Structural and magnetic properties of micropolycrystalline cobalt thin films fabricated by direct current magnetron sputtering

Pure cobalt(Co)thin films were fabricated by direct current magnetron sputtering,and the effects of sputtering power and pres-sure on the microstructure and electromagnetic properties of the films were investigated.As the sputtering power increases from 15 to 60 W,the Co thin films transition from an amorphous to a polycrystalline state,accompanied by an increase in the intercrystal pore width.Simultaneously,the resistivity decreases from 276 to 99μΩ·cm,coercivity increases from 162 to 293 Oe,and in-plane magnetic aniso-tropy disappears.As the sputtering pressure decreases from 1.6 to 0.2 Pa,grain size significantly increases,resistivity significantly de-creases,and the coercivity significantly increases(from 67 to 280 Oe),which can be attributed to the increase in defect width.Corres-pondingly,a quantitative model for the coercivity of Co thin films was formulated.The polycrystalline films sputtered under pressures of 0.2 and 0.4 Pa exhibit significant in-plane magnetic anisotropy,which is primarily attributable to increased microstress.

Energy Stabilities, Magnetic Properties, and Electronic Structures of Diluted Magnetic Semiconductor Zn1-xMnxS（001） Thin Films

We investigate the electronic and magnetic properties of the diluted magnetic semiconductors Zn1-xMnxS（001） thin films with different Mn doping concentrations using the total energy density functional theory. The energy stability and density of states of a single Mn atom and two Mn atoms at various doped configurations and different magnetic coupling state were calculated. Different doping configurations have different degrees of p-d hybridization, and because Mn atoms are located in different crystal-field environment, the 3d projected densities of states peak splitting of different Mn doping configurations are quite different. In the two Mn atoms doped, the calculated ground states of three kinds of stable configurations are anti-ferromagnetic state. We analyzed the 3d density of states diagram of three kinds of energy stability configurations with the two Mn atoms in different magnetic coupling state. When the two Mn atoms are ferromagnetic coupling, due to d-d electron interactions, density of states of anti-bonding state have significant broadening peaks. As the concentration of Mn atoms increases, there is a tendency for Mn atoms to form nearest neighbors and cluster around S. For such these configurations, the antiferromagnetic coupling between Mn atoms is energetically more favorable.

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.

First-principles study and electronic structures of Mn-doped ultrathin ZnO nanofilms

The first-principles density functional calculation is used to investigate the electronic structures and magnetic properties of Mn-doped and N-co-doped ZnO nanofilms.The band structure calculation shows that the band gaps of ZnO films with 2,4,and 6 layers are larger than the band gap of the bulk with wurtzite structure and decrease with the increase of film thickness.However,the four-layer ZnO nanofilms exhibit ferromagnetic phases for Mn concentrations less than 24% and 12% for Mn-doping performed in the whole layers and two layers of the film respectively,while they exhibit spin glass phases for higher Mn concentrations.It is also found,on the one hand,that the spin glass phase turns into the ferromagnetic one,with the substitution of nitrogen atoms for oxygen atoms,for nitrogen concentrations higher than 16% and 5% for Mn-doping performed in the whole layers and two layers of the film respectively.On the other hand,the spin-glass state is more stable for ZnO bulk containing 5% of Mn impurities,while the ferromagnetic phase is stable by introducing the p-type carriers into the bulk system.Moreover,it is shown that using the effective field theory for ferromagnetic system,the Curie temperature is close to the room temperature for the undamped Ruderman-Kittel-Kasuya-Yoshida（RKKY） interaction.

Magnetic property and recording performance of chemical deposition CoP thin films

The thickness of CoP thin films prepared by wet chemical deposition is of crucial importance on magnetic property and recording perform-ance. The coercivity of CoP films decreased with increasing film thickness. The coercivity was 45.37 kA m 1 at the thickness of 300 nm, and decreased to 21.65 kA m 1 at 5.7 μm. Recording performance tests indicate that, for drums with the same size, different recorded magnetic pole density have different thickness requirements. For 40 mm diameter magnetic drum, the optimal CoP thickness is 3～10 μm for 256 re-corded magnetic poles, 1～2 μm for 512 recorded magnetic poles, and 500～800 nm for 1024 recorded magnetic poles.

Structures and optical properties of tungsten oxide thin films deposited by magnetron sputtering of WO_3 bulk:Effects of annealing temperatures

Tungsten oxide thin films were deposited on glass substrates by the magnetron sputtering of WO3 bulk at room temperature. The deposited films were annealed at different temperatures in air. The structural measurements indicate that the films annealed below 300℃ were amorphous, while the films annealed at 400 ℃ were mixed crystalline with hexagonal and triclinic phases of WO3. It was observed that the crystallization of the annealed films becomes more and more distinct with an increase in the annealing temperature. At 400 ℃, nanorod-like structures were observed on the film surface when the annealing time was increased from 60 min to 180 min. The presence of W=O stretching, W-O-W stretching, W-O-W bending and various lattice vibration modes were observed in Raman measurements. The optical absorption behaviors of the films in the range of 450-800 nm are very different with changing annealing temperatures from the room temperature to 400 ℃. After annealing at 400 ℃, the film becomes almost transparent. Increasing annealing time at 400 ℃ can lead to a small blue shift of the optical gap of the film.

Structural and electrical properties of SrTiO3 thin films as insulator of metal-ferroelectric-insulator-semiconductor （MFIS） structures

SrTiOs （STO） thin films were deposited on p-Si（100） substrates at various substrate temperatures from 300℃ to 700℃ by radio frequency （RF） magnetron sputtering technique. Their structure and electrical properties were investigated. It was found that the transition from amorphous phase to polycrystalline phase occurred at the substrate temperatures 300-400℃. Their crystallinity became better when the substrate temperatures further increased. The dielectric and leakage current measurements were carried out by using the Si/STO/Pt metal-insulator-semiconductor （MIS） structures at room temperature. It was found that the fixed charge density decreased and both the interface trap density and the dielectric constant increased when the substrate temperatures were increased. The leakage current mechanisms for STO MIS structures with STO films prepared at 700℃ followed the space charge limited current （SCLC） under the low applied electric field and the Poole-Frenkel emission under the high one. In addition, the resistivity for films prepared at 700℃ was higher than 10^11Ω.cm under the voltage lower than 10V （corresponding to the electric field of 1.54×10^3kV.cm^-1）. It suggested that the STO films prepared at 700℃ were suitable for acting as the insulator of metal-ferroelectric-insulator-semiconductor （MFIS） structures.

Microstructures and Optical Properties of Sol-gel Derived Ba_(0.9)Sr_(0.1)TiO_3 Thin Films Formed by Different Annealing Process

We investigated the effect of annealing process on microstructures and optical properties of the sol-gel derived Ba0.9Sr0.1TiO3 （BST） films. The BST films, fabricated by layer-by-layer high-temperature （≥ 650 ℃） annealing process, had laminated structures consisting of alternating dense and porous BST layers, and exhibited excellent optical performance as Bragg reflectors. The Bragg reflection characteristic can be enhanced with increasing annealing temperature. Those BST films fabricated at temperatures lower than 650 ℃ displayed uniform cross-sectional morphologies even treated at a higher temperature. The difference in the microstructures of the BST thin films was also discussed.

Structural and optoelectronic properties of AZO thin films prepared by RF magnetron sputtering at room temperature

Al-doped ZnO thin films were prepared on glass substrate using an ultra-high density target by RF magnetron sputtering at room temperature. The microstructure, surface morphology, optical and electrical properties of AZO thin films were investigated by X-ray diffractometer, scanning electron microscope, UV-visible spectrophotometer, four-point probe method, and Hall-effect measurement system. The results showed that all the films obtained were polycrystalline with a hexagonal structure and average optical transmittance of AZO thin films was over 85 % at different sputtering powers. The sputtering power had a great effect on optoelectronic properties of the AZO thin films, especially on the resistivity. The lowest resistivity of 4.5×10^-4 Ω·cm combined with the transmittance of 87.1% was obtained at sputtering power of 200 W. The optical band gap varied between 3.48 and 3.68 eV.

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.

Influence of Substrate Temperature and Nitrogen Gas on Zinc Nitride Thin Films Prepared by RF Reactive Sputtering

Zinc nitride （Zn3N2） thin films were prepared by radio frequency （RF） magnetron sputtering on quartz glass at different substrate temperatures.The structure and composition were characterized by X-ray diffraction and Raman-scattering measurements,respectively.The polycrystalline phase Zn3N2 films appeared when the ratio of the N2 partial pressure to the total pressure reached 1/2.The effects of the substrate temperature on the electrical and optical properties of the Zn3N2 films were investigated by Hall measurements and optical transmission spectra.The electrical and optical properties of the films were highly dependent on the substrate temperature.With the substrate temperature increasing from 100 to 300℃,the resistivity of the Zn3N2 films decreased from 0.49 to 0.023Ω·cm,the carrier concentration increased from 2.7×10^16 to 8.2×10^19cm^-3,and the electron mobility decreased from 115 to 32cm^2/（V·s）.The deposited Zn3N2 films were considered to be n-type semiconductors with a direct optical band gap,which was around 1.23eV when the substrate temperature was 200℃.

Effect of crystallization temperature on microstructure and ferroelectric property of Bi_(3.25)Eu_(0.75)Ti_3O_(12) thin films prepared by MOD method

Europium-substituted bismuth titanate (Bi3.25Eu0.75Ti3O12) thin films were deposited on the Pt/Ti/SiO2/Si(111) substrates by metal-organic decomposition (MOD) method using a repeated coating/drying cycle. Effect of crystallization temperature on microstructure of Bi3.25Eu0.75Ti3O12(BET) thin films was investigated by X-ray diffractometry(XRD), scanning electron microscopy (SEM) and Raman spectroscopy, and ferroelectric property was studied by Precision Workstation Ferroelectric Tester. The crystallinity of BET thin films is improved and the average grain size increases with the crystallization temperature from 600 to 750 ℃. Under 9 V applied voltage, the remnant polarization (2Pr) of BET thin films annealed at 700 ℃ is 50.7 μm/cm2, which is higher than that of the films annealed at 600, 650 and 750℃.

Effect of annealing process on structures and ferroelectric properties of Ca_(0.4)Sr_(0.6)Bi_(3.95)Nd_(0.05)Ti_4O_(15) thin films

Ca0.4Sr0.6Bi3.95Nd0.05Ti4O15 （C0.4S0.6BNT） ferroelectric thin films were prepared on Pt/Ti/SiO2/Si substrates by sol-gel method. Effect of annealing process （time and temperature） on structures and ferroelectric properties of C0.4S0.6BNT thin film was investigated. The relative intensity of （200） peak increased first then decreased with annealing temperature and became predominant at 800 ℃. In contrast, no evident change could be observed in the （001） peak. The remnant polarization （Pr） and coercive field （Ec） for C0.4S0.6BNT film annealed at 800℃ for 5 min were 21.6μC/cm2 and 68.3 kV/cm, respectively.

SHORT-RANGE ORDER STRUCTURES OF Fe-Ge AMORPHOUS THIN FILMS

The short-range order structures of Fe_xGe_(1-x) amorphous thin films,(x=8.7,19.1 and 28.5%)have been studied by means of X-ray absorption spectrum.The nearest neighbors around a Ge or an Fe atom are constituted by two coordinate sub-shells with a very short dis- tance,In two films with lower Fe content,structural parameters of the nearest neighbors around a Ge atom are very near to that in amorphous germanium,and the positions of Fe at- oms are randomly substitutional.But when x=28.5%,some great changes occur on the short-range order structure of a-Fe_xGe_(1-x) film:its structure deviates from continuous ran- dora network and tends toward dense random packing of atoms.Meanwhile,there is a strong- er interaction between near neighboring Fe-Ge atoms in a-Fe_xGe_(1-x) films.

Effects of HfO_2 buffer layers on the dielectric property and leakage current of Ba_(0.6)Sr_(0.4)TiO_3 thin films by pulsed laser deposition

Ba0.6Sr0.4TiO3 （BST） thin films with and without HfO 2 buffer layer were fabricated on Pt/Ti/SiO2/Si substrates by pulsed laser deposition. Dependences of HfO 2 thickness on the dielectric property and leakage current of BST thin films were focused. The dielectric constant of BST thin films increased and then decreased with the increase of HfO 2 thickness, while the dielectric relaxation was gradually improved. The loss tangent and leakage current under positive bias decreased with the HfO 2 thickness increasing. The leakage current analysis based on the Schottky emission indicated an improvement of the BST/Pt interface with HfO 2 buffer layer. The loss tangent, tunability and figure of merit of optimized HfO 2 buffered BST thin film achieved 0.009 8, 21.91% （E max = 200 kV/cm）, 22.40 at 10 6 Hz, respectively.

Effects of PBr₃Addition to Polysilane Thin Films on Structures and Photovoltaic Properties

Organic thin film solar cells are potential next generation solar cells. Many p-type semiconductors have been used in organic solar cells, but there have been far fewer reports involving n-type organic semiconductors. Developing new n-type organic semiconductors is therefore desirable. Polysilane thin films were spin-coated from solutions containing phosphorus (P), and the effects of P addition on film microstructures and electronic properties as n-type semiconductors were investigated. Microstructures of poly-methyl-phenyl-silane (PMPS), dimethyl-polysilane (DMPS) and deca-phenyl-penta-silane (DPPS) thin films were investigated by X-ray diffraction and transmission electron microscopy. PMPS thin films doped with P (PMPS(P)) were amorphous upon annealing at 300&#176C, while DMPS(P) and DPPS(P) thin films exhibited crystalline structures. PMPS(P) and DMPS(P) thin films exhibited decreased electrical resistances upon P doping. The energy gaps of PMPS(P), DMPS(P) and DPPS(P) were 3.5, 3.9 and 3.8 eV, respectively. Decreased photoluminescence intensities of PMPS, DMPS and DPPS were observed upon P doping. The desorption of phenyl and methyl groups from PMPS(P) thin films was observed from Raman scattering measurements. Solar cells containing polysilane(P)/poly[3-hexylthiophene] heterojunction structures were fabricated and exhibited photovoltaic behavior.

Effect of substrate temperature on microstructures and dielectric properties of compositionally graded BST thin films

Compositionally graded Ba1-xSrxTiO3 (BST) (x = 0-0.3) thin films were prepared on Pt/Ti/SiO2/Si substrate at different substrate temperatures ranging from 550 ℃ to 650 ℃ by radio-frequency (rf) magnetron sputtering. The effect of substrate temperature on the preferential orientation, microstructures and dielectric properties of compositionally graded BST thin films was investigated by X-ray diffraction, scanning electron microscopy and dielectric frequency spectra, respectively. As the temperature increases, the preferential orientation evolves in the order: randomly orientation→ (111) → highly oriented (111) (α(111) = 60.2%). The surface roughness of the graded BST thin films varies with the substrate temperatures. No visible internal interface in the compositionally graded thin films can be observed in the cross-sectional SEM images. The graded BST thin films deposited at 650 ℃ possess the highest dielectric constant and dielectric loss, which are 408 and 0.013, respectively.

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.

Effects of Atomic Oxygen Irradiation on Transparent Conductive Oxide Thin Films

Transparent conductive oxide （TCO） thin film is a kind of functional material which has potential applications in solar cells and atomic oxygen （AO） resisting systems in spacecrafts. Of TCO, ZnO：Al （ZAO） and In2O3：Sn （ITO） thin films have been widely used and investigated. In this study, ZAO and ITO thin films were irradiated by AO with different amounts of fluence. The as-deposited samples and irradiated ones were characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and Hall-effect measurement to investigate the dependence of the structure, morphology and electrical properties of ZAO or ITO on the amount of fluence of AO irradiation. It is noticed that AO has erosion effects on the surface of ZAO without evident influences upon its structure and conductive properties. Moreover, as the amount of AO fluence rises, the carrier concentration of ITO decreases causing the resistivity to increase by at most 21.7%.

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.