Two-step Vapor Deposition Method Research Articles

Tunability of the Superconductivity of NbSe2 Films Grown by Two-Step Vapor Deposition.

Layered metallic transition-metal dichalcogenides (TMDCs) are ideal platforms for exploring their fascinating electronic properties at two-dimensional limits, such as their charge density wave (CDW) and superconductivity. Therefore, developing ways to improve the crystallization quality of TMDCs is urgently needed. Here we report superconductively tunable NbSe2 grown by a two-step vapor deposition method. By optimizing the sputtering conditions, superconducting NbSe2 films were prepared from highly crystalline Nb films. The bilayer NbSe2 films showed a superconducting transition temperature that was up to 3.1 K. Similar to the salt-assisted chemical vapor deposition (CVD) method, superconducting monolayer NbSe2 crystals were also grown from a selenide precursor, and the growth strategy is suitable for many other TMDCs. Our growth method not only provides a way to improve the crystalline quality of TMDC films, but also gives new insight into the growth of monolayer TMDCs. It holds promise for exploring two-dimensional TMDCs in fundamental research and device applications.

Synthesis of Octyl-Quaternary Ammonium Mixed-Mode Stationary Phase by Vapor Deposition Approach and Its Application in Compound Preparation Separation

An octyl-quaternary ammonium (Sil-C8-QA)-modified silica stationary phase was prepared by a two-step vapor deposition method which can substantially reduce the consumption of toxic organic solvents. The structure of the dual-functional ligands stationary phase was characterized by Fourier transform infrared spectroscopy and solid-state 13C CP/MAS NMR. Following elemental analysis, the surface density of octyl and quaternary ammonium bonding amount is 2.13 µmol m−2 and 0.77 µmol m−2, respectively. The efficiency and selectivity of the two-ligand phases were compared with two sole functional ligand phases: quaternary ammonium (Sil-QA)- and octyl-modified silica (Sil-C8). Chromatographic evaluation demonstrated a mixed-mode reversed-phase/anion-exchange retention property on the Sil-C8-QA column. The retention behavior of a homologous series of alkylbenzoic acids on the synthesized phase was systematically studied by changing the pH, ionic, and solvent strength of the mobile phase. A well-established mixed-model mechanism was confirmed. The Sil-C8-QA phase can predominantly enhance the retention of acidic drugs and improve their selectivity. It was also successfully applied to the simultaneous separation and determination of three kinds of compound preparations with large differences in component polarity.

Synthesis and Photoelectric Properties of Coaxial Schottky Junctions of ZnS and Carbon Nanotubes

One-dimensional (1D) nanostructures of the wide band gap semiconductors are promising building blocks for photoelectric nanodevices. However, some problems like strong 1D confinement largely hamper their applications. To avoid these problems, here, we provide another 1D configuration, in which an inner-wire coaxial Schottky junction exists, thus effectively avoiding the recombination of the photoexcited carriers. As an example, we produce ZnS/carbon nanotube nanocables with uniform morphologies by a two-step vapor deposition method and find that they have good conductance, obvious light response, and ohmic contacts with electrodes, avoiding the limitations of both the pristine nanomaterials. We believe that this configuration would be valuable for applying the 1D nanomaterials in photoelectronics.