagnetic Mn3Pt films were systematically explored. The results showed that the ferromagnetic signal derived from the tilt of the magnetic moment of Mn atoms in the kagome structures, as well as the anomalous Hall resistance originating from the non-zero Berry curvature, had comparable response tendency to the strain, differing from hexagonal chiral antiferromagnets. An anomalous Hall conductivity exceeding 100 (Ω cm)−1 was obtained by tuning the film thickness of Mn3Pt. In addition, the relationship among the Berry phase, magnetic properties, and AHE in Mn3Pt was further verified by regulating the crystal growth orientation. The results established Mn3Pt as a promising candidate for its integration with room-temperature antiferromagnetic spintronics.

Methylammonium thiocyanate seeds assisted heterogeneous nucleation for achieving high-performance perovskite solar cells

Thiocyanate (SCN-) has been reported to manage crystallization of perovskite films and improve their optoelectronic properties in solar cells. However, the mechanism of SCN- in preparation of high-quality (MAFA)Pb(IBr)3 based light-absorbing layers has not been well investigated yet. In this work, we investigate the effects of SCN- on phase transition of (MAFA)Pb(IBr)3 perovskite films and the corresponding device performance by introducing methylammonium thiocyanate (MASCN) in a PbI2 precursor solution which is used to make perovskite by a two-step sequential deposition method. Characterization of the perovskite films has shown that a proper amount (1 mg/mL) of MASCN in PbI2 can produce PbI2-MASCN seeds which act as a nucleation center for assisting heterogeneous nucleation of the (MAFA)Pb(IBr)3. Meanwhile, MASCN helps to effectively control crystallization of the perovskite film by obtaining preferential crystal growth orientation. Furthermore, MASCN is beneficial to eliminate residual PbI2 and prepare perovskite films with low trap-state density. Consequently, the power conversion efficiency (PCE) of the perovskite solar cells increases from 18.36% to 20.4%. An enhanced device stability against moisture is also observed in the MASCN-treated device which exhibits 90% retention of the initial efficiency after exposed to the ambient air for 1780 h.

Rayleigh and shear-horizontal surface acoustic waves simultaneously generated in inclined ZnO films for acoustofluidic lab-on-a-chip

There are significant challenges in controlling uniformity of crystal inclination angles, growth orientations and film thicknesses to generate dual-mode surface acoustic waves (e.g., Rayleigh ones and shear-horizontal ones) for lab-on-a-chip applications. In this study, we demonstrate large area (up to three inches) and uniformly inclined piezoelectric ZnO films, sputtering-deposited on silicon using a glancing angle deposition method. Characterization using X-ray diffraction showed that the inclined ZnO films have an average crystal inclination angle of 29.0°, apart from the vertical (0002) orientation, at a substrate tilting angle of 30o. Reflection signals of ZnO/Si surface acoustic wave devices clearly show the generations of both shear horizontal surface acoustic waves and Rayleigh waves. The Rayleigh waves enable efficient acoustofluidic functions including streaming and transportation of sessile droplets. Excitation direction of Rayleigh waves on the acoustofluidics versus the inclined angle direction has apparent influences on the acoustofluidic performance due to the anisotropic microstructures of the inclined films. The same device has been used to demonstrate biosensing of biotin/streptavidin interactions in a liquid environment using the shear-horizontal surface acoustic waves, to demonstrate its potential for integration into a complete lab-on-a-chip device.

Enhancing the photovoltaic properties of SnS-Based solar cells by crystallographic orientation engineering

Tin monosulfide (SnS) is a promising light-harvesting material for solar cell applications, owing to its potential for large-scale production, cost-effectiveness, eco-friendly source materials, and long-term stability. However, SnS crystallizes in an orthorhombic structure, which results in a highly anisotropic charge transport behavior. Tailoring the crystallographic orientation of the SnS absorber layer plays a critical role in the enhancement of the transfer of charge carriers and the power conversion efficiency (PCE). By controlling the substrate tilting angle and temperature ramp rate in vapor transport deposition, the crystal growth orientation was tuned to a preferred direction which significantly suppressed the unfavorable (040) crystallographic plane. Through the combination of these two approaches, the PCE could be increased from 0.11% to 2%. The effect of the tilting angle was numerically simulated to investigate its role in controlling the film uniformity and directing the film growth. In addition, the correlation between the texture coefficient of the (040) plane and the charge transport properties was determined by a combination of analytical methods such as device performance studies, electrochemical impedance spectroscopy, along with transient photovoltage, space-charge-limited current, and dark current measurements. These techniques were blended together to prove that the marked improvement in PCE can be ascribed to a reduced charge recombination (in both SnS bulk and interfaces) and an enhanced hole mobility.

SAPO-34 crystals with nanosheet morphology synthesized by pyrophosphoric acid as new phosphorus source

The nanosheet SAPO-34 zeolite crystals with a diameter of 300 nm and a thickness of 50 nm using a new phosphorus source (pyrophosphoric acid, H4P2O7) were synthesized. The roles of the pyrophosphate (P2O74−) species in the crystallization of SAPO-34 were elucidated. The results suggested that one P atom from the P2O74− species participated in the formation of the CHA framework structure while the other P atom served as a crystallization control agent, facilitating preferential crystal growth in [100] crystal plane. The SAPO-34 nanosheets have silica-rich shell and phosphorus-rich core leading to superior catalytic performance in methanol-to-olefin reaction (MTO). The catalytic lifetime of the SAPO-34 nanosheets was significantly improved due to the larger amount of medium-strong surface acidity and short diffusion pathway in comparison to the conventional SAPO-34 catalyst synthesized in the presence of the classical phosphorus source (H3PO4).

Improving the corrosion resistance and osteogenic differentiation of ZK60 magnesium alloys by hydroxyapatite/graphene/graphene oxide composite coating

Magnesium (Mg) alloys have better biocompatibility and biodegradability than conventional biomedical metal materials, but their corrosion resistance is poor, which limits their application in bone repair materials. In this study, ZK60 Mg alloys were fabricated with hydroxyapatite (HA) and hydroxyapatite/graphene/graphene oxide (HA/G/GO) composite coatings through the hydrothermal method. Results showed that the HA coating prepared in treatment solutions of pH = 9 had the highest corrosion resistance, which was 9.77 times higher than that of ZK60. In the HA/G/GO composite coatings, GO made the HA crystals cluster into flower clusters closely, while G changed the growth orientation of the HA crystals. Moreover, the HA/G/GO composite coatings improved the corrosion resistance of the Mg alloys, and promoted the osteogenic differentiation of mesenchymal stem cells (MSCs). The corrosion resistance of the HA/3G/2GO composite coating was 28.53 times higher than that of ZK60. And HA/3G/2GO displayed the highest osteogenic differentiation among the coatings, and the order was HA/3G/2GO > HA/05GO > HA > ZK60 Mg alloy. The findings in this study can virtually expand the application of Mg alloys in bone repair materials, thus increasing the practical usage of Mg alloys in clinical applications.

Membrane Scaling and Wetting in Membrane Distillation: Mitigation Roles Played by Humic Substances.

Membrane scaling and wetting severely hinder practical applications of membrane distillation (MD) for hypersaline water/wastewater treatment. In this regard, the effects of feedwater constituents are still not well understood. Herein, we investigated how humic acid (HA) influenced gypsum-induced membrane scaling and wetting during MD desalination. At low concentrations (5-20 mg L-1), HA notably mitigated membrane scaling and wetting. The morphological characterization of scaled membranes revealed that the antiwetting behavior could be ascribed to the formation of a compact and protective gypsum/HA scale layer, which blocked the flow channel of scaling ions and suppressed the intrusion of scale particles into membrane pores. Based on the comprehensive analysis of the scaling process, the formation of the scale layer was related to the heterogeneous crystallization of gypsum on the membrane surface. Moreover, deprotonated HA interfered with the heterogeneous crystallization process by inhibiting the formation of gypsum nuclei and altering the orientation of crystal growth, thus delaying membrane scaling and altering the morphology of the scale layer. Thermodynamic and kinetic analyses further demonstrated the mitigation mechanism of HA. Furthermore, improved fouling reversibility and antiwetting ability in synthetic seawater treatment endowed by HA were observed. This study provides new insight into the roles played by the organic constituents of water/wastewater during membrane desalination, providing a valuable reference for developing novel strategies to improve the performance of MD.

Large-Scale Synthesis of Metal Additively-Manufactured Microstructures Using Markov Random Fields

A data-driven framework is developed and examined for creating spatially-varying crystallographic textures over component-scale Computer-Aided Design (CAD) models. Here, a set of three orthogonal 2D micrographs of an Additively-Manufactured (AM) specimen are first obtained experimentally through Electron Backscatter Diffraction (EBSD) and subsequently converted to a 3D representative unit cell using the Markov Random Field (MRF) technique. Features such as grain size, crystallographic orientation, and grain boundary misorientation distributions are used to validate the reconstructed 3D microstructure against input experimental EBSD images. The variations of microstructural features during a powder-based additive manufacturing process are subsequently modeled by merging patches from the 3D snapshot of AM microstructural unit cell in a part-scale geometry using a tensor-based optimization process. The optimization algorithm repeatedly pastes microstructural elements from the reconstructed MRF unit cell onto the geometrical CAD domain until it is entirely covered. Here, through a simple Graphical User Interface (GUI), the user specifies a tensor field over the volumetric CAD model, defining the local control over grain-scale, anisotropy, and crystal growth orientation. This new approach provides a workflow for reconstructing global maps of AM microstructures in real-time by embedding site-specific images based on known AM microstructural patterns seen in experimental characterization techniques. The numerical results are helpful specifically for the visualization of process–microstructure relationships in metal additive manufacturing techniques.

One‐Step Bottom‐Up Growth of Highly Liquid Repellent Worm‐Like Surfaces on Planar Substrates

AbstractHighly liquid repellent (superhydrophobic, superoleophobic) surfaces are fabricated using mostly top‐down approaches and liquid‐based processing. Top‐down approaches, like lithography and templating, are highly process‐intensive, while liquid‐based processing, like etching and fluoropolymer solution coating, rely on solvents that often damage the substrate. Ultimately, to suppress liquids from spreading, the goal is to create a surface with low surface energy and a hierarchically roughened topology. Here, a bottom‐up approach that achieves these two prerequisite criteria in one single step is demonstrated. Relying on a liquid‐free initiated chemical vapor deposition (iCVD) process, worm‐like protrusions of a semicrystalline fluoropolymer (poly(perfluorodecyl acrylate)) directly grow on flat substrates without prior surface pretreatment. The nano/microworm surfaces display super‐liquid repellency (&gt;150° contact angle) to water and oil. Worm formation (as opposed to conformal thin film formation) is attributed to preferential crystal nucleation, orientation, and growth on the substrate plane.

A Covalent Organic Framework Membrane with Homo Hierarchical Pores for Confined Reactive Crystallization.

Gas-liquid (G-L) reactive crystallization is a major technology for advanced materials construction, which requires a short diffusion path on the interface to ensure the reactant supply and stable crystal nucleation under ultrahigh supersaturation. Herein, a covalent organic framework (COF) membrane with homo hierarchical pore structures was proposed as an effective interfacial material for the regulation of confined reactive crystallization. By combining the ordered nanopores of COFs and micropores of anodic aluminum oxide (AAO), the COF membrane simultaneously provided an excellent nanoscale diffusion-reaction regulation network as the molecular-level confined G-L reactive interface and adjustable submicrometer gas mass transfer channels. The highly selective construction of CaCO3 superstructures was then achieved. When the submicrometer primary pore size rp of the constructed COF membrane ranged from 120 to 1.6 nm, the diffusion mechanism of CO2 varied from viscous flow diffusion to Knudsen diffusion. The growth orientation of CaCO3 crystals was well confined to obtain spindle-shaped crystals with high selectivity. Meanwhile, the crystal selectivity factor (cube/sphere) increased from 0 to 3.53 under the low interfacial nuclear barrier. Thus, the COF membrane with coupled micro-nanostructures successfully screened the directional preparation conditions for diverse CaCO3 superstructures, which also paved a meaningful path for the functional application of COFs in accurate mass transfer control and confined chemical reactions.

Effect of nano-nucleation sites assisted crystallization on performance of perovskite photodetector

&lt;sec&gt;Photodetector occupies an important position in the sensor family, but most of the photoelectric conversion materials of photodetectors are inorganic semiconductors, such as GaAs, GaN, Ge and Si, these inorganic semiconductors are usually prepared by complicated methods and high cost, and furthermore, they have poor mechanical flexibility. Organic-inorganic hybrid perovskite materials serving as visible-light sensitizers have the advantages of balanced electron and hole mobilities, adjustable bandgaps, high absorption coefficients, low temperature solution preparation, which make the materials a suitable candidate for inorganic semiconductors.&lt;/sec&gt;&lt;sec&gt;For planar photodetectors, carriers have greater probabilities to be trapped by the defects in the perovskite films, therefore it is important to fabricate a high-quality perovskite film. However, owing to the low formation energy of perovskite crystals, defects prove to occur on the film surface and grain boundaries, which aggravate the performance of perovskite optoelectronic devices. In this work, we introduce a small quantity of graphene oxide nanosheets (GOSs) on bare glass substrate as effective nucleation sites of perovskite crystals. Owing to the extremely low density of GOSs and large exposed glass basement, the GOSs cannot be regarded as an interface layer. The existence of GOSs on smooth substance reduces the perovskite nucleation barrier, leading to a more preferential crystal growth in these locations, and binds tightly with glass substrate, which passivates the defects efficiently. Meanwhile, the element of O in the GOSs can create Pb–O bond with Pb in the CH&lt;sub&gt;3&lt;/sub&gt;NH&lt;sub&gt;3&lt;/sub&gt;PbI&lt;sub&gt;3&lt;/sub&gt;, further improving the crystal of perovskite. On this basis, planner perovskite photodetector with a structure of glass/GOSs/CH&lt;sub&gt;3&lt;/sub&gt;NH&lt;sub&gt;3&lt;/sub&gt;PbI&lt;sub&gt;3&lt;/sub&gt;/MoO&lt;sub&gt;3&lt;/sub&gt;/Au is fabricated. By adjusting the concentration of GOSs deionized water dispersion under the same spin-coating condition, the photoelectric conversion performance of perovskite photodetector is enhanced. Under the influence of the optimal concentration of GOSs, photocurrent of the champion photodetector (1.15 × 10&lt;sup&gt;–6&lt;/sup&gt; A) is an order of magnitude higher than that of reference device without GOSs modified (3.58 × 10&lt;sup&gt;–7&lt;/sup&gt; A) at 3 V bias, leading to a high ON/OFF current ratio of 5.22 × 10&lt;sup&gt;3&lt;/sup&gt;. Besides, improved photoresponse speed is also found in the champion device, with a rise time of 9.6 ms and a decay time of 6.6 ms, respectively. The enhanced performance of GOSs modified perovskite photodetector can be attributed to the significantly reduced defects bringing about an enhanced charge separation and collection performance in the CH&lt;sub&gt;3&lt;/sub&gt;NH&lt;sub&gt;3&lt;/sub&gt;PbI&lt;sub&gt;3&lt;/sub&gt; films.&lt;/sec&gt;&lt;sec&gt;By introducing extremely low quantity GOSs as the effective perovskite crystal nucleation sites, the perovskite crystallization and thin film can be effectively improved, leading to a positive effect on the performance of perovskite photodetector. This method has a certain universality, and therefore it has a reference value for other structures of perovskite photoelectric devices.&lt;/sec&gt;

Structural and optical behavior of gallium and cobalt co-doped ZnO thin films fabricated by a sol-gel spin coating technique

In this study, the ZnO thin films with varying Ga/Co co-doping concentrations were produced on the quartz substrates by spin-coating technique. The structural and optical behavior of the films were analyzed by X-ray diffraction (XRD) and UV–Vis spectroscopy, respectively. XRD results reveal that all the films possess a hexagonal wurtzite structure of ZnO and have crystallite sizes in the range 8–24 nm. The prominent peaks (relative intensity greater than 10%) observed in the XRD profiles correspond to (100), (002), (101) and (103) planes, whereas the most preferred orientation of crystal growth in all the films is (002) plane. A small variation in the lattice constant values has been found owing to the inclusion of dopants and co-dopants in the ZnO lattice, as well as defects created in the crystal lattice at the time of film growth. Compared to the undoped ZnO film, the optical transmittance improves beyond the 430 nm wavelength upon 1 at% Ga doping, while in (1 at% Ga + 1 at% Co) and (3 at% Ga + 1 at% Co) co-doped films, it improves beyond the 600 nm wavelength. The UV–Vis spectroscopy results show the optical band gap value of 3.28 eV for the undoped ZnO film, which changes by a small amount in the doped and co-doped films.

EFFECT OF COBALT DOPING AND ANNEALING ON PROPERTIES OF MANGANESE OXIDE THIN FILMS PREPARED USING JET NEBULIZER SPRAY PYROLYSIS TECHNIQUE

The controlled deposition and post-deposition treatments are fundamental steps in the synthesis of thin films in the range of nanometer to several micrometers in thickness for various applications. Because the uniform coating of nano-particles of doped metal oxide modifies the properties of metal oxide, thin films of cobalt-doped manganese oxide are prepared using the Jet nebulizer spray pyrolysis procedure at a temperature of 300°C in this study. The thin films are annealed in an air environment for two hours at various temperatures, including 350°C, 450°C, and 550°C. Cobalt thin films were produced and annealed for two hours at 550 °C in the air before being tested. The effect of annealing temperature and atomic percentage content of dopant cobalt in manganese oxide thin film on their properties were characterized by XRD, photoluminescence spectroscopy, UV-vis spectroscopic technique, scanning electron microscopy, and EDX. The characterization of the thin film reveals that these thin films are made up of uniformly coated doped metal oxide particles with (002) plan as a preferential orientation of crystal growth and band gap energy in the span of 2.5 -1.65 eV. The sensing property of the thin films towards ethanol was also characterized.