Mn-doped ZnO Thin Films Research Articles

Low thickness effect on the properties of Mn-doped ZnO thin films synthesized by sol-gel spin coating technique

In this study, 7% manganese-doped zinc oxide (MZO) thin films with varying low thicknesses were synthesized using the spin coating method. The structural, optical, and morphological properties of MZO films with different film thickness, were systematically investigated. The crystallite structure, superficial morphology, and optical characteristics were analyzed using X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and ultraviolet–visible spectroscopy (UV-Vis). Structural analysis confirmed that all films exhibit a hexagonal wurtzite phase with a pronounced peak along the c-axis, and slight variation in low thickness significantly affected the structural parameters. The surface morphology demonstrated good uniformity, characterized by rounded grain shapes in the plane, while surface roughness was found to be increased with increasing film thickness. Optical analysis revealed that as the number of coatings increased, both transmittance and band gap energy decreased, accompanied by a redshift in the absorption edge across all samples. This behavior is attributed to light scattering, as well as an increase in the refractive index and dielectric function with visible light energy, influenced by the number of layers and corresponding crystallite size.

Facile synthesis of Mn doped ZnO for the sensing of ammonia

The variation of possessions of Mn doped in ZnO thin films grown by SILAR technique for various Mn concentrations presented. Thin films of Mn doped ZnP were deposited and uniformly annealed at 300 °C for a 30 min. The annealed films are then characterized by various methods like XRD, SEM, EDAX, VSM respectively. The x-ray diffraction studies confirm the emergence of ZnO. From the SEM, various morphologies were identified based on concentration of the solution bath employed. Due to this reason, spherical shoot, rice and flower morphologies were observed on the surface of the films. These morphologies may influence the application of ammonia gas sensor. From compositional analysis (EDAX), the presence of dopant and the variation in composition of doped materials were estimated. Magnetic studies shows, these films show ferromagnetic behaviour at room temperature. The ammonia gas response of the Mn doped ZnO thin films varied with Mn concentration of 0, 5 and 10. The outcomes of the gas sensing experiments showed that the Mn doped ZnO thin film was more sensitive to ammonia, but that sensitivity decreased as gas pressure increased. Ammonia gas showed an increase in the acidic surface properties of Mn-doped ZnO thin film. At room temperature, Mn-doped ZnO (0 %, 5 % and 10 %) showed responses of 19.20, 27.61 and 32.26 to 100 ppm NH3 gas, which were significantly higher than those of ZnO. The Mn-doped ZnO sensor shows excellent selectivity compared to ZnO and has good stability.

Mn Doped ZnO Film for Ethanol Vapor Detection

It has become a major challenge to develop highly sensitive and selective ZnO gas sensors to detect the leakage of toxic and explosive gases due to their high operating temperature. This article reports the design, characterization, and application of a Mn-doped ZnO thin film for ethanol gas vapor detection at a relatively lower temperature. To achieve this, undoped (0%) and Mn doped ZnO thin films were prepared using a spin coating technique and their structural, morphological and optical characterizations were carried out using XRD, SEM, EDX and UV-vis spectrophotometer. The XRD analysis showed a polycrystalline ZnO structure with the preferred orientations along (100), (002), (101), (102), (110), (103), and (200) planes. Upon Mn doping, the average crystallite size and band gap of ZnO were found to be decreased, which indicated that Mn ions substitute into the lattice of ZnO. Interestingly, SEM images revealed the grainy like porous ZnO surfaces. The EDX results confirmed the presence of Mn dopant in the ZnO lattice. In the doped films, the changes in particle size and grain boundaries of nanocrystalline ZnO resulted changes in sensitivity and operating temperature of ZnO gas sensor. The sensitivity measurements towards ethanol vapor showed significant decrease of the operating temperature from 220°C to 160°C as Mn concentration was increased from 0 to 5%. As-prepared Mn-doped ZnO sensors will be useful for sensing ethanol vapor at relatively low temperature.

Tailoring the Structural, Optical and Electrical Properties of Mn Doped ZnO Thin Films for Gas Sensing Response

This manuscript presents a study on the photoinduced and gas sensing response of Mn-doped ZnO thin films (Zn1−xMnxO, x = 5, 10 mol %) synthesized using the spin coating method. The fabricated thin films were characterized to investigate their structural, bonding, optical, surface morphology, electrical, and gas sensing properties. SEM images displayed a homogeneous surface morphology across the fabricated films with typical grain size ranging from 25 to 30 nm. Optical absorption spectra demonstrated a variation in the optical band gap, ranging from 3.41 eV to 3.87 eV, indicating the tunability of the optical properties with the Mn doping concentration. Photoluminescence (PL) spectra exhibited Near Band Edge emission, as well as blue and green emission peaks, which can be attributed to the presence of defects and impurities in the Mn-doped ZnO thin films. The photoinduced effect was observed through the variation in I–V characteristics due to the excitation of electron-hole pairs, highlighting the influence of Mn doping on the charge transport properties of the thin films. Additionally, the gas sensing response of the Mn-doped ZnO thin films to hydrogen gas was investigated. The results indicated an improved gas sensing response with increasing Mn concentration in the doped ZnO thin films, suggesting the active role of Mn in enhancing the sensitivity of ZnO to hydrogen gas. Based on these findings, Mn-doped ZnO thin films show promise for application in gas sensors.

Structural and optical properties of chemically deposited Mn-doped ZnO thin films

Structural and optical properties of chemically deposited Mn-doped ZnO thin films

SILAR-deposited manganese doped zinc oxide thin films for NO2 gas detection applications

ABSTRACT The structural, optical and gas detection characteristics of Mn-doped ZnO thin films synthesised by the Successive Ionic Layer Adsorption and Reaction (SILAR) process with varied doping concentrations (4, 6 and 8%) were examined. X-ray diffraction data was used to investigate the structural properties and confirm the hexagonal wurtzite crystal structure. The surface morphology and the existence of all elements were verified using a field emission scanning electron microscope and energy dispersive X-ray spectroscopy, respectively. To explore the vibrational bands present in Mn-doped ZnO films, we used FTIR spectra at ambient temperature. Ultraviolet-visible analysis reveals the absorption edge, which is found in the ultraviolet area, with a minor shift towards high wave length, whereas the energy bandgap decreases as Mn concentrations increase. At 200°C operating temperature, the gas sensing properties of Zn0.92Mn0.08O showed good sensitivity, selectivity and shorter response time when compared to other prepared films.

WITHDRAWN: Investigation of the structural, optical bandgap, Urbach's tail, and photoluminescence properties of Mn-doped ZnO thin films

WITHDRAWN: Investigation of the structural, optical bandgap, Urbach's tail, and photoluminescence properties of Mn-doped ZnO thin films

Influence of Ion Beam Irradiation on Optical and Magnetic Properties of Transparent Mn Doped ZnO Thin Films, Suitable for Sensor Applications

The present work describes modification in physical properties of Zn0.95Mn0.05O films by ion beam irradiation. Films were prepared by spin coating and annealed at 500 °C. XRD patterns of these films show wurzite structure with good crystalline quality. However, Low energy irradiation could modify and induces new defect states. Characterization of those defects had been performed by analysing the UV-Visible absorption spectroscopy and Photoluminescence (PL) spectroscopy. Room temperature PL emission of Zn0.95Mn0.05O film shows a broad UV emission and pronounced visible emission ∼530 nm. At low temperature broad UV band become more prominent however it is completely quenched after irradiation. For all irradiated films we had notice only visible emission of comparable intensities, confined within the region 475 nm to 550 nm. Irradiated films are showing ferromagnetism at room temperature and most importantly the film irradiated at fluence F: 1016 ions cm−2 exhibit maximum saturation magnetic moment of 0.83 emu g−1. The magnetic response is strongly influenced by irradiation and we could say that magnetism is strongly correlated with intrinsic defects present in these films. Defect induced formation of bound magnetic polarons (BMP) actually control the ferromagnetic property of these films. These transparent ferromagnetic films could be used in optoelectronics.

Structural, Optical, Electrical and Magnetic properties of 100Mev Ni7+ irradiated Mn doped ZnO thin films

Structural, optical, electrical and magnetic properties of Mn doped ZnO thin films prepared using sol–gel route and modified by 100 MeV Ni7+ Swift Heavy Ion (SHI) irradiation with fluence rate of 1 × 1012 and 1 × 1013 ions/cm2 were studied. X-Ray Diffraction (XRD) studies revealed monophasic films with improved crystallinity after SHI irradiation. Field Emission Scanning Electron Microscopy and Atomic force microscopy indicates increment in grain size with enhanced surface roughness. Enhancement of defect structure such as oxygen vacancies (∼520 nm) and surface defects (∼480 nm) have been studied by Photoluminescence spectroscopy. UV–Vis spectroscopy revealed decrease in band gap and transmission values. SQUID magnetometer and Magnetic Force Microscopy studies provided the clear evidence of ferromagnetic hysteresis curve (Mv/sH) and presence of magnetic contrast in highly irradiated films. Presented results favor the role of SHI irradiation for inducing room temperature ferromagnetism in Mn doped ZnO thin films.

Optical and Electrical Properties of Mn-doped and Mn-Al co-doped ZnO Thin Films Annealed at Different Temperatures for Photosensor Applications

Optical and Electrical Properties of Mn-doped and Mn-Al co-doped ZnO Thin Films Annealed at Different Temperatures for Photosensor Applications

Investigation of the effects of thermal annealing on the structural, morphological and optical properties of nanostructured Mn doped ZnO thin films

The control of the optical properties of ZnO nanostructured thin films by using different dopant elements paves the way for the development of potential materials for photonic and optoelectronic applications. In this work manganese (Mn) doped ZnO thin films were fabricated by rapid thermal evaporation method on a glass substrate having the same Mn content level of ~10% and annealed at different temperatures. XRD analysis showed that the annealed layers have hexagonal wurtzite structure, however, the unannealed layers showed only Zn peaks without any preferential direction. The elemental analysis of the films has been investigated by XPS, which revealed the presence of Mn and oxygen atoms for all layers. In addition, it was observed by FIB-SEM that the morphology of thin films changed with the annealing temperature. For an anneal at 500 °C nanoneedles appeared. Raman spectroscopy showed E 1 (TO) mode in the sample annealed at 500 °C which was attributed with the formation of nanoneedles structures. The optical transmission of the annealed films was in the range of 75–77% and the optical bandgap varied from 3.97 to 3.72 eV. These variations are related to the structural and morphological changes of the thin films with annealing temperature. • The effect of thermal annealing on the physical properties of nanostructured Mn doped ZnO thin films was investigated. • XRD analysis revealed that MZO layers after annealing crystallize in hexagonal wurtzite phase. • The morphology of MZO films changed with the annealing temperature. For an anneal at 500 °C nanoneedles appeared. • Raman measurements have also shown an additional mode E 1 (TO) at 467 cm −1 associated with the apparition of nanoneedles. • The optical constants n, α and the thickness d were successfully identified and determined only from the transmittance spectra using the PSO algorithm.

SILAR Technique–Grown Mn-doped ZnO Thin Films

SILAR Technique–Grown Mn-doped ZnO Thin Films

Columnar structure growth of Mn-doped ZnO (MZO) thin films by radio frequency co-sputtering and studies on films properties

ABSTRACT The present investigation deals with the columnar structured growth of Mn doped ZnO (MZO) thin films by radio frequency sputtering technique. The X-ray diffraction and the processed electron diffraction pattern confirmed the hexagonal wurtzite structure and the film growth direction along (101) plane. The structure of grown film was compared with the pristine ZnO film and the JCPDS card No. 00-36-1451. The microstructures of the pristine ZnO and MZO films were studied by scanning electron microscopy and atomic force microscopy. The columnar structure growth of MZO was confirmed by transmission electron microscopy using TEM cross-section sample. The presence of constituent elements and their concentrations in the films were recorded by energy dispersive X-ray diffraction spectroscopy. The optical transmittance, absorption edge and band gap of the material were studied by UV-Visible transmission spectroscopy. The field dependent magnetization at room-temperature was analysed by using vibrating sample magnetometer and magneto-optic Kerr effect.

Study on structural and optical properties of Mn-doped ZnO thin films by sol-gel method

For ZnO, doping transition metal is one of the powerful tools to improve its photoelectric performance. In this study, Mn-doped ZnO thin films with various thickness and different doping concentration were synthesized by low cost sol-gel method. We systematically investigated structural and optical properties of Mn-doped ZnO with different concentrations and film thickness. Research showed that with the increase of Mn doping concentration, the crystallization of ZnO decreased, and the preferred orientation was weakened. Moreover, the ultraviolet–visible (UV–Vis) absorption coefficient rose as the energy gap (Eg) decreases and Urbach energy (EU) increases). In the intrinsic emission region below 380 nm and in the defect emission region of 440–600 nm, Mn-doped 1.5% ZnO showed the strongest emission, then the excessive doping would reduce photoluminescence of ZnO. However, in the defect emissions region of 380–440 nm, pure ZnO showed highest emission that decreased gradually with the increase doping concentration. Meanwhile, as the increase of film thickness, the crystallization properties of ZnO were improved, but there were more cracks which resulted in the decrease of UV–vis absorption coefficient, the decrease of Eg and the increase of EU). Meanwhile, the intrinsic emission enhanced and the defect emissions decreased.

Fastly steady UV response feature of Mn-doped ZnO thin films

Abstract When the conventional zinc oxide film is used as an ultraviolet detector, it has the disadvantages of slow response time, unstable signal. In order to solve this problem, Mn-doped ZnO films (MZO) were prepared by sol-gel method in this work. Results show that Mn doping can cause deterioration of crystal quality, photocurrent and dark current will decrease at the same time, but in low doping mode (1.5 at.%), the response time of the film can be greatly improved (from about 100 s to 10 s), and the photocurrent is very stable. Moreover, since the dark current is simultaneously weakened, the signal-to-noise ratio is not significantly reduced and is still acceptable. Further increasing the doping concentration, the photocurrent and the dark current continue to decrease. Although a faster photoelectric response is obtained, since the photocurrent is too weak, the electrode is extracted more than the rate at which the photocurrent is generated, and the photocurrent has a tendency to decrease.

Effects of Mn doping on the structural, morphological, electronic and optical properties of ZnO thin films by sol-gel spin coating method: An experimental and DFT+U study

The structural, electronic and optical properties of Mn-doped ZnO thin films were studied using density functional theory (DFT) with Hubbard U method. Supercell model and substitutional method were employed to achieve the considered doping concentrations (x). Antiferromagnetic phase of Zn1−xMnxO (x = 0.125) structure was adopted at different geometry configurations. On the other hand, Zn1−xMnxO (x = 7, 10 and 12.5) thin films, with good uniformity, were fabricated using sol–gel spin coating technique. Both grain size and surface roughness were decreased with x, leading to the decrease of the average transmittance. Calculations revealed that Mn atoms tend to be close to each other around the O atom. Besides, Mn3d states were found to be rarely distributed around Fermi level. Furthermore, Mulliken analysis demonstrated the coexistence of both ionic and covalent bonding. Both materials presented a similar behavior for optical properties with a slight shift toward the lower energy by increasing x.

Oxygen vacancy and Mn2+ induced ferromagnetism in Mn-doped ZnO thin films

With the purpose of investigating the origin of ferromagnetism (FM), Mn-doped ZnO thin films had been fabricated by radio frequency (rf) magnetron sputtering and subsequent anneal process. The characterization of the Mn-doped ZnO thin films was conducted by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and superconducting quantum interference device (SQUID). With increasing the anneal temperature from 300°C to 700°C for 3 min, the influence on magnetism of the Mn-doped ZnO thin films is slight. While extending the anneal time from 3 to 50 min at 300°C, the influence on magnetism is obvious and the Mn-doped ZnO thin films with 30 min clearly demonstrate FM. Compared with the effect of oxygen vacancy and substitutional Mn2+ on the ferromagnetic behavior, OV plays the main role in inducing FM of the Mn-doped ZnO thin films with good crystal structure.

Improved Magnetism in Mn-doped ZnO Thin Films by Inserting ZnO Layer

Compared to Ti/Mn doped ZnO/Pt (Ti/MZO/Pt) device, the Ti/MZO/ZnO/Pt device exhibits more excellent resistive switching (RS) performances and larger magnetic variation behaviors. The RS behavior is attributed to formation and rupture of oxygen vacancy (Vo) based conductive filaments (CFs), and magnetic variation was demonstrated by bound magnetic pole (BMP) model. Here ZnO buffer layer contribute to improve the RS and magnetism.

UV-Vis spectroscopy of Mn-doped ZnO thin films prepared by pulsed laser deposition

Mn-doped zinc oxide (ZnMnO) is of increasing interest to the optoelectronic community for thin film sensors, transistors and solar cells applications. Considerable variability exists in the literature on the growth and doping of ZnMnO films, especially as a function of growth approach, temperature, and oxygen partial pressure. We fabricated ZnMnO thin films on silicon substrates by pulsed laser deposition (PLD). The deposition pressure and the substrate temperature were varied from 2.67 Pa to 26.67 Pa, and from room temperature to 600 °C, respectively. The targets were fabricated with a nominal composition of 1, 5, 10, 15 and 20 wt.% Mn. The influence of the Mn composition, deposition pressure and the substrate temperature on optical properties of the ZnO films was investigated using ultraviolet– visible (UV–Vis) spectrometry. The optical band-gap of the films was evaluated in terms of the Kubelka-Munk function. The results show that the oxygen gas pressure has slightly affected the optical band-gap of the deposited films. Furthermore, the substrate temperature play significant role in the optical properties of the deposited ZnMnO thin films.

Enhancement of ferromagnetism in Thiol functionalized Mn doped ZnO thin films

Enhancement of ferromagnetism in Mn doped ZnO thin films by surface functionalization using dodecane thiol is reported. The Mn doped (5, 10 and 15 mol%) ZnO films grown by Radio Frequency (RF) Magnetron Sputtering have been functionalized using dodecane thiol by spin coating technique. The unfunctionalized and surface functionalized Mn doped ZnO thin films have been examined by x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), photoluminescence (PL), atomic force microscopy (AFM) and vibrating sample magnetometer (VSM) measurement. From XRD, it has been observed that all films are oriented along (002) plane. The XRD pattern reveals that no significant change in intensity of (002) peak upon surface functionalization with dodecane thiol. However, slight shift in (002) peak upon Mn doping due to lattice strain has been observed. The PL spectra of Thiol capped Mn doped ZnO thin films shows quenching of visible emission intensity relative to the unfunctionalized Mn doped ZnO thin films. The quenching of visible emission indicates that thiol passivates surface defects via Zn-S bonding. The saturation magnetization of Mn doped ZnO thin film was found to increase by 18% upon thiol functionalization. This enhanced ferromagnetic material can be used in fabrication of GMR devices.