During the synthesis of stanene monolayers, defects are inevitably present and always affect the properties. Here we used ab initio calculations to systemically investigate the structures, diffusion behaviors and related properties of several kinds of typical point defects, including the Stone–Wales (SW) defect, single vacancy (SV-1(55|66) and SV-2(3|555)) and double vacancy (DV-1(5|8|5) and DV-2(555|777)) defects. Scanning tunneling microscopy (STM) images were also simulated to help experimentalists identify these defects in stanene. The investigation of structures and diffusion behaviors of the defects revealed that SW can be easily recovered by annealing due to its low reverse barrier, both SV-1(55|66) and SV-2(3|555) are the most stable SVs, the energetically favored DV-1(5|8|5) can be formed from two SVs coalescing together, and DV-2(555|777) can arise from DV-1(5|8|5) via bond rotation by overcoming a diffusion barrier of 0.89 eV. The point defects exhibit nontrivial influences on the electronic properties of stanene: SW can open a direct gap in the energy band without harm to the high-velocity carriers, SV-1(55|66) makes stanene metallic, and SV-2(3|555), DV-1(5|8|5) and DV-2(555|777) may change stanene to an indirect or direct band gap semiconductor. Spin orbit coupling (SOC) effects have visible influences on the electronic bands, specifically the band gaps. Our theoretical results may provide valuable insights into the identification of point defects in further experiments and the understanding of their effects on the electronic properties and potential applications of stanene.

Viscous boundary layer chemical vapor synthesis is a novel technique that uses the viscous boundary layer between a laminar pyrolysed metallocene/Ar vapor flow and a rough surface to induce the nucleation and growth of radial carbon nanotube (CNT) structures highly filled with ferromagnetic materials. Here we report the synthesis and characterization of radial structures comprising multiwall CNTs filled with large quantities of Fe3C and FeCo alloys and low quantities of γ-Fe in the forms of small single crystals. Surprisingly high saturation magnetizations up to 80 emu g−1 and a very high coercivity of 1400 Oe at room temperature are found. Such values of magnetization suggest that no room-temperature magnetic interaction is present between γ-Fe and the ferromagnetic crystals in our samples. The presence of such large coercivity values may be associated with the small size of the encapsulated particles which is strongly dependent on the high evaporation temperature of the precursors for fixed pyrolysis temperatures and vapour flow rate. The addition of Cl-species is also considered in the attempt to slow down the growth-rate of the radial CNT-structure and further investigate their growth mechanism.

A key challenge in the fabrication of carbon nanotubes filled with ferromagnetic nanowires is the control of the number of nanotube-walls together with the nanowire continuity, composition and crystallinity. We report the serendipitous observation of novel radial carbon nanotube structures with few walls (2–5 walls) filled with nm-thin and many-micrometres long continuous single-crystalline Fe3C nanowires. These are the dominant reaction products in chemical vapour synthesis experiments involving the pyrolysis of ferrocene/sulfur mixtures in the viscous boundary layer between a rough surface and a laminar Ar flow. These nanowires are found with an unusual preferred 010 orientation along the nanotube capillary. The properties of these structures are investigated through the use of multiple techniques: SEM, TEM, HRTEM, EDX, STEM, XRD, Raman spectroscopy, FT-IR spectroscopy and VSM.

•The magnetic anisotropies in (Ga,Mn)As nanoribbons (NRs) are studied and revealed to be dependent on both the distribution directions of Mn atoms and the edge effect of the NRs.•The corresponding nearly 100% spin polarization makes (Ga,Mn)As NRs a type of candidate for low dimensional spin filter.•(Ga,Mn)As NRs can be used to generate a relatively stable spin-polarized current in a wide bias interval.The electronic and magnetic properties of Mn doped hexagonal GaAs nanoribbons ((Ga,Mn)As NRs) have been investigated using spin-polarized density functional theory (DFT), and the spin-resolved transport behaviors of (Ga,Mn)As NRs have also been studied with non-equilibrium Green function theory. The calculations show that every Mn dopant brings 4 Bohr magneton (μB) magnetic moment and the ground states of (Ga,Mn)As NRs are ferromagnetic (FM). The investigation of magnetic anisotropies shows that magnetic interactions are dependent on both the distribution directions of Mn atoms and the edge effect of the NRs. The studies of electronic structures and transport properties show that incorporation of Mn atom turns GaAs NR from semiconducting to half-metallic, which significantly enhances the spin-up conductivity and strongly weakens the spin-down conductivity, resulting in non-monatomic variations of spin-dependent conductivities. The nearly 100% spin polarization shown in (Ga,Mn)As NR may be used for low dimensional spin filters, even with as large a bias as 0.9 V. Also, (Ga,Mn)As NR can be used to generate a relatively stable spin-polarized current in a wide bias interval.

The transport properties of GaAs nanowire (NW)-based devices are investigated using non-equilibrium Green’s function technique combined with density functional theory (DFT). Two types of NW-based devices are studied, which include the electrodes that are made of half-metallic GaMnAs NWs grown along the [0 0 0 1] direction, and the scattering region that consists of a tunneling structure (GaMnAs/GaAs/GaMnAs) or a conducting structure (GaMnAs/GaAs:Be/GaMnAs), respectively. The proposed nanostructures both exhibit robust transport properties including spin-filtering, negative differential resistance (NDR) and giant magnetoresistance (GMR) effects, which are further analyzed with carrier channels and transmission spectra. These structures imply potential applications for low dimensional semiconductor spintronic devices such as spin valve.

We report an advanced chemical vapour deposition approach which yields not previously observed carbon-based foam-like films completely filled with a single phase of α-Fe. These films are found in the region of the chemical vapour deposition reactor where the temperature is relatively low (650–770 °C) and exhibit a high saturation magnetization as high as 200–220 emu/g at room temperature when small concentrations of Cl-radicals are added to the pyrolysing CVD system by mixing 0.15 ml of dichlorobenzene to ferrocene. Instead when the only ferrocene is used a lower saturation magnetization of 140–145 emu/g is found due to an amorphous arrangement of the Fe-phase in some parts of the foam. Also we show that for much higher concentration of Cl radicals (0.65 ml of dichlorobenzene mixed to ferrocene) a dramatic decrease of the quantity of crystalline α-Fe is found together with the formation of amorphous Fe and FexOx phases.

The electronic structures, and static and dynamic magnetic properties of monolayer iron dioxide and iron dichalcogenides (FeX2 (X = O, S, Se, Te)) are investigated using first-principle calculations in conjunction with Monte Carlo (MC) simulation and atomic spin dynamics (ASD) simulation. In this rarely studied family of monolayer binary compounds a variety of possible phases are discovered, including narrow bandgap a semiconductor (FeO2), half-metal (FeS2) and metal (FeSe2 and FeTe2), and all the ground states are ferromagnetic (FM). Based on the magnetic exchange interactions, the temperature dependence of the average magnetic moment per unit cell and magnetic susceptibility of monolayer FeX2 are predicted. The Curie temperatures (TCs) are estimated and magnon dispersions as a function of temperature are demonstrated, revealing a new family of pristine monolayers with transition temperatures (96–168 K) above the liquid-nitrogen temperature.

Recently it has been shown that FePd alloys can be encapsulated in graphitic carbon based systems for a better particle dispersion through addition of dichloro-cyclooctadiene palladium to ferrocene. Here we propose an advanced two-stage method which allows the synthesis of very thick deposits of planar rolled-like graphite structures filled with FePd3 alloys as dominant product in the entire reactor. The first stage is used to pyrolyze the Pd-containing hydrocarbon on the top of Si/SiO2 substrates for Pd deposition while the second stage is used for the evaporation and pyrolysis of the Fe-containing precursor (ferrocene) for the FePd alloy formation and encapsulation. Annealing studies also show that no changes in the unit cell of the FePd3 structure are found even after tens of hours at 600–650 °C under Ar/H2 flow. Instead a change in the encapsulated particle shape and spatial arrangement is found. The samples are characterized in detail through scanning and transmission electron microscopy, energy dispersive X-rays, Raman spectroscopy, thermogravimetric analyses, X-ray diffraction and room-temperature magnetometry.

We report an advanced chemical vapour deposition approach which allows the direct in situ synthesis of cm-length ultrathin buckypapers comprising carbon nanostructures filled with Fe3C, FeCo, FeNi, CoNi, Co and Ni by sublimation and pyrolysis of single or combined metallocenes with very low quantities of dichlorobenzene. As a result, extremely high saturation magnetizations of 117 emu g−1, 90 emu g−1 and 80 emu g−1 are obtained for the specific cases of Fe3C, FeCo and FeNi, respectively, while variable saturation magnetizations of 70 emu g−1, 58 emu g−1 and 6.7 emu g−1 are obtained for Co, CoNi and Ni respectively.

The electronic transport properties of zigzag phosphorene nanoribbon (ZPNR) homostructures are investigated using density functional theory calculations and the nonequilibrium Green’s function technique. The proposed devices have simple constructions but exhibit robust negative differential resistance (NDR) as well as quite large current, which implies great potential for building nanoelectronic devices. Through the analysis of the electronic structures and transmission spectra, we give a clear physical picture of the NDR mechanism, in which such current–voltage (I–V) behaviors originate from the bias-dependent interaction between the discrete density of states (DOS) peaks of the electrodes and the narrow states around the Fermi level in the scattering region.

We report an advanced chemical vapour deposition method which allows the synthesis-selection of thin walled carbon nanotubes filled with micrometre-length Fe3C single crystals, Fe3C tip-filled nanotubes or of empty thin walled carbon nanotubes by controlled addition of a not previously used precursor (6-bromohexyl)ferrocene to ferrocene.

•Single crystalline ferromagnetic ZnO:Co nanocrystals were synthesized by polymer assisted deposition.•Enhancement of the room temperature ferromagnetism in ZnO:Co nanocrystals was achieved by post-annealing treatment in both oxygen and hydrogen atmospheres.•The improvement of ferromagnetism upon annealing is found to be attributed to the decrease of oxygen interstitials (Oi) and the increase of Zn1− vacancies in the nanocrystals.Co-doped ZnO thin films were prepared by polymer-assisted deposition (PAD), and then treated by post-annealing in different atmospheres. XRD, SEM, TEM and SQUID were employed to characterize the samples, which demonstrate that all the samples are composed of nanocrystals and the annealing shows a robust effect on the enhancement of ferromagnetism at room temperature. PL measurements show that the improvement of ferromagnetism upon annealing is related to the decrease of oxygen interstitials (Oi) and the increase of Zn1− vacancies. XPS measurements indicate that post-annealing also induces oxygen vacancies, which have no positive contribution to the ferromagnetic ordering. Our results may suggest an effective way for modulation of structure and magnetic properties of Co-doped ZnO nanocrystal thin films.

Ultrafine single crystal silicon nanowires (SiNWs) were grown along the <110> direction by thermal evaporation without catalyst, and were studied by electron microscopy and optical spectroscopy. Simulation of the first-order Raman scattering spectrum of the wires indicates that the Raman shift and asymmetric broadening line shape are due to phonon confinement and a narrow diameter distribution of the SiNWs, and confirms that the mean diameter of the wires is 2 nm, which is smaller than the excitonic Bohr radius of Si. Further analysis shows that the unique intense purple photoluminescence (PL) peak and blue-shift of absorption spectrum of the wires result both from the increase of the energy band gap due to quantum confinement of the carriers, and from the confinement of excitons in the ultrafine SiNWs, suggesting potential applications of the wires in optical and optoelectronic nanoscale devices.

Electrical properties of Al2O3 thin films grown by atomic layer deposition on Si and GaAs substrates were characterized and compared by current–voltage and capacitance–voltage measurements. The interfacial oxide layers thicknesses, the flat band voltages and the doping levels in the semiconductor substrates were determined. The differences in dielectric constants and breakdown fields of Al2O3 films on different substrates are attributed to different energy band alignments and the existence of different oxide interfacial layers.Highlights► Demonstrates the difference between electrical properties of Al2O3 on Si and GaAs substrates by ALD with plasma enhancement. ► The breakdown fields and dielectric constants of the interfacial oxide layers were obtained by IV and CV measurements. ► The flat-band voltages and doping levels in the substrates were and compared by the Mott–Schottky plots. ► The thickness-dependent dielectric constants were obtained and explained for Al2O3 samples on both substrates. ► The relationship between the equivalent oxide thickness and interfacial oxide layers was exploited.

Nonlinear concentration-dependent electronic and optical properties of the Si1–xGex substitutional alloy nanowires are investigated using first-principles calculations. The nonuniform distribution of Ge (or Si) atoms is found, and the resulting orbital hybridization of the inner Ge or Si atoms results in the nonlinear Ge concentration dependence of electronic properties in the Si1–xGex alloy NWs, which suggests an effective approach to modulate band-gap properties of the NWs along all three directions. Moreover, a strong adsorption of solar radiation and a high quantum yield is predicted in (110)-oriented alloy NWs, which implies a great potential of Si1–xGex alloy NWs in the optical electronics applications on nanoscale.

•The uniform annealing effect of electron irradiation on GaMnAs films has been experimentally demonstrated for the first time.•Electron irradiation causes the bi-directional out-diffusions and passivations of compensating Mn interstitials, resulting in the enhancement of magnetic and electrical properties of GaMnAs films.•Electron irradiation is an alternative annealing tool to modulate magnetic and electrical properties of compounds such as GaMnAs with defects.For more than a decade, researchers have been searching for means to improve the Curie temperature of ferromagnetic GaMnAs samples, among which post-growth annealing in furnace has been treated as the most important one. In this work, we demonstrate that the Curie temperature can be improved by electron irradiation for the first time. Different doses of electron irradiation (1×1014,1×1015 and1×1016 electrons/cm2) at 1.7 MeV were applied, the enhancement of magnetic and electrical properties of ferromagnetic GaMnAs films was experimentally confirmed by HR-XRD, SQUID and Magneto-transport measurements. Further SIMS characterizations and analyses reveal that electron irradiation causes bi-directional out-diffusion and redistribution of compensating Mn interstitials towards both the upper surface and the lower interface, a newly found uniform effect clearly different from that of conventional post-growth annealing. The technique of electron irradiation annealing may provide an alternative way to improve the properties of electronic and magnetic compounds such as GaMnAs films.

•Models for anti-rumor dynamics on complex network are proposed.•The timing threshold emerges explicitly in anti-rumor dynamics.•The timing threshold comes into being earlier in a denser BA network.•Coreness is a better topological descriptor to identify hubs in anti-rumor dynamics.Anti-rumor dynamics is proposed on the basis of rumor dynamics and the characteristics of anti-rumor dynamics are explored by both mean-field equations and numerical simulations on complex network. The main metrics we study are the timing effect of combating rumor and the identification of influential nodes, which are what an efficient strategy against rumor may concern about. The results indicate that, there exists robust time dependence of anti-rumor dynamics and the timing threshold emerges as a consequence of launching the anti-rumor at different delay time after the beginning of rumor spreading. The timing threshold as a critical feature is further verified on a series of Barabási–Albert scale-free networks (BA networks), where anti-rumor dynamics arises explicitly. The timing threshold is a network-dependent quantity and its value decreases as the average degree of the BA network increases until close to zero. Meanwhile, coreness also constitutes a better topological descriptor to identify hubs. Our results will hopefully be useful for the understanding of spreading behaviors of rumor and anti-rumor and suggest a possible avenue for further study of interplays of multiple pieces of information on complex network.

•NiO-Ni bilayer tubular nanotubes were fabricated by electrodeposition and thermal oxidation.•The exchange bias effect in NiO-Ni nanotubes was induced by magnetic field cooling.•The competitive effect of annealing temperature and annealing time on the exchange bias coupling was analyzed.In this paper, we reported the synthesis of NiO/Ni bilayer nanotubes by electrodeposition and thermal oxidation using anodic aluminum oxide templates. The morphology, structure, chemical composition and magnetic properties, especially magnetic exchange bias induced by subsequent magnetic field cooling, in this one-dimensional antiferromagnetic/ferromagnetic hybrid system were investigated. It was found that the effect of the annealing temperature, which mainly dominated the thickness of the NiO layer, and the annealing time, which mainly dominated the grain size of the NiO, on the exchange bias field showed competitive relationship. The optimized exchange bias field was achieved by the combination of the shorter annealing time and higher annealing temperature.

•NiO-Ni bilayer tubular nanotubes were fabricated by electrodeposition and thermal oxidation.•The exchange bias effect in NiO-Ni nanotubes was induced by magnetic field cooling.•The competitive effect of annealing temperature and annealing time on the exchange bias coupling was analyzed.In this paper, we reported the synthesis of NiO/Ni bilayer nanotubes by electrodeposition and thermal oxidation using anodic aluminum oxide templates. The morphology, structure, chemical composition and magnetic properties, especially magnetic exchange bias induced by subsequent magnetic field cooling, in this one-dimensional antiferromagnetic/ferromagnetic hybrid system were investigated. It was found that the effect of the annealing temperature, which mainly dominated the thickness of the NiO layer, and the annealing time, which mainly dominated the grain size of the NiO, on the exchange bias field showed competitive relationship. The optimized exchange bias field was achieved by the combination of the shorter annealing time and higher annealing temperature.

We report an advanced chemical vapour deposition approach which allows the direct in situ synthesis of cm-length ultrathin buckypapers comprising carbon nanostructures filled with Fe3C, FeCo, FeNi, CoNi, Co and Ni by sublimation and pyrolysis of single or combined metallocenes with very low quantities of dichlorobenzene. As a result, extremely high saturation magnetizations of 117 emu g−1, 90 emu g−1 and 80 emu g−1 are obtained for the specific cases of Fe3C, FeCo and FeNi, respectively, while variable saturation magnetizations of 70 emu g−1, 58 emu g−1 and 6.7 emu g−1 are obtained for Co, CoNi and Ni respectively.