“…We utilized the shadow mask method to directly deposit TLM structures onto pre-selected 1T-TaS2 thin films obtained by mechanical exfoliation. The exfoliated layers of 50 nm -60 nm were relatively stable in the air, which allowed us to use the shadow mask method 65 . The method allowed us to avoid the damage from chemical contamination, typically associated with conventional lithographic lift-off processes.…”
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 utilized the shadow mask method to directly deposit TLM structures onto pre-selected 1T-TaS2 thin films obtained by mechanical exfoliation. The exfoliated layers of 50 nm -60 nm were relatively stable in the air, which allowed us to use the shadow mask method 65 . The method allowed us to avoid the damage from chemical contamination, typically associated with conventional lithographic lift-off processes.…”
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...
“…Also a number of computational efforts have been dedicated to the identification of new 2D materials and to the construction of computational databases with information about their stability and (photo-) electronic properties [5][6][7] . One of the driving forces behind this research has been an interest in ultra-small electronic components and this has also led to studies of 1D or quasi-1D materials as possible interconnects 8,9 . Furthermore, the possibility of combining materials of different dimensionality into new van der Waals bonded mixed-dimensional heterostructures has recently been discussed 10 .…”
The last decade has seen intense research in materials with reduced dimensionality. The low dimensionality leads to interesting electronic behavior due to electronic confinement and reduced screening. The investigations have to a large extent focused on 2D materials both in their bulk form, as individual layers a few atoms thick, and through stacking of 2D layers into heterostructures. The identification of low-dimensional compounds is therefore of key interest. Here, we perform a geometric analysis of material structures, demonstrating a strong clustering of materials depending on their dimensionalities. Based on the geometric analysis, we propose a simple scoring parameter to identify materials of a particular dimension or of mixed dimensionality. The method identifies spatially connected components of the materials and gives a measure of the degree of "1D-ness," "2D-ness," etc., for each component. The scoring parameter is applied to the Inorganic Crystal Structure Database and the Crystallography Open Database ranking the materials according to their degree of dimensionality. In the case of 2D materials the scoring parameter is seen to clearly separate 2D from non-2D materials and the parameter correlates well with the bonding strength in the layered materials. About 3000 materials are identified as one-dimensional, while more than 9000 are mixed-dimensionality materials containing a molecular (0D) component. The charge states of the components in selected highly ranked materials are investigated using density functional theory and Bader analysis showing that the spatially separated components have either zero charge, corresponding to weak interactions, or integer charge, indicating ionic bonding.
“…To date, many compositions of quasi‐1D vdW materials, such as MX 3 (M: transition metal atoms from either group IVB [Ti, Zr, Hf] or group VB [Nb, Ta]; X: chalcogen atoms from group VIA [S, Se, Te]), Bi 4 I 4 , 5 Nb 2 PdS 5 , 7 Ta 2 Pd 3 Se 8 , 8 Sb 2 Se 3 , 12,13 CsBi 4 Te 6 , 15 TaSe 3 , 22,23 and ZrTe 3 , 24,25 have been investigated, whereas only few true 1D vdW materials, including Te, 14 VS 4 , 16 and MoSI, 18 have been reported. We recently demonstrated the successful synthesis of a new 1D vdW material with the chemical formula Nb 2 Se 9 , 26 and its trend of bandgap with bundling effect, to estimate its potential in optical device application 27 .…”
Section: Introductionmentioning
confidence: 99%
“…10 They have immense practical applications and have shown excellent performance in transistors, 11 solar cells, 12,13 photodetectors, 14 thermoelectric devices, 15 magnesium batteries, 16 and water splitting. 17 To date, many compositions of quasi-1D vdW materials, such as MX 3 22,23 and ZrTe 3 , 24,25 have been investigated, whereas only few true 1D vdW materials, including Te, 14 VS 4 , 16 and MoSI, 18 have been reported. We recently demonstrated the successful synthesis of a new 1D vdW material with the chemical formula Nb 2 Se 9 , 26 and its trend of bandgap with bundling effect, to estimate its potential in optical device application.…”
In the present study, the experimental Raman spectrum of niobium‐selenide nanowires (Nb2Se9) is reported for the first time followed by an analysis of the Raman spectrum using the density functional theory (DFT). According to the group‐theoretical analysis, 33 Ag modes were identified as Raman active modes. In the experimental spectrum, 19 well‐resolved Raman modes were observed: 13 modes in the low‐wavenumber range (50–200 cm−1) and six modes in the high‐wavenumber range (220–340 cm−1). The DFT calculations were performed using the local‐density approximation (LDA) functional and generalized gradient approximation (GGA) functional of Perdew–Burke–Ernzerhof (PBE) with van der Waals corrections (PBE‐D3). PBE‐D3 showed better compatibility with the experimental data for the high‐wavenumber range. Our results provide an essential reference for the Raman scattering of newly synthesized Nb2Se9 nanowires and nanodevices in the future.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.