Mg-doped Films Research Articles

High-temperature protection performance of Mg-doped Al2O3 protective layers on the thin film thermocouples

Mg-doped Al2O3 protective layers were deposited on Pt–PtRh10 (S-type) thin film thermocouples (TFTCs) by reactive magnetron sputtering. The changes in the composition, microstructure, and element distribution of the Mg-doped Al2O3 films before and after annealing at 1200 °C for 3 h were investigated using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The results indicate that incorporating MgO into Al2O3 as an enhancement phase not only inhibits the crystallization and phase transformation of Al2O3 but also promotes the formation of MgAl2O4, sequentially further enhancing the material's high-temperature protective properties. The thermoelectric properties of S-type TFTCs with 1.6 μm thick Al2O3 and Mg-doped Al2O3 protective layers were explored, respectively. The results of static calibration at high temperatures demonstrate that the TFTCs with the Mg-doped Al2O3 protective layer can operate at 1148 °C for over 96 h and at 1480 °C for a brief period. Following 4 calibration cycles, compared to the TFTCs with the Al2O3 protective layer, the average Seebeck coefficients of the TFTCs with the Mg-doped Al2O3 protective layer exhibit a slower decline rate, and its drift rate during the 4th cycle is merely 3.28 °C/h. The TFTCs featuring Mg-doped Al2O3 protective layers demonstrate extended lifetimes, superior high-temperature stability, and enhanced reliability when contrasted with those utilizing undoped Al2O3 protective layers. These attributes offer valuable insights into the progression of TFTC technology.

Magnesium-doped zinc oxide film for hydrogen production from wastewater

Recently, developing resources for H2 production has been a supreme priority to maintain the current rate of global warming in waste and drinking water. Metal-doped zinc oixde (ZnO) film-based catalyst materials are better candidates for electrochemical water splitting. Herein, it will be demonstrated that Mg-doped ZnO films can significantly enhance the electrochemical water splitting and H2 production. Therefore, Mg-doped ZnO films were synthesized using the dip coating technique. The undoped and Mg-doped ZnO films' structure, chemical, and morphological properties were characterized using detalied measurements. The electrical and optical characteristics of ZnO and Mg–ZnO samples were investigated. ZnO and Mg–ZnO films coated on the proper reactor were utilized for electrochemical water splitting. The efficiency of the electrochemical water splitting increases from 29 % to 56 % as ZnO is doped with Mg. In addition, the yielding H2 concentration increases from 9.92 × 10−7 mol/L.h to 3.65 × 10−6 mol/L.h when ZnO is doped with Mg. Hence, the work sheds new insight into new ways of fabricating significant photocatalysts for low-cost hydrogen extraction and echo-friendly agents.

Wide band gap tuning of Mg doped ZnO thin films for optoelectronic applications.

Zinc oxide (ZnO) thin films with magnesium (Mg) doping have demonstrated significant potential due to their wide band gap, which enables efficient absorption of ultraviolet (UV) radiation while maintaining transparency to visible light. Sol-gel spin coating methods were used to deposit Mg-doped ZnO thin films. The solution was made with methanol as the solvent, and the starting materials were magnesium acetate tetrahydrate and zinc acetate dihydrate. The integration of Mg content in deposited ZnO films was investigated for structural, morphological, and optical properties using an X-ray diffractometer (XRD), scanning electron microscope (SEM), energy dispersive X-ray analysis (EDAX), and UV-VIS spectrophotometer. Mg-doped ZnO films were produced on quartz substrates and post-annealed at 400°C. According to absorption coefficient calculations, the optical band gap of Mg-doped ZnO films is in the range of 5.4 eV which is ideal for a variety of applications in the field of optoelectronic devices.

Communication—Annealing Strategies for Spray Deposited Precursor Films of p-Type CuCr1-xMgxO2

Annealing of sprayed pure and Mg doped CuCrO2 thin films by high intensity, short time light irradiation leads to a single delafossite phase at comparatively low temperatures compared with traditional furnace annealing. P-type crystalline undoped and Mg-doped CuCrO2 films were obtained within few minutes by annealing with halogen lamp between 550 °C and 650 °C in Ar atmosphere. Transport properties of Mg-doped thin films were comparable to furnace annealed samples despite much shorter annealing time. The results demonstrate that post-annealing of chemically deposited samples using light irradiation is an effective and fast method for obtaining transparent conducting delafossite thin films.

Synergistic effects of Mg doping on TiO2 for improved toxic gas sensing performance at room temperature

The gas sensing characteristics of magnesium (Mg)-doped titanium dioxide (TiO2) films were investigated using a spray pyrolysis method. TiO2 Thin films with varying Mg doping concentrations (0, 2.5, and 5 weight percentages) were deposited and tested for their gas detection ability to organic compounds such as ethanol, butanol, toluene, xylene, and formaldehyde at room temperature. Results disclosed that introducing Mg into TiO2 enhanced the gas sensing characteristics, particularly for formaldehyde. Mg-doped TiO2 film improved the change in electrical resistance during gas adsorption, leading to an increased response in formaldehyde detection. Additionally, XRD revealed the crystal structure, while Raman spectroscopy provided insights into molecular vibrational modes of the fabricated films. FESEM allowed for high-resolution imaging of surface morphology, and atomic force microscope assessed surface roughness and other properties of the as deposited samples. UV-Vis spectroscopy was utilized to examine the optical characteristics. The collective results strongly indicated that the introduction of Mg significantly improved the gas-sensing capabilities of TiO2 films, making them highly promising for various gas-sensing applications.

The Mg-Co3O4 coating on indium tin oxide film with improved electrochromic and energy storage properties by sol-gel spin coating

A magnesium-doped cobalt trioxide (Co3O4) film is fabricated on an indium tin oxide (ITO) substrate by sol-gel spin coating method. The microstructure and optics of the pristine and Mg-doped Co3O4 films and are analyzed using X-ray diffraction, scanning electron microscopy, and spectrophotometers. From electrochromic outcomes, at 250 °C annealing temperature, the transmittance of a 3 at% Mg-doped Co3O4 film can be increased by 12.32%, and the optical modulation amplitude can reach 1.71 times that of a pure Co3O4 film. Current work shows that incorporating Mg in Co3O4 improves its electrochromic and capacitive properties.

Structural and physical properties of Mg-doped CuCoO2 delafossite thin films

In this work, Mg-doped CuCoO2 (CCO) delafossite oxide was synthesized by a low-cost technique, namely spray pyrolysis. We investigated the effects of Mg doping on the structure, morphology, chemical composition, and optical properties of CCO with different percentages (1%, 2%, 3%, 4%, 5%). Using X-ray diffraction analysis, we observed an excellent agreement without any impurities in the Mg-doped CuCoO2 delafossite structure. To analyze the variations caused by doping on the quality, we examined the morphology of the produced films using field emission scanning electron microscopy. The deposited samples exhibited different textures and surfaces that were evenly distributed throughout the substrate. Furthermore, we utilized a transmission electron microscope to examine the Mg-doped CuCoO2 films. The CuCo1-xMgxO2 with x = 0.01 delafossite displayed excellent crystallinity. The results indicated that the fringe distances of 0.23 nm, 0.85 nm, and 0.16 nm corresponded to the spacings of the CuCoO2 lattice planes (110), (222), and (332) respectively. Optical properties were measured using UV–Vis spectroscopy at room temperature, revealing weak visible light absorption. It was found that CuCo1−xMgxO2 could be transparent to photons with energies in the visible range. Additionally, the band gap decreased in parallel with increasing Mg doping until a percentage of 3% (0.03), where a value of Eg = 1.75 eV was obtained.

Effect of Mg-doping and Fe-doping in lead zirconate titanate (PZT) thin films on electrical reliability

Uniformly acceptor doped Pb(Zr0.48Ti0.52)O3 (PZT) films with 2 mol. % Mg or Fe prepared by chemical solution deposition exhibited decreased dielectric constants and remanent polarizations relative to undoped PZT. For highly accelerated lifetime testing (HALT) at 200 °C and an electric field of 300 kV/cm in the field up direction, the HALT lifetimes (t50) for undoped, Mg-doped, and Fe-doped PZT films were shortened from 2.81 ± 0.1 to 0.21 ± 0.1 and 0.54 ± 0.04 h, respectively. Through thermally stimulated depolarization current measurement, significant VO∙∙ electromigration was found in homogeneously Mg-doped PZT thin films, a major factor in their short HALT lifetime. Because the concentration of oxygen vacancies increases with uniform acceptor doping, the lifetime decreases. In contrast, when a thin layer of Mg-doped or Fe-doped PZT was deposited on undoped PZT or Nb-doped PZT (PNZT), the HALT lifetimes were longer than those of pure PZT or PNZT films. This confirms prior work on PNZT films with a Mn-doped top layer, demonstrating that the HALT lifetime increases for composite films when a layer with multivalent acceptors is present near the negative electrode during HALT. In that case, the compensating electrons are trapped, presumably on the multivalent acceptors, thus increasing the lifetime.

Mg doping effects on the microstructure and piezoelectric characteristics of ZnO:Li films deposited at room temperature using an RF sputtering deposition method

In this work, Density functional theory (DFT + U) was used to simulate Mg doped LZO (ZnO:Li 3 mol%) based on an atomic substitution concept. The calculation results indicate the piezoelectric constants e33, e31 and lattice constant a have a tendency to increase significantly due to Mg doping effects. Also, an RF magnetron sputtering system was used to prepare Mg-doped LZO films (ZnO: Li 3 mol%) with Mg doping concentrations of 0, 3, 6, 9 mol% at room temperature. A further analysis shows that when the proposed films are deposited at room temperature, Li atoms will bond with oxygen atoms to form Li2O2 to help to enhance the piezoelectric properties of the films. This is also found to be one of the reasons for the error in the simulated lattice constants.In addition, the doping of Mg induces lateral tensile stress in the ZnO structure. This phenomenon can produce lattice distortion and change the asymmetry of the ZnO atomic center at room temperature, thus improving the piezoelectric properties (piezoelectric coefficient d33 is increased from 4.5 to 26.3 pm/V). The reported d33 value is the highest compared to other reports on ZnO-based films deposited at room temperature.

Effect of Gamma Radiation on Structural and Optical Properties of ZnO and Mg-Doped ZnO Films Paired with Monte Carlo Simulation

In space, geostationary electronics located within the outer van Allen radiation belt are vulnerable to gamma radiation exposure. In terms of application, implementing an electronic system in a high radiation environment is impossible via conventional engineering materials such as metal alloys as they are prone to radiation damage. Exposure to such radiation causes degradation and structural defects within the semiconductor component, significantly changing their overall density. The changes in the density will then cause electronic failure, known as the single event phenomena. Thus, the radiation response of material must be thoroughly investigated before the material is applied in a harsh radiation environment, specifically for flexible space borne electronic application. In this work, potential candidates for space-borne application devices: zinc oxide (ZnO) and Mg-doped ZnO thin film with a film thickness of 300 nm, were deposited onto an indium tin oxide (ITO) substrate via radio frequency (RF) sputtering method. The fabricated films were then irradiated by Co-60 gamma ray at a dose rate of 2 kGy/hr. The total ionizing dose (TID) effect of ZnO and Mg-doped ZnO thin films were then studied. From the results obtained, degradation towards the surface morphology, optical properties, and lattice parameters caused by increasing TID, ranging from 10 kGy–300 kGy, were evaluated. The alteration can be observed on the morphological changes due to the change in the roughness root mean square (RMS) with TID, while structural changes show increased strain and decreased crystallite size. For the optical properties, band gap tends to decrease with increased dose in response to colour centre (Farbe centre) effects resulting in a decrease in transmittance spectra of the fabricated films.

The enhancement of NIR transparency due to annealing and Mg-doping in [formula omitted] thin films

The effect of post-deposition annealing on the structural and optical properties of CuCrO2 and Mg-doped CuCrO2 thin films is reported. The prepared films were annealed in Helium atmosphere at 300 °C. X-ray diffraction analysis revealed the decreased crystallinity and Raman studies clarify the decreased copper defects at interstitials sites with annealing. The NIR wavelength transparency increases and the maximum transmission of 72% was obtained for Mg-doped annealed film of 211 nm thickness.

Magnesium doped spinel NiCo2O4 for improved hole extraction in efficient inverted perovskite solar cells

In recent years, p-type oxide semiconductors have been widely used as hole transport materials (HTMs) in halide perovskite solar cells (PSCs). Spinel NiCo2O4 has attracted much attention in this regard due to its environmental friendliness and rich elemental composition. In this work, a solution-processed Mg-doped NiCo2O4 film was prepared for the first time as HTM for inverted planar PSCs. The density functional theory calculations reveal that the Mg doping increases the electronic states at the Fermi energy level of NiCo2O4 to promote the carrier transport. Ultraviolet photoelectron spectroscopy (UPS) further shows that the valance band maximum (VBM) of the Mg-doped NiCo2O4 is increased by 0.08 eV compared to that of pristine NiCo2O4, thus reducing the energy level mismatch at the HTM/perovskite interface. As a result, the Mg-doped NiCo2O4 HTM enables a promising power conversion efficiency (PCE) of 16.71% for the inverted MAPbI3 PSCs, which is 18% higher than that of the pristine NiCo2O4 devices (14.07%). The improved PCE is attributed to the improved hole extraction and better matching of the interfacial energy levels of the Mg-doped NiCo2O4. Our result provides novel prospect for the electronic structure manipulation of spinel NiCo2O4 by element doping.

Optoelectronic and birefringence properties of weakly Mg-doped ZnO thin films prepared by spray pyrolysis

MgxZn1−xO thin films were deposited on glass substrate with x varied between 0.01 and 0.05 by spray pyrolysis at a temperature of 450 °C. The structural investigation showed that all thin films had ZnO wurtzite structure with a preferred (002) orientation. The gap energy was calculated using Tauc’s plot, and it decreased over the Mg content by 0.07 eV. The charge carriers’ density dropped by an order of 105 as Mg content increased whereas the resistivity and the mobility increased. SEM observations revealed a significant difference between undoped and doped thin films. A 632.8 nm laser source prism coupler revealed 2 optical modes for every thin film in each Transverse Electric and Transverse Magnetic mode, and the birefringence of the Mg-doped films was positive. Both ordinary and extraordinary refractive indices were found to decrease as the Mg content increased. Great intention has been paid to the relation between the refractive, charge carriers’ density, and the optical band gap.

Effect of Mg Doping on SnO2 Energy Band and Power Conversion Efficiency of Dye-Sensitized Solar Cells

In this work, Mg-doped SnO2 materials with different molar ratios were synthesized by hydrothermal method. Based on the UV-Vis study, band gap (Eg) of the Mg-doped SnO2 is adjusted from 3.76 eV to 3.65 eV via 3 at% concentrations. Results of photovoltaic measurement for dye-sensitized solar cells (DSCs) based on Mg-doped SnO2 film as photoanode indicate that the doping of Mg ions can improve the open-circuit voltage (V oc) of the DSCs, while the electric current density (J sc) of the DSCs is almost unchanged. The cells were measured at 3 days intervals within 24 days after fabrication. Power conversion efficiency (PCE) of 3 at% Mg-doped SnO2 DSCs increases step by step and achieves 4.38% as the cell is tested after 18 days. Electrochemical impedance spectroscopy (EIS) analysis shows that Mg doping enhances light collection, increased the number of photogenerated electrons and inhibits charge recombination.

Structural, optical, and electrical characterization of spray-deposited Mg0.02Zn0.98Se thin film for buffer layer application

In this work, spray-deposited Mg0.02Zn0.98Se thin films were characterized to determine their structural, optical, and electrical properties. The optical band gap of Mg-doped ZnSe thin film was observed to be around 3.05 eV, with high optical transmittance of about 50–70% in the visible region. The crystallite size of Mg-doped ZnSe thin film was about 8 nm, as observed from the X-ray diffraction (XRD) pattern. Elemental composition of Mg-doped ZnSe thin film was confirmed from X-ray energy-dispersive analysis (EDAS). Raman study showed the development of minor strain in ZnSe system due to the incorporation of Mg. The resistivity of the Mg-doped ZnSe film was about 3.82 ohm-m with a carrier concentration of 8.2 × 1011 cm− 3. Mg0.02Zn0.98Se thin films exhibited promising opto-electronic properties such as high transparency and conductivity that are essential for a solar buffer layer that could replace relatively toxic CdS layer.

Effects of ZnMgO Electron Transport Layer on the Performance of InP-Based Inverted Quantum Dot Light-Emitting Diodes.

An environment-friendly inverted indium phosphide red quantum dot light-emitting diode (InP QLED) was fabricated using Mg-doped zinc oxide (ZnMgO) as the electron transport layer (ETL). The effects of ZnMgO ETL on the performance of InP QLED were investigated. X-ray diffraction (XRD) analysis indicated that ZnMgO film has an amorphous structure, which is similar to zinc oxide (ZnO) film. Comparison of morphology between ZnO film and ZnMgO film demonstrated that Mg-doped ZnO film remains a high-quality surface (root mean square roughness: 0.86 nm) as smooth as ZnO film. The optical band gap and ultraviolet photoelectron spectroscopy (UPS) analysis revealed that the conduction band of ZnO shifts to a more matched position with InP quantum dot after Mg-doping, resulting in the decrease in turn-on voltage from 2.51 to 2.32 V. In addition, the ratio of irradiation recombination of QLED increases from 7% to 25% using ZnMgO ETL, which can be attributed to reduction in trap state by introducing Mg ions into ZnO lattices. As a result, ZnMgO is a promising material to enhance the performance of inverted InP QLED. This work suggests that ZnMgO has the potential to improve the performance of QLED, which consists of the ITO/ETL/InP QDs/TCTA/MoO3/Al, and Mg-doping strategy is an efficient route to directionally regulate ZnO conduction bands.

Modification of oxide film on Zircaloy-2 by magnesium ions in high temperature aqueous solution

Inorganic metal ion additives are being explored for controlling the corrosion and deposition of activated corrosion products on out of core surfaces in Pressurized Heavy Water Reactors (PHWRs). Mg2+ ions can modify the oxides on heat transfer surfaces like Zircaloy and thus influence its corrosion properties. Zircaloy-2 coupons were exposed to simulated Primary Heat Transport (PHT) system environment in the presence and absence of Mg2+ ions and were characterized to understand the surface morphology, defect density and the corrosion protectiveness. Incorporation of Mg into the oxide was confirmed by XPS. GIXRD and Raman spectra showed presence of predominantly monoclinic zirconia with traces of tetragonal phase. GIXRD on Mg-doped films showed that, the monoclinic ZrO2 fraction increased by 2% from 7d to 42d exposure. The films formed in presence of Mg always had higher impedance and lower passive current density than that formed in the absence of Mg for the same duration. This study shows that the Mg doped oxide imparted corrosion protectiveness and the doping is not detrimental to the material.

Influence of dopant valence on the thermochromic properties of VO2 nanoparticles

The effect of valence of dopants on thermochromic properties of VO2 nanoparticles are investigated. In the present work, VO2 nanoparticles were synthesized by hydrothermal method and subsequently spin coated on a glass substrate. Dopants with various valences can break the structural symmetry of the V4+-V4+ chains, which results in various degrees of lattice distortion and changes in the crystal structure of VO2. Therefore, the transition temperature (Tc) can be associated with the valence of transition metal dopants, and it decreases with the increase of elements’ valence. Meanwhile, various valence results in the changeable optical band gap (Eg). The doping of lower valence elements results in narrowing of Eg, thus leading to enhancements in both luminous transmittance (Tlum) and solar energy modulation ability (ΔTsol). The phase transition temperature is significantly reduced by 20.2 °C for 1% doping of W. The Zr-doped film exhibits the highest Tlum and ΔTsol of 61.4% and 10.3%, respectively. The Mg-doped film has shown Tlum and ΔTsol of 59.4% and 9.5%, respectively, which is slightly inferior to Zr-doped sample. It can be deduced that W/Zr and W/Mg co-doped VO2 films can improve Tc, Tlum, and ΔTsol, simultaneously, which can provide a potential solution for manufacturing smart windows.

Ultra-wide bandgap corundum-structured p-type α -(Ir,Ga)2O3 alloys for α -Ga2O3 electronics

Ultra-wide bandgap p-type α-(Ir,Ga)2O3 films with bandgaps of up to 4.3 eV have been obtained by unintentional doping or Mg doping. For Mg-doped films, Hall-effect measurements revealed a hole concentration of 9.9 × 1018 to 8.1 × 1019 cm−3 and a mobility of 0.13 − 0.92 cm2/V s, respectively. A preliminary test of a pn junction diode composed of p-type α-(Ir,Ga)2O3 and n-type α-Ga2O3 did not show catastrophic breakdown in the reverse direction until 100 V and the current on/off ratio at +3 V/−3V was 5 × 105. Since α-(Ir,Ga)2O3 and α-Ga2O3 take the same crystal structure and are well lattice-matched (with a lattice mismatch of <0.3%), the formation of a high-quality pn heterojunction is encouraged; this is one of the advantages of the corundum material system.

Tailoring Bandgap and Electrical Properties of Magnesium-Doped Aluminum Zinc Oxide Films Deposited by Reactive Sputtering Using Metallic Mg and Al–Zn Targets

Bandgap enlarged Mg-doped aluminum zinc oxide (Mg-doped AZO) film is a potential transparent conducting oxide for applications in photonics devices. The oxide film normally deposited by sputtering, particularly using ceramic targets, while maintaining its pristine property for the film deposited using metallic targets is rarely addressed. This study investigated the optical and electrical properties of Mg-doped AZO films that were performed by a magnetron reactive co-sputtering method using metallic Mg and Al–Zn targets. Doping of Mg in the AZO significantly affects the electrical resistivity and optical transmission of the films because Mg tends to replace part of Zn lattice sites. The 1.2 at.% Mg-doped AZO film had an electrical resistivity of 7.9 × 10−4 Ω·cm, an optical transmittance of 92.6% in the visible light range, and a bandgap of 3.66 eV when the film was post-annealed at 600 °C. The Mg doping widens the bandgap and, thus, increases the transmittance of the AZO film. Because of the superior electrical and optical characteristics, the Mg-doped AZO films prepared using the metallic targets can be a reliable transparent conducting oxide for applications.