We report direct imaging of standing waves of the nontrivial surface states of topological insulator Bi2Te3 using a scanning tunneling microscope. The interference fringes are caused by the scattering of the topological states off Ag impurities and step edges on the Bi2Te3(111) surface. By studying the voltage-dependent standing wave patterns, we determine the energy dispersion E(k), which confirms the Dirac cone structure of the topological states. We further show that, very different from the conventional surface states, backscattering of the topological states by nonmagnetic impurities is completely suppressed. The absence of backscattering is a spectacular manifestation of the time-reversal symmetry, which offers a direct proof of the topological nature of the surface states.

3D N-doped graphene-CNT networks (NGCs) can be obtained by hydrothermal treatment, freeze-drying and subsequent carbonization of graphene oxide-dispersed pristine CNTs in the presence of pyrrole. The resulting NCGs used as a supercapacitor show high specific capacitance, good rate capability and still retain ∼96% of the initial capacitance even after 3000 cycles.

We report on molecular beam epitaxy growth of stoichiometric and superconducting FeSe crystalline thin films on double-layer graphene. Layer-by-layer growth of high-quality films has been achieved in a well-controlled manner by using Se-rich condition, which allow us to investigate the thickness-dependent superconductivity of FeSe. In situ low-temperature scanning tunneling spectra reveal that the local superconducting gap in the quasiparticle density of states is visible down to two triple layers for the minimum measurement temperature of 2.2 K, and that the transition temperature T c scales inversely with film thickness.

One-dimensional YVO4:Ln and Y(V, P)O4:Ln nanofibers and quasi-one-dimensional YVO4:Ln microbelts (Ln = Eu3+, Sm3+, Dy3+) have been prepared by a combination method of sol−gel process and electrospinning. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG−DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), low-voltage cathodoluminescence (CL), and time-resolved emission spectra as well as kinetic decays were used to characterize the resulting samples. Due to an efficient energy transfer from vanadate groups to dopants, YVO4:Ln phosphors showed their strong characteristic emission under ultraviolet excitation (280 nm) and low-voltage electron beam excitation (1−3 kV). The energy transfer process was further studied by the time-resolved emission spectra as well as kinetic decay curves of Eu3+ upon excitation into the VO4 3− ion. Furthermore, the PL emission color of YVO4:Ln nanofibers can be tuned from blue to green, orange-red, and red easily by partial replacement VO4 3− with PO4 3− and changing the doping concentrations (x) of Ln, making the materials have potential applications in fluorescent lamps and field emission displays (FEDs).