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In this paper, the optical properties of ZnO (0001) and ZnO (000–1) films were systematically studied. ZnO polar films were deposited on sapphire substrates by Molecular beam epitaxy (MBE). The morphology, structure and optical properties of the ZnO polar films were measured by atomic force microscopy (AFM), X-ray diffraction (XRD), photoluminescence spectra (PL), absorption spectra and spectroscopic ellipsometry (SE), and the results show that the bandgap obtained by SE was consistent with that obtained by absorption spectrum. Moreover, compared with ZnO (000–1) films, the optical bandgap appears red shift on ZnO (0001) films, which may be caused by impurity states near the bottom of the ZnO conduction band. • Comparison of optical properties of Zn polar and O polar film. • Very consistent optical bandgap results are obtained by two means. • Red shift appears in optical band gap of Zn polar films compared with O polar films. [ABSTRACT FROM AUTHOR]

Amorphous films of MoOx have both structural disorder and also chemical disorder for x<3. We have shown that this disorder can introduce localised states in thin films and have shown that the existence of localised states can be deduced from the XPS data that identifies the relevant occupations of different ionisation states of the Mo ions. This effect, which depends on both the oxygen concentration and the method of fabrication, is more important than electron-electron interactions in producing the observed localisation. We have also shown that magneto-optical dichroism is also a powerful technique to determine the energy distribution of localised and delocalised states. [ABSTRACT FROM AUTHOR]

Different concentrations of arsenic ions have been introduced into high quality O polar ZnO films prepared by rf-plasma assisted molecular beam epitaxy on sapphire substrates by ion implantation. Rutherford Backscattering/Channeling, x-ray diffraction, Raman spectroscopy and optical absorption measurements have been carried out to characterize the implantation induced disorder in the ZnO films. Room temperature ferromagnetism has been observed for the films implanted with As dose higher than 6×10 18 cm −3 . The size of the observed moment is too large to be attributed to the As related defect complex (As Zn -2V Zn ) and is attributed to defects introduced by the ion implantation process. This was confirmed by the observation that the magnetization could be removed by annealing the films. [ABSTRACT FROM AUTHOR]

Optical emission spectra of the plasma produced by 1.06-µm Nd:YAG laser irradiation of a potassium titanyl phosphate (KTP) crystal were recorded and analyzed in a time- and spatially resolved manner. The composition and evolution of the plasma plume were studied in low vacuum conditions. Emission lines associated with Ti(I), Ti(II) and K(I) were identified in the plasma. The delay times of emission peaks for the ablated species were investigated as a function of the observation distance from the target surface, and the velocities of these species were derived accordingly. Two emission peaks corresponding to a fast and a slow component of ablated Ti(I) were observed by optical time-of-flight spectroscopy. The origins of the two peaks and a possible mechanism for the laser ablation are discussed. [ABSTRACT FROM AUTHOR]

It is found that ZnO has half-metallic properties by using Mn atoms instead of Zn atoms in ZnO. [Display omitted] • ZnO films on the sapphire substrate were prepared by molecular beam epitaxy. • Mn ions and As ions were injected into ZnO films by ion implantation. • The absorption edges of the films were blue-shifted as the ion concentration increased. • The half-metallic properties of Mn ion implanted ZnO thin films were verified by first principles calculations. • Refractive index and extinction coefficient of ZnO films were explored by spectroscopic ellipsometry. In this work, we use ion implantation to implant Mn ions and As ions into the ZnO films prepared by molecular beam epitaxy. The surface morphology and crystalline structure of ZnO thin films are investigated by X-ray diffraction, atomic force microscopy and Raman spectroscopy. First-principles calculations discover the half-metallic property of the ZnO films implanted with Mn ions. The effects of Mn ions and As ions implantation on the absorption edges, refractive index (n), extinction coefficient (k) and dielectric constant of ZnO films are studied by transmission spectra, absorption spectroscopy and spectroscopic ellipsometric technique. From the spectroscopic ellipsometry (SE), the n and k of the films have increased after ion implantation. Due to the half-metallic properties of the Mn-implanted ZnO film, the variation trend of the peaks of n and k with wavelength is much gentler than the peak of unimplanted ZnO film. The dielectric constant measured by SE and the results of photoluminescence spectra reveal that the electron transition of ZnO films is weakened by Mn ions implantation. The results provide a new direction for the design and optimization of optoelectronic devices based on ZnO thin films with semi-metallic properties. [ABSTRACT FROM AUTHOR]

• O-polar ZnO films on the sapphire substrate were prepared by molecular beam epitaxy. • Co ions and Sm ions were injected into O-polar ZnO films by ion implantation. • The structure, optical and dielectric properties of the films were studied. • The band gap of the co-implanted film was the smallest after ion implantation. • Dielectric constants of ZnO films were explored by spectroscopic ellipsometry. In this paper, molecular beam epitaxy (MBE) was used to prepare O-polar ZnO films on the sapphire substrate. Co ions and Sm ions were respectively injected into the O-polar ZnO films by ion implantation, so that Co-implanted O-polar ZnO film, Sm-implanted O-polar ZnO film, and (Co and Sm) co-implanted O-polar ZnO film were prepared. We adopted X-ray diffraction (XRD), Atomic Force Microscope (AFM), Raman spectroscopy, photoluminescence spectra (PL), absorption spectroscopy and Spectroscopic Ellipsometry (SE) to study the structure, optical and dielectric properties of all samples. XRD showed that Co atoms and Sm atoms had entered the crystal lattice and the high-quality ZnO films had been prepared. Compared with the unimplanted sample, the surfaces of the implanted samples were granular and the roughness became larger. The co-implanted sample had the smaller roughness than the single-implanted samples. It was found from Raman spectra that two modes related to the LO vibration mode appeared near 50–230 cm−1 and 520–570 cm−1 after implantation. The PL spectra indicated that the intensity of the Sm-implanted sample was greater than the (Co and Sm) co-implanted sample. After ion implantation, the results measured by SE showed the band gap values of the (Co and Sm) co-implanted sample was reduced, and a transition peak around 3.15 eV appears in the second-order derivative spectra of the imaginary part ε 2 of the dielectric function. These paved the way for their application and development in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Optical emission spectra of the plasma produced by 1.06 μm Nd:YAG laser ablation of SnO2:Sb transparent conducting thin film were recorded and analyzed as functions of distance from the target surface and incident laser power density in air and in vacuum. Ambient gas effects on pulsed laser ablation of target were analyzed in detail. We also discussed how the air takes part in the plasma evolution process and confirmed that the ignition of the air plasma is by the collisions between the energetic electrons and the nitrogen atoms through a cascade avalanche process. [Copyright &y& Elsevier]

Optical emission spectra of Nd:YAG laser ablation of KTiOPO4 (KTP) crystal and SnO2:Sb transparent conducting thin film were recorded and analyzed in vacuum and in air. The integral intensities of spectral lines from laser-ablated KTP crystal were obtained as functions of distance from the target surface and laser power density in vacuum and in air. The ambient gas effects on pulsed laser ablation of target were discussed. We also performed laser ablation of SnO2:Sb transparent conducting thin film in air and the electron temperature and full-width at half-maximum (FWHM) of atomic and ionic spectral lines in the plasma were quantified using Boltzmann plot method and Lorentzian fit, respectively. Integral intensities of atomic and ionic Sn spectral lines were also obtained as functions of distance from the target surface and laser irradiance. The intensity ratio of ionic and atomic Sn spectral lines as a function of laser power density was got which gives some information about the variation of ionization ratio with laser irradiance in the plasma produced by high-power laser. [Copyright &y& Elsevier]

The energy levels in AlGaAs/GaAs multiple quantum well (MQW) were calculated with transfer matrix method (TMM) and compared with experimental results from photoluminescence (PL) measurements. The comparison shows good agreement. A thin layer of sputtered SiO2 film was deposited on AlGaAs/GaAs MQW samples and a subsequent rapid thermal annealing (RTA) was carried out. Photoluminescence (PL) measurements showed that the PL characteristics of the wells at different depths beneath the surface of the AlGaAs/GaAs MQW behave differently with the change of RTA condition. The PL intensities of the wells close to the surface and the bottom of the AlGaAs/GaAs MQW are sensitive to the RTA condition, while those of the wells in the middle of the MQW show little variations with the change of RTA condition. [Copyright &y& Elsevier]

Optical emission spectra of the plasma produced by 1.06 μm Nd:YAG laser irradiation of a potassium titanium phosphate (KTP) crystal in vacuum and in air were recorded and analyzed in a spatially resolved manner. Electron temperatures and densities in the plasma in vacuum were determined with the Boltzmann plot method using five Ti(II) emission lines and the Stark-broadened linewidths of neutral K atoms, respectively. The dependence of the electron densities and temperatures on distance from the target surface and on laser irradiance were manifested. In order to see the effect of backing gas, we also performed laser ablation of a KTP crystal in air and compared the results with that of the ablation in vacuum. Gas dynamical parameters of the laser-induced KTP evaporation wave were simulated using a hydrocode developed in our group based on the self-similar solutions of the gas dynamical equations. Moreover, the velocity of the evaporating wave and the vapor pressure were calculated under different laser power densities. [Copyright &y& Elsevier]

A thin layer of sputtered SiO2 film was deposited on AlGaAs/AlGaInAs multiple quantum well (MQW) samples and a subsequent rapid thermal annealing (RTA) was carried out. Photoluminescence (PL) studies showed a 60 meV band-gap shift for the AlGaAs/AlGaInAs MQW. An interdiffusion length of 10.7 A˚ corresponding to the above band-gap shift in the MQW was obtained using transfer matrix method (TMM). An apparent diffusion coefficient was evaluated to be 1.43×10−16 cm2/s. We also calculated the energy levels of the AlGaAs/GaAs MQW with four single wells using TMM and compared the calculated results with the experimental values from the PL measurements. The comparison shows good agreement. To see the influence of RTA condition on PL characteristics of the wells at different depth beneath the surface of the sample, we annealed the SiO2 film covered AlGaAs/GaAs MQW at 650–780 °C for 20–80 s. A subsequent PL measurement shows that the photoluminescence characteristics of the four single quantum wells behave differently with the change of RTA condition. The PL intensities of the wells close to the surface and the bottom of the AlGaAs/GaAs MQW are sensitive to the RTA condition while those of the wells in the middle of the MQW show little variations with the change of RTA conditions. [Copyright &y& Elsevier]

O-polar and Zn-polar ZnO films were prepared by rf-plasma assisted molecular beam epitaxy (MBE) on sapphire substrates. Arsenic ions have been implanted into high quality ZnO with a definite polarity. Substantial temperature-independent ferromagnetism has been observed for both films, with the O-polar film having approximately twice the magnetization as the Zn-polar film. The saturation magnetization is shown to be due to the defects introduced during implantation, rather than to local moments associated with the As ion. Rutherford Backscattering/Channeling and optical absorption measurements confirm that the implantation introduces more defect states in the O-polar films, while X-ray absorption near-edge structure measurements show that the environment of the arsenic ions was similar for both polarities. [ABSTRACT FROM AUTHOR]

In this work, TiAlSiN/NiCr multilayer coatings with different modulation periods were deposited by cathodic-arc techniques, which combined filtered cathode vacuum arc (FCVA) and cathodic-arc ion plating (CAIP) techniques to deposit sublayers at different bias voltages. The nanoscale multilayer coating (TiAlSiN: 88 nm; NiCr: 9 nm) exhibited excellent oxidation resistance and thermal stability. Annealed coatings at 900 °C in air for 1 h, the thickness of the oxide layer of N32 coating is only 0.91 μm and the increase in coating thickness was only 9.01%, while the thickness of oxide layer of monolayer TiAlSiN coating is 3.02 μm and thickness increasing of 122.28%. Due to the existence of numerous interfaces, the N32 coating exhibited the lowest wear rate of 1.92 × 10−7 mm3N−1m−1 at 600 °C under abrasive wear and adhesive wear mechanisms. In parallel, a new AlNi intermetallic compound with excellent thermal stability was characterized by high-resolution transmission electron microscopy (HRTEM) at the coating interfaces. This compound is derived from different cathodic-arc techniques and bias voltages used to deposit coatings, which provides a reference for the structural design of coatings facing thermal environments. [ABSTRACT FROM AUTHOR]

Understanding of the structure and optical properties of films is important for their optoelectronic applications. In this paper, O-polar ZnO thin films were prepared by molecular beam epitaxy (MBE) on sapphire substrates, and Kr ions were doped into one of the films by ion implantation. Lattice structure and surface morphology of films were characterized by X-ray diffraction (XRD), Atomic force microscopy (AFM), respectively. The results show that compared with undoped O-polar ZnO film, the doped sample had granulated surface and enhanced absorption. Absorption Spectra, photoluminescence spectra (PL) and Spectroscopic Ellipsometry (SE) were used to characterize optical properties of films. The bandgap values obtained by absorption and SE method demonstrated that the bandgap decreases slightly as Kr ion implantation, and a new transition peak (3.56eV) appears from the SE result. This study provides information for controlling the band gap of ZnO materials by ion implantation and guidance for the application research of ZnO. • High quality O-polar ZnO thin films were grown by molecular beam epitaxy (MBE) on sapphire substrates. • Kr ions were implanted into O-polar ZnO film by ion implantation. • The surface morphology, crystal structure and some optical properties of the samples were characterized. • We obtained the optical bandgap of films by SE, and found that Kr ion implantation caused a blue shift in O-polar ZnO films. • We found that Kr ion implantation can modify the optical band gap of materials. [ABSTRACT FROM AUTHOR]

In this paper, DI defects are studied via experiments and calculations. The 2 MeV H+ is used to carry on an ion-beam-induced luminescence (IBIL) experiment to measure the in-situ luminescence of untreated and annealed 4H-SiC at 100 K. The results show that the luminescence intensity decreases rapidly with increasing H+ fluence, which means the losses of optical defect centers. In addition, the evident peak at 597 nm (2.07 eV) is the characteristic peak of 4H-SiC, and the weak peak between 400 nm and 450 nm is attributed to the DI optical center. Moreover, the first-principles calculation of 4H-SiC is adopted to discuss the origin of DI defects. The optical transition of the defect SiC(CSi)2 from q = 0 to q = 1 is considered the experimental value of the DI defect center. [ABSTRACT FROM AUTHOR]

In this paper, N ions are implanted into ZnO and ZnAlO films with different carrier concentrations prepared by radio frequency reactive magnetron sputtering on sapphire substrates. The structural, electrical, optical and magnetic properties of N-doped and (Al, N) co-doped ZnO films is investigated, and the particular emphasis is placed on the effects of carrier concentration on the defects induced magnetism in the films. Our results show that all the doped ZnO films are ferromagnetic at room temperature. A trace amount of additional Al doping has a significant effect on the improvement of ferromagnetic properties, and a maximum saturation magnetization of 73 emu/cm3 is obtained for (Al, N) co-doped ZnO films. The optical band gaps of ZnO films increase with the increasing Al doping content, which is owing to the combined effect of high carrier concentration and the Burstein Moss effect. The average transmittance of all ZnO films exceeds 80%. Our results confirm that appropriate electron doping can effectively enhance the magnetic moment in N implanted ZnO which may also apply to other ZnO systems with d0 magnetism. • N-doped ZnO and AZO films were made by ion implantation and thus contain both N ions and defects due to implantation. • The band gap and carrier concentration of ZnO films increase after Al doping. • Electron doping can effectively enhance the d0 magnetism in the N doped films. • Magnetization was correlated with lattice defects and carrier concentration. [ABSTRACT FROM AUTHOR]

To address corrosion and friction problems in complex environments, traditional protective coatings are gradually replaced by multicomponent coatings. In this work, a (TiAlCrSi)C multicomponent coating with ultralubrication (COF < 0.1) and excellent corrosion resistance was prepared by FCVAD technology with regulated C2H 2 flow. The composition, structure, roughness, dry friction, corrosion and tribocorrosion of the (TiAlCrSi)C coating were analyzed. The results show that the (TiAlCrSi)C coating shows an amorphous structure, and the addition of carbon improves the degree of amorphization of the coating. Carbon exists in the form of carbide and amorphous carbon in the (TiAlCrSi)C coating, the carbon content saturation of the coating is about 70 at.%. The formed carbides and sp2-C in the (TiAlCrSi)C coating have extremely low COFs and good wear resistance. The high proportions of amorphous carbon and sp2-C improve the self-lubricating and nonmetallic properties of the (TiAlCrSi)C coating, which makes the coating have good tribocorrosion resistance in 5.0 wt% H 2 SO 4 solution. The wear mode of the coating changes from abrasive wear to adhesive wear. Therefore, the (TiAlCrSi)C coating has great potential application value for tribocorrosion surface protection in a 5.0 wt% H 2 SO 4 solution environment. • (TiAlCrSi)C coatings were prepared by FCVA deposition. • The carbon content saturation of the (TiAlCrSi)C coating is about 70 at.%. • (TiAlCrSi)C coatings exhibit an amorphous structure. • (TiAlCrSi)C coatings show ultralubrication (COF < 0.1) and excellent corrosion resistance. • The effect of carbon content on the tribosorrosion properties in 5.0 wt% H 2 SO 4 solution of the coating was systematically studied. [ABSTRACT FROM AUTHOR]

Herein we report a prototypical electronic substrate specifically designed to serve the weakly interacting massive particles (WIMPs) detectors at the China Dark Matter Experiment (CDEX). Because the bulky high-purity germanium (HPGe) detectors operate under liquid-nitrogen temperatures and ultralow radiation backgrounds, the desired electronic substrates must maintain high adhesivity across different layers in such cold environment and be free from any radioactive nuclides. To conquer these challenges, for the first time, we employed polytetrafluoroethylene ((C2F4)n) foil as the base substrate, in conjunction with ion implantation and deposition techniques using an independently developed device at Beijing Normal University for surface modification prior to electroplating. The remarkable peeling strengths of 0.88±0.06 N/mm for as-prepared sample and 0.75±0.05 N/mm for that after 2.5-days of soaking inside the liquid nitrogen were observed, while the regular standards commonly require 0.4 N/mm ∼ 0.6 N/mm for electronic substrates. [ABSTRACT FROM AUTHOR]

Defects play an important role in causing room temperature ferromagnetism in ZnO films. Multi-energy ion implantation has been employed to introduce different concentrations of non-magnetic ions, including argon, arsenic and krypton, into high-quality ZnO films and room temperature ferromagnetism has been observed for As and Kr implanted ZnO while none was observed for Ar doped films. The Monte Carlo simulation code SRIM was adopted to simulate the distributions of the implanted ions, the induced zinc and oxygen vacancies and the resulting interstitials. A common radiation damage parameter, known as the atomic displacements per atom (dpa), was calculated to quantify the primary radiation damage production. Our results show that the observed magnetic moment measured at low temperatures due to implantation with a given ion is proportional to the dpa. The constant of proportionality between the magnetism and the dpa depends on the implanted ion. This constant is largest for heavy, large ions. To obtain room temperature d0 magnetism in ZnO, non-magnetic ions with high mass are suggested to be implanted into ZnO films. [ABSTRACT FROM AUTHOR]

Interaction of hydrogen atom with (5, 5) single-walled carbon nanotube (SWNT) has been studied over the collision energy range from 1 to 30 eV using a molecular dynamics simulation method. In the energy interval of 1–3 eV, the hydrogen atom can be chemisorbed on the outer wall of the SWNT, provided the impact point is near a vertex carbon atom of a hexagon. The lowest incident energy needed for a hydrogen atom to pass through a hexagon ring on the SWNT is estimated to be 14 eV. Hydrogen atoms that enter into the SWNT would either be encapsulated in it to form endohedral H@tube complex, or escape out of it. The hole on the sidewall of the nanotube induced by the collision of hydrogen atom can be healed after relaxation for several picoseconds. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

A diamond-like carbon film doped with TiC nanocrystallites (TiC-DLC) with a thickness of 35.8 μm was successfully prepared on a stainless steel substrate by employing a combination of metal vapor vacuum arc and filtered cathode vacuum arc techniques. A maximum deposition rate of 0.25 μm/min was achieved for TiC-DLC films. The structure and properties of the TiC-DLC films were systematically analyzed using different methods such as transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, X-ray diffraction, and friction and wear tests. The results indicated that typical a-C:H films containing nano-sized TiC grains were deposited which exhibit improved mechanical properties such as high cohesive strength, Vickers hardness, and capacity against high temperature. Parameter windows for CH flow rate and solenoid current were also provided for the deposition of TiC-DLC films to meet the requirements for using the material for specific commercial applications. [ABSTRACT FROM AUTHOR]

• A filtered cathode vacuum arc (FCVA) system was used to grow MgO films on sapphire substrates. • The magnetic moment for the Er implanted MgO film is higher than that of Co implanted MgO. • The magnetization is enhanced by Co-Er co-doping compared with Co doped and Er doped MgO. • The origin of the magnetism can be described by the bound magnetic polaron (BMP) model. The present study reports a high ferromagnetism acquired by co-implanting Co and Er ions in MgO films prepared by filtered cathode vacuum arc on Al 2 O 3 substrates. The resulting MgO films were analyzed with respect to their structures, surface morphologies, and magnetic properties. Magnetic measurements show that substantial intrinsic ferromagnetism has been found for all the doped MgO. The ferromagnetism for the Er-doped MgO is larger than that of the Co-doped MgO and it is further strengthened by Er-Co co-doping. The X-ray photoelectron spectroscopy analysis substantiates that a large number of oxygen vacancies (V o) are generated after the doping of Er and Co ions. The origin of the magnetism can be described by the V o mediated bound magnetic polaron (BMP) model. The increased number of BMP with higher moments and the coupling interaction of Er and Co accounts for the strong ferromagnetism in the co-doped films. Our research provides a new idea for manufacturing high-quality diluted magnetic oxides by co-doping rare earth and transition metal ions in MgO samples. [ABSTRACT FROM AUTHOR]

Robust room-temperature ferromagnetism with saturation magnetization as high as 58 μ B /Cu was successfully induced in monolayer MoS 2 after low energy Cu implantation. [Display omitted] • low-energy Cu ions was implanted into monolayer MoS 2 introducing both Cu and defects. • Robust room temperature ferromagnetism of 58μ B /Cu was successfully induced in monolayer MoS 2. • First principles density functional theory calculations reveal that nanohole, Cu Mo , Cu i + v S and Cu Mo + v S can induce higher magnetic moment. • Cu Mo and Cu i + v S have lower formation energies and may contribute significantly to the large magnetization. • The magnetic moments origin from the strong interaction between Mo 4d and S 3p or among Mo 4d, Cu 3d and S 3p orbits. Magnetism in two-dimensional materials is of great importance for exploring new physical phenomena and developing novel devices in nanoscale. It's still a challenge to induce robust room temperature ferromagnetism in monolayer transition metal dichalcogen compound materials. In this paper, high quality monolayer MoS 2 was prepared by chemical vapor deposition and low energy Cu ions were implanted into MoS 2 via ion implantation. The surface morphology, chemical states, optical and magnetic properties were systematically investigated. Robust room-temperature ferromagnetism with saturation magnetization as high as 58 μ B /Cu (∼2148 emu/cm3) was successfully induced in monolayer MoS 2 after Cu implantation. Moreover, the magnetic properties are weakly temperature dependent, which is clearly the characteristic of defect-induced magnetism. First principles density functional theory calculations reveal that various structural defects, including nanohole, Cu Mo , Cu i + V S and Cu Mo + V S can induce high magnetic moments. Meanwhile, Cu Mo and Cu i + V S have lower formation energies and may contribute significantly to the extremely large magnetism in the implanted monolayer MoS 2. Our work has demonstrated that through defects engineering by Cu implantation, robust room temperature ferromagnetism can be achieved in monolayer MoS 2 , which provides a potential way to induce large magnetization in other transition metal dichalcogen compound materials, and opens up new opportunities for their applications in nano-spintronics. [ABSTRACT FROM AUTHOR]

The microstructural, electrical and magnetic properties of Gd-doped and (Al, Gd) codoped Zn-polar and O-polar ZnO wafers manufactured by the ion implantation method are systematically and comparatively investigated. We report an intrinsic ferromagnetic behaviour of Gd-implanted polar ZnO wafers enhanced by Al codoping. It was found that the saturation magnetization for the doped O-polar ZnO wafer is stronger than that of the implanted Zn-polar ZnO wafer. The introduction of Al ions into Gd-implanted polar ZnO enables a further improvement in the ferromagnetism that is directly relevant to the carrier concentration. This finding suggests that the carrier-mediated exchange mechanism may account for the establishment of the long-range ferromagnetic order in the doped ZnO wafers. First-principles calculations confirm that the interaction between the Gd-4 f state and the O-2p state is stronger in oxygen polar ZnO, producing a higher magnetic moment. The increase in the magnetic moment of (Al, Gd) co-implanted ZnO is mainly derived from hybridization of the Al and O orbitals. Our results confirm that larger ferromagnetism can be obtained in Gd-doped O-polar ZnO wafers and that the magnetization can be effectively improved by controlling the electron doping concentration, which highlights the viability of developing spintronic devices based on polar ZnO by codoping magnetic ions and group Ⅲ elements. [Display omitted] • The magnetic moments for the Gd-implanted and (Al, Gd) co-implanted O-polar ZnO wafers are higher than these of Zn-polar wafers. • The magnetization is enhanced by (Al, Gd) co-doping compared with Gd doped ZnO wafer. • The magnetization shows carrier concentration-dependent behaviour. • First principle calculations reveal that Gd-4 f states have strong hybridizations with O-2p state in O-polar ZnO. • The increase of magnetic moment of (Al, Gd) codoped polar ZnO mainly comes from the hybridization of O and Al orbitals. [ABSTRACT FROM AUTHOR]

Microstructural and magnetic properties of ion implantation method prepared Co doped Zn polar and O polar ZnO wafers are investigated by a combined experimental and theoretical approach. Substantial intrinsic ferromagnetism is observed in all the doped ZnO wafers. The ferromagnetism of Co implanted oxygen polar ZnO wafer is found to be larger than that of zinc polar ZnO. First principle calculations reveal that the magnetic moments mainly come from the Co-3d and O-2p states. The O-2p state has a stronger hybridization with the Co-3d state in oxygen polar ZnO, resulting in higher magnetic moments of Co implanted oxygen polar ZnO. These results not only benefit to a better understanding of the origin of surface-polarity dependent ferromagnetism in ZnO diluted magnetic semiconductors but also may open up the possibility to employ these polar ZnO in spintronic devices. abstract [Display omitted] [ABSTRACT FROM AUTHOR]

The present study reports room temperature ferromagnetism observed in Co implanted, Er implanted and (Co, Er) co-implanted ZnO films deposited by filtered cathode vacuum arc (FCVA) on sapphire substrates. The microstructures, surface morphologies, electrical and magnetic properties of pure and implanted ZnO films were investigated. X-ray diffraction results confirm that the implantation of Co and Er ions cause the substitution of Zn ions without the formation of secondary phases. The results of X-ray photoelectron spectroscopy indicate that the Er ions and Co ions are in trivalent and divalent states, respectively. After ions implantation, the electrical properties of the films are improved and the carrier concentration of Er implanted ZnO film is higher than that of Co implanted ZnO film. Substantial intrinsic ferromagnetism has been observed for all the implanted ZnO films. The saturation magnetization for the Er implanted ZnO film is higher than that of the Co implanted ZnO film and the magnetization is further enhanced by (Co, Er) co-implanting. The carrier mediated exchange mechanism can well describe the origin of ferromagnetism in the doped ZnO films. Our results can provide a reference for preparing high-quality diluted magnetic semiconductors (DMSs) by RE elements and TM elements co-doping in ZnO films. [Display omitted] • A filtered cathode vacuum arc (FCVA) deposition system was used to grow ZnO films on sapphire substrates. • The saturation magnetization for the Er implanted ZnO film is higher than that of Co implanted ZnO. • The magnetization is enhanced by Co-Er co-doping compared with Co doped and Er doped film. • The magnetization shows carrier concentration-dependent behavior. [ABSTRACT FROM AUTHOR]

The titanium oxycarbide films were deposited on Si(1 0 0), 304 stainless steel (SS) and quartz glass by Filtered Cathodic Vacuum Arc (FCVA) technique using CO 2 as a reactive gas. The effect of CO 2 gas flow rate on the composition and phase structure of films was investigated by XRD, SEM, XPS and Raman spectroscopy. The results showed that the crystal structure of titanium oxycarbide films was transformed from Ti(C,O) nanocrystal phase to nc-TiO 2 /a-C nanocomposite phase with increasing CO 2 gas flow rate. Ti(C,O) nanocrystal film had a hardness of 28.25 GPa, determined by nanoindentation test. The nc-TiO 2 /a-C nanocomposite films with low friction coefficient (0.17) and good anti-corrosion ability were obtained. The optical band gap of films was 3.2 eV for Ti(C,O) nanocrystal film and 3.3 eV for nc-TiO 2 /a-C film, indicating the great potential in the area of photocatalytic and optoelectronic application. [ABSTRACT FROM AUTHOR]

Metal bipolar plates (BPPs) are candidates with great promise to replace conventional carbon-based BPPs. However, the drawbacks caused by the corrosion and passivation of metal bipolar plates need to be addressed urgently. In present study, corrosion-resistant and interfacial conductive high-entropy alloy and ceramic coatings possess great potential in the application of surface modification of bipolar plates in proton exchange membrane fuel cells (PEMFCs). An original co-filtered cathodic vacuum arc deposition (C-FCVAD) is designed to prepare AlTiVCrMo high-entropy alloy (HEA) and (AlTiVCrMo)N x high-entropy ceramic (HEC) coatings with different nitrogen content, and their feasibility as surface modification methods of bipolar plates is investigated by analyzing the microstructure, corrosion properties, interfacial conductivity and hydrophobicity of the coatings. The obvious body-centered cubic (BCC) structure can be observed in HEA coating, and amorphous structure is gradually formed as the nitrogen content increases to 28.12 at. %. Finally, polycrystal structure is formed when nitrogen content reached the maximum. The electrochemical corrosion and interfacial contact resistance (ICR) results significantly demonstrate that the coatings have enhanced corrosion resistance and conductivity. The bipolar plates with AlTiVCrMo HEA and (AlTiVCrMo)N x HEC coatings as surface modification methods have good application potential in PEMFCs operating environment. • The novel idea of HEA and HEC coatings adopting for bipolar plates in PEMFCs. • Development of Co-filtered cathodic vacuum arc deposition technique for HEC coating. • The HEC coatings show excellent corrosion resistance and super-low ICRs. [ABSTRACT FROM AUTHOR]

• Er-doped ZnO films were made by ion implantation, thus contain both Er ions and defects. • The magnetization of ZnO can be enhanced significantly by annealing in Ar and vacuum. • The enhancement of ferromagnetism is strongly correlated with the increase of oxygen vacancies in Er-doped ZnO. • Proper annealing is a good way to enhance the magnetization for magnetic ions doped ZnO. The Er ions have been introduced into ZnO films prepared by radio-frequency magnetic sputtering (RFMS) on sapphire substrates by ion implantation. The annealing effect on structural and magnetic properties for Er-implanted ZnO films under air, Ar, and vacuum atmospheres at 650 °C have been investigated systematically by a combined characterization of X-ray diffractions, Raman spectroscopy, Photoluminescence, X-ray photoelectron spectroscopy and Superconducting Quantum Interference Device. Strong room-temperature ferromagnetism has been observed for the as-implanted and annealed films. We found that the saturation magnetization varied greatly for different annealing conditions. A considerable enhancement in magnetization is observed for Er-doped ZnO annealed in vacuum, which is accompanied by an enhancement in the concentration of oxygen vacancy. Our results give clear evidence that the enhancement of ferromagnetism is strongly correlated with the increase of oxygen vacancies in Er-doped ZnO. [ABSTRACT FROM AUTHOR]

In this work, amorphous hydrogenated carbon and titanium carbide composite (a-C: H/TiC) films are deposited on titanium bipolar plates which are used in proton exchange membrane fuel cells (PEMFCs). It was fabricated by high power pulsed magnetron sputtering (HiPIMS) with TiN and TiCN transition layers. The microstructure results indicated that the titanium element was introduced in the films with a form of titanium carbide, and the increasing ID/IG values imply the graphitization of films. Amorphous carbon with a large content of sp2 hybrid bonds leads to an excellent conductivity of 1.6 mΩ·cm2 at 1.4 MPa and improves the corrosion resistance by inhibiting the growth of columnar crystal. In addition, a number of sp2-riched clusters on the surface enhance the hydrophobicity of the film. The a-C: H/TiC films prepared in this work significantly improved the hydrophobicity, corrosion resistance and interfacial conductivity of titanium bipolar plates, showing a great potential for applications in PEMFCs. [Display omitted] • Amorphous hydrogenated carbon and TiC composite films are deposited on Ti bipolar plates in PEMFCs. • The interfacial contact resistance of the modified bipolar plate is as low as 1.6 mΩ·cm2 at 1.4 MPa. • The corrosion current density of the modified bipolar plate is less than 10−6 A/cm2 in PEMFCs. [ABSTRACT FROM AUTHOR]

Electronic stopping powers for 80–350 keV 19F ions in molybdenum were obtained by range measurement. Depth profiles of 19F in molybdenum were measured by using the 19F(p,αγ)16O resonant nuclear reaction at ER=872.1 keV. A proper convolution calculation method was used to extract the true distribution of fluorine from the experimental excitation yield curves. The electronic stopping powers were derived through fitting the projected range distributions, simulated by using the TRIM/XLL code, to the experimentally measured range distributions. The electronic stopping cross sections were compared with those obtained from Monte Carlo simulation codes. [Copyright &y& Elsevier]

Range distributions for bismuth ions implanted in AgGaS2 in an energy range of 80–300 keV were investigated by using 2.1 MeV He2+ Rutherford backscattering spectrometry (RBS). A convolution calculation method was used to extract the true distributions of bismuth from the measured RBS spectra. The range distribution parameters, Rp and ΔRp, were obtained and compared with that obtained from Monte Carlo simulation. The experimental Rp values agree with the Monte Carlo simulation values very well, but the experimental ΔRp values are systematically larger than those from the theoretical simulation. [Copyright &y& Elsevier]

Density functional theory (DFT) calculation of various segments of DNA have been performed to aid our understanding of DNA damages under the conditions of irradiation. These damages studied include strand breaks, base releasing from backbone, and amidogen/methyl removing from bases. In the calculation, the effect of the hydrogen bond interaction between bases in the base-pair, as well as, that of the stacking interaction between the base pairs in adjacent turns of the double helix are both considered. In addition, we also evaluated the effect of the biochemical environment, such as sodium counterions and water molecules, on the stabilization of DNA segment. Base release damage is found to have lowest energy threshold. The remove of an atom or a radical from sugar backbone, which may result in single-strand breaks or double-strand breaks, has the highest energy threshold. All the energy thresholds of these DNA damages are determined to be in the range from 4.5 to 8.7 eV. [Copyright &y& Elsevier]

Molecular-dynamics simulations were used to investigate the structures of hydrogen molecules formed within (5,5), (9,0) and (10,10) single-walled carbon nanotubes (SWNT). In the (5,5) and (9,0) SWNTs, H2 molecules preferably form linear lines and helical curves, showing the strong confinement of small-diameter SWNTs. The structure of H2 molecules in the (5,5) and (9,0) SWNTs is different, showing the dependence on the helicities of the SWNTs. The accumulation process of H2 molecules in the (10,10) SWNT is also presented, showing the formation of H2 molecules cylindrical shells. [Copyright &y& Elsevier]

Electronic stopping powers for 50–180 keV 19F ions in tin-oxide films were obtained by range measurement. Depth profiles of 19F in tin-oxide films were measured by using the 19F(p,αγ)16O resonant nuclear reaction at ER=872.1 keV. A proper convolution calculation method was used to extract the true distribution of fluorine from the experimental excitation yield curves. The electronic stopping powers were derived through fitting the projected range distributions, simulated by using the TRIM/XLL code, to the experimentally measured range distributions. It is shown that the electronic stopping cross-sections obtained in this work agree well with those calculated by using TRIM90 and can be well described by the four-parameter formulae. But they are systematically larger than the results obtained from the TRIM98 code. [Copyright &y& Elsevier]

• 50-μm-thick DLC films with hardness of 27 GPa were fabricated. • Anti-sand erosion performance of DLC films were studied. • The erosion resistance of thick film is nearly 25 times higher than the thin film. • Surface polishing of thick DLC film can greatly improve its tribological properties. In order to improve the abrasion and erosion resistance in severe environments, 50-μm-thick diamond like carbon (DLC) films with a hardness of 27.3 GPa were fabricated using filtered cathodic vacuum arc technique coupled with a high-voltage pulse power. The microstructures, mechanical properties and tribological and anti-sand erosion performance of DLC coatings with different thicknesses were evaluated. The increase in thickness from 3 to 50 μm, resulting the adhesion of the coatings increased from HF1 to above HF1 level. Radial cracks or delamination were not observed at the edge of the indentation of 50-μm-thick coating. The coefficient of friction (COF) was decreased but wear rate was increased as coating growing thicker due to the stacking of graphited debris between the asperities. Mechanical polish was carried out on the 50-μm-thick films, which lead to the COF and wear rate decreased from 0.079 to 0.067 and 14.7 to 6.78 × 10−8 mm3/N·m at 20 N. The sand erosion test demonstrated that as the increase in thickness from 3 to 50 μm, average mass loss rate significantly decreased from 0.81 to 0.035 mg/g. High load-bearing capacity and ability to restrain the initiation and propagation of cracks were responsible for the great erosion resistance for thick coating. [ABSTRACT FROM AUTHOR]