Big Grains Research Articles

Effect of the Al2O3 additive on the high temperature ablation behavior of the ZrC–ZrO2 coating for SiC-coated carbon/carbon composites

The Al2O3 additive content in the ZrC–ZrO2 composite coating is adjusted by using the supersonic atmosphere plasma spraying method and the coatings are then tested by the oxyacetylene torch. The influence of the Al2O3 additive content on the anti-ablation property is studied. Results show that the ZrC–ZrO2 coating containing 10 vol% Al2O3 owns the lowest surface porosity and the best ablation resistance property. The ablated area is compact and mainly consists of big grains, which is because the addition of Al2O3 can promote the sintering of liquid ZrO2. The formed Al–Zr–O structure can promote the completeness and stability of the ZrO2 scale, which can inhibit the penetration of oxygen.

Wheat NILs contrasting in grain size show different expansin expression, carbohydrate and nitrogen metabolism that are correlated with grain yield

Two wheat near-isogenic lines (NILs; -GS (small grain size) and + GS (large grain size)) were obtained by backcrossing. We found that the grain volume and weight of + GS were significantly higher than those of -GS. There was a corresponding increase in grain yield associated with the + GS line. For analysis of causes, we investigated and compared the anatomic and physiological characteristics of two NILs during the grain filling stage. The bigger grain size in + GS likely resulted from the longer endosperm cells, which is related to the higher IAA content and expansin activity accompanied by the up-regulation of some expansin-related genes. For the higher grain weight of + GS, starch accumulation was higher in + GS than in -GS, which was consistent with relatively higher glucose (Glu), fructose (Fru), and sucrose (Suc) contents. Elevated sugar level may be correlated with sucrose synthase (SuSy) activity and up-regulation of GBSS I, SSS III, and SBE I. The amount of soluble protein in + GS grains also exceeded that in -GS grains, possibly because of increased NR, NiR, and GS activities and up-regulation of nitrogen assimilation and nitrate transporter genes in + GS grains. Furthermore, the photosynthetic rate was higher in + GS and -GS at the early filling stage before 21 DAA. The same trends were observed in sugar content (Suc, Fru, and Glu) and SPS activity. However, the increase in the rate of grain length and width in + GS plants at the late filling stage was significantly higher than that at the early filling periods. These suggest that high accumulation of dry matter (such as starch and protein) at early filling stage was the important factor in achieving the final increased size of wheat grains, besides cell expansion.

G.A.S.

Context. Dust is a crucial component of the interstellar medium of galaxies. The presence of dust strongly affects the light produced by stars within a galaxy. As these photons are our main information vector to explore the stellar mass assembly and therefore understand a galaxy’s evolution, modeling the luminous properties of galaxies and taking into account the impact of the dust is a fundamental challenge for semi-analytical models. Aims. We present the complete prescription of dust attenuation implemented in the new semi-analytical model called G.A.S. This model is based on a two-phase medium originating from a physically motivated turbulent model of gas structuring (G.A.S. Paper I). Methods. Dust impact is treated by taking into account three dust components: polycyclic aromatic hydrocarbons, very small grains and big grains. All three components evolve in both a diffuse and a fragmented/dense gas phase. Each phase has its own stars, dust content and geometry. Dust content evolves according to the metallicity of it associated phase. Results. The G.A.S. model is used to predict both the ultraviolet (UV) and the infrared (IR) luminosity functions from z = 9.0 to z = 0.1. Our two-phase ISM prescription catches the evolution of UV and IR luminosity functions very well. We note a small overproduction of the IR luminosity at low redshift (z < 0.5). We also focus on the infrared-excess (IRX) and explore its dependency with the stellar mass, UV slope, stellar age, metallicity and slope of the attenuation curves. Our model predicts large scatters for relations based on IRX, especially for the IRX–β relation. Our analysis reveals that the slope of the attenuation curve is more driven by absolute attenuation in the far-ultraviolet (FUV) band than by disk inclination. We confirm that the age of the stellar population and the slope of the attenuation curve can both shift galaxies below the fiducial star-birth relation in the IRX–β diagram. Main results presented in this paper (e.g., luminosity functions) and in the two other associated G.A.S. papers are stored and available in the GALAKSIENN library through the ZENODO platform.

Ultraviolet Extinction Properties of the 30 Dor Nebula and Interpreting Observations of Starburst Clusters

Abstract Recent investigations of the extinction law in 30 Dor and the Tarantula Nebula, at optical and near-infrared wavelengths, have revealed a ratio of total to selective extinction R V = A V /E(B − V) of about 4.5. This indicates a larger fraction of big grains than in the Galactic diffuse interstellar medium (ISM). Possible origins include coalescence of small grains, small grain growth, selective destruction of small grains, and fresh injection of big grains. From a study of the ultraviolet extinction properties of three massive stars in the 30 Dor nebula (R139, R140, R145), observed with the International Ultraviolet Explorer, we show that the excess of big grains does not come at the expense of small grains, which are still present and possibly even more abundant. Fresh injection of large grains appears to be the dominant mechanism. A process able to naturally account for this in environments such as the Tarantula nebula, where formation of massive stars has been ongoing for over ∼20 Myr, is the explosion of massive stars as SNe II. The ensuing change in the conditions of the ISM is only temporary, lasting less than ∼100 Myr, because shattering and shocks will eventually break and destroy the bigger grains. However, this is the only time when star-forming regions are detectable as such in starburst and high-redshift galaxies, and we highlight the complexity inherent in interpreting observations of star-forming regions in these environments. If the extinction characteristics are not known properly, any attempts to derive quantitative physical parameters are bound to fail.

Highly Reversible Conversion Anodes Composed of Ultralarge Monolithic Grains with Seamless Intragranular Binder and Wiring Network

Conversion anodes enable a high capacity for lithium-ion batteries due to more than one electron transfer. However, the collapse of the host structure during cycling would cause huge volume expansion and phase separation, leading to the degradation and disconnection of the mixed conductive network of the electrode. The initial nanostructuring and loose spatial distribution of active species are often resorted to in order to alleviate the evolution of the electrode morphology, but at the cost of the decrease of grain packing density. The utilization of ultralarge microsized grains of high density as the conversion anode is still highly challenging. Here, a proof-of-concept grain architecture characterized byendogenetic binder matrix and wiring network is proposed to guarantee the structural integrity of monolithic grains as large as 50-100 μm during deep conversion reaction. Such big grains were fabricated by self-assembly and pyrolysis of a Keggin-type polyoxometalate-based complex with protonated tris[2-(2-methoxyethoxy)-ethyl]amine (TDA-1-H+). The metal-organic precursor can guarantee the firm adherence of numerous Mo-O clusters and nuclei into a highly elastic monolithic structure without evident grain boundaries and intergranular voids. The pyrolyzed TDA-1-H+ not only serves as in situ binder and conductive wire to glue adjacent Mo-O moieties but also acts as a Li-ion pathway to promote sufficient lithiation on surrounding Mo-O. Such a monolithic electrode design leads to an unusual high-conversion-capacity performance (1000 mAh/g) with satisfactory reversibility (reaching at least 750 cycles at 1 A/g). These cycled grains are not disassembled even after undergoing long-term cycling. The conception of the intragranular binder is further confirmed by consolidating the MoO2 porous network after in situ stuffing of MoS2 nanobinders.

Quantification of Corn Grains Losses in Road Transport

The present work had the objective of quantifying corn grain losses in road transportation along a section of highway BR 163 in the state of Mato Grosso. The survey was done in July and August of 2016 in the section between the Imigrantes Highway, within the city of Cuiabá - MT, and the municipality of Nova Mutum – MT. This stretch is considered to be the one with the highest flow of grain loads in the state of Mato Grosso. Twenty one collect points were established along the stretch, with a distance of 10 km from one point to the other, at each collect point 3 areas of 1 m² were delimited with the aid of a fixed frame of wood with the same area, in a distance of 1.3 m from the highway margin, in the north-south direction, which is the direction of the grain flow. The samples were placed in identified plastic bags and taken to the laboratory for separation and weighing. The points of the biggest grain losses were points 06 and 12 of the section, where it was verified pavement in poor quality with much road surfacing, and the points of lower losses were collected in the top quality asphalt range.

Significantly Enhanced Detectivity of CIGS Broadband High-Speed Photodetectors by Grain Size Control and ALD-Al2O3 Interfacial-Layer Modification.

The Cu(In,Ga)Se2 (CIGS) thin film has been commercialized as solar cells with great success, but its application for photodetectors still faces some practical challenges, including low detectivity and long response time. In this paper, the structure of the Mo/CIGS/CdS/ZnO/ITO heterojunction has been fabricated, and satisfactory performances of high detectivity and fast response time have been achieved by suppressing the dark current and enhancing the carrier mobility. The controllable growth of CIGS grains is accomplished through optimizing the selenization process, demonstrating that bigger grain sizes resulted in higher carrier mobility and better response characteristics. Particularly, the high rise/decay speed of 3.40/6.46 μs is achieved. Furthermore, the interface of the CIGS/CdS heterojunction has been modified by the Al2O3 layer via the atomic-layer deposition (ALD) process. The dark current of the device is effectively suppressed by the ALD-Al2O3 layer, which remarkably drops from ∼10-7 to ∼10-9 A. As a consequence, the detectivity rises from 3.08 × 1011 to 1.84 × 1012 Jones. In addition, the ALD-Al2O3 layer shows a protective effect as well, which is positive for photoelectrical conversion. Besides, the wide linear dynamic range of 102.1 dB and large -3 dB bandwidth of 78 kHz are acquired. This work suggests that the CIGS-based heterojunction has great potential for high-performance thin-film photodetectors.

Hole/electron transport layers in tin-doped SBLN nano materials for hybrid solar cell applications

In this work, layered perovskite SBN was investigated in a new doped form for hole as well as electron transport layer (HTL/ETL) in perovskite solar cells. This work was targeted to conclude the effect of tin doping in lanthanum-bismuth layer SBN on optical energy band gap besides dominant electron-hole transportation to assist in perovskite solar cell applications. Thoroughly hard ball-milled compositions Sr1-xSnxBi1.95La0.05Nb2O9 (x=0.0, 0.01, 0.03, 0.05, 0.1 and 0.2) were prepared by special microwave synthesis to obtain fine (~10-60nm) mesoporous particle network of atomic level substitutions. Microwave synthesis was crucial in modifying dielectric, semiconducting and optical characteristics of prepared SBN materials. The band gap reduced in continuous manner and carrier mobility was increased by 112% for maximum tin doping. Nano particle formation assisted in raising carrier mobility by bridging bigger grains through nano particles. The effect of macro-sized grains and nano-sized grain boundaries on carrier transport were further investigated in detail using impedance spectroscopy.

Effect of grain size on α-variant selection in a ZrTiAlV alloy

Local crystallographic orientation characteristics of grains with different sizes in a ZrTiAlV alloy after interrupted cooling from β phase region are investigated by electron backscatter diffraction (EBSD) technique. A statistical analysis of EBSD data shows that bigger parent β grains present weaker variant selection than smaller grains. The relevant influences are studied by comparing the nucleation behavior of grain boundary α (GBα) and succedent growth stage in varisized grains. In-depth analysis indicates that the deviation between pole of GBα and common pole of adjacent parent β grains is responsible for the smaller degree of variant selection inside the bigger parent β grains. The formation of more than one GBα type at the β/β grain boundary with common pole in bigger grains results in obstructing each other for these variants during the following growth stage, while only one type of GBα nucleate at the β/β grain boundary with common pole in smaller grains and it can freely grow into the interior of the grains, leading to stronger variant selection in smaller β grains.

Influence of structural components placement on casting technological damages formation

The technological processes designing main criterion are identified. The reliability parameters: infallibility, durability, repairability, preservation are described with machine part life cycle’s substages and stages are described. The reliability support principles of difficult engineering systems for mechanical engineering production are analyzed. The insufficient researches level regarding influence of casting’s structural components on defects formation on it surface is argued. The reliability varieties are considered, its place in the machine part life cycle’s structure is identified and mathematical dependences for potential reliability definition are suggested. Inexpediency of potential reliability using as the part condition forecasting’s criterion during it machining is justified. The blanks operations i mportance in the t echnological process planning structure of cast blanks is confirmed. The mathematical dependence for technological processes infallible implementation’s estimated probability (the technological process reliability coefficient) is confirmed. The defects types and its formation mechanisms for blanks are analyzed. The casting defects main types: burnt-on sands, cavities, flashes and cracks are characterized. The deficiencies role as surface layer’s infringements during parts work in machine is installed. The p arameters for the deficiencies control according to ISO 8785: 1998 are presented. The metal destruction phases during machining are considered. It is installed that big angle grains boundaries have an important role in technological damages and processes of alloys destruction situating between grains boundaries formation. The material damageability degree evaluation's modern conceptions as the operating time result of direct and indirect measurements are considered and its main deficiencies are specified. The LM-hardness method for definition of the castings damageability W as part infallibility parameter is presented. The technological fixture and the experimental researches execution and implementation technique are described. The received results justification and analysis are presented. The further researches directions are scheduled.

Improving polycrystalline GaN by controlling annealing temperature of ScN interlayer

This work describes crystal and surface properties of a ScN interlayer, which was deposited on GaAs substrate with successive ammonia annealing at different temperature; 700 °C, 800 °C, 850 °C and 900 °C. The crystal and surface of the ScN interlayer changed with the annealing temperature and this has influenced the crystal, surface and optical properties of an over-deposited polycrystalline GaN layer. The ScN interlayer formed well at the annealing temperature above 850 °C with the presence of GaN and ScAs inclusions, arising from the out-diffusion of Ga and As atoms from the GaAs substrate due to high temperature. Furthermore, the presence of voids on the surface was observed due to the decomposition of Sc and N atoms from the surface of the ScN interlayer at high temperature. However, the voids were insignificant at 900 °C. This is because the ScN interlayer was initially formed with bigger grains at 900 °C as compared other temperature. These bigger grains attracted the decomposed Sc and N atoms to re-deposit on them, thereby suppressing the voids. All samples of the over-deposited polycrystalline GaN layer were found to be preferably crystallized in (0002) orientation. In the case for the polycrystalline GaN layer deposited on the 900 °C annealed ScN interlayer, the layer was evidently formed towards (100), (101) and (110) orientations, in addition to the (0002) orientation. This can be associated to that presence of the aforementioned GaN inclusions, which served as the nucleation sites for the GaN to crystallize in such orientations. Moreover, the surface of the polycrystalline GaN layer exhibited more distinguishable and bigger GaN grains with improved coalescence compared to other samples. Therefore, it showed strong signals in Raman scattering.

Equal channel angular sheet extrusion (ECASE) as a precursor of heterogeneity in an AA6063-T6 alloy

We study the deformation inducing heterogeneity in an aluminum alloy 6063-T6 in the form of a sheet processed at room temperature by equal channel angular sheet extrusion (ECASE) up to a maximum equivalent strain of 1.86 following route C. The through thickness strain distribution showed higher strains in the edge vicinities than in the sheet core. The texture was heterogeneous between the edges and the sheet core with a strong cube component in the initial deformation stages, and a rolling texture with the S component in the sheet edges. Different microstructural characteristics, like grain size, average misorientation, and fraction of high angle grain boundaries (HAGB), decreased by increasing the deformation. The geometrically necessary dislocation (GND) calculations corroborated the existence of a heterogeneous microstructure along the sheet thickness, giving rise to gradients of plastic deformation which allowed to obtain a good strength-ductility relationship. It was demonstrated that ECASE process was a good alternative to produce heterogeneous microstructures. The material heterogeneity was found not to be randomly distributed across the sheet thickness but rather showing higher dislocation concentration and bigger grain size reductions in the edge’s vicinities than in its middle zone.

Modeling of [formula omitted] and [formula omitted] versus the grain size in CdTe, CZTS and Perovskite thin film solar cells

A modeling approach is presented for the first time to model the dependence of short-circuit current density (Jsc) and open-circuit voltage (Voc) on the grain size g in three thin film solar cells including the emerging perovskites. The variation of Jsc and Voc with the grain size (g) of three different solar cells with CdTe, CZTS and perovskite absorber layers are modelled and fitted with the experimental dataset collected from relevant literature. The experimental literature suggested that the grain size of absorber layers in solar cells is controlled during the deposition process by adjusting the growth rate, temperature and ambient. The model has been successfully applied to the experimental data obtained from CdTe, CZTS and MAPbI3 Perovskite solar cells by adjusting a few parameters which are affected by grain size such as mobility, diffusion length, and carrier lifetime. A bigger grain size leads to a higher short-circuit current density and open circuit voltage. However, the polycrystalline nature of thin film materials is still an impediment for the fabrication of large grain absorber layers compared to single crystalline Si materials. The modeling results show almost similar trends of dependency of device parameters on grain size: both Jsc and Voc follow the g trend (g1/2) and for larger grain sizes it tends to a constant level. CZTS and perovskite cells show an almost polynomial quadratic dependency on grain size. The grain size of 2 μm seems to be a turning point for the CdTe materials, 1.5 μm for CZTS and 250 nm for perovskites. However, in most cases, the increasing slope of the Jsc and Voc tends to a constant value because the effect of increasing the grain size on diffusion length and mobility (or carrier lifetime) becomes negligible.

The effect of lime Ca(OH)2 to the constant of granulation rate (k) of Sidoarjo mud (LuSi) and its grain size distribution

Sidoarjo mud (LuSi) is very hot and sticky mud-like substance produced by eruption of Kujung, Kalibeng, and Pucangan formations caused by well exploration for gas in Porong, Sidoarjo, East Java, Indonesia. LuSi submerged villages, industrial areas, and rice fields in Porong. The eruption is still taking place so that it needs more area and higher dike surrounded to retain the mud. Therefore, it is very urgent to use LuSi in huge volumes such as for borrowed materials. LuSi grain size and its strength, however, do not meet the borrowed materials requirement. Therefore, the grain size was improved using granulator drum and lime Ca(OH)2 was used to increase its strength. The grain size produced by granulator was affected by length, diameter, and rotation rate of granulator drum, and also by constant of granulation rate ‘k’ that was function of other parameters, inclination angle of granulator drum (S), moisture content (W), and water temperature (T). The results show that lime needed for stabilization is 10% of LuSi dry weight. The “k” is affected by lime where parameters (S) and (W) become smaller and (T) is higher. Lime also produces dryer granular, higher water resistance, and shorter granulation process. Besides, higher water temperature during granulation process is needed to develop bigger grain size for granular stabilized-LuSi.

Microstructural, mechanical and corrosion properties of dissimilar joint between AISI A321 stainless steel and ASTM A537CL1 structural steel produced by GTAW process

In this research, the microstructural, mechanical and corrosion properties of the dissimilar joint of ASTM A537CL1 to AISI A321 steels produced by GTAW process were studied. The welding process was done with ER308L filler metal without pre and post weld heat treatment. The scanning electron microscope and optical microscope were used to study the microstructure and fracture surface of the welded samples. Also, the mechanical behavior of the joint was evaluated by impact, tensile, bending and microhardness tests. The results illustrated that the microstructure of the weld metal was austenite with dendritic structure contained skeletal and lathy ferrite. In tension tests, all weldments failed from A537 base metal. The results of impact test indicated that all specimens exhibit ductile fracture and indicated high impact energy of about 205 J. In fine grain HAZ of A537 steel, because of formation of fine equiaxed grains due to the allotropic transformation, high microhardness was seen. While, in coarse grain HAZ, due to the formation of bigger grains, carbon migration and decreasing in the amount of pearlite phase, the microhardness slightly decreased. The exsistence of chromium in microstructure improved the corrosion resistance and the weld metal indicated acceptable corrosion resistance as compared with both base metals.

Morphological regulation of all-inorganic perovskites for multilevel resistive switching

Enormous attention has been paid to all-inorganic cesium lead halide perovskites in various photoelectronic fields for their remarkable performances. However, comparing to their analogue organic-inorganic hybrid perovskites, the film morphology of such all-inorganic lead halide perovskites is difficult to control due to the low solubility of cesium salt. Here, we propose a new fabrication routine to control the film morphology of CsPbBr3. A series of CsPbBr3 thin films with big grains (≈800 nm) were successfully prepared. The memristors based on such CsPbBr3 thin films take on typical bipolar resistive switching behavior and remarkable characteristics such as high Ron/Roff ratio (≈105), very low working voltage (≈±1 V), and long data retention (≥104 s). Furthermore, through modulating the film morphology, memristors with multilevel resistive switching behavior can be easily prepared. These advantages demonstrate that the all-inorganic cesium lead halide memristors possess great potential for future application.

Physical properties of Cd-doped ZnS thin films

In this research, un- and Cd-doped ZnS nanostructures were synthesized using an electrodeposition method. The electrolyte contained 20 mM ZnCl2, 20 mM Na2S2O3 and the various amounts of CdCl2 solution. The X-ray diffraction (XRD) patterns of the as-deposited samples exhibited that Cd doping leads to decrease the crystallite size (D) of ZnS meanwhile the lattice strain, lattice stress, dislocation density (γ), and stacking fault energy (SF) were increased. Field emission scanning electron microscopy (FESEM) images depicted very fine equiaxed grains (20–50 nm), in addition to big grains (200–400 nm) with the preferential orientation. The reflectance spectra of ZnS thin films indicated a decrease in the reflectance peaks and refractive index (n), after Cd doping. Based on the transmission spectra, the un- and Cd-doped ZnS samples showed an absorption edge between 328 and 357 nm. The band gap energy for undoped ZnS sample was estimated as 3.95 eV, which it was reduced to 3.63 eV for the Cd-doped ZnS samples owing to the presence of imperfections and crystalline disorder in the Cd-doped ZnS samples. Furthermore, the obtained dielectric constant of the Cd-doped ZnS thin films was smaller than undoped ZnS sample, which means that the Cd-doped ZnS samples were more appropriate than the undoped ZnS sample for application in the fast photodetectors. The photoluminescence (PL) spectra of the undoped ZnS thin film was presented six emission peaks at 340, 413, 536, 574, 748, and 878 nm as an outcome of near band emission (NBE) and crystalline defects such as zinc interstitials (IZn), zinc vacancies (VZn), sulfur interstitials (IS), ZnS self-defect, and the defect states between the valence band (VB) and the conduction band (CB) of ZnS. Moreover, the PL emission of the Cd-doped ZnS samples demonstrated a red-shift relative to the undoped sample, which verified the UV–vis spectroscopy results.

Rising dynamics and lift effect in dense segregating granular flows

In order to explore the rising dynamics and the existence of a lift effect in dense segregating granular flows, we perform two-dimensional discrete numerical simulations in the case of single free intruders and bi-disperse granular mixtures. In both configurations, we do not observe a measurable lift force acting on the larger grains. The large force fluctuations acting on the bigger grains reduce to the weight of the latter, following the mere action-reaction principle. This suggests that the rising dynamics is driven by the force fluctuations, coupled with the properties of the surrounding granular bed itself. We propose the strong asymmetry displayed by granular bed resistance to downward (plunging) and upward (withdrawing) motion, as reported in detail by Hill et al. [“Scaling vertical drag forces in granular media,” Europhys. Lett. 72(1), 137–143 (2005)], as a key ingredient for segregation. Accordingly, moving an object toward the free surface is about 10 times easier than moving an object toward the rigid bottom. This asymmetry allows for an effective upward motion when large grains are submitted to upward force fluctuations, without being counterweighted by sinking episodes when large grains are submitted to downward force fluctuations. In addition to gravity, the existence of two different boundary conditions formed by the free surface and the rigid bottom explains this difference of resistance to motion. In this respect, the mechanism allowing size segregation in dense granular flows would be the same as that allowing legged locomotion in sand [Li et al., “A terradynamics of legged locomotion on granular media,” Science 339, 1408–1412 (2013)].In order to explore the rising dynamics and the existence of a lift effect in dense segregating granular flows, we perform two-dimensional discrete numerical simulations in the case of single free intruders and bi-disperse granular mixtures. In both configurations, we do not observe a measurable lift force acting on the larger grains. The large force fluctuations acting on the bigger grains reduce to the weight of the latter, following the mere action-reaction principle. This suggests that the rising dynamics is driven by the force fluctuations, coupled with the properties of the surrounding granular bed itself. We propose the strong asymmetry displayed by granular bed resistance to downward (plunging) and upward (withdrawing) motion, as reported in detail by Hill et al. [“Scaling vertical drag forces in granular media,” Europhys. Lett. 72(1), 137–143 (2005)], as a key ingredient for segregation. Accordingly, moving an object toward the free surface is about 10 times easier than moving an object toward th...

Al-doped ZnS thin films: Physical and electrochemical characterizations

This study evaluated the effect of Al incorporation on the structural, optical, electrical and electrochemical properties of ZnS thin films. An electrochemical route was used to synthesize the studied un- and Al-doped ZnS thin films on indium tin oxide (ITO) glass substrates using an aqueous solution of ZnCl2 and Na2S2O3. The Al-doped ZnS samples were prepared by adding different amounts of AlCl3 to the main electrolyte. Cyclic voltammetry determined −0.9 to −1.1 V as the appropriate potential range for deposition of the ZnS thin films. In addition, appearance of a new reduction peak in the cyclic voltammograms of the Al-doped ZnS samples approved the presence of the Al dopant in the structure of the electrodeposited films. The recorded X-ray diffraction (XRD) patterns exhibited that all deposited samples contain cubic ZnS crystals and indicated that Al-doping decreases the crystallite size of the ZnS samples. Field emission scanning electron microscopy (FESEM) demonstrated that all samples are composed of big grains with 150–600 nm dimension distributed in a background phase including 15–60 nm grains. The photoluminescence (PL) spectra showed that all samples emit five PL peaks due to their different crystal defects. UV–Vis spectroscopy clarified that Al-doping decreases the band gap energy of the ZnS samples from 3.93 to 3.50 eV. Furthermore, it showed that the Al-doped ZnS samples present a lower capacitance and a shorter response time, which are suitable properties for application of these materials in fast photodetectors. The Mott-Schottky plots demonstrated n-type conductivity for all samples and revealed that the existence of the Al dopant increases the carrier concentration of the ZnS thin films. The electrochemical impedance spectroscopy (EIS) results confirmed that Al incorporation reduces the time constant and capacitance of the ZnS samples. Consequently, all results declared that Al incorporation has significant effects on the physical, optical and electrical properties of ZnS thin films.

Reactively Magnetron Sputter-Deposited Ti (C,N) Nanocomposite Thin Films: Composition and Thermal Stability

Titanium carbonitride thin films were grown by reactive magnetron sputtering deposition of titanium carbide target in Ar/N2 gas mixture on p-type silicon (100) substrates. With the increase of sputtering power up to 125W, the deposition rate and films thickness reached a maximum of 14nm/min and 430nm, respectively. A thick film of about 2200nm could be deposited for 120 min at the optimum deposition pressure of 20mTorr. Cathode current decreased from about 290mA to reach a value of about 235mA as the N2 flow percentage increased from 0 to 100%. X-ray diffraction analyses of the deposited films confirmed the formation of titanium carbide and carbonitride layers as the nitrogen gas concentrations in the process gas were increased. SEM image of the deposited titanium carbonitride thin film for 5 min deposition time showed that the film started to grow as tiny particles of size as low as about 140nm, which in later stage coalesced together to form bigger grains and finally a continuous film. The deposited film shows good thermal stability upon annealing in air and in vacuum at 700oC for 2 hours.