UV Photoluminescence Research Articles

Inflated electronic and optical assessment of gC3N4/ZnO nanocomposite as a potential emissive layer material for OLED application

Organo-inorganic nanocomposite materials have been proven to be novel hybrid materials with inflated electronic and optical performance that can be tailored with the judicious selection of the building units or their combinations. Here, hydrothermal, thermal polycondensation, and ultrasonication techniques were used to synthesize pure ZnO, gC3N4, and gC3N4/ZnO with varying weights % such as 10%, 15%, 20%, and 25% of ZnO inorganic filler elements in gC3N4 matrix. The crystalline phase (hexagonal wurtzite) and crystallite size (10.0 nm, 17.6 nm, and 15.90 nm) of the synthesized materials were examined by X-ray diffractometer. The FESEM and HRTEM characterizations revealed the sheet-like gC3N4 and spherical-type ZnO nanoparticle-like microstructures of the samples. The present functional groups, corresponding vibrational frequency, chemical states, and binding energy were investigated using FTIR and XPS spectroscopic methods. Optical parameters such as optical band gap energy (Eg = 3.24 eV), Urbach energy (Eu = 0.41 eV), refractive index (n= 1.99), emission quantum yield (∼ 69.03%), and color purity of the nanocomposites were examined using UV visible and photoluminescence spectroscopic techniques. IV and Hall measurements techniques were used to determine the semiconducting parameters of the optimized sample, such as conductivity (∼62.90×10−5 S/cm), carrier mobility (∼ 44.1 cm2/Volt. Sce), carrier concentrations (∼1.825×1014 cm−3), and sheet resistance (∼1.062×103 Ω/cm2). Due to their excellent optical and electrical behavior, the nanocomposite materials were found to be fairly suitable as a potential emissive layer material for OLED applications.

Anthropogenic modification of a giant ground sloth tooth from Brazil supported by a multi-disciplinary approach

Identifying evidence of human modification of extinct animal remains, such as Pleistocene megafauna, is challenging due to the similarity of anthropogenic and non-anthropogenic taphonomic features observed under optical microscopy. Here, we re-investigate a Late Pleistocene ground sloth tooth from northeast Brazil, previously suggested as human-modified based only on optical observation. To characterize the macro- and micro-morphological characteristics of the marks preserved in this tooth and evaluate potential human modification, we used stereomicroscope and scanning electron microscopy (SEM) supplemented by energy dispersive spectroscopy (EDS), UV photoluminescence (UV/PL), synchrotron-based X-ray fluorescence (SR-XRF), and synchrotron micro-computed tomography (SR-µCT). These methods allowed us to discriminate non-anthropogenic taphonomic features (root and sedimentary damage), anthropogenic marks, and histological features. The latter shows the infiltration of exogenous elements into the dentine from the sediments. Our evidence demonstrates the sequence of anthropogenic and non-anthropogenic taphonomic modification of this tooth and supports its initial intentional modification by humans. We highlight the benefits of emerging imaging and spectral imaging techniques to investigate and diagnose human modification in fossil and archaeological records and propose that human modification of tooth tissues should be further considered when studying possibly anthropogenically altered fossil remains.

Development of MnWO4:Ag nanodilute magnetic semiconductors with tunable magnetic and optoelectronic properties

The bandgap engineered MnWO4 nanoparticles doped with Ag were developed using a facile one-pot synthesis method. The impurity doping concentration of Ag was varied from 1 to 5 wt percentages to tune the interactions between manganese tungstate and silver ions to obtain desirable magnetic and optoelectronic properties. The structural properties of the MnWO4 particles with various concentrations of Ag were investigated using X-ray diffraction. The optical properties of the pristine and Ag-doped MnWO4 particles were determined using UV‒Vis and photoluminescence spectroscopy. The impurity concentration-dependent structural transformations and changes in the vibrational modes, lattice dynamics, electronic transitions and optoelectronic properties of the prepared materials were analyzed using Raman spectroscopy. The topology, morphology and elemental analysis of the synthesized nanoparticles were elucidated using HRTEM, SAED, SEM and EDX techniques. The magnetic properties of the MnWO4:Ag nanoparticles were measured using a vibrating sample magnetometer (VSM). The obtained results suggested that Ag-doped MnWO4 nanosystems show enhanced and tunable magnetic properties suitable for nanodilute magnetic semiconductor (nDMS) applications. The presented work opens a range of possibilities for the development of advanced materials with applications in optoelctronics, nanomedicine, energy-efficient electronic devices and energy conversion.

Reversible mechanoresponsive luminescence based on an unsymmetrical D-π-A type phenanthroimidazole derivative

Abstract A kind of D-π-A mechanoresponsive luminescent molecule 2- (4- (1H-phenanthro[9,10-d] imidazol) benzylidene) malononitrile (ANPPI) was synthesized and characterized by UV absorption, photoluminescence, and other techniques. The obvious mechanoresponsive properties of ANPPI were reversible upon grinding and fuming, and were demonstrated by X-ray diffraction, scanning electron microscopy, and differential scanning calorimetry.

Synthesis, cation exchange, and optical properties of pyrene-based chromophores containing [CB9H9]− and [CB11H11]− cluster units

Abstract Four monocarborane anion-based compounds connected to a pyrene moiety were synthesized by combining two monocarborane anion scaffolds and two counter cations. The effects of the cage structure and the counter cation on the optical properties were investigated from UV‒vis absorption and photoluminescence (PL) measurements. The PL spectra in the solid state were unique for each compound, derived from the different shapes of the carborane cage and counter cation. These results suggest great potential for designing a monocarborane anion-based chromophore.

High-Performance Ultraviolet Organic Light-Emitting Diodes Enabled by Double Boron-Oxygen-Embedded Benzo[m]tetraphene Emitters.

Ultraviolet organic light-emitting diodes (UV OLEDs) have attracted increasing attention because of their promising applications in healthcare, industry, and agriculture; however, their development has been hindered by the shortage of robust UV emitters. Herein, we embedded double boron-oxygen units into nonlinear polycyclic aromatic hydrocarbons (BO-PAHs) to regulate their molecular configurations and excited-state properties, enabling novel bent BO-biphenyl (BO-bPh) and helical BO-naphthyl (BO-Nap) emitters with hybridized local and charge-transfer (HLCT) characteristics. They could be facilely synthesized in gram-scale amounts via a highly efficient two-step route. BO-bPh and BO-Nap showed strong UV and violet-blue photoluminescence in toluene with full width at half-maximum values of 25 and 37 nm, along with quantum efficiencies of 98 and 99%, respectively. A BO-bPh-based OLED showed high color purity UV electroluminescence peaking at 394 nm with Commission Internationale de l'Eclairage (CIE) coordinates of (0.166, 0.021). Moreover, the device demonstrated a record-high maximum external quantum efficiency (EQE) of 11.3%, achieved by successful hot exciton utilization. This work demonstrates the promising potential of double BO-PAHs as robust emitters for future UV OLEDs.

Sol-gel synthesis and photoluminescent properties of metal oxide-metal oxide coupled nanocomposites

Tin oxide (SnO2) and zinc oxide (ZnO) coupled metal-oxide nanocomposites or SnO2–ZnO were prepared using a sol-gel method. The stretching mode frequencies and crystal structures were examined by using Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. The microscopic analyses by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed a flower-like morphology of the nanocomposites. The analysis of surface chemical and electronic states was conducted by X-ray photoelectron spectroscopy (XPS). The band gap energies as confirmed from the ultraviolet–visible spectroscopy (UV–Vis) data were found to be larger than those of the bulk band gaps due to the increase between energy levels associated with smaller particle sizes. The UV (380 nm) and orange (595) photoluminescence (PL) emissions observed from the SnO2:ZnO nanocomposites were attributed to a combinatorial contribution from radiative transitions in SnO2 and ZnO components. The proposed mechanisms of these emissions are discussed.

Synthesis and Luminescent Properties of Barium Molybdate Nanoparticles.

BaMoO4 was obtained via facile mechanochemical synthesis at room temperature and a solid-state reaction. An evaluation of the phase composition and structural and optical properties of BaMoO4 was conducted. The influence of different milling speeds on the preparation of BaMoO4 was explored. A shorter reaction time for the phase formation of BaMoO4 was achieved using a milling speed of 850 rpm. A milling speed of 500 rpm led to partial amorphization of the initial reagents and to prolongation of the synthesis time of up to 3 h of milling time. Solid-state synthesis was performed via heat treatment at 900 °C for 15 h. X-ray diffraction analysis (XRD), infrared (IR) and UV diffuse reflectance (UV-Vis) and photoluminescence (PL) spectroscopy were carried out to characterize the samples. Independently of the method of preparation, the obtained samples had tetragonal symmetry. The average crystallite sizes of all samples, calculated using Scherrer's formula, were in the range of 240 to 1540 Å. IR spectroscopy showed that more distorted structural MoO4 units were formed when the compound was synthesized via a solid-state reaction. The optical band gap energy of the obtained materials was found to decrease from 4.50 to 4.30 eV with increasing crystallite sizes. Green- and blue-light emissions were observed for BaMoO4 phases under excitation wavelengths of 330 and 488 nm. It was established that the intensity of the PL peaks depends on two factors: the symmetry of MoO4 units and the crystallite sizes.

Design and preparation of novel LaFeO3/NiFe2O4 nanohybrid for highly efficient photodegradation of methylene blue dye under visible light illumination

Most dyes are carcinogenic; thus, they must be removed from the water to save aquatic and human life. Among the various methods, the photocatalytic degradation of dyes is attracting much attention due to the easy strategy driven by the solar light. Herein, we report the fabrication of nickel ferrite (NiFO), lanthanum ferrite (LFO) and their composite are utilized as a light-driven catalyst for the deprivation of significant commercial dyes. The straightforward microemulsion method is used to produce both pure ferrite materials and their composite counterparts. The phases of the synthesized materials were verified through XRD analysis while scanning electron microscopy was employed to examine their morphology. The average crystallite size of the LFO, NiFO and their composite was 53, 62 and 42 nm, respectively. The elemental composition of the pristine and composite was confirmed by the energy dispersive spectroscopic analysis, indicating no other impurity in the materials. The optical properties are analyzed via UV visible and photoluminescence to measure the band gap value of 2.05, 1.73 and 1.9 eV for LFO, NiFO and their composite, respectively. It is observed that the LaFeO3/NiFe2O4 has the highest photodegradation efficiency (92 %) as compared to the LFO (LaFeO3) and NiFO (NiFe2O4). The composite material also showed excellent reusability as well as good stability. It was also confirmed that OH radicals are the major contributor toward the dye degradation, as confirmed by the scavenger tests. The higher mineralization of methylene blue in the occurrence of composite as a catalyst may cause rapid charge transfers, as confirmed by EIS, and it may stop the recombination of electrons/hole pairs due to suitable band alignments.

The impact of dimethylformamide on the synthesis of graphene quantum dots derived from graphene oxide

Graphene quantum dots (GQDs) have garnered immense interest in recent years due to their unique optical, electrical, and chemical properties, making them promising candidates for various applications in optoelectronics, bioimaging, and sensing. However, enhancing the control over the size, surface chemistry, and optical properties of GQDs remains a significant challenge. In this study, a novel recipe was proposed to successfully synthesize various GQDs via a typical solvothermal process, which has proven to be a versatile and scalable approach. In addition to the main ingredient – graphene oxide suspension, dimethylformamide (DMF) and hydrogen peroxide serving as a cutting agent were added to the reaction mixture. This synthesis method was found to be more promising than the reference one in which DMF was replaced by double distilled water. Through systematic experimentation, we demonstrated that the addition of DMF enables the successful GQD production over a wider range of reaction times; hence, the UV absorption band and photoluminescence properties of GQDs can be better adjusted. The dependence of photoluminescence on the excitation wavelength was observed in the as-prepared materials as they were excited with a range of wavelengths from 360 to 480 nm. The obtained insights not only advance our understanding of GQD synthesis but also open up avenues for tailoring their properties for specific applications.

Beyond the Visible: A Review of Ultraviolet Surface-Enhanced Raman Scattering Substrate Compositions, Morphologies, and Performance.

The first observation of ultraviolet surface-enhanced Raman scattering (UV-SERS) was 20 years ago, yet the field has seen a slower development pace than its visible and near-infrared counterparts. UV excitation for SERS offers many potential advantages. These advantages include increased scattering intensity, higher spatial resolution, resonance Raman enhancement from organic, biological, and semiconductor analytes, probing UV photoluminescence, and mitigating visible photoluminescence from analytes or substrates. One of the main challenges is the lack of readily accessible, effective, and reproducible UV-SERS substrates, with few commercial sources available. In this review, we evaluate the reported UV-SERS substrates in terms of their elemental composition, substrate morphology, and performance. We assess the best-performing substrates with regard to their enhancement factors and limits of detection in both the ultraviolet and deep ultraviolet regions. Even though aluminum nanostructures were the most reported and best-performing substrates, we also highlighted some unique UV-SERS composition and morphology substrate combinations. We address the challenges and potential opportunities in the field of UV-SERS, especially in relation to the development of commercially available, cost-effective substrates. Lastly, we discuss potential application areas for UV-SERS, including cost-effective detection of environmentally and militarily relevant analytes, in situ and operando experimentation, defect engineering, development of materials for extreme environments, and biosensing.

Evaluating the use of UV photoluminescence for surveying the immature stages of rare butterflies: a case study using the Black Hairstreak (Satyrium pruni)

Conservation of rare and elusive butterflies can benefit from the use of contrasting survey techniques to confirm their presence and to understand the lifecycle in more detail. This case study trialed different survey techniques for all stages of the lifecycle (ova, larva, pupa and adult) to assess their value for monitoring Black Hairstreak (Satyrium pruni) populations in Britain.Daytime surveys for well camouflaged ova, larvae and pupae yielded little success. However, the novel use of UV flashlights in nocturnal surveys for photoluminescent larvae was found to be an effective technique when compared to surveying adult butterflies. Critically, combined surveying for larvae and adults provides unique insights into the behaviour of the species at different stages in the lifecycle and, when used in combination, gives a more holistic understanding of the true nature of a colony of Black Hairstreak butterflies.Implications for insect conservation: our results show that the novel use of nocturnal surveys for larvae with UV flashlights is a valuable technique for surveying for Black Hairstreak butterflies. It therefore has potential to be used in conjunction with other survey techniques for assessing the health of a colony and supporting conservation at different stages of the lifecycle of the butterfly.

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

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

Ultraviolet-photoluminescence and trace element analyses in Ga-rich sphalerite from the Djebel Gustar Zn-Pb deposit, Algeria

The Djebel Gustar Zn-Pb deposit in northeastern Algeria is one of many carbonate-hosted base metal deposits in the Atlas metallogenic province of North Africa. The sphalerite in this deposit occurs in five distinct types that differ in texture, mineral assemblage, chemical composition, and UV photoluminescence signature. Detailed investigation of trace elements by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) showed that the sphalerite is significantly enriched in the critical metal Ga. The trace element concentrations of the different sphalerite types correlated well with their photoluminescence color; with Mn2+ (orange-yellow), Cu+ (green), and Ga3+ (red) being the dominant activators. We suggest that the Ga enrichment in the Djebel Gustar deposit is the result of formation conditions that include the mixing of a Cl-rich fluid carrying mainly Zn and Pb with a more reduced and Cl-poor fluid containing considerable organic matter and/or calcite with adsorbed Ga(OH)3. This Ga was subsequently incorporated into sphalerite, rather than forming a stoichiometric Ga phase. Furthermore, our study demonstrates that UV photoluminescence of low Fe sphalerite has the potential to become a simple and affordable tool for preliminary characterization of sphalerite ores in mining and exploration with respect to critical elements such as Ga.

Monoclinic Y2O3: Ce nanophosphors synthesized by wet chemical precipitation method

UV emitting nanophosphors draws attention from many researchers currently due to the diverse applications ranging from UV LEDs to phototherapy. The current work is an investigation of monoclinic yttrium oxide doped with cerium synthesized by means of wet chemical precipitation at low temperature (90 °C). Raman analysis and TEM experiments confirmed the formation of monoclinic phase and XPS analysis proves the presence of Ce3+ energy levels. UV experiments delivered strong absorption in the short UV region and photoluminescence experiments demonstrated the material's capability to emit in the long UV region. Surface area measurements by BET analysis established the relationship between the BET surface area and luminescence intensity. This emission range is suitable for therapeutical application especially for skin diseases which further extends the scope of the work.

Synthesis of zinc oxide nanoparticles mediated by Dictyota dichotoma endophytic fungi and its photocatalytic degradation of fast green dye and antibacterial applications

• Seaweed was collected from Ramanathapuram coastal area and the endophytic fungus was isolated. • ZnO nanoparticle was synthesized by utilizing extra cellular products of fungal endophytes is not yet predicted. • ZnO NPs show the high efficacy of antimicrobial and antibiofilm activity. • Excellent photocatalytic dye degradation was observed in the ZnO NPs treated samples. Biosynthesis of nanoparticles has received considerable importance because of their ecofriendly, cost effective and wide applications in biological fields. Aim of this study is to synthesis zinc oxide nanoparticle (ZnO NPs) using extra cellular product from isolated marine ( Dictyota dichotoma ) endophytic fungi Aspergillus sp (Accession number - MZ467123) . The properties of synthesized ZnO NPs have been characterized by UV–Vis spectrophotometer, FTIR, Field Emission Scanning Electron Microscope (FE-SEM), and Energy Dispersive X-Ray (EDX). The UV photoluminescence study exhibited the absorbance peak at the resonance of 270 nm which confirms the presence of ZnO NPs in the aqueous solution. The perfect sphere shape with ∼80–100 µm in size of ZnO NPs has been observed under FESEM and confirmed the presence of elemental composition of nanoparticles by EDX. The synthesized nanoparticles showed potential dye degradation efficiency (∼90%) under photo illumination. In addition, ZnO NPs have shown significant antibacterial effects in terms of zone of inhibition and antibiofilm activity against pathogenic bacteria. Fig. Schematic representation of ZnO NPs synthesis, characterization and its biological activities.

Optimization of reduced Graphene oxide synthesis using central composite design analysis-A waste to value approach.

In recent times, reduced graphene oxide has gained more attention in various fields. In our study, a direct synthesis of reduced graphene oxide using a novel carbon-rich agro-waste from Pennisetum glaucum was used. Ferrocene acted as an oxidizing agent during thermal degradation at 300°C for 15 and 20min to promote graphene oxide and reduced graphene oxide formation. The X-ray diffraction peak at 2θ indicating a shift from 16.86 to 24.28°, presence of functional groups like -OH stretching, -C = C-, C = O, C-O, and C-OH by Fourier transmission infrared spectroscopy, prominent D and G bands at 1308cm-1 and 1578cm-1 by Raman spectra and UV-visible spectroscopy peak shift from 235 to 245nm (π-π*, C = C bonds) confirmed the reduction of graphene oxide to reduced graphene oxide. The average particle size values 233.3nm for graphene oxide and 63.57nm for reduced graphene oxide illustrate the nanoscale range of our synthesized material. The negative zeta potential values in the range - 45.5mV and - 29.5mV for graphene oxide and its reduced forms infer the dispersion stability along with surface oxygen group presence. We have also highlighted the formation of graphene oxide quantum dots by magnetic stirring and confirmed by UV transilluminator and photoluminescence spectra. The photodegradation efficiency was optimized using central composite design for dosage, dye concentration, pH, and time for both malachite green and reactive blue dye. The kinetic studies report pseudo-first-order kinetic model for catalytic degradation and statistical Analysis of variance proved the significance of the process for p value < 0.05. Thus, the synthesized graphene materials could be used as a potential candidate for environmental applications.

Exciton-Assisted UV Stimulated Emission with Incoherent Feedback in Polydisperse Crystalline ZnO Powder

A comparative analysis of the features of UV-stimulated emission (SE) of various disordered active materials based on ZnO crystallites for a random laser (RL) was carried out. The superlinear increase in the intensity of the UV photoluminescence (PL) band of polydisperse nano-micro-crystalline (PNMC) ZnO powder at a wavelength of λ = 387 nm and some narrowing of its halfwidth in the range of 20 ÷ 15 nm with increasing pump intensity indicates random lasing with incoherent feedback (FB). The properties of similar UV PL bands under the same conditions of a thin film containing hexagonal ZnO microdisks, as well as samples of monodisperse ZnO nanopowder with nanoparticle sizes of 100 nm, indicate stimulated radiation with coherent feedback. It is shown that, among the studied materials, PNMC ZnO powder with widely dispersed crystallites ranges in size from 50 nm to several microns, which in turn, consists of nanograins with dimensions of ~25 nm, is the most suitable for creating a random laser with incoherent feedback at room temperature. The dominant factor of UV SE in PNMC ZnO powder is radiation transitions under exciton–exciton scattering conditions. The possible mechanisms of this random emission with the continuous spectrum are discussed. The average optical gain coefficient αg at λ = 387 nm in this RL system is estimated as αg~150 cm−1.

Efficient photocatalytic degradation of emerging pollutants by green synthesized Prussian blue analogue nanocomposite

AbstractWorldwide consumption, toxicity, and bioaccumulation of paracetamol (PCM) and atenolol (ATL) has drawn attention of researchers over last decades. A small portion of these drugs is absorbed by human body and rest of them is excreted through urine and feces to the environment (water bodies and soil) which might result in negative impacts. Nanocomposite of chromium oxide coupled with zinc hexacyanocobaltates (Cr2O3@ZnHCC) was synthesized by a green‐method using Sapindus mukorossi seed‐extract for the removal of targeted drugs. Microscopic and spectroscopic analysis of Cr2O3@ZnHCC showed uniformly incorporated prisms into cubic structure having ~75 nm particle size. Well‐characterized Cr2O3@ZnHCC and individuals (Cr2O3 &amp; ZnHCC) were utilized for the degradation of PCM and ATL under direct sunlight and dark conditions. Highest degradation of targeted drugs (91%–94%) resulted at 20 mg L−1 concentration of pollutant, 25 mg of catalyst dose, and pH ~ 7 under daylight exposure (5 h). First‐order kinetics followed with a high adsorption capacity, Xm (13.4–14.5 mg g−1) value was obtained to confirm the strong binding with the pollutants. Moreover, Cr2O3@ZnHCC substantially suppressed the half‐life of targeted drugs (PCM: 0.6 h; ATL: 2.9 h) and converted them into safer‐small metabolites as confirmed by liquid chromatography‐mass‐spectrometry analysis, and the reduction of carbon content was confirmed by total organic carbon analysis. The charge separation mechanism was assisted by UV reflectance and photoluminescence data. The synthesized green‐nano photocatalyst displayed high reproducibility (up to 10th cycle), sensitivity, and stability during the degradation process which makes this a suitable candidate for industrial applications.

Effect of substrate temperature and RF power on the structural and optical properties of sputtered ZnO thin films

ZnO thin films have been deposited on glass substrates by radio frequency (RF) magnetron sputtering from a zinc oxide target in order to investigate the effect of RF power and substrate temperature on the properties of the deposited films. The structural and optical properties of the films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-Vis transmission spectra and photoluminescence (PL). All ZnO thin films exhibited diffraction peak of (002) corresponding to c-axis orientation and the film deposited at 450°C exhibited the larger grain size as a result of stress relaxation. It is observed that the increase in substrate temperature or sputtering power can facilitate the growth of ZnO in (100) and (101) direction. PL emission was obtained at UV and visible region for the excitation wavelengths of 280 nm and 390 nm respectively. PL study indicated that both the crystal quality and stoichiometry can influence the UV PL emission in ZnO thin films. Dependence of temperature and power on transmission spectra was studied and the optical band gap was calculated.