Li Thin Films Research Articles

Innovative synthesis, structural characteristics, linear and nonlinear optical properties, and optoelectric parameters of newly developed A2ZnGeO4 (A = K, Li) thin films.

The synthesis of high-quality thin films through spin coating deposition on meticulously cleaned glass substrates is presented. Optical band gaps E g of both samples using the Kubelka-Munk function are determined. The data analysis uncovers the presence of optical allowed direct transition for A2ZnGeO4 (A = K, Li). Spectroscopic ellipsometry measurements on A2ZnGeO4 (A = K, Li) thin films and an analysis of their optical properties using the Cauchy model are presented. Furthermore, the increase of the thickness of the thin film results in improvements in their optoelectrical parameters, such as electrical conductivity, optical mobility, and optical conductivity. Using the Kubodera and Kobayashi comparative model, the third order nonlinear susceptibility (χ (3)) was estimated based on the compounds' high linear absorption of the generated third harmonic wavelength (355 nm). This paper presents remarkable NLO results that reveal potential uses in optoelectronics and photonics.

Influence of Magnesium Degradation on Schwannoma Cell Responses to Nerve Injury Using an In Vitro Injury Model.

Nerve guidance conduits for peripheral nerve injuries can be improved using bioactive materials such as magnesium (Mg) and its alloys, which could provide both structural and trophic support. Therefore, we investigated whether exposure to Mg and Mg-1.6wt%Li thin films (Mg/Mg-1.6Li) would alter acute Schwann cell responses to injury. Using the RT4-D6P2T Schwannoma cell line (SCs), we tested extracts from freeze-killed cells (FKC) and nerves (FKN) as in vitro injury stimulants. Both FKC and FKN induced SC release of the macrophage chemoattractant protein 1 (MCP-1), a marker of the repair SC phenotype after injury. Next, FKC-stimulated cells exposed to Mg/Mg-1.6Li reduced MCP-1 release by 30%, suggesting that these materials could have anti-inflammatory effects. Exposing FKC-treated cells to Mg/Mg-1.6Li reduced the gene expression of the nerve growth factor (NGF), glial cell line-derived neurotrophic factor (GDNF), and myelin protein zero (MPZ), but not the p75 neurotrophin receptor. In the absence of FKC, Mg/Mg-1.6Li treatment increased the expression of NGF, p75, and MPZ, which can be beneficial to nerve regeneration. Thus, the presence of Mg can differentially alter SCs, depending on the microenvironment. These results demonstrate the applicability of this in vitro nerve injury model, and that Mg has wide-ranging effects on the repair SC phenotype.

Sol–Gel Synthesis of ZnO:Li Thin Films: Impact of Annealing on Structural and Optical Properties

A sol–gel deposition approach was applied for obtaining nanostructured Li-doped ZnO thin films. ZnO:Li films were successfully spin-coated on quartz and silicon substrates. The evolution of their structural, vibrational, and optical properties with annealing temperature (300–600 °C) was studied by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), UV-VIS spectroscopic, and field emission scanning electron microscopic (FESEM) characterization techniques. It was found that lithium doping maintains the wurtzite arrangement of ZnO, with increasing crystallite sizes when increasing the annealing temperature. Analysis of the FTIR spectra revealed a broad main absorption band (around 404 cm−1) for Li-doped films, implying the inclusion of Li into the ZnO lattice. The ZnO:Li films were transparent, with slightly decreased transmittance after the use of higher annealing temperatures. The porous network of undoped ZnO films was transformed to a denser, grained, packed structure, induced by lithium doping.

Structural characterisation and degradation of Mg–Li thin films for biodegradable implants

Freestanding thin films of Mg–Li (magnesium–lithium) alloys with a Li mass fraction between 1.6% (m/m) and 9.5% (m/m) were prepared and studied with respect to their structure and degradation properties. With increasing Li content, the microstructure deviates from hexagonal Mg–Li with strict columnar growth and preferred orientation, and additional cubic Mg–Li and Li2CO3 occur. The corrosion rate was measured in Hanks’ balanced salt solution by potentiodynamic polarisation and weight loss measurements to investigate biodegradation. Influences of the orientation, phase and protective layer formation lead to an increase in corrosion from 1.6 to 5.5% (m/m) from 0.13 ± 0.03 to 0.67 ± 0.29 mm/year when measured by potentiodynamic polarisation but a similar corrosion rate for 9.5% (m/m) and 3% (m/m) of Li of 0.27 ± 0.07 mm/year and 0.26 ± 0.05 mm/year.

NON-THERMAL PLASMA EFFECT OF LI DOPED NIO THIN FILMS PREPARED BY THE SPRAY PYROLYSIS TECHNIQUE FOR SENSOR APPLICATIONS226

In, this research, pure nickel oxide NiO and Lithium-nickel oxide NiO:Li films were prepared on to glass substrates at a temperature of 450°C, by using the spray pyrolysis technique to develop the gas sensor, utilizing nickel and lithium chlorides as precursors. The effect of non-thermal plasma at (3,5,7sec) on the structural, optical, and electrical properties for NiO:Li thin films were studied. XRD pattern shows all films are polycrystalline belonging to cubic structure and the intensity was around the plane of (111).In addition, using SEM images, all samples exhibit porous with nanoparticles in the range (16-33nm ) as size. Optical measurements revealed that pure NiO and NiO:Li films have direct energy gaps (Eg) and decrease (from 3.65eV to 3.60eV), respectively. The optical energy gap was reduced after exposure to non-thermal plasma for 3,5,7 seconds (3.50, 3.45, 3.30eV) respectively. The results of Hall effect showed that the electrical conductivity of all films were of the p-type. The gas sensing performance of the prepared films towards NO2 gas was studied at various working temperatures, including (RT, 100 oC, 200 oC, and 300 oC). The current study found that pure NiO and NiO:Li films deposited can detect nitrogen dioxide gas at low work temperatures, where showed pure NiO, NiO:Li films sensitivity towards nitrogen dioxide NO2 gas at an operating temperature RT about 26.1% , 36.8% respectively. After exposure to non-thermal plasma at (3,5,7sec), the sensor NiO:Li showed an increase in sensitivity, and the best sensitivity was towards NO2 gas at room temperature for the sample exposed to non-thermal plasma at (7 sec) (49.9 percent ). The same sample showed a maximum sensitivity towards NO2 gas at 200 oC about (80.2%) with moderate response and recovery time. The influence of non-thermal plasma leads to good sensing performance for NiO:Li films, as shown in the study.

Effect of Lithium on Structural and Optical Properties of Nanostructured CuS Thin Films

In this study, the chemical bath deposition (CBD) strategy was applied for preparation of pure and Lithium-doped copper sulfide (CuS) thin film on glass. The CuCl2.2H2O, as a copper source and thiourea as a sulfur source were used. The structural, topographical, and optical properties of products were characterized via powder X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-Vis spectroscopy. Results showed that the crystalline size is increased via Lithium doping, though the strain (%) parameter decrease from 30.39 to 27.47. Obtained results revealed that doing of lithium has a significant effect on the optical properties of prepared CuS-based thin films. The optical properties of samples was investigated through band gap calculation. The bands gap were calculated 2.4, 2.5, and 2.6 eV for CuS:3% Li, CuS:1% Li and pure CuS thin films respectively. Based on attractive properties of prepared thin films, Lithium-doped CuS thin film has potential application in optoelectronic fields.

Rietveld refinement of X-ray diffraction, impedance spectroscopy and dielectric relaxation of Li-doped ZnO-sprayed thin films

In this paper, thin films of lithium-doped zinc oxide (ZnO: Li) were prepared by spray pyrolysis in a monophase hexagonal wurtzite structure as shown by X-ray analysis. Rietveld refinement of the X-ray diffraction diagram was applied to calculate the crystalline structure parameters. Impedance spectroscopy, electrical conductivity and dielectric measurements, at various temperatures 340–440 °C and in a frequency spectrum from 5 Hz to 1 MHz, were performed using the EC-Lab V10.12 system. During the electrical conduction processes in the sample, the physical parameters of ZnO:Li thin films such as dielectric constant, relaxation frequency and electrical conductivity σac and σdc, were examined. In addition, AC conductivity analysis resulted in a power law (σac = ωs). Obviously, the temperature dependence of the exponent s fitted well with the correlated barrier hopping (CBH) model proposed by Elliott. Finally, the dependence of conductivity and dielectric constants with frequency and temperature was discussed.

Study of preparation and characteristics of transition metal-doped ZnO: Li thin films deposited by magnetron co-sputtering*

The metals (Co, Cu) -doped ZnO: Li films are prepared on Si (100) by using the magnetron co-sputtering method. Using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and vibrating sample magnetometer (VSM), the structure, surface morphology and magnetic properties of the films are measured. All the samples show room temperature ferromagnetism. The saturation magnetization intensity increases from 3.67 emu/cm3 to 5.78 emu/cm3, and the coercive force increases from 70Oe to 82Oe after annealing for Co-doped ZnO: Li films. The magnetism does not significantly change before and after annealing for Cu-doped ZnO: Li films.

Preparation and characterization of p- NiO:Li thin films as schottky photodiode

Nickel oxide was prepared using the chemical method. Li-doped NiO thin films with concentrations (0.04) was deposited on glass substrate using drop casting technique with thickness 150nm, and then the annealing at 300 ° C for 60 sec. The effect of the lithium doping on the structural and optical properties of Li: NiO films were examined. The structure of the prepared films were described by x-ray diffraction (XRD) and Atomic Force Microscopy (AFM). The results of X-ray pattern showed the NiO and Li: NiO films to have a polycrystalline structure of a cubic type and preferred orientation (111). (AFM) data indicated that the structure was nanoscale and surface of the films is highly smooth. The study of optical properties included the transmittance spectrum of the prepared films of the wavelengths of (300-900) nm, It was found that the transmittance of pure nickel oxide is 79% in the visible area after doping by Li The transmittance decreases and the absorption increases. The energy gap was also calculated and found to be decreasing by increasing the doping concentration. Other important optical properties of the absorption coefficient and extinction coefficient were calculated. The electrical properties of the prepared films were studied, It was found that the concentration of the carriers increases with increasing doping concentration and mobility decreases. The thin films were deposited on a substrate of FTO to make of schottky diode. The characteristics of I-V, C-V were studied. A solar cell was found the efficiency of the cell was increased by doping.

The s-d exchange model as the underlying mechanism of magnetoresistance in ZnO doped with alkali metals

High field magnetoresistance has been studied in epitaxial n-type ZnO:Na and ZnO:Li thin films in a temperature range between 4 K and 150 K. The resulting negative magnetoresistance can be well fitted using a semiempirical model of Khosla and Fischer based on third order contributions to the s-d exchange Hamiltonian. The parameters obtained from this model were carefully analyzed. One of these parameters is related to a ratio between electron mobilities at zero field (a non-exchange scattering mobility and an exchange or spin dependent one ). From Hall effect measurements was obtained, displaying a weak temperature dependence in accordance with highly n-doped ZnO while the extracted exhibits an anomalous T-dependence. On the other hand, our magnetoresistance data cannot be properly fitted using Kawabata’s expression based on a weak-localization model.

Effects of lithium doping on: microstructure, morphology, nanomechanical properties and corrosion behaviour of ZnO thin films grown by spray pyrolysis technique

Li-doped ZnO thin films were prepared on glass substrate by a chemical spray pyrolysis method, in the temperature of 460 °C. The effects of Li content on the microstructural, morphological and mechanical characteristics of the doped (ZnO:Li) thin films were also examined. The XRD study showed a sharp preferred c-axis orientation and showed that (ZnO:Li) films have a wurtzite structure and grow principally along the c-axis orientation with a preferred orientation (002). The film morphology was examined by (AFM) and (SEM). Results of SEM observations showed that sprayed thin films, exhibited uniform and harmonious texture. Furthermore, ZnO:Li thin films revealed uniform and spherical shaped crystallites with an approximate medium size of 200 nm. AFM characterization demonstrated an amelioration of the surface roughness of the ZnO:Li thin films. The mechanical characteristics of ZnO:Li thin films have been investigated by the nano-indentation experiment. It has been found that the addition of lithium enhances the hardness and Young’s modulus. On the other hand, the corrosion behaviour of Li-doped thin films is examined in chloride solutions. The electrochemical experiments confirmed that the lithium doping could ameliorate the anti-corrosion performance.

Structural, morphological, optical and photodetector properties of sprayed Li-doped ZnO thin films

Lithium-doped zinc oxide thin films (ZnO:Li) at different percentages (0–4%) were deposited on glass substrates at 460 °C using the spray pyrolysis technique. The effect of lithium content on the structural, morphological and optical properties of ZnO:Li thin films was investigated. First, X-ray diffraction study revealed that undoped and Li-doped ZnO thin films crystallize in hexagonal wurtzite structure with a preferred orientation of the crystallites along (002) direction. The scanning electron microscopy (SEM) showed a clear hexagonal-shaped granular onto the surface of such films. Indeed, the averaged grain size, visualized by SEM, varied from 100 nm, for undoped ZnO, to 200 nm for ZnO:Li 4%. Second, the optical analysis by means of the transmittance and the reflectance measurements revealed that in UV–Vis domain, the average transmittance of the ZnO:Li thin films was 75%, while the average reflectance was <35% in the visible range. Moreover, the band gap energy, E g, decreased from 3.285 to 3.264 eV as Li content increases. On the other hand, the photoluminescence spectra revealed emission with multiple peaks and exhibited especially two emission bands in UV and visible regions. Finally, the ZnO photodetectors showed superior performance in the view of photocurrent.

Study on the electroluminescence properties of the p-NiMgO:Li/MgO/n-ZnO nanowires/ITO heterojunction

We fabricated a p-NiMgO:Li/MgO/n-ZnO NWs/ITO heterojunction device and studied its electroluminescence characteristics. Emission from n-ZnO was observed under forward biases. Significantly the random lasing was achieved. Besides, to investigate the characteristics of NiMgO:Li material, we carried out a comparative study on NiMgO:Li and NiO:Li. The p-NiMgO:Li thin films were deposited on c-sapphire substrates by radio-frequency magnetron sputtering using high-purity NiO and MgO ceramic targets. Although, the hole concentration of NiMgO:Li thin film was low compared with the NiO:Li thin film, the electronic mobility and the optical transmittance have obviously improvements.

Growth and characterization of nanocrystalline PbS:Li thin films

The structural, electrical and opto-electronic properties of PbS thin films doped with Li+ ion were investigated. The crystallite size showed a strong dependence on Li doping, the crystal size changed from 36 nm to 12 nm due to Li incorporation in PbS. Optical band gap showed a shift in the range ∼1.5–2.3 eV with Li incorporation. Urbach tailing in the band gap was observed and the Urbach energy has a dependence on the amount of incorporated Li. SEM images showed a notable change in grain size with Li doping, however the morphology changes from large grains to agglomerations of smaller grains when doped with Li. The electric conductivity of the films showed a dependence on Li doping, reached a maximum value and later decreased for higher Li containing films. The doped samples showed better photosensitivity.

Effect of annealing conditions on the structural, electrical and optical properties of Li-doped NiO thin films

Transparent conductive oxide (TCO) p-type Li-doped NiO thin films were deposited on the (0001) sapphire substrates by magnetron sputtering technique with a high purity NiO:Li2O ceramic target. We systematically investigated the structural, electrical and optical properties of NiO:Li thin films annealed in different conditions. We found that annealing in different conditions greatly affects the physical properties of NiO:Li thin films. Compared with the NiO:Li thin film annealed in oxygen, the hole concentration of NiO:Li thin film annealed in nitrogen at the same processing temperature is obviously lower. Annealed in oxygen at 500 °C, NiO:Li films show excellent crystal quality with single (111) orientation, high hole concentrations. When the annealing temperature increased, the transmittance of NiO:Li thin films become better for wavelength range from ultraviolet (UV) to visible with a significant absorption edge near 350 nm.

Hydrogen sensing by sol–gel grown NiO and NiO:Li thin films

Hydrogen sensors have been prepared using nickel oxide (NiO) and lithium-doped nickel oxide (NiO:Li) thin films, deposited on glass substrates by the sol–gel spin coating technique. The surface morphology, structure, optical and electrical properties of the obtained films were studied. Hydrogen sensing results are presented for three operating temperatures (140, 160, and 180°C) and for hydrogen concentrations ranging from 1000 to 15,000ppm in synthetic air. The NiO and NiO:Li (2% and 8% doping concentrations) sensors show maximum responses for the operating temperature of 180°C. When tested at different hydrogen concentrations in air, the lithium-doped NiO sensors showed a higher response than the undoped NiO films.

A new p-Ni1−xO : Li/n-Si heterojunction solar cell fabricated by RF magnetron sputtering

This study reports the fabrication of p-type Ni1−xO : Li/n-Si heterojunction solar cells (HJSCs) by depositing Li-doped Ni1−xO (p-Ni1−xO : Li) on a n-Si substrate (P+/n) using RF magnetron sputtering. Films deposited on glass substrates at various working pressures were first analysed to estimate the optoelectrical properties of p-Ni1−xO : Li thin films. These experimental results show that the best working pressure was 6 mTorr, which produced a surface roughness of 2.85 nm, a grain size of 19.8 nm, a resistivity of 2.7 Ω cm, a visible transmittance of 49.16%, a work function of 5.32 eV, and a refractive index of 2.54. Although the p-Ni1−xO : Li thin film has a relatively high work function, its conversion efficiency is 2.338% (Voc: 345 mV, Jsc: 22.048 mA cm−2, and FF: 0.307). This study proposes that reduce interface states and improve the optoelectrical properties of p-NiO are two important issues because they can directly and significantly affect the conversion efficiency of p-Ni1−xO : Li/n-Si HJSC. In summary, this high Voc value indicates that p-Ni1−xO : Li thin film is more suitable than ZnO/n-Si structures as an emitter layer for transparent conducting oxide/n-Si HJSC applications.

Electrical and Optical Properties of Electron Irradiated ZnO: Li Thin Films

The effects of 8 MeV electron irradiation (with variable fluence) on the electrical and optical properties of Lithium doped Zinc oxide thin films prepared by sol-gel synthesis are reported. There is a decrease in crystallinity and crystallite size with increase in fluence, as confirmed by XRD and SEM. We observe a decrease in transmittance, band gap and refractive index, while there is an increase in the extension coefficient with the fluence. I-V measurements have shown a decrease in leakage current and interestingly, the metal-semiconductor-metal (M-S-M) device shows only the ohmic behavior after irradiation.

Enhancement of electron emission and long-term stability of tip-type carbon nanotube field emitters via lithium coating

Carbon nanotubes (CNTs) were deposited on conical tip-type substrates via electrophoresis and coated with lithium (Li) thin films with diverse thicknesses via electroplating. For the as-deposited (i.e., without Li coating) CNT, the turn-on (or triggering) electric field was 0.92V/μm, and the emission current, which was generated at an applied field of 1.2V/μm was 56μA. In the case of the 4.7nm-thick Li-coated CNT, the turn-on field decreased to 0.65V/μm and the emission current at the same applied field increased more than ten times to 618μA. The analysis based on the Kelvin probe measurement and Fowler–Nordheim theory indicated that the coating of Li caused a loss in the structural-aspect-ratio of the CNTs and it reduced their effective work functions from 5.36eV to 4.90eV, which led to a great improvement of their electron emission characteristics. The results obtained in this study also showed that the long-term emission stability could be enhanced by the coating of thin Li films on CNTs.

Absorption spectra of ZnO:Li thin films in the region of a phase transition

We have studied the temperature variation of the intrinsic absorption edge for ZnO:Li films obtained by high-frequency magnetron sputtering. We have observed anomalous behavior of the optical bandgap width in the vicinity of the temperature of a ferroelectric phase transition at T = 327 K. For the first time, we have observed the appearance of this phase transition on the thermally stimulated depolarization (TSD) current curves.