MoO3 Thin Films Research Articles

Effect of low energy nitrogen ion irradiation on MoO3 films

In the present work, Molybdenum trioxide (MoO3) thin films were deposited by the electrophoretic deposition (EPD) method. Low energy ion irradiation was used to alter the materials properties of MoO3 films. Ion irradiation was carried out at a constant ion fluence of 2.16 x 1016 ions/cm2 for energies varying from 10 keV to 40 keV. The X-ray diffraction (XRD) and Raman spectroscopy revealed the orthorhombic α-MoO3 phase. The optical band gap was observed to change from 3.73 eV to 3.08 eV in a controlled manner due to ion irradiation. Morphology of nanobelt-like structures was seen at the highest energy of ion irradiated films. Atomic force microscopy (AFM) revealed a decrease in the surface roughness with an increase in irradiated ion energy. All results are in corroboration with each other and comprehend the process of tailoring the material properties of MoO3 thin film due to low energy ion irradiation. These tailored properties could be useful for electronic or optical device applications.

Tunability of near infrared opto-synaptic properties of thin MoO3 films fabricated by atomic layer deposition

Thin MoO3 films with different thickness at nanoscale were fabricated by atomic layer deposition technique over Au electrodes on the Si/SiO2 wafers. Bis(t-butylimido)bis(dimethylamino)molybdenum(VI) (C12H30N4Mo) and O2 plasma were used as Mo precursor and oxygen source, respectively. Both crystalline phase stabilization and oxygen vacancies enhancement of thin MoO3 films were observed after their annealing in inert atmosphere at 250 °C for 1.0 h. Memristive and opto-synaptic functionalities of thin MoO3 films were investigated under λ = 785 nm light illumination. Long-term plasticity and tunablity of the infrared (IR) light plasmonic synapses based on thin MoO3 can significantly simplify circuits of the advanced opto-electronic systems and neuro-opto-electronic instruments.

Effect of solution flow rate on the physical properties of spray pyrolyzed MoO3 thin films as silicon-based heterojunction device

Molybdenum trioxide (MoO3) films were synthesized on n-type silicon via spray pyrolysis technique. In this study, the influence of arriving aerosol on the silicon substrate was controlled by varying the solution flow rate (ranged from 3.0 to 1.5 ​ml/min) at substrate temperature of 300 ​± ​5 ​°C. The X-ray diffraction (XRD) analysis indicates the co-existence of orthorhombic (α-MoO3) and hexagonal (h-MoO3) crystal phases. As the flow rate decreases, the peaks correspond to the hexagonal phases were disappeared. Meanwhile, the Raman spectral analysis showed peaks mode of unshared oxygen at 979 ​cm−1. Moreover, a morphological study using Field Emission Scanning Electron Microscope (FESEM) and Atomic Force Microscope (AFM) demonstrated the reducing grains size with decreasing flow rate, which promotes the homogeneity and smoothness of the film. The basic diode parameters: ideality factor (n) and barrier height (ΦB), were effectively determined and analyzed by the thermionic emission (TE) theory. It has been observed that the ideality factor reduced while the barrier height broadened by lowering the solution flow rate. Moreover, when the diode exposes to light illumination, both the barrier heights and ideality factors decrease. The obtained results signify that the solution flow rate is a crucial parameter affecting the MoO3 film growth and its selective carrier properties.

Room-temperature growth optimization and PL characteristic of polytype h/α-MoO3 thin films by chemical precipitation method

In this study, MoO3 thin films were coated using a simple chemical precipitation technique at room temperature, without using an autoclave or other complex equipment. Films were deposited on precoated MoO3 seed layers prepared by spray pyrolysis on glass substrates. The effects of the seed layer growth conditions and pH value of the precipitation method’s solution on the characteristics of MoO3 films were investigated. The Raman and X-ray diffraction techniques showed that MoO3 films have grown in mixed hexagonal (h) and orthorhombic (α) crystal structures and the scanning electron microscope verified that the samples’ surface was covered of both hexagonal micro rods and lamellar micro belts. The XRD patterns indicated that the crystallinity was significantly improved using a seed layer sprayed under lower carrier gas pressure, and lower pH value of the precipitation method’s solution. The UV–Visible spectra showed that using seed layers prepared at higher carrier gas pressure decreases the bandgap of the films prepared by precipitation, due to the incorporation of more oxygen vacancies. The photoluminescence studies showed that the film deposited at a higher solution’s pH value has higher PL intensity, which indicates that this sample is a suitable candidate for optoelectronic applications.

Inverted Bulk Heterojunction (BHJ) Polymer (PCDTBT-PC70BM) Solar Photovoltaic Technology

Inverted Bulk heterojunctions (Ag/MoO3/PCDTBT-PC70BM/ZnO/ITO) Organic Solar cells, based on Organic (Polymer) materials is fabricated and characterized in this work. PCDTBT-PC70BM was synthesized by chloroform, chlorobenzene and o-dichlorobenzene (organic solvent). Surface morphology of ZnO and PCDTBT-PC70BM were studied. Bulk heterojunctions of active material are formed by the mixture of PCDTBT donor and PC70BM an acceptor in a random manner. For Sufficient transportation of charge carrier (electron and hole), hole transport (HT) and electron transport (ET) layers was deposited. ZnO is used as an ETM and synthesized by using Sol-Gel technique. MoO3 thin film deposited over the active material, enhances hole transformation because of band gap tuning with Ag and active materials. Absorbance and Photoluminescence spectra of polymer material with different organic solvents were studied and results were discussed in this work. o-dichlorobenzene enhance the absorption of PCDTBT/PC70BM. At 400 nm, 90% of sun light is absorbed, and 70% absorption is figure out in 500- 550nm wavelength. The Photo-luminescence of PCDTBT/PC70BM thin film in different organic solvents is ranging from 650nm to 750nm. At 700nm, 20% is shown for chloroform, 40% for chlorobenzene and highest 80% is achieved by o-dichlorobenzene. J-V value is obtained from a solar simulator which irradiates the sun spectrum 1.5 AM, for all the devices having cell area 0.045 cm2. For concentration (1:1) ratio in different organic solvents like chloroform, chlorobenzene and o-dichlorobenzene, (3.5, 4.2, and 5.8) %, PCE were obtained respectively.

A general and facile solution approach for deposition of high-quality metal oxide charge transport layers

Metal oxide charge transport layers (CTLs) are significant components for fabricating high-performance thin film solar cells. Generally, sol-gel methods have been widely used to deposit high-quality metal oxide CTLs, but they usually suffer from the choices of solvents, ligands and metal precursors. Here we report a general and facile ionic liquid (n-butylammonium butyrate) approach to prepare V2O5, MoO3, WO3, NiO, ZnO and SnO2 thin films, which exhibits strong dissolving ability and good film-forming property. The thermal volatilization of ionic liquid is mild, which provides a slow and stable decomposition process of metal compounds and favors the formation of smooth and compact CTLs. All thin films are highly transparent in the visual range from the optical transmittance spectra and suitable to be CTLs in photovoltaic devices. Encouragingly, we have received the efficiencies of 15.06% and 13.38% based on the area of 0.09 and 1.21 cm2 (NiO as the hole transport layer), and 19.13% and 16.71% based on the area of 0.09 and 1.21 cm2 (SnO2 as the electron transport layer), which are obviously higher than those of devices prepared by traditional sol-gel methods.

Hybrid Enhancement of Surface-Enhanced Raman Scattering Using Few-Layer MoS2 Decorated with Au Nanoparticles on Si Nanosquare Holes.

By combining the excellent biocompatibility of molybdenum disulfide (MoS2), excellent surface-enhanced Raman scattering (SERS) activity of Au nanoparticles (Au NPs), and large surface area of Si nanosquare holes (NSHs), a structure in which MoS2 is decorated with Au NPs on Si NSHs, was proposed for SERS applications. The NSH structure fabricated by e-beam lithography possessed 500 nm of squares and a depth of approximately 90 nm. Consequently, a few-layer MoS2 thin films (2–4 layers) were grown by the sulfurization of the MoO3 thin film deposited on Si NSHs. SERS measurements indicated that MoS2 decorated with Au NPs/Si NSHs provided an extremely low limit of detection (ca. 10−11 M) for R6G, with a high enhancement factor (4.54 × 109) relative to normal Raman spectroscopy. Our results revealed that a large surface area of the NSH structure would probably absorb more R6G molecules and generate more excitons through charge transfer, further leading to the improvement of the chemical mechanism (CM) effect between MoS2 and R6G. Meanwhile, the electromagnetic mechanism (EM) produced by Au NPs effectively enhances SERS signals. The mechanism of the SERS enhancement in the structure is described and discussed in detail. By combining the hybrid effects of both CM and EM to obtain a highly efficient SERS performance, MoS2 decorated with Au NPs/Si NSHs is expected to become a new type of SERS substrate for biomedical detection.

Photochromic and hydrophilic self-cleaning nature of MoO3 thin films

Photochromic and hydrophilic self-cleaning nature of MoO3 thin films

Amorphous molybdenum trioxide thin films for gas sensing applications

Uniform and smooth substoichiometric Molybdenum trioxide (MoO3−x) films have been achieved via thermal evaporation technique. MoO3 thin films were deposited onto glass and fluorine doped tin oxide (FTO) coated glass slides. The field-emission scanning electron microscopy micrographs reveal the amorphous behavior for films deposited either on glass or FTO substrates. The two thicknesses 500 and 650 nm of MoO3−x films which are deposited on glass and FTO coated glass slides were electrically examined as sensors towards NO,CO2 and HCl gases. The sensing process have been explained based on the electrical dipole layer formation consisting of the two unlike charged ion- layers and causing an energy band bending at the surface region of the film as a result of the gas adsorption. MoO3−x films on glass substrate is a perfect sensor towards oxidizing CO2 and NO gasses. The sensors are very sensitive towards low gas flow rate (20 standard cubic centimeters per minute (sccm)) and manifest the highest sensitivity values at relatively low temperatures compared with the other MOS with short response and recovery times (4 min for CO2 and 2 min for NO). The recorded sensitivity of MoO3−x sensor towards CO2 and NO gases at temperature 200 0 C shows that these samples are more sensitive towards CO2 gas, so this sensor is selective to CO2 gas more than NO. These results confirm that MoO3−x film deposited on glass of 500 nm thick can solve a large section of detecting CO2 gas problems such as selectivity, sensitivity to low gas concentrations, short response, recovery time, reversibility and low working temperature. Finally, the MoO3−x films (with thickness of 500 nm) deposited on FTO substrate was examined as gaseous HCl sensor at room temperature. It manifests a very high sensitivity towards gaseous HCl but cannot be applied for detecting it due to irreversibility and no stability of their properties after HCl vapor adsorption.

Multiscale Investigation of the Structural, Electrical and Photoluminescence Properties of MoS2 Obtained by MoO3 Sulfurization.

In this paper, we report a multiscale investigation of the compositional, morphological, structural, electrical, and optical emission properties of 2H-MoS2 obtained by sulfurization at 800 °C of very thin MoO3 films (with thickness ranging from ~2.8 nm to ~4.2 nm) on a SiO2/Si substrate. XPS analyses confirmed that the sulfurization was very effective in the reduction of the oxide to MoS2, with only a small percentage of residual MoO3 present in the final film. High-resolution TEM/STEM analyses revealed the formation of few (i.e., 2–3 layers) of MoS2 nearly aligned with the SiO2 surface in the case of the thinnest (~2.8 nm) MoO3 film, whereas multilayers of MoS2 partially standing up with respect to the substrate were observed for the ~4.2 nm one. Such different configurations indicate the prevalence of different mechanisms (i.e., vapour-solid surface reaction or S diffusion within the film) as a function of the thickness. The uniform thickness distribution of the few-layer and multilayer MoS2 was confirmed by Raman mapping. Furthermore, the correlative plot of the characteristic A1g-E2g Raman modes revealed a compressive strain (ε ≈ −0.78 ± 0.18%) and the coexistence of n- and p-type doped areas in the few-layer MoS2 on SiO2, where the p-type doping is probably due to the presence of residual MoO3. Nanoscale resolution current mapping by C-AFM showed local inhomogeneities in the conductivity of the few-layer MoS2, which are well correlated to the lateral changes in the strain detected by Raman. Finally, characteristic spectroscopic signatures of the defects/disorder in MoS2 films produced by sulfurization were identified by a comparative analysis of Raman and photoluminescence (PL) spectra with CVD grown MoS2 flakes.

Study of thermochromic and photocatalytic properties of MoO3 thin films

Molybdenum trioxide (MoO 3 ) thin films with thicknesses 300, 400 and 500 nm were deposited on an FTO substrate by thermal evaporation method. The prepared thin films showed both thermochromic and photocatalytic dye degradation properties. The thermochromic property of the prepared thin films was induced by exposing the thin films to argon gas at a temperature varying from 100 °C to 300 °C (in steps of 50 °C). The photocatalytic dye degradation ability of the films were examined by the photodegradation of methylene blue (MB) dye solution under visible light irradiation. MoO 3 thin film with 300 nm thickness is seen to have good thermochromic and photocatalytic dye degradation ability and both of these properties are necessary for smart window applications. • Synthesis of MoO 3 thin films by thermal evaporation method. • Thermochromic property of MoO 3 thin films. • Photocatalytic activity under direct sunlight irradiation. • Promising thin film for eco-friendly smart window application.

Effect of lattice mismatch on film morphology of the quasi-one dimensional conductor K0.3MoO3.

High quality epitaxial thin films of the quasi-one dimensional conductor K0.3MoO3 have been successfully grown on SrTiO3(100), SrTiO3(110), and SrTiO3(510) substrates via pulsed laser deposition. Scanning electron microscopy revealed quasi-one dimensional rod-shaped structures parallel to the substrate surface, and the crystal structure was verified by using X-ray diffraction. The temperature dependence of the resistivity for the K0.3MoO3 thin films demonstrates a metal-to-semiconductor transition at about 180 K. Highly anisotropic resistivity was also observed for films grown on SrTiO3(510).

Study of Concentration and Temperature Dependent Structural, Optical, Photocatalytic and Antimicrobial Activity of MoO3 Thin Films by Ultra Spray Pyrolysis

Molybdenum trioxide was used as a precursor for the deposition of thin films of varied concentrations onto the glass substrate by ultra-spray pyrolysis technique. Solutions of different concentrations viz. 0.05 M, 0.025 M, 0.0125 M were prepared and the substrate temperature varied to study the structural properties like XRD, UV-visible spectroscopy and FESEM of the MoO3 thin films. Being transition metal oxide molybdenum oxide (MoO3), exhibits fascinating chemical, structural, electrical and optical properties. The samples were prepared at different temperatures of 150, 250 and 350 ºC with the spray concentrations varying between 0.05 M, 0.025 M and 0.0125 M while the other spray operating parameters were fixed at their optimum values. X-ray diffraction technique was used to determine the crystalline size and nature of the films. For the substrate temperature 150 ºC, the films obtained are amorphous in nature while the films deposited at 250 and 350 ºC were found to be crystalline in nature giving α-MoO3 phase, which is evident from the X-ray diffraction pattern. The size of the crystal varied from 43 to 65 nm for the prepared samples. The band-gap energy by plotting Tauc plots was found to be in the range 2.51-3.01 eV. FESEM revealed two different types of morphological structures viz., spherical and nanorods. The photocatalytic activity of thin films obtained was estimated from their ability to degrade methylene blue (MB) under UV irradiation with excellent results. Antibacterial activity of thin films was checked against Pseudomonas aeruginosa for 1, 6, 10 and 96 h.

Reliable high work-function molybdenum dioxide synthesis via template-effect-utilizing atomic layer deposition for next-generation electrode applications

An atomic layer deposition (ALD) method for coating metastable MoO2 thin films onto substrates was investigated. It is the first reported growth of metastable phased thin films based on chemical reaction-mediated thin film deposition processes, such as chemical vapor deposition or ALD.

Structural, electrical, and linear/nonlinear optical characteristics of thermally evaporated molybdenum oxide thin films

Homogeneous thin films of Molybdenum oxide (MoO3) were grown on quartz and glass substrates using the thermal evaporation method. XRD results showed that the MoO3 powder has a polycrystalline structure with an orthorhombic crystal system whereas the MoO3 thin films have amorphous nature. SEM images showed that the MoO3 thin films have a nearly uniform surfaces with worm-like shape grains. The film thickness influences on the linear and nonlinear optical characteristics of MoO3 thin films that were examined using spectrophotometric measurements and from which, the linear optical constants of the MoO3 thin films were estimated. The electronic transition type was determined as a direct allowed one. The values of the optical band gap were obtained to be in the range of 3.88–3.72 eV. The dispersion parameters, third-order nonlinear optical susceptibility, and the nonlinear refractive index of the MoO3 thin films were determined and interpreted in the light of the single oscillator model. The temperature dependence of the DC electrical conductivity and the corresponding conduction mechanism for the MoO3 films were investigated at temperatures ranging from 303 to 463 K.

Lattice Orientation Heredity in the Transformation of 2D Epitaxial Films.

The ability to control lattice orientation is often an essential requirement in the growth of both 2D van der Waals (vdW) layered and nonlayered thin films. Here, a unique and universal phenomenon termed "lattice orientation heredity" (LOH) is reported. LOH enables product films (including 2D-layered materials) to inherit the lattice orientation from reactant films in a chemical conversion process, excluding the requirement on the substrate lattice order. The process universality is demonstrated by investigating the lattice transformations in the carbonization, nitridation, and sulfurization of epitaxial MoO2 , ZnO, and In2 O3 thin films. Their resultant compounds all inherit the mono-oriented crystal feature from their precursor oxides, including 2D vdW-layered semiconductors (e.g., MoS2 ), metallic films (e.g., MXene-like Mo2 C and MoN), wide-bandgap semiconductors (e.g., hexagonal ZnS), and ferroelectric semiconductors (e.g., In2 S3 ). Using LOH-grown MoN as a seeding layer, mono-oriented GaN is achieved on an amorphous quartz substrate. The LOH process presents a universal strategy capable of growing epitaxial thin films (including 2D vdW-layered materials) not only on single-crystalline but also on noncrystalline substrates.

Tuning of physical properties in MoO3 thin films deposited by DC sputtering

Tuning of physical properties in MoO3 thin films deposited by DC sputtering

Hydrothermal temperature effect on the growth of h-MoO3 thin films using seed layers and their photoluminescence properties

In this work, thin films of molybdenum trioxide were successfully deposited via the facile and cost-effective hydrothermal technique. The films were grown at different temperatures of 50, 80, 110, and 130 °C on glass substrates. The growth temperature effects on the optical, morphological, and structural properties of samples were studied. X-ray diffraction (XRD) pattern analysis and Raman spectroscopy revealed that all deposited MoO3 thin films were crystallized in a hexagonal crystal structure. Field emission scanning electron microscope (FESEM) images exhibited that MoO3 thin films were coated by well-shaped hexagonal micro-rods. Also, the diameter of the micro-rods was decreased from 8.95 to 3.60 μm by increasing the hydrothermal growth temperature. At 130 °C, micro-rods were accumulated in the form of micro-flowers. By increasing the growth temperature, the estimated optical bandgap of films was increased from 2.94 to 3.04 eV, respectively. All h-MoO3 fabricated thin films showed photoluminescence (PL) emission at room temperature, and increasing the growth temperature caused the enhancement of the PL intensity. This study provides a simple and low-cost synthesis route at low temperatures to deposit h-MoO3 films for further investigations as in gas sensing and optoelectronic applications.

Evaluation on output parameters of the inverted organic solar cells depending on transition-metal-oxide based hole-transporting materials

The study was focused on evaluating the effects of different hole transport layers (HTL) on optical, morphological, and electrical properties of organic solar cell (OSC) structures. Structuring the photoactive layer with blends of poly (3-hexylthiophene) (P3HT), and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) was practiced via spin coating technique. Transition-metal-oxides of vanadium pentoxide (V2O5), tungsten trioxide (WO3), and molybdenum trioxide (MoO3) as thin films with 10 nm thick were used for the HTL layers. The deposition of all interface layers except for P3HT:PCBM photoactive layer were radio-frequency (RF) magnetron sputtered. The surface morphological and optical properties of structures produced were examined by analyzing the UV–Vis–NIR and atomic force microscopy (AFM) measurements. The solar cell output parameters of the inverted OSCs produced were identified depending on transition-metal-oxide (TMO) based hole-transporting materials. MoO3 HTL was exhibited as smoothest interface with a root mean square (RMS) surface roughness value of 7.11 nm. The power conversion efficiency (PCE) values of OSCs with HTL of V2O5, WO3 and MoO3 were found as 1.91%, 2.04% and 2.11%, respectively. With a comparative investigation was reported that an OSC structure with HTL of MoO3 thin film providing optimal device performance in the present study might be preferred as an alternatively effective material for opto-electronic applications.

Residual Oxygen Effects on the Properties of MoS2 Thin Films Deposited at Different Temperatures by Magnetron Sputtering

Molybdenum disulfide (MoS2) thin films were deposited at different temperatures (150 °C, 225 °C, 300 °C, 375 °C, and 450 °C) on quartz glass substrates and silicon substrates using the RF magnetron sputtering method. The influence of deposition temperature on the structural, optical, electrical properties and deposition rate of the obtained thin films was investigated by X-ray diffraction (XRD), Energy Dispersive Spectrometer (EDS), Raman, absorption and transmission spectroscopies, a resistivity-measuring instrument with the four-probe method, and a step profiler. It was found that the MoS2 thin films deposited at the temperatures of 150 °C, 225 °C, and 300 °C were of polycrystalline with a (101) preferred orientation. With increasing deposition temperatures from 150 °C to 300 °C, the crystallization quality of the MoS2 thin films was improved, the Raman vibrational modes were strengthened, the deposition rate decreased, and the optical transmission and bandgap increased. When the deposition temperature increased to above 375 °C, the molecular atoms were partially combined with oxygen atoms to form MoO3 thin film, which caused significant changes in the structural, optical, and electrical properties of the obtained thin films. Therefore, it was necessary to control the deposition temperature and reduce the contamination of oxygen atoms throughout the magnetron sputtering process.