Values Of Dislocation Density Research Articles

Dislocation-density-related constitutive model and its applicability to cyclic deformation and damage behavior of 316LN SS at 823 K

In the present investigation, an in-depth understanding of the relationship between dislocation kinetics and cyclic plasticity, along with the description of yield asymmetry behavior during loading and unloading in nuclear grade 316LN austenitic stainless steel at 823 K, was examined by employing a constitutive framework using the evolution of physically-based internal-state variables. The formulation encompassed a set of first-order simultaneous differential equations that governed the evolution of dislocation density, mean free path of dislocations, and back stress. These variables were interdependent with the power law which described the kinetics of plastic strain rate. The evolution equations were numerically integrated, and the simulated data were fitted to the experimental data up to stabilized cycle at a temperature of 823 K and total strain amplitudes of ±0.004, ±0.006, ±0.008 and ± 0.010. The predicted cyclic stress response as a function of the cyclic number displayed the continuous cyclic hardening from the first cycle to the initiation of stabilized cycle. Further, good agreement between the predicted and experimental hysteresis loops was found at different cycle numbers. The predicted dislocation density and tensile peak values of back/effective stress increased with cyclic hardening and approached the value of saturation at the stabilized cycle. On the other hand, a rapid decrease in mean free path with cycle number was noticed. An increase in total strain amplitude resulted in a systematic increase in dislocation density, peak stress, back stress and effective stress. At the total strain amplitudes above ±0.006, the predicted higher rates of dislocation accumulation and annihilation, and the faster evolution rate of back stress towards saturation led to the development of stable dislocation substructure configurations with a clear distinction between dislocation high/low dense regions. Furthermore, the applicability of the model was extended by including an empirical relationship between the damage variable and cycle number within the power law, thereby enabling predictions of the cyclic stress-strain response beyond the stabilized cycle.

Revealing 3D intragranular micromechanical fields at triple junctions

Triple junctions, intersections of three or more grains in polycrystalline solids, are known locations of potential stress concentration and strain localization. In this work, intragranular lattice curvatures and elastic strains are measured at triple junctions via a novel zoom-in style combination of synchrotron X-ray techniques. Additionally, this work revisits the impact of including elastic strain gradients while calculating the dislocation density within embedded grains via the Nye dislocation tensor. Without elastic strain gradients, the dislocation density is underestimated at a hotspot by 27% of the maximum dislocation density value. Spatial regions near triple junctions are found to contain both the highest values of the intragranular misorientations metrics and generally higher values than grain boundaries (between two grains). A heterogenous distribution of intragranular misorientation, elastic strain, and dislocation density is measured within a grain along a single triple junction line, and the triple junction line end points (quad points) exhibit substantially different micromechanical fields. This work provides a unique 3D view of triple junctions within individual grains and highlights their spatially heterogenous intragranular micromechanical response along triple junction lines, especially when compared to relatively less complex behavior along grain boundaries. While a grain averaged example is provided of intergranular strain across grains, several examples of intragranular strain were visualized near a triple junction. The combined analysis of intragranular lattice curvature (associated with strain metrics) and elastic strain (associated with stress) provides a more complete characterization of the 3D sub-grain fields than previously reported.

Analysis of dominant and intense XRD peak of (111) plane of ZnS nanocrystals for microstructural study through single line Voigt method: Calculated low dislocation density value emphasizes larger stacking of (111) plane

In this work, a wet chemical synthesis method has been used for the preparation of ZnS nanocrystals using the precursor Zn(NO3)2 (Zinc Nitrate) and Na2S (Sodium sulfide), where 3-Mercaptopropionic acid has been used as a capping agent. Morphological characterization of the prepared ZnS nanocrystals has been performed through HR-TEM and FE-SEM analysis and the average particle size has been obtained as approximately 26 nm. The HR-TEM image also suggests the formation of smooth crystalline ZnS nanoparticles with dominance of the (111) plane. The XRD pattern firmly indicates dominance of (111) crystalline planes over the other planes. For this, different microstructural properties of prepared ZnS nanoparticles have been studied considering only the dominant (111) diffraction peak using single line Voigt method. Finally, the average particle size calculated from morphological analysis has been compared with the crystallite size calculated by XRD analysis through the Single line Voigt method. Calculated dislocation density value indicates presence of less defects states in the sample and confirms the growth of ZnS nanoparticles in a particular direction of (111) plane with pure crystalline nature.

Interfacial investigations on the microstructure evolution and thermomechanical behavior of explosive welded CLAM/316L composite

In this paper, a comprehensive study combined multiple characterizations and SPH numerical simulation was conducted to investigate the microstructure evolution, extreme thermomechanical behavior and consequences of the explosive welded CLAM/316L interface. The interfaces of the two welding materials underwent remarkable temperature rise and rapid cooling under high-speed collision conditions, forming a tight bond that presents a wavy structure with vortices. The SPH simulation adequately reproduced the heating and cooling process of the interface during explosive welding, revealing the high heterogeneity of the thermodynamic behavior during the impact process. Furthermore, the EBSD analyses showed the perplexing evolution of crystal structure at the bonding interface with vortex, including ultra-fine grains, columnar grains, equiaxed grains, deformed grains and serious lattice distortion. By correlating the temperature histories and grain characteristics at different positions of the interface, the formation mechanism of diverse grains was revealed, referring to crystallization from liquid, recrystallization from the solid and plastic deformation. The recrystallization at the interface was closely related to the material properties, and the significant variations in dislocation density and plastic strain values at the interface, as well as the thermal softening of the material, could be explained by different degrees of dynamic recovery and recrystallization.

Structural, spectroscopic and morphology studies on green synthesized ZnO nanoparticles

Zinc oxide nanoparticles (ZnO NPs) were synthesised using Tabernaemontana divaricata flower extract (TFE) in different weight percentages by facile, eco-friendly and cost-effective green synthesis method. Formation and structure of the ZnO NPs were studied by powder XRD, FT−IR, Raman and TEM studies. The crystals formed are of hexagonal wurtzite structure with biological functional groups attached. Average crystallite size of the ZnO NPs (17.5−23.3 nm) was obtained from the analysis of powder XRD data which increased with increase of TFE amount while the estimated values of dislocation density and micro-strain exhibited an opposite behaviour. The optical (direct and indirect) energy band gap values estimated using UV–vis DRS spectral data decreased with increasing amount of TFE. The photoluminescence spectra for the ZnO NPs exhibited multiple peaks spread over the visible region with one peak in the NIR region indicating the existence of various defect levels of Zn and O. Position of these defect levels within the band gap was assigned which is significantly modulated by TFE. TFE amount-dependent peak shift and/or peak broadening were observed in the Raman spectra of the ZnO NPs which were correlated with the growing disorder in the crystals induced by the extract molecules. FESEM study showed the agglomerated NPs with quasi-spherical morphology. Particle size of the ZnO NPs was estimated from FESEM images. EDX study indicated that increased presence of TFE in ZnO decreased the oxygen content in the synthesised material. HRTEM study revealed the agglomeration of nanoparticles with single crystalline nature. Present study convincingly established that flower extract used for the green synthesis efficiently modified the structure and optical property, defect levels and morphology of the potentially useful ZnO nanoparticles.

Fabrication of praseodymium-doped ceria (PDC) films by slurry spin-coating technique and its structural, morphological and optical properties

The current study is on the fabrication of PDC films prepared by slurry spin-coating technique for photoluminescence activity. At lower spin rates (1000 rpm), thicker and uniform PDC films were obtained. The structural evolution of the sintered PDC films on a dense alumina substrate was studied using Grazing Incidence X-ray diffraction (GIXRD) and Raman Spectroscopy. Crystallite size, microstrain, and dislocation density values remain almost the same with the increase in the coating cycles. The A568/A463 ratio for 3, 5, and 10 coating cycles are 0.52, 0.49, and 0.61, respectively. Surface roughness studies of PDC films using a 3D Noncontact Profilometer. The mean surface roughness values are 12.55, 13.74, and 22.25 μm for the 3rd,5th, and 10th coating cycles, respectively. Microstructure observation by Field Emission Scanning Electron Microscope (FE-SEM). The average thickness of the films for the 3rd, 5th, and 10th coating cycles are 50.93, 41.64, and 109.95 μm, respectively. The PDC films obtained on a dense alumina substrate were porous. FE-SEM micrographs showed a particle aggregation of several irregular and smaller grains, indicating the sintering activity of PDC films. Optical properties were studied using ultraviolet-visible (UV–Vis) absorption spectra and photoluminescence spectra (PLS). The band gap values slightly increased with the increase in the coating cycles. A decrease in PL intensity with an increase in the coating cycle is related to higher oxygen vacancy concentration. PDC films fabricated by the slurry spin-coating technique can be successfully used for optoelectronic applications.

Investigation of the microstructure, hardness and electrical conductivity properties of Fe/Graphene compacts

ABSTRACT The effects of graphene nanoplatelets added to pure Fe powders at different rates on microstructure, hardness and electrical conductivity were investigated. Prepared mixed powders were compressed at 700 MPa pressure and sintered at 1250°C. Densities of samples were measured Archimedes technique. Scanning electron microscope was used for microstructure investigations. The hardness was measured according to ASTM E384. Phase types, average crystallite size and dislocation density calculations in sintered samples were made. Electrical resistance measurements were made with the four-point probe measurement technique. Powder mixtures containing ≤5 wt-% graphene nanoplatelets were sintered into compact samples. The smallest grain size, highest dislocation density, highest hardness and electrical conductivity values were obtained in samples containing 2 wt-% of graphene nanoplatelets.

High temperature annealing on vertical p-n junction p-NiO/n-β-Ga2O3 nanowire arrays for high performance UV photodetection

The authors of this article reported the effects of annealing on performance of GLAD synthesized vertical p-NiO/n-β-Ga2O3 heterostructure (HS) nanowire (NW) arrays based UV photodetector (PD). The authors further investigated the structural, optical and electrical properties at various annealing temperatures (200 °C, 400 °C, 600 °C, 800 °C, and 1000 °C) including as deposited sample to find the best sample for UV PD application. The XRD analysis showed improved crystallinity and least dislocation density and micro strain values for 800 °C sample. However, the sample degrades beyond 800 °C owing to crystallographic defects that are formed at higher annealed temperatures. Furthermore, the photoluminescence analysis showed that the defect levels decreased at 800 °C annealed temperature which was also analogous to the XPS analysis. The FE-SEM analysis also showed the impact of high temperature annealing (800 °C) with increased in nanowire diameter and length. The surface roughness was also found to be smoother for 800 °C sample from TEM analysis. Moreover, the fabricated 800 °C annealed vertical p-NiO/n-β-Ga2O3 axial NW arrays based UV PD showed the largest responsivity (Rλ) of 940 A/W as compared to all the samples. Also, the 800 °C annealed UV PD exhibited fast response speed along with rise time and fall times of 0.32 s and 0.49 s respectively. The superior performance of 800 °C sample was ascribed to the large grain size, defect reduction and improvement of interference quality.

Efficient photo-adsorptive eradication of endocrine disrupting pesticides by chitosan co- decorated metal oxide bio-nanocomposite.

Extensive consumption, toxicity and bioaccumulation of malathion (MLT) and lindane (γ-HCH) pesticides collectively attract the world's attention. Herein, the nanocomposite of chitosan wrapped NiO@ZnO was synthesized by a green methodology usingAzadirachta indicaleaves extract. Structural and morphological analysis of chitosan-NiO@ZnO showed hollow sphere-flake shaped image adsorbed on a solid chitosan surface with a large surface area of 73 m2g-1. A decrease in values of lattice strain, dislocation density and crystallite size described the imperfection in crystal geometry and new peaks in FT-IR spectra at 698cm-1 and 448cm-1 of Ni-N and Zn-N, which respectively confirm the coupling. Chitosan-NiO@ZnO and individual nanoparticles (NiO and ZnO) were well-characterized and utilized for degradation MLT and γ-HCH under direct sunlight and dark conditions. The highest degradation of pesticides (above 94%) resulted with 2mg L-1 and 10mg L-1 of MLT (π-π) and γ-HCH, respectively with a 20mg catalyst dose, and pH of ~ 7 under daylight exposure (5h). Chitosan-NiO@ZnO substantially suppressed the half-life of the targeted pesticides (MLT: 0.48h; HCH 0.51h) and demonstrated the first-order kinetics with a high adsorption capacity, Xm (MLT: 14.5mgg-1 and γ-HCH 20.7mgg-1), which also confirmed the strong binding with the pesticides, followed by their conversion into safer and smaller metabolites. The charge separation mechanism was elucidated by UV reflectance and photoluminescence data. Hydroxyl radicals were most frequently responsible for the degradation of pesticides as confirmed by scavenger analysis. The synthesized green-nano photocatalyst showed high reusability (up to 10th cycles), sensitivity and stability within the degradation process, presumably making it suitable for industrial applications.

Optical and Morphological Properties of Cu2FeSnS4 Chalcogenide Films

P-type Cu2FeSnS4 (CFTS) and Cu2ZnSnS4 (CZTS) quaternary chalcogenide films have been grown by the method of spin coating on glass substrates relate to 30 and 40 sccm sulfur flux. Physical properties of obtained samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and ultraviolet visible spectroscopy (UV-Vis) to see the effect of deposition parameters on the thin film. The crystal parameters including crystal size, dislocation density and strain value of the samples were changed related to the deposition parameters. XRD results indicated an improvement of the crystalline quality of quaternary chalcogenide CFTS with a maximum crystal size of about 50 nm for (112) peak orientation. SEM images illustrated that the particle size was changed with an increase in the flux of sulfur, which was confirmed with both XRD and AFM images. It was seen that the absorption and energy band gap value of the samples changed the effect of sulfur flux and CZTS film for 40 sccm exhibited more strong absorption all samples in the UV-Vis region. The band gap values of the samples were calculated 1.51, 1.53, 1.82 and 1.91 eV for CZTS (30 sccm), CZTS (40 sccm), CFTS (30 sccm) and CFTS (40 sccm) films annealed H2S gas, respectively.

Effect of cold working on mechanical properties of pure-304L stainless steel with variable temperature - an experimental study

ABSTRACT In the current investigation, cold work influence on mechanical strength, microstructure, hardness and ductile to brittle transition (DBT) in pure (P) 304 L-stainless steel (SS) (with ultra-low content of sulphur (0.001%) and phosphorus (nil) at several levels of cold work (5%, 10%, 20% and 30%) are reported, which provide valuable information regarding beneficial effects of reduced level of sulphur for the material selection in structural design. The cold work results in dual-phase (γ + α ′ ) with distinct values of dislocation densities and grain size that are used in the modified Hall-Petch equation to obtain the corresponding change in yield strength. Cold working up to 30% increased yield strength ( σ y ) from 280 to 900 MPa, whereas ultimate tensile strength ( σ u ), increased from 620 to 950 MPa, i.e. an increase of 34.73%. The hardness values increased from 172 to 360 Hv, i.e. an enhancement of 110.5% for a cold work of 30%. The material showed a remarkable enhancement in the impact energy absorption from 200 to 390 J for a temperature change from 77 to 473 K. It is observed that cold working at 5% level reduces the impact energy absorption from 390 to 250 J, i.e. reduction of 35.89% at 298 K. The value of impact energy absorbed by P-304 L-SS was 37% higher than the commercial grade 304 L-SS (sulphur (0.03%), phosphorous (0.04%). The study succinctly brings out the importance of reduced content of sulphur and phosphorus in obtaining superior mechanical properties through cold work.

Synthesis, optical and AC electrical characteristics of nanocomposites (Bi2O3/ZnO) films prepared by thermal evaporation technique

In this paper, pure bismuth oxide (Bi2O3) and ZnO-doped with a ratio of (0, 0.12, 0.24, 0.36 and 0.48 wt.%) thin films are prepared by thermal evaporation methods under pressure 1×10-7 bar with a rate of deposition 0.5 nm.s-1 , at ambient temperature on glass substrates (RT) with thickness 50 nm and annealed at temperature 573 K for 2 hours. The phase structures of Bi2O3 (monoclinic) and Bi2O3/ZnO NCPs are confirmed by X-ray diffraction (XRD) investigation. The concentration of ZnO-doping reduces the average crystallite size from 17,35 nm to 8.67 nm. Moreover, using XRD data, the average strain, stress, and dislocation density values are computed. The spectroscopy techniques such as Fourier transform infrared (FT-IR) and scanning electron microscopy with field emission probes were used to examine the structures. The FT-IR results showed no chemical interactions between the (Bi2O3/ZnO) NPs. The results of the field emission-scanning electron microscope (FE-SEM) analysis the (Bi2O3/ZnO) NPs were distributed uniformly throughout. The actually result of optical characteristics for (Bi2O3/ZnO) showed that the absorbance, and absorption coefficient, increase with the increased concentrations of (ZnO). At the same time, the transmittance and energy band gaps were decreased with a rise in concentrations (ZnO) that have a high ability to absorb UV-light. The dielectric characteristics were checked in the frequency range from 100 Hz to 5 MHz. The results of the insulating characteristics showed that the dielectric constant and the dielectric loss of thin films (Bi2O3/ZnO) decreased with increasing frequency. In contrast, they increase when the concentration of (ZnO NPs) increases. The A.C conductivity of the thin films (Bi2O3/ZnO) increases with the frequency and concentration of (ZnO) NPs. Finally, the structural and insulating results the indicated characteristics of the (Bi2O3/ZnO) thin films may be helpful in various nano-electronic devices and sensors.

Creep deformation study of squeeze cast AZ91 magnesium alloy

The AZ91 magnesium alloy has excellent mechanical properties; however, its application is limited by its poor creep resistance. In this study, AZ91 magnesium alloy prepared by squeeze casting technique has been tested for its creep performance at varying stresses and temperatures. The governing creep mechanism was examined in the wake of deformation. The microstructure for as-cast AZ91 alloy confirmed the massive dendritic β-Mg17Al12 phase. The creep study indicated that the governing creep mechanisms were dislocation creep and dislocation climb governed by lattice diffusion in the test regime of 50 MPa stress at 150oC to 175oC. The measured dislocation density values showed good agreement with the expected dislocation density in the power law creep mechanism.

Effect of ionic liquids on the performance of dye-sensitized solar cells using poly(vinyl alcohol)/ polypyrrole based polymer electrolytes

ABSTRACT A novel quasi-solid-state polymer electrolyte was prepared using poly(vinyl alcohol)-polypyrrole, potassium iodide, iodine, and ethylene carbonate mixed with two types of ionic liquids, 1-methyl-3-propylimidazolium iodide (MPII) and 1-ethyl-3-methylimidazolium iodide (EMII). The prepared polymer electrolyte was structurally characterized by FTIR spectroscopy. The lowest degree of crystallinity and activation energy were found in the MPII-incorporated polymer electrolytes. Higher values of dislocation density and microstrain are obtained for ionic liquid-incorporated polymer electrolytes. The lowest value of series resistance was observed in MPII-based polymer electrolyte and thereby the conduction was increased. The average roughness of the MPII-based polymer electrolyte at 17.901 nm was strongly dependent on the influence of the MPII content. The dye-sensitized solar cells (DSSC) built with MPII-based polymer electrolytes have achieved the highest photo-conversion efficiency of 4.51% under 100mWcm−2 illumination.

Dislocation Density of Electron Beam Powder Bed Fusion Ti–6Al–4V Alloys Determined via Time-Of-Flight Neutron Diffraction Line-Profile Analysis

Ti–6Al–4V alloys undergo a multiple phase transformation sequence during electron beam powder bed fusion (EB-PBF) additive manufacturing, forming unique dislocation substructures. Thus, determining the dislocation density is crucial for comprehensively understanding the strengthening mechanisms and deformation behavior. This study performed time-of-flight neutron diffraction (TOF-ND) measurements of Ti–6Al–4V alloys prepared via EB-PBF and examined the dislocation density in the as-built and post-processed states using convolutional multiple whole profile (CMWP) fitting. The present TOF-ND/CMWP approach successfully determined the bulk-averaged dislocation density (6.8 × 1013 m−2) in the as-built state for the α-matrix, suggesting a non-negligible contribution of dislocation hardening. The obtained dislocation density values were comparable to those obtained by conventional and synchrotron X-ray diffraction (XRD) measurements, confirming the reliability of the analysis, and indicating that the dislocations in the α-matrix were homogeneously distributed throughout the as-built specimen. However, the negative and positive neutron scattering lengths of Ti and Al, respectively, lowered the diffraction intensity for the Ti–6Al–4V alloys, thereby decreasing the lower limit of the measurable dislocation density and making the analysis difficult.

Effects of High-Temperature Growth of Dislocation Filter Layers in GaAs-on-Si

GaAs-on-Si templates with two different dislocation filter layers (DFLs) were grown at 550 °C low-temperature (LT)-DFL and 660 °C high-temperature (HT)-DFL using metal organic vapor-phase epitaxy and the effects of the growth temperature were studied. The threading dislocation density (TDD) values of LT-DFL and HT-DFL were 5.2 × 107 cm−2 and 1.5 × 107 cm−2, respectively. The 1.5 × 107 cm−2 of TDD in HT-DFL is reduced by almost one order compared to the 1.2 × 108 cm−2 of that in the control sample without DFLs. The annihilation process was mainly observed in the HT-DFL by a transmission electron microscope, resulting in a lower TDD. The 500-nm-thick GaAs bulk layer and InAs QDs were regrown on GaAs-on-Si templates and the optical properties were also evaluated by photoluminescence (PL). The highest PL peak intensity of the HT-DFL indicates that less non-radiative recombination in both the GaAs bulk and QDs occurred due to the reduced TDD. The GaAs p–i–n diodes were also fabricated to analyze the bulk leakage (JB) and the surface leakage current. The JB of HT-DFL shows the lowest value of 3.625 × 10–7 A/cm−2 at applied bias voltage of 1 V, which is 20 times lower than the JB of the control sample without DFLs. This supports that the high-temperature growth of DFL can make a good performance GaAs device on Si.

Facile fabrication, structural and electrical investigations of cadmium sulfide nanoparticles for fuel cell performance

In the present work, CdS nanoparticles were synthesized and analyzed for use in fuel cell applications. The X-ray diffraction investigation showed that CdS possesses a cubic polycrystalline structure. For the (111) plane, the average values of mean crystallite size, microstrain, and dislocation density were calculated and found to be 1.935 nm, 0.0758, and 0.267 nm−2. The average crystallite size was additionally calculated and found to be 2.02 nm using the modified Scherrer’s plot. The observed blue shift in the photoluminescence of CdS is caused by the quantum size impact of the nanocrystalline structure. A broad emission band at 590 nm is produced by the recombination of a hole in the valence band of CdS with an electron confined in a sulfur vacancy. The average Cd/S ratio is good and comparable, according to the EDS analysis, which is close to the theoretical values and almost exactly fits the ideal structure. A thermogravimetry diagram was used to establish the thermal stability of CdS across a wide range of temperatures. Fuel cell application features peaks were investigated by the cyclic voltammetry of CdS under various conditions. The linear sweep voltammetry was used to analyze the electrochemical performance of CdS electrodes in fuel cells. Electrochemical impedance spectroscopy (EIS) was also used and the results confirmed that nickel substrate is regarded as being superior to stainless steel in terms of performance.

Assessment of activation volume in 304L SS at high temperatures

The variation in apparent and true activation volumes of 304L SS with true plastic strain has been evaluated at three temperatures (973 K, 1073 K and 1123 K) over the strain rates of 3 × 10−3 s−1, 3 × 10−4 s−1 and 3 × 10−5 s−1. The instantaneous strain rate sensitivity parameter was derived from strain-rate jump tests across different strain levels to estimate apparent activation volume. The values of apparent activation volume were higher at 973 K than at other temperatures. In contrast to the apparent activation volume, the estimated values of true activation volume using internal-stress-based kinetic rate law systematically increase with the increasing temperature from 973 K to 1123 K. The higher flow stress with a larger strain hardening rate at 973 K leads to a lower true activation volume in the steel compared to other temperatures. The model outcomes revealed that the instantaneous strain rate jump-up or jump-down leads to the change in the internal and effective stresses. The observed variations in geometrically necessary dislocation density (GND) and intra-grain reference orientation deviation (GROD) in the substructure substantiated the predicted variation in the internal stress level upon strain rate jump up/down. The true activation volume was estimated for a fixed value of mobile dislocation density (ρm = 5 × 1011 m−2) and for varying mobile dislocation density. Irrespective of ρm values, the estimated true activation volume values for 304L SS were in the order of 102 b3 to 103 b3, thereby implying that the intersection of dislocations coupled with the climb of jogged dislocations is the dominant mechanism during tensile deformation at high temperatures. Based on the analysis using the kinetic rate law with a fixed value of mobile dislocation density, it has been realized that the multiplication of effective stress and true activation volume remains constant across the plastic strain levels for the given combination of strain rate and temperature.

Structural, electrical, and optical properties of rare-earth Sm3+ doped SnO2 transparent conducting oxide thin films for optoelectronic device applications: Synthesized by the spin coating method

Various concentrations of Sm (1, 2, 3, 4, and 5 at%) doped SnO2 thin films were synthesized by the sol-gel spin coating method and investigated the structural, optical, and electrical properties. According to X-ray diffraction studies, all deposited films exhibited the polycrystalline rutile tetragonal structure. The average crystallite size decreased with Sm doping concentration in SnO2, while the dislocation density and lattice strain values were increased. Both XPS and Raman spectra confirm that Sm3+ enters the host SnO2. The higher average optical transmittance is above 86% in pure SnO2, while Sm: SnO2 films exhibit a decreasing trend with the increase of Sm doping concentration and reached up to 77% in 5 at% Sm: SnO2 film. The optical bandgap energy increased with the increase of Sm doping concentration up to 3 at % Sm: SnO2 film (4.23 eV) which is attributed to the Moss-Burstein (MB) effect and then slightly decreased for 4 at% and 5 at% Sm: SnO2 films. Further, the room temperature sheet resistance and resistivity values were found to decrease with the increase of Sm doping concentration up to 3 at % Sm: SnO2 film then it slightly increased in 4 and 5 at% Sm: SnO2 films. Additionally, the efficiency parameter figure of merit (φ) for all the deposited films was calculated.

The effect of rGO and chemical reduction under hydrazine on the structural, electrical and optical properties of nanostructured SnO2:F/rGO thin films

In this study, SnO2:F-rGO thin films were prepared by spray pyrolysis method on glass substrates. The effect of rGO and chemical reduction with Hydrazine on the structural, electrical, and optical properties of FTO:rGO thin films has been investigated. To deposition FTO: rGO thin films, different atomic ratios of fluorine to tin were changed as [F/Sn] = 0, 0.25, 0.5, 0.7 and 1 with a constant value of reduced graphene oxide (rGO). The X-ray diffraction study showed that all FTO: rGO thin films have a polycrystalline structure with tetragonal crystal structure and were preferably oriented in (200) direction. FE-SEM images showed that hydrazine as a reduction agent increased grain size and decreased porosity of FTO: rGO samples. The results of electrical measurements of thin films showed that the minimum sheet resistance equal to 118 Ω/□ was obtained for FTO: rGO with [F/Sn] = 0.5 thin films. The Hall Effect test showed the conductivity of all samples to be n-type and the carrier concentration was obtained from the order of 1021 cm−3. Also, the values of dislocation density and, micro-strain of FTO: rGO thin films were calculated. Finally, the results of UV–Vis spectroscopy showed that the energy gap of thin films varies in the range of 3.10–3.64 eV.