We report on switching among three charge-density-wave phases -commensurate, nearly commensurate, incommensurate -and the high-temperature normal metallic phase in thin-film 1T-TaS2 devices induced by application of an in-plane electric field. The electric switching among all phases has been achieved over a wide temperature range, from 77 K to 400 K. The low-frequency electronic noise spectroscopy has been used as an effective tool for monitoring the transitions, particularly the switching from the incommensurate charge-density-wave phase to the normal metal phase. The noise spectral density exhibits sharp increases at the phase transition points, which correspond to the step-like changes in resistivity. Assignment of the phases is consistent with low-field resistivity measurements over the temperature range from 77 K to 600 K. Analysis of the experimental data and calculations of heat dissipation suggest that Joule heating plays a dominant role in the electric-field induced transitions in the tested 1T-TaS2 devices on Si/SiO2 substrates. The possibility of electrical switching among four different phases of 1T-TaS2 is a promising step toward nanoscale device applications. The results also demonstrate the potential of noise spectroscopy for investigating and identifying phase transitions in materials. Keywords: charge-density-wave effects; van der Waals materials; resistive switching, lowfrequency noise, 1T-TaS2; normal metallic phase Electric Switching of the Charge-Density-Wave and Normal Metallic Phases in 1T-TaS2 Thin-Film Devices -UC Riverside 2019 3 | P a g eSwitching between various material phases at room temperature by the application of electric field has the potential of becoming a new device paradigm for future electronic and optoelectronic technologies 1-4 . Among the promising material candidates, which must exhibit phase changes characterized by abrupt resistivity changes and hysteresis, is the 1T polymorph of tantalum disulfide (TaS2). The quasi-two-dimensional (2D) van der Waals layered crystalline 1T-TaS2 exhibits charge-density-wave (CDW) effects, i.e. periodic modulation of the charge density and the underlying lattice resulting from the interplay between the electron-electron and electronphonon interactions [5][6][7][8][9][10][11][12][13]14 . The CDW state becomes fully commensurate with the lattice below ~200 K 15-17 . The commensurate CDW (C-CDW) consists of a √13 × √13 reconstruction within the basal plane that forms a star-of-David pattern in which each star contains 13 Ta atoms. The Fermi surface, composed of 1 d-electron per star, is unstable, so that the lattice reconstruction is accompanied by a Mott-Hubbard transition that fully gaps the Fermi surface and increases the resistance 15,18-21 . As the temperature increases above 180 K, the C-CDW phase breaks up into a nearly commensurate CDW (NC-CDW) phase that consists of ordered C-CDW regions separated by domain walls 22 . This C-CDW to NC-CDW transition is revealed as an abrupt change in the resistance with a large hysteresis window i...

We show that one-dimensional (1D) nanostructures and two-dimensional (2D) supramolecular crystals of organic semiconductors can be grown on substrates under ambient conditions directly from three-dimensional (3D) organic crystals. The approach does not require dissolving, melting or evaporating of the source crystals and is based on the Organic SolidSolid Wetting Deposition (OSWD). We exemplify our approach by the pigment quinacridone (QAC). Scanning Tunnelling Microscopy (STM) investigations show that the structures of the resulting 2D crystals are similar to the chain arrangement of the alpha and beta QAC polymorphs and are independent of the 3D source crystal polymorph (gamma). Furthermore, distinct 1D chains can be produced systematically.

Many material device applications would benefit from thin diamond coatings, but current growth techniques, such as chemical vapor deposition (CVD) or atomic layer deposition require high substrate and gas-phase temperatures that would destroy the device being coated. The development of freestanding, thin boron-doped diamond nanosheets grown on tantalum foil substrates via microwave plasma-assisted CVD is reported. These diamond sheets (measuring up to 4 × 5 mm in planar area, and 300-600 nm in thickness) are removed from the substrate using mechanical exfoliation and then transferred to other substrates, including Si/SiO 2 and graphene. The electronic properties of the resulting diamond nanosheets and their dependence on the free-standing growth, the mechanical exfoliation and transfer processes, and ultimately on their composition are characterized. To validate this, a prototypical diamond nanosheet-graphene field effect transistor-like (DNGfet) device is developed and its electronic transport properties are studied as a function of temperature. The resulting DNGfet device exhibits thermally activated transport (thermionic conductance) above 50 K. Below 50 K a transition to variable range hopping is observed. These findings demonstrate the first step towards a low-temperature diamond-based transistor. HeterojunctionsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

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