Band Gap Of Films Research Articles

Impact of annealing temperature on structural, optical and photovoltaic properties of bismuth oxysulfate thin films

The nanostructure of inorganic Bi2S3 semiconductor materials has been studied in recent years due to the wide range of features in optoelectronics and nanotechnology. The fundamental properties like low band gap (1.3–1.7 eV), high absorption coefficient, and nontoxic nature have captivated the attention of researchers in the solar cell sector. There are numerous factors to enhance the performance of the solar cell, likewise, annealing temperature is one of the important factors in thin film fabrication to change the morphology, optical, electrical, and structure of the material. In this work, the effects of annealing temperature on Bi2S3 thin films were studied and coincidently it was transformed into the new bismuth oxysulfate material of high band gap and transparent nature in high annealing temperatures. Both open circuit voltage (Voc = 0.75 V) and short circuit current (Isc = 0.06 mA/cm2) have been improved in bismuth oxysulfate thin film than the Bi2S3 phase. We have studied the photovoltaic properties of bismuth sulfide and bismuth oxysulfate materials along with their structure, optical, and surface morphology by using spin coating. The thin films of Bi2S3 material were formed up to 300 °C and above this temperature material was changed to bismuth oxysulfate material supported by XRD, band gap, and EDS results. The band gap of Bi2S3 thin film slightly increases from 1.6 eV to 1.8 eV and is almost constant at 3.7 eV in bismuth oxysulfate structure in increasing the annealing temperature. The nanowire structure of Bi2S3 was changed to the nanowire of bismuth oxysulfate at 420 °C and above this temperature, nanowires changed to spherical nanoparticles at 450 °C.

Influence of solution pH dependency on structure, optical with photoelectrochemical characteristics of SILAR deposited copper oxide thin films

Photoelectrochemical (PEC) technology is a promising approach for converting solar energy into chemical energy, offering significant potential for renewable energy applications. In this work, the CuO thin film was fabricated with different pH value in between 8.5 ± 0.1 and 10.5 ± 0.1 via Successive Ionic Layer Adsorption and Reaction (SILAR) method. The Effect of pH on thickness, structural, morphological, elemental composition and optical properties were investigated by using stylus profilometry, XRD, SEM, TEM, EDX, UV–vis and PL. The XRD results showed that as the pH increased, the crystallite size increased from 19.24 nm to 25.62 nm, with a monoclinic phase along the (111) direction. The CuO film deposited at pH value 10.5 ± 0.1 exhibit well defined identical particle with its size in the range between 200 and 300 nm was confirmed by SEM and TEM analysis. As the pH increased from 8.5 ± 0.1 to 10.5 ± 0.1, the CuO film bandgap (Eg) value reduced from 1.52 eV to 1.42 eV with indirect transition. The CuO photocathode deposited at pH 10.5 ± 0.1 shows maximum photocurrent density of 1.45 mA/cm2 at −0.1 V vs. RHE in 0.5 M Na2SO4 solution. Furthermore, the Electrochemical Impedance Spectroscopy (EIS) analysis shows, the CuO (pH 10.5 ± 0.1) electrode have higher conductivity value of 0.6862 S/cm compared CuO at pH 8.5 ± 0.1 (0.2779 S/cm) and CuO at pH 9.5 ± 0.1 (0.4646 S/cm) electrodes.

Synthesis of thermochromic CdHgI4 thin film: Insight into the thickness-dependent structural, morphological, linear, and nonlinear spectroscopic properties

This study introduces an in-depth exploration of structural, morphological, linear, and nonlinear optical properties of CdHgI4 thin films deposited by the thermal evaporation technique. In this study, cadmium tetra iodomercurate (CdHgI4) nanopowder was synthesized by fusion method from which thin films of various thicknesses (150 to 450 nm) were deposited on glass substrates by thermal evaporation technique. The Structural investigation conducted by X-ray diffractometer (XRD) established that both CdHgI4 nanopowder and thin film formed in a single phase with a tetragonal crystallographic system. However, the CdHgI4 nanopowder and films display a different preferred orientation as corroborated by texture coefficient determination (Tc). The microstructural features obtained by High-resolution transmission electron microscopy (HRTEM) revealed that the powder particles were agglomerated; however, the particles of thin film were well-defined with high compactness and uniform size. The purity as well as stoichiometry were judged by energy dispersive X-ray analysis confirming the absence of any impurities and samples adopted near stoichiometry features. The surface morphology done by field emission scanning electron microscope revealed that films constituted of nanostructured grains with noticeable growth particles with increasing thickness. The CdHgI4 nanopowder had a direct optical transition of band gap of about 1.41 eV evaluated from diffuse reflectance spectroscopy. The band gap of thin films determined from specular optical spectroscopy varied from 2.20 to 1.58 eV, as the thickness changed from 150 to 450 nm. The thickness dependence of other linear optical parameters, such as Urbach energy (Eu), refractive index (n), optical dielectric constants (ε1, ε2), the surface and volume energy loss (SELF, VELF), were elaborately discussed. The nonlinear optical properties including first-order linear susceptibility, third-order susceptibility (χ(1), χ(3)), NL refractive index (n2), and two-photon absorption coefficients (βc) were greatly dependent on the film thickness.

Impact of Graphene oxide (GO) and reduced Graphene Oxide (rGO) on the TiO2 thin film composite (TiO2: GO/ rGO) photoanodes

Graphene and its derivatives have several advantages such as large surface area, great chemical stability, high transmittance, and good electrical conductivity, which are the fundamental qualities required by photovoltaic industries. GO and rGO are mixed in various proportions ranging 0 wt.% - 15 wt.% to spin coat TiO2: GO/rGO composite thin films. The effect of graphene oxide and reduced graphene oxide on the performance the TiO2 based composite photoanodes are obtained. A tetragonal anatase phase of TiO2 was confirmed by the XRD analysis. The calculated crystallite size decreases with lower concentrations of GO and rGO but starts to increase for higher concentrations. The spectrophotometer studies have confirmed that the optical bandgap of pure TiO2 films is decreased on doping with GO and rGO. The SEM analysis have confirmed that the surface is tightly packed with the uniformly distributed grains, and they are very compact.

The role of Cu and film thickness on the photocatalytic activity of mesoporous spin coated TiO2 films

Most practical applications of photocatalysts will involve coatings on an inert support; here we have examined how copper doping of spin coated porous TiO2 films affects their physical characteristics and photocatalytic activity. The photocatalytic degradation of stearic acid was used as a measure of photocatalytic activity for catalysts spin coated from a sol-gel onto glass with 0, 0.1, 0.5, 1, 2.5 and 5 wt% copper introduced into the catalyst lattice before gelation. The effects of spin coating speed on film thickness, structure and band gap were studied and the nature of the copper incorporated into the films examined with XPS and XANES measurements. Increased spin coating speeds reduces the thickness of the deposited films from ∼ 50 μm to ∼ 20 μm until a spin speed of ∼ 3000 rpm at which point non-Newtonian behaviour of the gels prevents further reductions in film thickness. A larger effect on film thickness is the presence of the added copper nitrate which results in thinner films. After calcining, XANES shows the bulk of the copper to be in a Cu(II) state but at the surface of the thinnest, most active films XPS shows only Cu(I). Photocatalytic activity is much more strongly affected by the presence of the copper than the thickness of the films with 0.1 wt% Cu catalysts as much as 10 times more active than the undoped catalysts. Increasing the copper content, however, reduces activity until at ∼ 5 wt% activity is lower than for the pure TiO2 films.

Investigation of structural and optical properties of ZnTiO3 thin films irradiated with 50 MeV oxygen ions

This paper aims to investigate the effects of high-energy ion irradiation on the structural, morphological, optical, and luminescent characteristics of ZnTiO3 (ZTO) films. ZTO films were grown on silicon and quartz substrates via RF magnetron sputtering in pure argon ambiance and annealed at 800 °C for crystallization. The annealed (pristine) samples were irradiated with 50 MeV oxygen ions at three distinct fluences: 1 × 1012, 5 × 1012, and 1 × 1013 ions/cm2. X-ray diffraction (XRD) data demonstrates that the intensity of highly oriented (311) peak first increases with fluence up to 5 × 1012 and then decreases at 1 × 1013 ions/cm2. The root mean square roughness (RMS) increases initially from 8.22 (pristine) to 9.10 nm (1 × 1012 ions/cm2) and decreases to 8.25 nm for 1 × 1013 ions/cm2 fluence. Transmittance spectra indicate an enhancement in the transmission of irradiated films. The calculated band gap of pristine and irradiated films lies in the range of 3.93–3.84 eV. X-ray photoelectron spectroscopy (XPS) analysis reveals a reduction in oxygen vacancies up to a fluence of 5 × 1012 and then rises at 1 × 1013 ions/cm2. The enhancement of peak intensity is observed in photoluminescence (PL) spectra on increasing the ion fluence due to a reduction in the non-radiative recombination centers.

Optical Investigation of In2O3/ Quartz Nano-films Deposited at Different Laser Energies

The study conducted in this research focuses on the deposition of In2O3 thin films onto quartz substrates using the pulsed laser deposition technique (PLD). The importance of this study lies in the exploration of the optical properties of these thin films under varying laser energies (1200 mJ, 1400mJ, 1600mJ, 1800 mJ, and 2000 mJ), and the subsequent determination of their energy band gaps. In the pursuit of enhancing our understanding of In2O3 thin films, this research exhibits a direct relationship between the laser energy and laser band gap. It was discovered that the energy band gap of thin In2O3 films increased due to the increase in laser energy. This phenomenon resulted in an overall blue shift from the fundamental energy gap of In2O3 thin films. The significance of this study extends to potential applications in various fields. In2O3 thin films with tunable energy band gaps can find applications in optoelectronics, photovoltaic and other emerging technologies. This research not only contributes to the fundamental understandings of thin film properties but also offers a pathway for tailoring their characteristics for specific applications, thus advancing the field of materials science and engineering.

Investigations on temperature dependent properties of spray deposited tin oxide thin films

The present study reported the temperature dependent properties of tin oxide (SnO2) thin films deposited by using conventional, cost effective and non-vacuum-based spray pyrolysis technique (SPT). The as deposited films were characterized by various characterization techniques such as X ray diffraction (XRD), UV-Vis spectroscopy and Scanning electron microscopy (SEM) to study their structural, optical and morphological properties respectively. XRD analysis revealed tetragonal rutile crystal structure of SnO2 with preferred orientation along (200) plane. The refinement of XRD data was also carried out by Rietveld refinement to obtain the fitting parameters, crystallite size and lattice parameters. UV-Vis study showed considerable change in optical absorbance and transmittance with change in substrate temperature. Effect of substrate temperature on film thickness, refractive index and band gap energy were determined by Swanepoel method and by Tauc’s plot respectively. The Urbach energy was also calculated and were correlated to the defects in SnO2 films. SEM micrograph showed the transformation from granules to nanospheres as a function of substrate temperature. Electrical properties were determined by Hall effect measurements which gives carrier concentration, electrical resistivity and mobility in the order of 1019-1020 /cm3, 10−2-10−3 Ω.cm and 4–23 cm2/Vs respectively.

Effects of oxygen sources on the growth characteristics and dielectric properties of atomic-layer-deposited TiO2 films for aluminum electrolytic capacitors

TiO2 is a promising high dielectric material which can be introduced into aluminum anode foils for realizing miniaturization, lightweight, and high quality of aluminum electrolytic capacitors because of its excellent permittivity. However, the complex porous framework of etched aluminum foil gives rise to the low step coverage and residual carbon impurities of TiO2 films, which can restrict the specific capacitance improvement. In this work, the TiO2 films were deposited by atomic layer deposition (ALD) using O3, O2 plasma (O2*), H2O as oxygen sources, respectively. The effects of oxygen sources on step coverage, carbon impurity content, crystalline structure, oxygen vacancies (OVs) concentration and band gap (Eg) of TiO2 films were studied. Besides, the capacitor performances of aluminum foils were investigated. The O3–TiO2 films showed the best conformability and the least carbon impurity content, while the O2*-TiO2 films exhibited the lowest step coverage due to the directionality of plasma. And the highest carbon impurity content in H2O–TiO2 films was caused by the poor reactivity of H2O. Moreover, the anatase TiO2 peak intensity of H2O–TiO2 films through sintering and anodization was the highest due to the highest deposited mass. The O3–TiO2 films were found to be optimally insulating by characterization of OVs concentration and Eg. Surprisingly, the composite dielectric films using O3 as oxygen source exhibited the excellent withstanding voltage of 21.9 V, while the specific capacitance of 159.9 μF cm-2 was maintained, and there were about 45.89% and 33.63% enhancements in the specific capacitance and CV compared with those without TiO2. These outstanding properties demonstrate that O3 is more favorable for depositing high-performance ALD TiO2 films on aluminum electrolytic capacitors.

Preparation and properties of rGO-Co-NiO composite films: Low attenuation and high coloration efficiency

The study of electrochromic materials has far-reaching significance for the regulation of light and heat as well as the reduction of energy consumption. In this study, rGO-Co-NiO composite films were prepared by combining graphene oxide, which has excellent conductivity and stability, with Co-NiO films. The particle size, band gap, conductivity and response time of the electrochromic films were improved by precisely adjusting the component modulation amount of graphene oxide. The results show that with the incorporation of GO it is easy to form oxygen vacancies, which is conducive to ionic conduction and diffusion, in which the film with a GO doping concentration of 4 % has excellent performances in terms of response time and coloring efficiency, and the response time is reduced from 10.2 to 5.8 seconds, and it still possesses 57.25 % of the light modulation amplitude after 600 cycles, of which the attenuation rate is only 2 % for the period from 100 to 600 cycles, The coloring efficiency after 100 cycles is 48.21 cm2/C. In summary, the investigated rGO-Co-NiO composite films have a broad potential for future application in electrochromic devices.

Investigation of the effects of coating numbers of thin films and metal contact type on physical properties of undoped ZnO, Fe-doped ZnO, and Fe–B co-doped ZnO thin films

This study was designed for three purposes. The first objective was to examine the effects of iron (Fe) and boron (B) elements on the physical properties (structural, electrical, optical, and optoelectronic) of zinc oxide (ZnO) material. For this reason, pristine ZnO, 6% Fe-doped ZnO (Zn0.94Fe0.06O), and 6% Fe-4% B co-doped ZnO (Zn0.90Fe0.06B0.04O) thin films with different thicknesses (4, 6, 8, and 10 layers of coatings for each sample type) were produced using sol–gel dip coating and spraying method on glass and silicon (Si) substrates. In the second stage, we examined the effects of film thickness on optical, electrical, and optoelectronic properties for these three sample types. In the final stage, the MIS (metal/interlayer/semiconductor) structures were created using the three groups of samples produced as interlayers. Gold (Au) was initially applied as the metal contacts in these MIS structures. We investigated optoelectronic and electrical properties such as ideality factor, barrier height, and series resistance for all samples with Au contacts. Afterward, aluminum (Al) contacts were coated on the sample that yielded the best results with Au contacts, and the same properties were re-examined, thereby determining the effects of the contact material, especially on optoelectronic properties. All samples were produced as pure and wurtzite ZnO polycrystalline with preferred orientation along the (002) plane. Although Hall measurement results indicated that all sample groups were n-type semiconductors, the carrier density decreased from − 7.5 × 1013 for pristine ZnO to − 8.7 × 1011 with Fe–B co-doping. The irregular nanodots-shaped surface morphology of ZnO transformed into a homogeneous and smooth one by incorporating boron into the structure. In all sample groups except the 6% Fe-doped ZnO thin films, the band gaps of the thin films decreased as the film thickness increased. For pure ZnO and Fe-B co-doped ZnO sample groups, the band gap energy decreased from 3.245 to 3.215 eV, and from 3.540 to 3.180 eV, respectively, depending on the thicknesses of films. On the other hand, the band gap energy of only Fe–doped ZnO samples increased from 3.34 eV to 3.46 eV. It was observed that as the thicknesses of films increased, the ideality factor of Au/ZnO/p-Si, Au/Zn0.94Fe0.06O/p-Si, and Au/Zn0.90Fe0.06B0.04O/p-Si diodes increased, and the barrier heights of them decreased in the three sample groups. However, when we look at the average value of the electrical properties including all layers, we can say that the best results were obtained for the Fe–B co-doped sample group. Specifically, Fe–B co-doped ZnO sample with 6 layers of coating exhibited an ideality factor of 3.25, a barrier height of approximately 0.51 eV, and a serial resistance of 8.42 kΩ. The best performance as solar cell and photodiode was again obtained for this sample. While the solar cell efficiency of this sample (6 layers of coated Zn0.90Fe0.06B0.04O) was 0.04% with Au contacts, it increased to 0.08% with Al contacts.In summary, it was observed that the electrical, optical, structural, and optoelectronic (as solar cell and photodiode) properties of ZnO material were improved very well made with Al contact and 6 layers of coated Fe and B co-doping. Therefore, Zn0.90Fe0.06B0.04O sample may be promising material for optoelectronic devices.

Nanofilms based on superstructured niobium tungsten oxide have high dual-functional potential for electrochromism and energy storage

Niobium-tungsten oxide represents a novel type of bimetallic cathode electrochromic material. The superstructure is capable of accommodating a greater number of ions, which has been a hot material for research in recent years. In this paper, composite niobium-tungsten oxide materials were prepared on fluorine-doped tin oxide (FTO) substrates using the sol–gel spin-coating method. The particle size, band gap and response time of the electrochromic films were improved by regulating the film annealing temperature. As the annealing temperature was increased, the particle size of the Nb18W16O93 film increased from 7.54 nm to 31.8 nm. Concurrently the band gap decreased, which enhanced the electrical conductivity of the material. The electrochemical and optical measurements show that the film has excellent properties, and by choosing the appropriate annealing temperature, the coloring efficiency reaches 55.3 cm2 C−1 from 34.1 cm2 C−1, the switching time reaches tc = 4.3 s, tb = 3.5 s, and the energy storage capacity reaches 21.086 mF cm−2 at a surface current density of 0.05 mA cm−2. The present work demonstrates that adjusting the annealing temperature can enhance the electrochromic and energy storage performance of the proposed films, which have for the potential to be utilized in electrochromic bifunctional applications.

Thickness dependence of the room-temperature ethanol sensor properties of Cu2O polycrystalline films

This study investigates the fabrication process of copper thin films via thermal evaporation, with precise control over film thickness achieved through Z-position adjustment. Analysis of the as-fabricated copper films reveals a discernible relationship between grain size (〈D〉) and Z-position, characterized by a phenomenological equation 〈D〉XRDn(Z)=〈D〉0n1+32rZ2+158rZ4 , which is further supported by a growth exponent (n) of 0.41 obtained from the analysis. This value aligns well with findings in the literature concerning the growth of copper films, thus underlining the validity and reliability of our experimental outcomes. The resulting crystallites, ranging in size from 20 to 26 nm, exhibit a resistivity within the range of 3.3–4.6 μΩ · cm. Upon thermal annealing at 200 °C, cuprite Cu2O thin films are produced, demonstrating crystallite sizes ranging from ∼9 to ∼24 nm with increasing film thickness. The observed monotonic reduction in Cu2O crystallites relative to film thickness is attributed to a recrystallization process, indicating amorphization when oxygen atoms are introduced, followed by the nucleation and growth of newly formed copper oxide phase. Changes in the optical bandgap of the Cu2O films, ranging from 2.31 to 2.07 eV, are attributed mainly to the quantum confinement effect, particularly important in Cu2O with size close than the Bohr exciton diameter (5 nm) of the Cu2O. Additionally, correlations between refractive index and extinction coefficient with film thickness are observed, notably a linear relationship between refractive index and charge carrier density. Electrical measurements confirm the presence of a p-type semiconductor with carrier concentrations of ∼1014 cm−3, showing a slight decrease with film thickness. This phenomenon is likely attributed to escalating film roughness, which introduces supplementary scattering mechanisms for charge carriers, leading to a resistivity increase, especially as the roughness approaches or surpasses the mean free path of charge carriers (8.61 nm). Moreover, ab-initio calculations on the Cu2O crystalline phase to investigate the impact of hydrostatic strain on its electronic and optical properties was conducted. We believe that our findings provide crucial insights that support the elucidation of the experimental results. Notably, thinner cuprite films exhibit heightened sensitivity to ethanol gas at room temperature, indicating potential for highly responsive gas sensors, particularly for ethanol breath testing, with significant implications for portable device applications.

Miniature spectrometer based on graded bandgap perovskite filter

Abstract Miniature spectrometer is powerful tool for scientific research and industrial inspection. Here, we report the fabrication of graded perovskite filters with tunable bandgap and their application in constructing miniature spectrometer. The graded perovskite filters were fabricated using a Finkelstein reaction between in-situ formed halogen ion with a preformed MAPbX3 film. The graded bandgap of perovskite films can be well tunned from 400 to 750 nm by controlling the volume ratio between 5,5-dimethyl-1-pyrroline N-oxide and benzyl chloride(bromide). By combining a deep residual network, graded bandgap perovskite film and commercial CMOS sensor chip, a miniature spectrometer is demonstrated, achieving an accurate spectrum reconstruction (PSNR = 40.749) with monochromatic spectral resolution of 1.31 nm.

Influence of annealing temperature on nano crystalline description for CuZnS thin films

Copper Zinc Sulphide (Cu0.5Zn0.5S) alloy and thin films were fabricated in a vacuum. Nano crystallized (CZS) film with thick 450±20 nm was deposit at substrates glasses using thermal evaporation technique below ~ 2 × 10− 5 mbar vacuum to investigated the films structural, morphological and optical properties depended on annealing temperatures ( as-deposited, 423, 523 and 623) K for one hour. The influences annealed temperature on structurally besides morphologically characteristics on these films were investigated using XRD and AFM respectively. XRD confirms the formation a mixed hexagonal phase of CuS-ZnS in (102) direction with polycrystalline in nature having very fine crystallites size varying from (5.5-13.09) nm. AFM analysis shows the uniform distribution of closely packed grains, grain size for that film diverge on ranges as of (52.37 to 89.25) nm after annealed. The optical properties of all films prepared had been examined for the wavelength range 400 - 1000 nm using UV-Vis-NIR spectrometer. The band gaps of (Cu0.5Zn0.5S) films are obtained in the range of 2.4 to 1.9 eV, which makes it a suitable absorber as well as buffer/window layer for solar cell applications.

Structural, Optical, and Thermal Properties of PVA/SrTiO3/CNT Polymer Nanocomposites.

Successful preparation of PVA/SrTiO3/CNT polymer nanocomposite films was accomplished via the solution casting method. The structural, optical, and thermal properties of the films were tested by XRD, SEM, FTIR, TGA, and UV-visible spectroscopy. Inclusion of the SrTiO3/CNT nanofillers with a maximum of 1 wt% drastically improved the optical and thermal properties of PVA films. SrTiO3 has a cubic crystal structure, and its average crystal size was found to be 28.75 nm. SEM images showed uniform distribution in the sample with 0.3 wt% of SrTiO3/CNTs in the PVA film, while some agglomerations appeared in the samples of higher SrTiO3/CNT content, i.e., at 0.7 and 1.0 wt%, in the PVA polymer films. The inclusion of SrTiO3/CNTs improved the thermal stability of PVA polymer films. The direct and indirect optical band gaps of the PVA films decreased when increasing the mass of the SrTiO3/CNTs, while the single-oscillator energy (E0) and dispersion energy (Ed) increased. The films' refractive indices were gradually increased upon increasing the nanofillers' weight. In addition, improvements in the optical susceptibility and nonlinear refractive indices' values were also obtained. These films are qualified for optoelectronic applications due to their distinct optical and thermal properties.

Effect of Picosecond Laser Irradiation on the Properties of Nanostructured Zinc Oxide Thin Films

In this article, a picosecond laser source was employed to irradiate the nanostructured ZnO thin film prepared by the sol-gel method. The impact of laser irradiation on the characteristics of a nanostructured ZnO thin film was investigated. Analysis using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy confirmed a significant influence on the structure of the ZnO thin film. As the duration of laser irradiation (the number of laser pulses) increased, there was a remarkable decrease in both the electronic and photoluminescence intensities of the nanostructured film. Tauc's plot indicates a noticeable change in the optical band gaps of the thin film with the increase in irradiation time. The morphological image suggests that the laser irradiation energy induces both degradation and modification of the film surface, consequently causing changes in the structural, absorption, and photoluminescence properties of nanostructured ZnO. The observed effects are attributed to alterations in the crystal structure and size of the nanostructured ZnO film, as confirmed by XRD. The reduction in photoluminescence intensity observed over the laser irradiation times may be a result of potential degradation in the crystalline structure of the nanostructured ZnO film.

Low-temperature deposition of β-Ga2O3 thin films employing in situ pulsed laser-assisted RF sputtering system

Monoclinic β-phase Ga2O3, the most thermodynamically stable phase, is an interesting material for power electronics applications. In this study, we present an efficient approach, diverging from existing methods, for the successful deposition of β-Ga2O3 thin films at low substrate temperatures without any post-annealing. Instead of relying on high substrate temperatures, we supplied sufficient thermal energy to the substrate by directly irradiating it with a 1064 nm ytterbium pulsed laser during RF sputtering. This eliminated the need for post-annealing and significantly reduced processing time. It also allowed for excellent control over the crystal structure and crystallinity formation of the thin films by providing excellent particle energy through heat transfer on the surface. The X-ray diffraction (XRD) scan of the sample deposited by irradiating a pulse laser to the substrate shows only three peaks corresponding to (−201), (−402) and (−603) of β-Ga2O3, indicating superior crystalline quality. The sample deposited at 2.5 mTorr working pressure maintained a thin film thickness of 207 nm and a grain size of 40.07 nm, and the energy band gap of the thin films was measured in the range of 4.45–4.64 eV. XPS, Auger, and PL optical analysis observed characteristic core-level peaks of β-Ga2O3 and the suppression of oxygen vacancies due to the high binding energy. The oxygen content increased by 4.39 %, resulting in the O/Ga ratio rising to 1.19, which leads to a positive shift in the O 1s binding energy. Consequently, we demonstrated the induction of phase transition of Ga2O3 into a stable β phase by introducing an in-situ pulse laser process during low temperature RF sputtering. These results have significant potential in various applications and are expected to contribute significantly to technological advancements.

Tailoring the optical properties of dye–polymer composite films based on polyvinyl alcohol doped with phenol red toward flexible optoelectronic applications

The composite films of polyvinyl alcohol (PVA) incorporating varying concentrations of phenol red (PR) dye were fabricated using the solution casting method. Structural characteristics of the prepared films were explored through XRD and FTIR spectroscopy analyses. The inclusion of PR dye within the PVA matrix induced cross-linking, enhancing the amorphous nature of the doped PVA samples, as evidenced by XRD patterns. In the presence of PR dopants, the FTIR peaks for PVA exhibited altered intensities and increased width, indicating physical interactions between the functional groups of PVA and PR dopants. The impact of PR additives on the optical properties of PVA was investigated across the spectral range of 190–2500 nm. The PVA/phenol red composite demonstrated enhanced UV blocking in the 190–400 nm wavelength range, rendering it suitable for applications such as UV notch filters, including laser blocking filters. The indirect and direct optical band-gaps of PVA polymer films were reduced from 5.20 eV and 5.78 eV to 4.30 eV and 5.28 eV, respectively, with an increase in the PR filling ratio from 0 wt% to 1.8 wt%. The dispersion region of the refractive index was analyzed using the single oscillator model (Wemple-DiDomenico). Calculation and discussion of values such as dispersion and oscillation energies (Ed and Eo), permittivity at infinite frequency (ε ∞), and lattice contribution to the dielectric function (ε L) of PVA/PR composite films were conducted. These advancements position PVA/PR composite films for potential applications in flexible optoelectronic devices, including light-emitting diodes and photodetectors.

Hexagonal Ta2O5 (10 [formula omitted] 0) single-crystalline films grown on LaAlO3 (010) substrates by MOCVD

Single-crystalline hexagonal tantalum pentoxide (δ-Ta2O5) films were grown on LaAlO3 (010) substrates by MOCVD. A high substrate temperature of 840 °C was required to achieve the best crystalline quality and the root-mean-square surface roughness of the optimum film was 0.26 nm. The films grew along the δ-Ta2O5 [100] direction and the heteroepitaxial relationship between the film and the substrate was confirmed as δ-Ta2O5 (100) ‖ LaAlO3 (010) with δ-Ta2O5 [0001] ‖ LaAlO3 <001>. The film showed a stoichiometric ratio of Ta2O5 and a pentavalent state of Ta element. The optical band gap of the single-crystalline δ-Ta2O5 film was determined as 4.19 eV.