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ZnO thin film has been fabricated on sapphire substrate (0001) using RF magnetron sputtering at room temperature. The influence of sputtering power ranging from 10 W to 70 W on the microstructural and optical properties of ZnO films is investigated by atomic force microscopy (AFM), X-ray diffraction (XRD), ultraviolet-visible spectrophotometer. The AFM results show that with the increase of sputtering power, the size of ZnO crystalline increases first, then decrease and the maximum grain size occurs at 50 W. The XRD measurements indicate that the ZnO films with wurtzite structure are highly c-axis orientation and the film fabricated at 50 W has the best crystalline quality. Optical transmission spectra of the ZnO samples demonstrate that the ZnO film obtained at 50 W has the higher average transmission (above 90%) in the visible-light region and its optical band gap is 3.26 eV.

A time-dependent mean-field Landau-type model is established based on the dipole energies in epitaxial film in order to investigate thickness dependence of the remanent polarization. It is found that the deviations of the mean-field Landau-type theoretical prediction from the experimental data for size effect can be eliminated in SrRuO 3 /BaTiO 3 /SrRuO 3 capacitor.

Landau-type phenomenological theory is extended to the polycrystalline ferroelectrics by defining a volume fraction of polarization to simulate polarization hysteresis loops. Using this simple model, polarization hysteresis loops of a model Pb(Zr 0.52 Ti 0.48 )O 3 ceramic at different fields or temperatures are simulated, it is found that our results are in very good agreement with the experimental data for the saturated as well as the unsaturated loops. Moreover, this model can accurately predict the coercive fields and remnant polarizations under arbitrary applied fields.

In the present paper, the lattice structure, band structure and density of state of LaAlO3 and LaAlO3:Mg are calculated by first-principle method based on density functional theory. Firstly, we select the different cutoff energy and k-point grid in the calculations, and obtain the most stable geometry structure of single crystal LaAlO3. The calculated lattice parameters are a=b=5.441 Å, c=13.266 Å, which matches with experimental values. To deeply understand the electronic structure of LaAlO3, a 2×1×1 super-cell structure is established and the doping concentration of Mg at Al sites is 25%. From the band structure and density of states, it can be seen that LaAlO3 has a direct band gap Eg=3.6 eV. However, LaAlO3:Mg has a larger band gap Eg=3.89 eV and the Fermi level enters into the valence band, which indicates the holes are introduced. The calculated results show that the conductivity of LaAlO3:Mg is better than pure LaAlO3, which is in good agreement with experimental results.

In the present paper, the lattice structure, band structure and density of state of pure and P-doped ZnO are calculated by first-principle method based on density functional theory. By analyzing the Mulliken charge overlap population and bond length, it is found that the bond of P-Zn is longer and stronger than O-Zn bond for PO-ZnO. But for PZn-ZnO, the O-P bond becomes shorter and more powerful than O-Zn bond. Also, weak O-O bonds are formed in this case. Our results show that the final total energy of PO-ZnO is lower than PZn-ZnO. The lattice structure of PO-ZnO is more stability than PZn-ZnO. For PO-ZnO, The Fermi level moves into the valence band, which expresses that the holes appear on the top of valence band and thus the PO-ZnO exhibits p-type conductivity. For PZn-ZnO, the Fermi level moves up to the conductor band and the total density of states shifts to the lower energy region, thus PZn-ZnO shows the n-type conductivity.

Density functional theory plane-wave pseudopotential with the general gradient approximation (GGA) was used to investigate electronic structural properties and the bulk spontaneous polarization (Ps) of PbZr0.4Ti0.6O3. It is found that there are strong hybridizations between Ti 3d states or Zr 4d states and O 2p states, which can reduce short-range repulsion in atoms and enhance the stability of the ferroelectric phase of PbZr0.4Ti0.6O3. Compared with cubic ideal structure, the calculated internal electronic structural data indicate that the slightly distorted O6 octahedrons around the central Ti and Zr atoms change to the Ti-O5 and Zr-O5 pyramid in the optimized structure, respectively. The major contribution to the spontaneous polarization along [001] comes from the stronger interaction along the c axis between the Ti and O rather than the Zr and O ions. The Pb atom’s relative displacement of oxygen octahedral implies that the Pb-O bonding interaction is also a key factor impacting the ferroelectricity of PbZr0.4Ti0.6O3. A theoretical spontaneous polarization of 0.78 C/m2 was computed in the tetragonal PbZr0.4Ti0.6O3 along [001] direction, consistent with the single crystal experimental data.

We have investigated systematically the oxygen pressure dependences of the crystalline phases and the crystallographic orientations of BaTiO3 thin films by means of asymmetric rocking curves. Epitaxial BaTiO3 thin films were grown on SrTiO3 (001) substrates by pulsed laser deposition (PLD) under different oxygen pressures. The X-ray diffraction theta/2 theta scans showed no diffraction peaks from impurity phases or randomly oriented grains, indicating that the thin films were single phase BaTiO3. The XRD omega rocking curves indicated that the BaTiO3 thin films had a very high degree of crystallinity. The XRD phi scans showed that no in-plane misorientation existed in the BaTiO3 thin films. The results of asymmetric rocking curves showed that the BaTiO3 thin films grown under higher oxygen pressures(> 12 Pa) were tetragonal with a-axis orientation, those grown under lower oxygen pressures (

The plasma emission spectra generated during the deposition process of Si-based thin films by radio frequency (RF) magnetron sputtering using Cu and Al targets in an argon atmosphere were acquired by the plasma analysis system, which consists of a magnetron sputtering apparatus, an Omni-lambda300 series grating spectrometer, a CCD data acquisition system and an optical fiber transmission system. The variation in Cu and Al plasma emission spectra intensity depending on sputtering conditions, such as sputtering time, sputtering power, the target-to-substrate distance and deposition pressure, was studied by using the analysis lines Cu I 324. 754 nm, Cu I 327. 396 nm, Cu I 333. 784 nm, Cu I 353. 039 nm, Al I 394. 403 nm and Al I 396. 153 nm. Compared with the option of experimental parameters of thin films deposited by RF magnetron sputtering, it was shown that emission spectra analysis methods play a guiding role in optimizing the deposition conditions of thin films in RF magnetron sputtering.

Epitaxial BiFe 0.95 Mn 0.05 O 3 (BFMO) film was deposited on (001)-oriented SrRuO 3 (SRO) coated SrTiO 3 (STO) substrate by radio-frequency (rf) magnetron sputtering. Indium tin oxide (ITO) was grown on BFMO/STO heterojunction to fabricate ITO/BFMO/SRO capacitor for investigating the ferroelectric and photovoltaic properties. The ITO/BFMO/SRO capacitor exhibits large remanent polarizations of 92.2 μC/cm2, 101 μC/cm2 and 109 μC/cm2 measured at 20 V, 25 V and 30 V, respectively. An observed abnormal capacitance–voltage (C–V) curve can be explained based on the ITO/BFMO interface. The calculated capacitance and junction width of ITO/BFMO interface are 105 pF and 32 nm, respectively. Additionally, it is found that photovoltaic effect of the ITO/BFMO/SRO capacitor is mainly attributed to ferroelectric polarization and internal electric field induced by defects. The photocurrent densities coming from ferroelectric polarization and internal field are 36 μA/cm2 and 23 μA/cm2, respectively. The photovoltaic output from the ferroelectric polarization is obviously larger than that from the internal electric field.

The adsorption and dissociation of oxygen molecule on Ti3Al (0001) surface have been investigated by density functional theory (DFT) with the generalized gradient approximation (GGA). All possible adsorption sites including nine vertical and fifteen parallel sites of O2 are considered on Ti3Al (0001) surface. It is found that all oxygen molecules dissociate except for three vertical adsorption sites after structure optimization. This indicates that oxygen molecules prefer to dissociate on the junction site between Ti and Al atoms. Oxygen atoms coming from dissociation of oxygen molecule tend to occupy the most stable adsorption sites of the Ti3Al (0001) surface. The distance of O–O is related to the surface dissociation distance of Ti3Al (0001) surface. The valence electron localization function (ELF) and projected density of states (DOS) show that the bonds of O–O are breakaway at parallel adsorption end structures.

Ta (3.3 nm)/ Ni – Al (3.3 nm) integrated films deposited on Si substrates by magnetron sputtering, annealed at various temperatures in a ultra-high vacuum, have been studied as diffusion barrier layers between Cu and Si for application in Cu interconnection. The images of transmission electron microscopy (TEM) prove that the cross-sectional interfaces of Cu / Ta / Ni – Al / Si sample annealed at 600°C are clear and sharp. No Cu –silicide peaks can be found from the X-ray diffraction (XRD) patterns of the 850°C annealed sample, but the sheet resistance of the sample increases abruptly. Moreover, large grooves are found from the image of atomic force microscopy (AFM) for the 850°C annealed sample, implying the failure of the diffusion barrier. The integrated Ta / Ni – Al barrier layer retains thermally stable nature up to at least 800°C, indicating that the Ta / Ni – Al integrated film is an excellent diffusion barrier between Cu and Si .

Polycrystalline Bi 0.975 La 0.025 Fe 0.975 Ni 0.025 O 3 (BLFNO) film is fabricated on Pt / Ti / SiO 2/ Si (111) substrate by sol–gel method. It is found that the well-crystallized BLFNO film is polycrystalline, and the Pt / BLFNO / Pt capacitor possesses good ferroelectric properties with remnant polarization of 74 μC/cm2 at electric field of 833 kV/cm. Moreover, it is also found that the leakage current density of the Pt / BLFNO / Pt capacitor increases with the increase of measurement temperature ranging from 100 to 300 K. The leakage density of the Pt / BLFNO / Pt capacitor satisfies space-charge-limited conduction (SCLC) at higher electric field and shows little dependence on voltage polarity and temperature, but shows polarity and temperature dependence at lower applied electric field. With temperature increasing from 100 to 300 K at lower applied electric field, the most likely conduction mechanism is from Ohmic behavior to SCLC for positive biases, but no clear dominant mechanism for negative biases is shown.

Polycrystalline Bi0.975La0.025Fe0.975Ni0.025O3 (BLFNO) film is fabricated on Pt/Ti/SiO2/Si(111) substrate by sol–gel method. It is found that the well-crystallized BLFNO film is polycrystalline, and the Pt/BLFNO/Pt capacitor possesses good ferroelectric properties with remnant polarization of 74 μC/cm2 at electric field of 833 kV/cm. Moreover, it is also found that the leakage current density of the Pt/BLFNO/Pt capacitor increases with the increase of measurement temperature ranging from 100 to 300 K. The leakage density of the Pt/BLFNO/Pt capacitor satisfies space-charge-limited conduction (SCLC) at higher electric field and shows little dependence on voltage polarity and temperature, but shows polarity and temperature dependence at lower applied electric field. With temperature increasing from 100 to 300 K at lower applied electric field, the most likely conduction mechanism is from Ohmic behavior to SCLC for positive biases, but no clear dominant mechanism for negative biases is shown.