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Structure and optical of polycrystalline NiO films fabricated by reactive sputtering and its resistive switching properties in Au/NiO/Pt structures are investigated. The size of surface uniform pyramid-like islands and average surface roughness increase with the increase of NiO film thickness ( t ). The NiO films grow with the preferred (111) orientation at 400 °C, but both (100) and (110)-oriented grains exist in the films fabricated at room temperature. Raman results reveal that the crystallinity of the films fabricated at 400 °C becomes good by comparing with that at room temperature. The optical band gap monotonically decreases from 4.44 eV at t =22 nm to 3.55 eV at t =800 nm. The resistance of the Au/NiO/Pt/Ti/glass structures could be switched between two stable states including low and high resistance states. The bipolar endurance performance of the resistive switching remains nondegradable after 200 cycles. The resistive switching can be ascribed to the carrier trapping and detrapping induced by the electric field, which can change the thickness of the depletion layer at Au/NiO interface. [ABSTRACT FROM AUTHOR]

Highlights: [•] The average surface roughness changes with oxygen partial pressure (P O). [•] The films are composed of Co0, Co2+, Ti3+, Ti4+ and O2− ions, and small Co grains appear. [•] The saturation magnetization decreases with the increase of P O. [•] Magnetoresistance saturates at 10kOe, and satisfies a relation of log MR= C log T. [Copyright &y& Elsevier]

Highlights: [•] The preferred lattice orientation changes from (200) to (111) with the increase of x. [•] The surface morphology evolves from spherical to triangular-pyramid-like islands as x increases. [•] Weak grain-boundary ferromagnetism with a Curie temperature of higher than 305K appears. [•] The films show semiconducting-like behavior with a mechanism of thermal fluctuation-induced tunneling. [Copyright &y& Elsevier]

Highlights: [•] Non-uniform amorphous Fe x Ti1−x O δ films are semiconducting. [•] Below 50K, resistivity satisfies the variable-range hopping conductance. [•] Magnetoresistance (MR) largely increases with decreasing temperature below 50K. [•] Large low-temperature MR is related to the antiferromagnetic disordered moments. [ABSTRACT FROM AUTHOR]

Abstract: The surface morphology, structure and electrical transport properties of the polycrystalline TiN films fabricated using reactive sputtering at different N2 partial pressures (P N2) have been investigated systematically. The films grow with the preferred (200) orientation. The room-temperature resistivity first deceases, then slightly increases with the increase of P N2. The minimum room-temperature resistivity is about 1.7 × 10−3 Ω cm at P N2 = 0.5 Pa. The low temperature conductance mechanism turns from tunneling across the grain boundaries to variable-range hopping as P N2 increases. The decreased density of states at EF with the increase of N vacancies should be the reason for the increased resistivity of the films fabricated at different P N2. [Copyright &y& Elsevier]

Abstract: Polycrystalline Ti1−x Fe x N films with different Fe atomic fractions (x) were fabricated by reactive facing-target sputtering. The lattice orientation changes from (200) to (111) with the increase of x, which makes the surface morphology evolve from spherical, triangular-pyramid-like islands to random-leafs-like ones. The films are ferromagnetic with a Curie temperature of higher than 305K, and the saturation magnetization (M s ) is very small. Obvious asymmetric M–H curves are observed at low temperatures, and the shift of M–H curves decreases with the increasing temperature because of the relaxation of the pinned moments at low temperatures. All of the samples show semiconducting-like behavior with a mechanism of variable-range hopping at low-temperature range. Magnetoresistance (MR) is very small. The small M s and MR can be explained by the facts that the interaction between Fe3+–N3−–Fe3+ is antiferromagnetic superexchange coupling, and no double exchange exists in Fe3+–N3−–Ti3+, which is different from that in the Cr-doped TiN films. [Copyright &y& Elsevier]

Abstract: Microstructure, magnetic and optical properties of polycrystalline Fe-doped ZnO films fabricated by cosputtering with different Fe atomic fractions (x Fe) have been examined systematically. Fe addition could affect the growth of ZnO grains and surface morphology of the films. As x Fe is larger than 7.0%, ZnFe2O4 grains appear in the films. All the films are ferromagnetic. The ferromagnetism comes from the ferromagnetic interaction activated by defects between the Fe ions that replace Zn ions. The average moment per Fe ion reaches a maximum value of 1.61μB at x Fe =4.8%. With further increase in x Fe, the average moment per Fe ion decreases because the antiferromagnetic energy is lower than the ferromagnetic one due to the reduced distance between the adjacent Fe ions. The optical band gap value decreases from 3.245 to 3.010eV as x Fe increases from 0% to 10%. Photoluminescence spectra analyses indicate that many defects that affect the optical and magnetic properties exist in the films. [Copyright &y& Elsevier]

Abstract: Polycrystalline ZnO films were fabricated using rf magnetron sputtering under different oxygen flow rates (P O). The surface morphology of the films can be affected by changing P O, and the average surface roughness decreases with the increasing P O. The increasing P O can improve the grain growth with (002) orientation. Typical ZnO infrared vibration bands have been observed at 408 and 513cm−1, and the full width at half maximum of the infrared peak decreases with the increase of P O due to the improved crystallinity. The optical band gap (E g) of the polycrystalline ZnO films increases from 3.22eV at P O =0sccm to 3.25eV at P O =10sccm because the defects decrease with the increasing P O. The photoluminescence peaks in the region of 2.4–2.7eV are from the transition between conduction band edge and oxide antisite defects (OZn), and also be influenced by oxygen vacancies (VO). [Copyright &y& Elsevier]

Abstract: N atoms were incorporated into sp2-rich a-C networks using DC facing-target reactive sputtering at various N2 fraction () and their structure and opto-electrical properties were investigated systematically. As increases, the fraction of CN bonded carbons (or the N content) increases primarily at the expense of the CC bonded carbons and then reaches its saturated value at >40%. The incorporated N preferentially forms different kinds of non-aromatic CN phase, leading to more localization of π electrons and the loss of the connectivity of nanographite fragments in the films, which is different from the case in N-doped sp3-rich a-CN x films. Hence, with increasing , the a-C(:N) film converts from a semiconductor with a narrower optical band gap to an insulator-like material with a wider gap. Additionally, the variation of optical constants (n and k) and spin defects are related to the enhancement of the non-aromatic CN phase. [Copyright &y& Elsevier]

Abstract: N-incorporated ZnO films were fabricated using rf magnetron sputtering under different nitrogen flow rates (P N). The surface roughness and ZnO grain size are dependent on P N. Meanwhile, Zn nitride appears in the films as P N increases. N incorporation affects the intensity of the diffraction peaks from the different lattice planes. At P N =20%, the film grows with ZnO (002) lattice. The incorporated N exists in the forms of Zn nitride and atomic N. The optical band gap (E g) of the N-incorporated ZnO films decreases from 3.17 to 2.95eV linearly with the increase of P N. The photoluminescence peaks in the region of 2.4–2.7eV come from the transition between conduction band edge and oxide antisite defects (OZn), and also be influenced by oxygen vacancies (Vo). [Copyright &y& Elsevier]

Abstract: ZnO films were prepared using radio frequency magnetron sputtering on Si(111) substrates that were sputter-etched for different times ranging from 10 to 30min. As the sputter-etching time of the substrate increases, both the size of ZnO grains and the root-mean-square (RMS) roughness decrease while the thickness of the ZnO films shows no obvious change. Meanwhile, the crystallinity and c-axis orientation are improved by increasing the sputter-etching time of the substrate. The major peaks at 99 and 438cm−1 are observed in Raman spectra of all prepared films and are identified as E2(low) and E2(high) modes, respectively. The Raman peak at 583cm−1 appears only in the films whose substrates were sputter-etched for 20min and is assigned to E1(LO) mode. Typical ZnO infrared vibration peak located at 410cm−1 is found in all FTIR spectra and is attributed to E1(TO) phonon mode. The shoulder at about 382cm−1 appearing in the films whose substrates were sputter-etched for shorter time (10–20min) originates from A1(TO) phonon mode. The results of photoluminescence (PL) spectra reveal that the optical band gap (Eg) of the ZnO films increases from 3.10eV to 3.23eV with the increase of the sputter-etching time of the substrate. [Copyright &y& Elsevier]