Mo Substrate Research Articles

Studies on mutual diffusion between Mo and α-Ti during thermal evaporation

Mutual diffusions between Mo substrate and α-Ti film have great impacts on the performance of metal hydride films. In this study, the diffusion behavior between Mo substrate and α-Ti film during thermal evaporation deposition was investigated in the temperature range of 500–1000 K by both experiment and molecular dynamic simulation. The experimental results show that the coefficient changes abnormally with temperature. The results of SEM, TEM and molecular dynamics simulation indicated that in addition to temperature, grain boundary also has great effects on their mutual diffusion behavior. After taking account of the influence from grain boundary, the mutual diffusion coefficients of simulation and experiment can be well consistent in the whole Mo concentration range, especially in the middle region where Mo concentration is 0.1–0.85. Base on the results obtained, the mutual diffusion coefficients between Mo substrate and α-Ti film are appreciable, which is conducive to the selection of appropriate substrate temperature.

Preparation of MoSi2 Coating on Mo Substrate for Oxidation Resistance by a Facile Method

A MoSi2 coating layer with a MoB protected layer was simply prepared by using a combined method, which involved slurry painting and an embedded method via a hot press sintering process. The microstructure and phase composition of the coatings were investigated and determined. The experimental time and the B addition are considered as important factors to be discussed in this study. All the results proved that when B is added, it was found that the formation of MoB played an important role of a diffusion barrier to Si and hindered the production of the poor oxidation resistance phases (Mo5Si3 and Mo3Si).

Carbon Monoxide Oxidation over Gold Nanoparticles Deposited onto Alumina Film Grown on Mo(110) Substrate: An Effect of Charge Tunneling through the Oxide Film.

Formation of gold nanosized particles supported by aluminum oxide film grown on Mo(110) substrate and oxidation of carbon monoxide molecules on their surface have been in-situ studied in ultra-high vacuum by means of Auger electron spectroscopy (AES), reflection-absorption infrared spectroscopy (RAIRS), low energy electron diffraction (LEED), atomic force microscopy (AFM), temperature-programmed desorption (TPD), and work function measurements. The main focus was to follow how the thickness of the alumina film influences the efficiency of CO oxidation in an attempt to find out evidence of the possible effect of electron tunneling between the metal substrate and the Au particle through the oxide interlayer. Providing the largest degree of surface identity of the studied metal/oxide system at different thicknesses of the alumina film (two, four, six, and eight monolayers), it was found that the CO oxidation efficiency, defined as CO2 to CO TPD peaks intensity ratio, exponentially decays with the oxide film thickness growth. Taking into account the known fact that the CO oxidation efficiency depends on the amount of excess charge acquired by Au particle, the latter suggests that electron tunneling adds efficiency to the oxidation process, although not significantly.

SiOxNy back-contact barriers for CZTSe thin-film solar cells.

The formation of molybdenum diselenide (MoSe2) is widely observed at the back-contact interface for copper zinc tin selenide (CZTSe) thin-film solar cells. Depending on individual selenium (Se) supply and thermal conditions for forming CZTSe absorbers on molybdenum (Mo) substrates, the thickness of MoSe2 can vary from a few hundreds of nanometers up to ≈ 1 μm, which is comparable to the commonly adopted thickness of 1 ~ 1.5 μm for CZTSe absorbers. In this study, for controlling the thickness of interfacial MoSe2, thin diffusion barrier layers of silicon oxynitride (SiOxNy) are deposited onto Mo layers prior to the growth of CZTSe absorbers in the fabrication process. As a result, a reduction in the thicknesses of MoSe2 layers is achieved. In terms of energy conversion efficiency (η), CZTSe solar cells grown on Mo/SiOxNy back contacts suffer a deterioration as the SiOxNy layers get thicker. CZTSe solar cells grown on Mo/SiOxNy/Mo back contacts preserve their efficiencies at ≈ 11% with thin 10 nm SiOxNy layers.

Effect of SiC Nano Particulate Reinforcement on the High Temperature Oxidation Behavior of MoSi <sub>2</sub> Coating Grown on Mo Substrate

Effect of SiC Nano Particulate Reinforcement on the High Temperature Oxidation Behavior of MoSi <sub>2</sub> Coating Grown on Mo Substrate

Investigation of the influence of substrate materials on oxidation resistance of TaSi2 and Ta-Si-N coatings using SEM, EDS and GDOES methods

Coatings were obtained by magnetron sputtering of a Ta-Si target onto Al2O3, Mo, Si and Ni-based substrates. Samples were studied in terms of their structure, mechanical properties and oxidation resistance by SEM, EDS, nanoindentation and GDOES methods. It was found that an increase in the concentration of nitrogen leads to an increase in the hardness of coatings by 60%. The behavior of coatings and various types of substrates during annealing at a temperature of 1000-1200 ˚C.

Microstructure and oxidation behaviour of MoSi2 coating combined MoB diffusion barrier layer on Mo substrate at 1300 °C

To improve the oxidation resistance of a Mo substrate at high temperatures, MoSi2–MoB double layers were prepared on the surface of the substrate using a two-step pack cementation method. The isothermal oxidation tests indicate that the weight loss of MoSi2–MoB double layers was only 6.3824 mg/cm2 after oxidation at 1300 °C for 15 h, whereas the untreated Mo experienced serious weight loss and the weight loss was 606.775 mg/cm2 after only 90 min. Following oxidation exposure, the oxidized coating became six complex layers due to correlation diffusion among Mo, Si and B. The double layers showed excellent high-temperature oxidation resistance due to the formation of a dense and continuous SiO2 layer with low O2 permeability. Meanwhile, in situ fabrication of a novel Mo5SiB2 layer could prevent inward diffusion of Si.

An Evaluation on the Electrochemical Recovery of Indium from Water Insoluble Indium Oxide in a Choline Chloride-Malonic Acid Eutectic Electrolyte

The use of deep eutectic solvents for the dissolution and electrochemical recovery of indium from water insoluble In2O3 was evaluated. While In2O3 did not dissolve appreciably in choline chloride/ethylene glycol (molar ratio 1:2) and choline chloride/urea (molar ratio 1:2), it dissolved well in choline chloride/malonic acid (molar ratio 1:2) up to 0.1 M at 373 K. Cyclic voltammograms recorded on several types of electrode including GC, Cu, and Mo indicated that the reduction of In(III) to In on Cu and Mo substrates was complicated by hydrogen evolution reaction (HER) but not so seriously on GC due to the higher overpotential required for HER on GC electrode. Because of the HER, the current efficiency of the electrodeposition of In on Cu Mo electrodes was lower than on carbon electrode. Chronoamperometry results indicated that the deposition of In was possibly involved with the three-dimensional (3D) progressive nucleation on the Cu electrode, and 3D instantaneous nucleation on the GC electrode, respectively. Images taken by scanning electron microscopy (SEM) revealed the surface morphology of In electrodeposits was dependent on the electrode materials and applied potential. Crystalline In deposits on these substrates was confirmed by X-ray powder diffraction (XRD) patterns.

Oxidation mechanism of refractory Molybdenum exposed to oxygen-saturated lead-bismuth eutectic at 600 °C

The oxidation mechanism of refractory Molybdenum exposed to oxygen-saturated lead-bismuth eutectic (LBE) at 600 °C was investigated. The results show a hierarchical structure of multiple corrosion layers. Specifically, a nanostructured tetragonal MoO2 is the first scale that forms on the Mo substrate, followed by development of an ultrafine-grained tetragonal lead molybdate (PbMoO4) layer. On the top of this ultrafine-grained layer, there is a thicker scale that consists of micron-sized columnar PbMoO4 and its upper part can be further oxidized into blocky monoclinic-structured Pb2MoO5. The formation of these multilayered scales is likely predominated by inward diffusion of oxygen and Pb.

Comparative study on microstructure, bio-tribological behavior and cytocompatibility of Cr-doped amorphous carbon films for Co–Cr–Mo artificial lumbar disc

Cr-doped amorphous carbon (a-C:Cr) film is a promising protective coating to extend the lifetime of Co–Cr–Mo implants. Here, a-C:Cr films with the same doping concentration of Cr and thickness are deposited on Co–Cr–Mo substrates using the closed-field unbalanced magnetron sputtering (UBMS) and the plasma-enhanced chemical vapor deposition (PECVD) methods. A comparative study on the microstructure, bio-tribological behavior, and cytocompatibility of two kinds of a-C:Cr films in the air and different simulated body fluids is conducted. Microstructural analysis results show that the a-C:Cr films prepared by UBMS and PECVD methods belong to graphite-like carbon (GLC) and diamond-like carbon (DLC) films, respectively. Nanohardness of the UBMS a-C:Cr film is found to be lower than that of the PECVD counterpart. However, the UBMS a-C:Cr film exhibits better lubrication, lower wear depth and lower wear volume under all the three simulated body fluids, because of the slight polishing wear and boundary lubrication mechanisms. Moreover, both kinds of a-C:Cr films significantly improve the cytocompatibility of Co–Cr–Mo substrate alloy.

The enhanced structure stability and the reinforcement mechanism of 0.1Al2O3-ZrO2 reinforced MoSi2 composite coating

The 0.1Al2O3-ZrO2 reinforced MoSi2 composite coating was prepared on pure Mo substrate to improve its high-temperature oxidation resistance, of which the MoSi2 coating was prepared by a modified pack siliconizing process and subsequently the 0.1Al2O3-ZrO2 layer was generated on the as-prepared MoSi2 layer by a non-hydrolytic sol-gel method. The phase composition and microstructure of the as-prepared composite coating before and after oxidation exposure were investigated by XRD, SEM and EDS. Different from the loose structure of the single MoSi2 coating after oxidation exposure, the 0.1Al2O3-ZrO2 reinforced MoSi2 composite coating exhibited a relatively compact internal structure with less through-thickness cracks. The introduction of 0.1Al2O3-ZrO2 layer effectively prevented the cracking and spalling of the glassy SiO2 scale formed on the surface of MoSi2 during the oxidation, and then the SiO2 scale could be well stabilized on the coating surface. The protective SiO2 glassy scale embedded with stable ZrO2 and ZrSiO4 phase was formed, contributing to the improvement in the structure stability of the composite coating. It was proposed that ZrO2, ZrSiO4 and SiO2 developed a special glass-ceramic skeleton structure, in which ZrO2 and ZrSiO4 played the role of “Zr nail” to the SiO2 scale. In addition, the reinforcement mechanism of 0.1Al2O3-ZrO2 layer to the MoSi2 coating was also discussed.

Graphene as reusable substrate for bialkali photocathodes

Bialkali photocathodes, such as cesium potassium antimonide (CsK2Sb), can generate a high-brightness electron beam using a high-power green laser. These photocathode materials have potential applications in advanced accelerators and electron microscopes. It is known that the quantum efficiency (QE) of these photocathodes is affected severely by their substrates; however, reusability of the substrates is not well known. Here, we use graphene, silicon (Si), and molybdenum (Mo) substrates to evaluate the effects of substrates on the QE of redeposited CsK2Sb photocathodes after thermal cleanings. We found that the QE of CsK2Sb photocathodes redeposited on a graphene substrate after thermal cleaning at 500 °C remained largely unchanged. On the other hand, the QE of redeposited photocathodes on Si and Mo substrates after thermal cleaning at the same temperature decreased drastically. We used x-ray photoelectron spectroscopy to quantitatively evaluate the residues of photocathodes after thermal cleaning at 400 °C and 500 °C. We found that Sb, K, and Cs are removed by thermal cleaning at 500 °C for the graphene substrate, but all or the majority of these elements remained on the Si and Mo substrates. The results were consistent with our density functional theory calculations for the case of Si, which we investigated. Furthermore, our angle-resolved photoemission spectroscopy on graphene indicated that its intrinsic electronic structure is preserved after photocathode deposition and thermal cleaning at 500 °C. Hence, we attributed the difference in the amount of photocathode residue to the unique dangling-bond-free surface of inert graphene. Our results provide a foundation for graphene-based reusable substrates for high-QE semiconductor photocathodes.

A Novel Metal Precursor Structure for Electrodepositing Ultrathin CIGSe Thin-Film Solar Cell with High Efficiency.

The two-step process of electrodeposition and selenization is one of the most effective methods for producing CIGSe and CZTSe solar cells at a low cost. However, it is difficult to prepare the ultrathin CIGSe absorber by electrodeposition due to the nonuniform deposition of Cu on the Mo substrate. In this study, Cu was deposited on a Sb film instead of a Mo film, and the 3D growth mode of Cu was changed. Uniform and smooth ultrathin Cu films were fabricated on the Sb film using a pulse frequency over a range from 1000 to 10,000 Hz and a pulse current density ranging from 31.25 to 62.5 mA/cm2. Owing to the improved uniformity of Cu/In/Ga films, the thickness of the CIGSe absorber was reduced from 2 to 0.36 μm with Sb incorporation. In addition, the effects of Sb-doping on the CIGSe absorbers and the device performance were investigated. The crystallinity of the CIGSe films was improved, and the interface recombination of the solar cells was reduced by Sb incorporation. Ultimately, CIGSe thin-film solar cells with efficiencies of 5.25 and 11.27% were obtained with CIGSe absorber thicknesses of 0.36 and 1.2 μm, respectively.

Piezotronic AlGaN nanowire Schottky junctions grown on a metal substrate

The non-centrosymmetric crystal structures of polar-semiconductors comprising GaN, InN, AlN, and ZnO intrigued the scientific community in investigating their potential for a strain-induced nano-energy generation. The coupled semiconducting and piezoelectric properties produce a piezo-potential that modulates the charge transport across their heterostructure interfaces. By using conductive-atomic force microscopy, we investigate the mechanism that gives rise to the piezotronic effect in AlGaN nanowires (NWs) grown on a molybdenum (Mo) substrate. By applying external bias and force on the NWs/Mo structure using a Pt–Ir probe, the charge transport across the two adjoining Schottky junctions is modulated due to the change in the apparent Schottky barrier heights (SBHs) that result from the strain-induced piezo-potential. We measured an increase in the SBH of 98.12 meV with respect to the background force, which corresponds to an SBH variation ∂ϕ∂F of 6.24 meV/nN for the semiconductor/Ti/Mo interface. The SBH modulation, which is responsible for the piezotronic effect, is further studied by measuring the temperature-dependent I–V curves from room temperature to 398 K. The insights gained from the unique structure of AlGaN NWs/Mo shed light on the electronic properties of the metal-semiconductor interfaces, as well as on the potential application of AlGaN NW piezoelectric nanomaterials in optoelectronics, sensors, and energy generation applications.

Structural, morphological and electrical properties of the Al/p-Cu2FeSnS4 thin film Schottky diode grown by two method

This work highlights some physical properties of Al/p-Cu2FeSnS4 Schottky diode fabricated by a two-stage method. Foremost, the Cu2FeSnS4 (CFTS) thin film was grown using thermal evaporation method onto heated Mo substrate temperature at 150 °C. After that, the as-deposited CFTS sample was annealed in a sulfur atmosphere at 400 °C for 30 min. Structural and morphological characterization were carried out by X-Ray diffraction, Raman scattering and scanning electron microscopy, whereas electrical study of Al/p-Cu2FeSnS4 junction was performed by using the current-voltage (I-V) measurement. Structural study revealed the presence of stannite CFTS phase and other peaks like Mo and MoS2. The hot probe method indicates that CFTS thin film exhibit p-conductivity type, also the film thickness was around 500 nm. The I-V characteristics showed that a Schottky contact was obtained between Aluminum and p-Cu2FeSnS4 absorber layer. The saturation current, the ideality factor and series resistance were determined from I-V experimental data. These parameters show important electrical properties such as a low series resistance and an ideality factor between 1 and 2.

BIXS for tritium analysis with Ar gas and Al thin film as β-ray stopping layers and comparison with EBS

β-ray induced X-ray spectrometry (BIXS) and elastic backscattering spectrometry (EBS) were utilized in this study for the tritium analysis of samples of tritium/deuterium-containing titanium films with thick Mo substrates. Using the BIXS method which incorporates Monte Carlo simulated data, we used Ar gas filler (BIXS-Ar) or placed Al film (BIXS-Al), respectively, between the sample and X-ray detector as β-ray stopping layers. Using the EBS method to confirm whether or not the tritium will volatilize under the impact of the proton beams, we conducted two measurements at the same point of the sample surfaces. A TiH film sample with thick Mo substrate was used in our EBS experiment to remove the influence of the Mo spectrum on the EBS experimental spectra of tritium/deuterium-containing samples. We well fit using the SIMNRA code the tritium and deuterium EBS spectra that were obtained by removing the Mo spectra. The tritium content and depth profiles in the titanium films were obtained via these different methods and the results were compared. It was found that the total tritium content measured using the EBS, BIXS-Al, and BIXS-Ar methods were in agreement within the experimental uncertainties, and the BIXS-Al method may be better at measuring the tritium depth profiles than the BIXS-Ar method.

Effect of Etchant Concentration on the Optical Properties and Surface Topography of MoO3 Selective Solar Absorber Thin Films

ABSTRACTA novel technique providing a cost effective sustainable wet chemical etching method of synthesizing black Moly thin films rapidly has been presented. A top- down method for fabricating MoO3 has been investigated to understand the effect of chemical etchant concentration on the structural, morphological and optical properties of the thin films on Mo substrates. The XRD patterns demonstrated the formation of Tugarinovite MoO2 films on Mo substrate after annealing at 500°C in a vacuum. In this work, we developed nanostructured MoO3 on Mo substrate solar absorber, with a high solar absorptance of over 89%. These results suggest that solar absorbers made from refractory metal oxide nanostructures can be used for solar thermal applications.

Current improvement in substrate structured Sb2S3 solar cells with MoSe2 interlayer**Project supported by the National Key R & D Program of China (Grant Nos. 2019YFB1503500, 2018YFE0203400, and 2018YFB1500200), the National Natural Science Foundation of China (Grant No. U1902218), the YangFan Innovative and Entrepreneurial Research Team Project of China (Grant No. 2014YT02N037), and the 111 Project, China (Grant No. B16027).

Sb2S3 solar cells with substrate structure usually suffer from pretty low short circuit current (JSC) due to the defects and poor carrier transport. The Sb2S3, as a one-dimensional material, exhibits orientation-dependent carrier transport property. In this work, a thin MoSe2 layer is directly synthesized on the Mo substrate followed by depositing the Sb2S3 thin film. The x-ray diffraction (XRD) patterns confirm that a thin MoSe2 layer can improve the crystallization of the Sb2S3 film and induce (hk1) orientations, which can provide more carrier transport channels. Kelvin probe force microscopy (KPFM) results suggest that this modified Sb2S3 film has a benign surface with less defects and dangling bonds. The variation of the surface potential of Sb2S3 indicates a much more efficient carrier separation. Consequently, the power conversion efficiency (PCE) of the substrate structured Sb2S3 thin film solar cell is improved from 1.36 % to 1.86 %, which is the best efficiency of the substrate structured Sb2S3 thin film solar cell, and JSC significantly increases to 13.6 mA/cm2. According to the external quantum efficiency (EQE) and C–V measurements, the modified crystallization and elevated built-in electric field are the main causes.

Nacre-like Co–Cr–Mo/Ti2O3 coating on the Co–Cr–Mo substrate prepared using spark plasma sintering

Despite the common use of Co–Cr–Mo based prostheses in orthopedics, wider medical applications of such implants are often limited by their inherent bioinertness and inadequate adhesion to bone. A bioactive ceramic coating can improve their bonding to bone. In this study, a nacre-like Co–Cr–Mo/Ti2O3 coating on the Co–Cr–Mo substrate was prepared in one single step using spark plasma sintering (SPS). The microstructure, mechanical properties, and biocompatibility of the pellet were extensively studied. The lamellar Co–Cr–Mo and Ti2O3 layers with a thickness of several microns were alternated, resembling the “bricks‐and‐mortar” microstructure of nacre. Co–Cr–Mo consisted of γ phase, ε phase and carbide. The interfacial bonding between Co–Cr–Mo and Ti2O3 was strong, which is essential to achieving high ductility. The incorporation of Ti2O3 to form a composite coating led to improved biocompatibility, with MG63 human osteosarcoma cells cultured on the surface exhibiting faster proliferation and higher viability.

Structure of Diamond Films Grown Using High-Speed Flow of a Thermally Activated CH4-H2 Gas Mixture.

Diamond films are advanced engineering materials for various industrial applications requiring a coating material with extremely high thermal conductivity and low electrical conductivity. An approach for the synthesis of diamond films via high-speed jet deposition of thermally activated gas has been applied. In this method, spatially separated high-speed flows of methane and hydrogen were thermally activated, and methyl and hydrogen radicals were deposited on heated molybdenum substrates. The morphology and structure of three diamond films were studied, which were synthesized at a heating power of 900, 1700, or 1800 W, methane flow rate of 10 or 30 sccm, hydrogen flow rate of 1500 or 3500 sccm, and duration of the synthesis from 1.5 to 3 h.The morphology and electronic state of the carbon on the surface and in the bulk of the obtained films were analyzed by scanning electron microscopy, Raman scattering, X-ray photoelectron, and near-edge X-ray absorption fine structure spectroscopies. The diamond micro-crystals with a thick oxidized amorphous sp2-carbon coating were grown at a heating power of 900 W and a hydrogen flow rate of 1500 sccm. The quality of the crystals was improved, and the growth rate of the diamond film was increased seven times when the heating power was 1700–1800 W and the methane and hydrogen flow rates were 30 and 3500 sccm, respectively. Defective octahedral diamond crystals of 30 μm in size with a thin sp2-carbon surface layer were synthesized on a Mo substrate heated at 1273 K for 1.5 h. When the synthesis duration was doubled, and the substrate temperature was decreased to 1073 K, the denser film with rhombic-dodecahedron diamond crystals was grown. In this case, the thinnest hydrogenated sp2-carbon coating was detected on the surface of the diamond crystals.