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The microstructure and chemical bonding states of pure and Ce-doped BiFe[O.sub.3] (BFO) films are characterized by scanning electron microscope (SEM) and Raman spectrum. The enhanced magnetic properties for the [Bi.sub.1-x][Ce.sub.x]Fe[O.sub.3] (BCFO) films are attributed to the presence of [Fe.sup.2+] caused by oxygen vacancies, the suppressed spiral spin structure, and/or the increase canting angle induced by Ce doping.

First-principles methods are used for studying the mechanism of defect formation and electronic structures for 3d transition-metal impurities doped in silicon nanowires. The results have shown that the defect formation energies of Mn and Fe impurities are lower than those of V, Cr, and Co impurities in silicon nanowires.

Sol-gel-derived ([Ba.sub.0.65], [Sr.sub.0.35])Ti[O.sub.3] (BST) films are etched in C[F.sub.4]/Ar and C[F.sub.4]/Ar/[O.sub.2] plasmas by using magnetically enhanced reaction ion etching technology (MERIE) technology. The results have indicated that there are no significant differences between the unetched BST film and the postannealed after etched film with respect to the fitted formulas and average valences of Ti cations.

Abstract  Bi1−x Ce x FeO3 (x = 0, 0.05, 0.1, 0.15 and 0.20) (BCFO) thin films were deposited on Pt/TiN/Si3N4/Si substrates by sol–gel technique. Crystal structures, surface chemical compositions and bonding states of BCFO films were investigated by X-ray diffraction and X-ray photoelectron spectroscopy (XPS), respectively. Compared to BiFeO3 (BFO) counterparts, the fitted XPS narrow-scan spectra of Bi 4f7/2, Bi 4f5/2, Fe 2p3/2, Fe 2p1/2 and O 1s peaks for Bi0.8Ce0.2FeO3 film shift towards higher binding energy regions by amounts of 0.33, 0.29, 0.43, 0.58 and 0.49 eV, respectively. Dielectric constants and loss tangents of the BCFO (x = 0, 0.1 and 0.2) film capacitors are 159, 131, 116, 0.048, 0.041 and 0.035 at 1 MHz, respectively. Bi0.8Ce0.2FeO3 film has a higher remnant polarization (P r = 2.04 μC/cm2) than that of the BFO (P r = 1.08 μC/cm2) at 388 kV/cm. Leakage current density of the Bi0.8Ce0.2FeO3 capacitor is 1.47 × 10−4 A/cm2 at 388 kV/cm, which is about two orders of magnitude lower than that of the BFO counterpart. Furthermore, Ce cations are feasibly substituted for Bi3+ in the Bi0.8Ce0.2FeO3 matrix, possibly resulting in the enhanced ferroelectric properties for the decreased grain sizes and the reduced oxygen vacancies. [ABSTRACT FROM AUTHOR]

The sequential resonant tunneling in La0.5Sr0.5CoO3-δ (LSCO) semiconductor quantum dots (QDs) arrays were observed by current-voltage measurements under room temperature. A series of spikelike current peaks are found, which are resulted from the accumulation and depletion of electrons tunneling through the QDs embedded in insulated barriers. Temperature dependent onset-voltage blueshift and number variation in current peaks are also observed. These results confirm the size-induced metal-to-semiconductor transition in LSCO. [ABSTRACT FROM AUTHOR]

Bi1-xCexFeO3 (x=0, 0.05, 0.1, 0.15, and 0.20) (BCFO) thin films were deposited on Pt/TiN/Si3N4/Si and fluorine-doped SnO2 glass substrates by sol-gel technique, respectively. The effect of Ce doping on the microstructure, electrical and magnetic properties of BCFO films was studied. Compared to counterparts of BiFeO3 (BFO) film, the fitted Bi 4f7/2, Bi 4f5/2, Fe 2p3/2, Fe 2p1/2, and O 1s peaks for Bi0.8Ce0.2FeO3 film shift toward higher binding energy regions by amounts of 0.33, 0.29, 0.43, 0.58, and 0.49 eV, respectively. Raman redshifts of 2–4 cm-1 and shorter phonon lifetimes for the Bi0.8Ce0.2FeO3 film might be related to anharmonic interactions among Bi–O, Ce–O, (Bi, Ce)–O, and Fe–O bonds in the distorted oxygen octahedron. Compared to the pure counterparts, the dielectric and ferroelectric properties of the Bi0.8Ce0.2FeO3 film are improved due to the decreased oxygen vacancies by the stabilized oxygen octahedron. Current density values for the BFO and Bi0.8Ce0.2FeO3 film capacitors are 9.89×10-4 and 5.86×10-5 A/cm2 at 10 V, respectively. The current density–applied voltage characteristics indicate that the main conduction mechanism for the BCFO capacitors is the interface-controlled Schottky emission. Both the in-plane and out-of-plane magnetization–magnetic field hysteresis loops reveal that the saturation magnetization values of the BCFO films increase with increasing the Ce concentration. The enhanced magnetic properties for the BCFO films might be attributed to the presence of Fe2+ caused by oxygen vacancies, the suppressed spiral spin structure, and/or the increased canting angle induced by Ce doping. [ABSTRACT FROM AUTHOR]

Sol-gel-derived (Ba0.65,Sr0.35)TiO3 (BST) thin films were etched in CF4/Ar and CF4/Ar/O2 plasmas using magnetically enhanced reactive ion etching technology. Experimental results show that adding appropriate O2 to CF4/Ar can better the etching effects of BST films for the increase of etching rate and decrease of etched residues. The maximum etching rate is 8.47 nm/min when CF4/Ar/O2 gas-mixing ratio is equal to 9/36/5. X-ray photoelectron spectroscopy (XPS) data confirm accumulation of reaction products on the etched surface due to low volatility of reaction products such as Ba and Sr fluorides, and these residues could be removed by annealing treatment. The exact peak positions and chemical shifts of the interested elements were deduced by fitting XPS narrow-scan spectra with symmetrical Gaussian-Lorentzian product function for Ba 3d, Sr 3d, and O 1s peaks, meanwhile asymmetrical Gaussian-Lorentzian sum function was used to fit Ti 2p doublet to adjust the multiple splitting and/or shake-up process of transition-metal Ti cations. Compared to the unetched counterparts, the etched Ba 3d5/2, Ba 3d3/2, Sr 3d5/2, Sr 3d3/2, Ti 2p3/2, Ti 2p1/2, and O 1s peaks shift towards higher binding energy regions by amounts of 1.31, 1.30, 0.60, 0.79, 0.09, 0.46, and 0.50 eV, respectively. While the etched Ti 2p3/2 and Ti 2p1/2 peaks have small chemical shifts for two reasons. One is that Ti fluoride (TiFz) is mostly removed from the etched surface because of its higher volatility in the process of thermal desorption. The other is that there is a shift compensation between TiFz and the etched BST matrix in which Ti4+ cations are partially reduced to form Tix+ (00.65,Sr0.35)Ti0.97O2.86, (Ba0.70,Sr0.30)Ti0.24O1.39, and (Ba0.68,Sr0.32)Ti0.95O2.74, and then the average valence of Ti cations is estimated to be +3.84, +3.25, and +3.66 with respect to the electroneutrality principle, respectively. It is inferred that electrical properties of the etched BST film may be partially recovered by postannealed after etched. [ABSTRACT FROM AUTHOR]

Double‐side‐fixed triboelectric nanogenerator (DTENG) arrays, compared to single‐side‐fixed triboelectric nanogenerator arrays for harvesting single‐pathway wind energy, are developed by Zhong Lin Wang and co‐workers in article number 1501799, to harvest bidirectional wind energy. Short‐circuit current, durability, and stability of the optimized DTENG can be dramatically improved by a 4 × 1 array connected in parallel because of the improved device configuration, stickiness, and abrasion by adhering Ti buffer layers. [ABSTRACT FROM AUTHOR]

Wind-driven triboelectric nanogenerators (TENGs) play an important role in harvesting energy from ambient environments. Compared to single-side-fixed triboelectric nanogenerator (STENG) arrays for harvesting single-pathway wind energy, double-side-fixed triboelectric nanogenerator (DTENG) arrays are developed to harvest bidirectional wind energy. Electrical performances of the STENG and DTENG can be improved due to sticky, abrasive, and electrical properties of the Ti buffer layers among Al, polytetrafluoroethylene (PTFE), and polyimide (Kapton), configuring in triboelectric PTFE/Ti/Al and Al/Ti/Kapton/Ti/Al thin films. Short-circuit current ( ISC), open-circuit voltage ( VOC), and frequencies of the STENG and DTENG increase with increasing wind velocity ranging from 9.2 to 18.4 m s21, revealing that the moderate ISC, VOC, frequencies, and output powers of the STENG and DTENG reach 67 μA, 57 μA, 334 V, 296 V, 173 Hz, 162 Hz, 5.5 mW and 3.4 mW with a matched load of 4 MΩ at airflow rate of 15.9 m s21, respectively. Compared with counterparts of the single-pathway-harvested STENG arrays, the ISC, durability, and stability of the bidirectional-harvested DTENG can be dramatically improved by a 4 3 1 array connected in parallel because of the improved device configuration, stickiness, and abrasion by adhering Ti buffer layers. The durable DTENG arrays present a step toward practical applications in harvesting bidirectional wind energy for self-powered systems and wireless sensors. [ABSTRACT FROM AUTHOR]

The 12% Cerium (Ce) and 10% Manganese (Mn) were doped at A and B sites respectively in BiFeO3(BFO) thin films along with incorporation of 5% excess Bi. Pure and undoped BFO thin film capacitors are fabricated on indium tin oxide (ITO) coated corning glass and silicon substrate by chemical solution deposition (CSD) method. Film becomes preferred oriented along (110) directionswith introduction of Mn and Ce in the host BFO lattice. Leakage current density is reduced by about 4 orders from (4.59 × 10−3A/cm2) to about 2.91 × 10−7A/cm2at 100 KV/cm field after 12% Ce doping in BFO (BCFO) thin film. Enhanced ferroelectric response with saturatedP-Eloop is observed for BCFO thin film in compare to that obtained for 10% Mn doped BFO (BFMO) thin film. Improved capacitance-voltage characteristics with good butterfly loop is obtained for Bi0.88Ce0.12FeO3thin film, indicating an increased degree of ferroelectricity. However, enhanced M-H loop with well saturation magnetization (Ms ∼ 19.65 emu/g) is observed for BFMO thin films while wasp waist loops (pinched) are observed for BCFO thin films with slightly degraded ferromagnetic properties. [ABSTRACT FROM AUTHOR]