Structural and Electrical Properties of Single Crystalline Ga-Doped ZnO Thin Films Grown by Molecular Beam Epitaxy

High-quality Ga-doped ZnO （ZnO：Ga） single crystalline films with various Ga concentrations are grown on a- plane sapphire substrates using molecular-beam epitaxy. The site configuration of doped Ga atoms is studied by means of x-ray absorption spectroscopy. It is found that nearly all Ga can substitute into ZnO lattice as electrically active donors, a generating high density of free carriers with about one electron per Ga dopant when the Ga concentration is no more than 2%. However, further increasing the Ga doping concentration leads to a decrease of the conductivity due to partial segregation of Ga atoms to the minor phase of the spinel ZnGa2O4 or other intermediate phase. It seems that the maximum solubility of Ga in the ZnO single crystalline film is about 2at.% and the lowest resistivity can reach 1.92 ×10-4Ω·cm at room temperature, close to the best value reported. In contrast to ZnO：Ga thin film with 1% or 2% Ga doping, the film with 4% Ga doping exhibits a metal semiconductor transition at 80 K. The scattering mechanism of conducting electrons in single crystalline ZnO：Ga thin film is discussed.

Structure,ferroelectric,and enhanced fatigue properties of sol–gel-processed new Bi-based perovskite thin films of Bi(Cu_(1/2)Ti_(1/2))O_(3)–PbTiO_(3)

Bi-based perovskite ferroelectric thin films have wide applications in electronic devices due to their excellent ferroelectric properties.New Bi-based perovskite thin films Bi(Cu_(1/2)Ti_(1/2))O_(3)–PbTiO_(3)(BCT–PT) are deposited on Pt(111)/Ti/SiO_(2)/Si substrates in the present study by the traditional sol–gel method.Their structures and related ferroelectric and fatigue characteristics are studied in-depth.The BCT–PT thin films exhibit good crystallization within the phase-pure perovskite structure,besides,they have a predominant(100) orientation together with a dense and homogeneous microstructure.The remnant polarization(2P_(r)) values at 30 μC/cm^(2) and 16 μC/cm^(2) are observed in 0.1BCT–0.9PT and 0.2BCT–0.8PT thin films,respectively.More intriguingly,although the polarization values are not so high,0.2BCT–0.8PT thin films show outstanding polarization fatigue properties,with a high switchable polarization of 93.6% of the starting values after 10^(8) cycles,indicating promising applications in ferroelectric memories.

Numerical Analysis for High⁃Throughput Elastic Modulus Measurement of Substrate⁃Supported Thin Films

Micro/nano-thin films are widely used in the fields of micro/nano-electromechanical system(MEMS/NEMS)and flexible electronics,and their mechanical properties have an important impact on the stability and reliability of components.However,accurate characterization of the mechanical properties of thin films still faces challenges due to the complexity of film-substrate structure,and the characterization efficiency of traditional techniques is insufficient.In this paper,a high-throughput determination method of the elastic modulus of thin films is proposed based on the strain variance method,the feasibility of which is analyzed by the finite element method(FEM),and the specific tensile configuration with array-distributed thin films is designed and optimized.Based on the strain difference between the film-substrate region and the uncoated region,the elastic modulus of multiple films is obtained simultaneously,and the influences of film width,spacing,thickness,and distribution on the measurement of elastic modulus are elucidated.The results show that the change in film width has a more obvious effect on the elastic modulus determination than film spacing and thickness,i.e.,the larger the film width is,the closer the calculation results are to the theoretical value,and the change in calculation results tends to be stabilized when the film width increases to a certain length.Specifically,the simultaneous measurement of the elastic modulus of eight metal films on a polyimide(PI)substrate with a length of 110 mm and a width of 30 mm can be realized,and the testing throughput can be further increased with the extension of the substrate length.This study provides an efficient and low-cost method for measuring the elastic modulus of thin films,which is expected to accelerate the development of new thin film materials.

Tuning of Optical Properties via Annealing of Bismuth Ferrite (BiFeO3) Thin Films

In this study we are reporting annealing induced optical properties of bismuth ferrite (BiFeO3) thin films deposited on glass substrate via spin coating at 5000 rpm. The structural, optical and surface morphology of BiFeO3 (BFO) thin films have been studied via X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Optical absorption (UV-Vis) and Photoluminescence (PL) spectroscopy. XRD spectra confirm annealing induced phase formation of BiFeO3 possessing a rhombohedral R3c structure. The films are dense and without cracks, although the presence of porosity in BFO/glass was observed. Moreover, optical absorption spectra indicate annealing induced effect on the energy band structure in comparison to pristine BiFeO3. It is observed that annealing effect shows an intense shift in the UV-Vis spectra as diffuse absorption together with the variation in the optical band gap. The evaluated optical band gap values are approximately equal to the bulk band gap value of BiFeO3.

Temperature-mediated structural evolution of vapor–phase deposited cyclosiloxane polymer thin films for enhanced mechanical properties and thermal conductivity

Polymer-derived ceramic(PDC) thin films are promising wear-resistant coatings for protecting metals and carbon-carbon composites from corrosion and oxidation.However,the high pyrolysis temperature hinders the applications on substrate materials with low melting points.We report a new synthesis route for PDC coatings using initiated chemical vapor deposited poly(1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane)(pV_3D_3) as the precurs or.We investigated the changes in siloxane moieties and the network topology,and proposed a three-stage mechanism for the thermal annealing process.The rise of the connectivity number for the structures obtained at increased annealing temperatures was found with strong correlation to the enhanced mechanical properties and thermal conductivity.Our PDC films obtained via annealing at 850℃ exhibit at least 14.6% higher hardness than prior reports for PDCs synthesized below 1100℃.Furthermore,thermal conductivity up to 1.02 W(mK)^(-1) was achieved at the annealing temperature as low as 700℃,which is on the same order of magnitude as PDCs obtained above 1100℃.Using minimum thermal conductivity models,we found that the thermal transport is dominated by diffusons in the films below the percolation of rigidity,while ultra-short mean-free path phonons contribute to the thermal conductivity of the films above the percolation threshold.The findings of this work provide new insights for the development of wear-resistant and thermally conductive PDC thin films for durable protection coatings.

Investigation of UV photosensor properties of Al-doped SnO_(2) thin films deposited by sol-gel dip-coating method

Transparent conducting aluminum doped tin oxide thin films were prepared by sol-gel dip coating method with differ-ent Al concentrations and characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Vis spectrophotometry and photoconductivity study. The variation observed in the properties of the measured films agrees with a difference in the film's thickness, which decreases when Al concentration augments. X-ray diffraction analysis reveals that all films are polycrystal-line with tetragonal structure, (110) plane being the strongest diffraction peak. The crystallite size calculated by the Debye Scher-rer’s formula decreases from 11.92 to 8.54 nm when Al concentration increases from 0 to 5 wt.%. AFM images showed grains uni-formly distributed in the deposited films. An average transmittance greater than 80% was measured for the films and an en-ergy gap value of about 3.9 eV was deduced from the optical analysis. Finally, the photosensitivity properties like current-voltage characteristics, ION/IOFF ratio, growth and decay time are studied and reported. Also, we have calculated the trap depth energy using the decay portion of the rise and decay curve photocurrent.

Metal-Halide Perovskite Submicrometer-Thick Films for Ultra-Stable Self-Powered Direct X-Ray Detectors

Metal-halide perovskites are revolutionizing the world of X-ray detectors,due to the development of sensitive,fast,and cost-effective devices.Self-powered operation,ensuring portability and low power consumption,has also been recently demonstrated in both bulk materials and thin films.However,the signal stability and repeatability under continuous X-ray exposure has only been tested up to a few hours,often reporting degradation of the detection performance.Here it is shown that self-powered direct X-ray detectors,fabricated starting from a FAPbBr_(3)submicrometer-thick film deposition onto a mesoporous TiO_(2)scaffold,can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss,demonstrating ultra-high operational stability and excellent repeatability.No structural modification is observed after irradiation with a total ionizing dose of almost 200 Gy,revealing an unexpectedly high radiation hardness for a metal-halide perovskite thin film.In addition,trap-assisted photoconductive gain enabled the device to achieve a record bulk sensitivity of 7.28 C Gy^(−1)cm^(−3)at 0 V,an unprecedented value in the field of thin-film-based photoconductors and photodiodes for“hard”X-rays.Finally,prototypal validation under the X-ray beam produced by a medical linear accelerator for cancer treatment is also introduced.

Generation of lossy mode resonances(LMR)using perovskite nanofilms

The results presented here show for the first time the experimental demonstration of the fabrication of lossy mode resonance(LMR) devices based on perovskite coatings deposited on planar waveguides. Perovskite thin films have been obtained by means of the spin coating technique and their presence was confirmed by ellipsometry, scanning electron microscopy, and X-ray diffraction testing. The LMRs can be generated in a wide wavelength range and the experimental results agree with the theoretical simulations. Overall, this study highlights the potential of perovskite thin films for the development of novel LMR-based devices that can be used for environmental monitoring, industrial sensing, and gas detection, among other applications.

Investigation of Sprayed Lu2O3 Thin Films Using XPS

Spray pyrolysis method was used to deposit Lutetium Oxide (Lu2O3) thin films using lutetium (III) chloride as source material and water as oxidizer. Annealing was carried out in argon atmosphere at 450°C for 60 minutes of the films. To investigate the composition and stoichiometry of sprayed as-deposited and annealed Lu2O3 thin films, depth profile studies using X-ray photoelectron spectroscopy (XPS) was done. Nearly stoichiometric was observed for both annealed and as-deposited films in inner and surface layers.

XPS Depth Profile Study of Sprayed Ga2O3 Thin Films

Ga2O3 thin films were fabricated by spray pyrolysis method using gallium acetylacetonate as source material and water as oxidizer. The films were annealed at 450°C for 60 minutes in argon atmosphere. X-ray photoelectron spectroscopy (XPS) depth profile studies were carried out to analyze the stoichiometry and composition of sprayed as-deposited and annealed Ga2O3 thin films. Surface layers and the inner layers of as-deposited and annealed films were found nearly stoichiometric.

Electrical and nonlinear optical properties of TGZO transparent conducting films deposited by magnetron sputtering

Thin transparent oxide conducting films(TCOFs)of titanium and gallium substituted zinc oxide(TGZO)were fabricated via radio frequency(RF)magnetron sputtering technique.The effects of RF power on electrical,linear and nonlinear optical characteristics were investigated by Hall tester,Ultraviolet(UV)-visible spectrophotometer and optical characterization method.The results indicate that RF power significantly influences the electrical and optical properties of the deposited films.As RF power raises,the resistivity and Urbach energy fall initially and then rise,while the figure of merit,mean visible transmittance and optical bandgap show the reverse variation trend.At RF power of 190 W,the TGZO sample exhibits the highest electro-optical properties,with the maximum figure of merit(1.14×10^(4)Ω^(-1)∙cm^(-1)),mean visible transmittance(86.9%)and optical bandgap(3.50 eV),the minimum resistivity(6.26×10^(-4)Ω∙cm)and Urbach energy(174.23 meV).In addition,the optical constants of the deposited films were determined by the optical spectrum fitting method,and the RF power dependence of nonlinear optical properties was studied.It is observed that all the thin films exhibit normal dispersion characteristics in the visible region,and the nonlinear optical parameters are greatly affected by the RF power in the ultraviolet region.

Effect of boron/phosphorus-containing additives on electrodeposited CoNiFe soft magnetic thin films

CoNiFe,CoNiFeB and CoNiFeP soft magnetic thin films were prepared by cyclic voltammetry method.The morphologies,composition and structures were characterized by scanning electron microscope（SEM）,energy-dispersive X-ray spectroscope（EDS） and X-ray diffractometer（XRD）.The soft magnetic properties were investigated through vibrating sample magnetometer（VSM）.The corrosion resistance was investigated through Tafel polarization and electrochemical impedance spectroscopic（EIS）.The results show that all the electrodeposited CoNiFe,CoNiFeB and CoNiFeP films are mixtures of crystalline and amorphous phases,and high amount of boron/phosphorus-containing additives favors the formation of amorphous state.Nanostructure is obtained in CoNiFe and CoNiFeB films.The inclusion of boron causes the film more dense and also increases its corrosion resistance.Meanwhile,the inclusion of boron lowers its coercivity（Hc） from 851.48 A/m to 604.79 A/m,but the saturation magnetic flux density（Bs） is almost unchanged.However,the addition of phosphorus greatly increases the film particle size and decreases its corrosion stability.The coercivity（Hc） of CoNiFeP film is also highly increased to 12485.79 A/m,and its saturation magnetic flux density（Bs） is greatly decreased to 1.25 T.

Microstructure evolution of copper doped beryllium thin films

Copper （Cu） doped beryllium （Be） thin films were deposited on silicon substrates by using a simple ion beam sputtering method, which can also realize the varying of Cu doping concentration. Detailed morphological and structural characterizations of the samples clearly disclose a microstructure evolution of films upon doping Cu. Doping Cu can effectively suppress film grain growth, causing a small grain size as well as uniform size distribution. Furthermore, doping Cu affects the crystallographic texture of film, which leads to the formation of more compact film structure. In particular, the surface smoothness of the doped films is significantly improved, which makes them promising candidates for various applications.

Fabrication of Hydrogenated Microcrystalline Silicon Thin Films at Low Temperature by VHF-PECVD

Using H 2 diluted silane,series of μc Si∶H films are fabricated at low temperature with VHF PECVD.The thickness measurements reveal that the deposition rates are obviously enhanced with higher plasma excitation frequency or working pressure,but increase firstly and then decrease with the increase of plasma power density.Raman spectra show that the crystallinity and the average grain sizes of the films strongly depend on the temperature of substrate and the concentration of silane.However,the plasma excitation frequency only has effect on the crystallinity,and a maximum occurs during the further increase of plasma excitation frequency.From XRD and TEM experiments,three preferential crystalline orientations (111),(220) and (311) are observed,and the average grain sizes are different for every crystalline orientation.

Plasma Treatment Enhanced Magnetic Properties in Manganese Doped Titanium Nitride Thin Films

The ferromagnetic manganese doped TiN films were grown by plasma assisted molecular beam epitaxy on MgO（001） substrates. The nitrogen concentration and the ratio of manganese at Ti lattice sites increase after the plasma annealing post treatment. TIN（002） peak shifts toward low angle direction and TiN（111） peak disappears after the post treatment. The lattice expansion and peak shift are mainly ascribed to the reduction of nitrogen vacancies in films. The magnetism was suppressed in as-prepared sample due to the pinning effect of the nitrogen vacancies at defect sites or interface. The magnetism can be activated by the plasma implantation along with nitrogen vacancies reduce. The decrease of nitrogen vacancies leads to the enhancement of ferromagnetism.

Accuracy analysis of plane-strain bulge test for determining mechanical properties of thin films

The effect of a variety of geometrics, initial conditions and material properties on the deformation behavior of thin films in the plane-strain bulge test was systematically scrutinized by performing the finite element analysis, and then the accuracy of the plane-strain bulge test in determining the mechanical properties of thin films in terms of our finite element results was analyzed. The results indicate that although the determination of the plane-strain modulus in the light of the plane-strain bulge equation is fairly accurate, the calculation of the residual stress is not satisfied as expected, especially for low residual stress. Finally, an approach is proposed for analyzing bulge test data, which will improve the accuracy and reliability of this bulge test technique.

Influence of pyrolysis temperature on ferroelectric properties of La and Mn co-doped BiFeO_3 thin films

Bi0.9La0.1Fe0.95Mn0.05O3 （BLFMO） ferroelectric thin films were fabricated on Pt/Ti/SiO2/Si/ substrates by the sol-gel process at different pyrolysis temperatures. The mass loss of BLFMO powder was investigated by thermo gravimetry analyser （TGA）, and the polycrystalline structure and smooth surface of BLFMO thin films were characterized by X-ray diffraction （XRD） and atomic force microscopy （AFM）, respectively. The remnant polarization （Pr） of the BLFMO films pyrolyzed at 420 ℃ is 21.2 μC/cm2 at the coercive field （Ec） of 99 kV/cm and the leakage current density is 7.1×10-3 A/cm2, which indicates that the BLFMO thin films display relatively good ferroelectric property at this temperature.

Effect of annealing treatment on the structural, optical, and electrical properties of Al-doped ZnO thin films

Highly conductive and transparent Al-doped ZnO （AZO） thin films were prepared from a zinc target containing Al （1.5 wt.%） by direct current （DC） and radio frequency （RF） reactive magnetron sputtering. The structural, optical, and electrical properties of AZO films as-deposited and submitted to annealing treatment （at 300 and 400℃, respectively） were characterized using various techniques. The experimental results show that the properties of AZO thin films can be further improved by annealing treatment. The crystallinity of ZnO films improves after annealing treatment. The transmittances of the AZO thin films prepared by DC and RF reactive magnetron sputtering are up to 80% and 85% in the visible region, respectively. The electrical resistivity of AZO thin films prepared by DC reactive magnetron sputtering can be as low as 8.06 x 10-4 Ωcm after annealing treatment. It was also found that AZO thin films prepared by RF reactive magnetron sputtering have better structural and optical properties than that prepared by DC reactive magnetron sputtering.

MICROWAVE PERMEABILITY SPECTRA OF SPUTTERED Fe-Co-B SOFT MAGNETIC THIN FILMS

Permeability characteristics of sputtered soft magnetic Fe40Co40B20 thin films are investigated in the range of O. 5 to 5 GHz by a shortened microstrip transmission line perturbation method. Excellent microwave permeability is achieved at 0.4 Pa argon pressure： fr is 3.32 GHz, the real and imaginary part of permeability at 0.5 GHz are 104 and 61, respectively. In addition, the thickness effect on permeability is also studied. The minimum damping can be achieved at the thinnest film. Different sources contributed to in-plane anisotropy are discussed briefly. The deviation between the peak frequency of the imaginary part and the zero-crossing frequency of the real part of permeability is also presented.

Influence of oxygen gas content on the structural and optical properties of ZnO thin films deposited by RF magnetron sputtering at room temperature

Zinc oxide （ZnO） thin films were deposited on sapphire （0001） substrates at room temperature by radiofrequency （RF） magnetron sputtering at oxygen gas contents of 0%, 25%, 50% and 75%, respectively. The influence of oxygen gas content on the structural and optical properties of ZnO thin films was studied by a surface profile measuring system, X-ray diffraction analysis, atomic force microscopy, and UV spectro- photometry. It is found that the size of ZnO crystalline grains increases first and then decreases with the increase of oxygen gas content, and the maximum grain size locates at the 25% oxygen gas content. The crystalline quality and average optical transmittance （〉90%） in the visi- ble-light region of the ZnO film prepared at an oxygen gas content of 25% are better than those of ZnO films at the other contents. The obtained results can be attributed to the resputtefing by energetic oxygen anions in the growing process.