A new two-dimensional (2D) layered material, namely, titanium trisulfide (TiS3) monolayer, is predicted to possess novel electronic properties. Ab initio calculations show that the perfect TiS3 monolayer is a direct-gap semiconductor with a bandgap of 1.02 eV, close to that of bulk silicon, and with high carrier mobility. More remarkably, the in-plane electron mobility of the 2D TiS3 is highly anisotropic, amounting to about 10 000 cm2 V−1 s−1 in the b direction, which is higher than that of the MoS2 monolayer, whereas the hole mobility is about two orders of magnitude lower. Furthermore, TiS3 possesses lower cleavage energy than graphite, suggesting easy exfoliation for TiS3. Both dynamical and thermal stability of the TiS3 monolayer is examined by phonon-spectrum calculation and Born–Oppenheimer molecular dynamics simulation. The desired electronic properties render the TiS3 monolayer a promising 2D atomic-layer material for applications in future nanoelectronics.

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Titanium Trisulfide Monolayer: Theoretical Prediction of a New Direct‐Gap Semiconductor with High and Anisotropic Carrier Mobility

Here, we isolate thin TiS3 ribbons, a layered direct band gap semiconductor (1.1 eV, well suited for detection all across the visible spectrum), thus far almost unexplored. We fabricate field effect transistors and study their electrical characteristics and optoelectronic properties. The measured FET characteristics show mobilities up to 2.6 cm^2/Vs and ON/OFF ratios up to 10^4. Under illumination, the TiS3 NR-FETs present an ultrahigh photoresponse of 2910 A/W and fast rise/fall times of ~4 ms. In addition, we measure cutoff frequencies (f3dB) up to 1000 Hz. The strong combination of ultrahigh sensitivity all along the visible spectrum and fast time response of TiS3 nanoribbon transistors put them among the best nanoscale photodetectors to date.

Ultrahigh Photoresponse of Few‐Layer TiS3 Nanoribbon Transistors

Control over the morphology of TiS3 is demonstrated by synthesizing 1D nanoribbons and 2D nanosheets. The nanosheets can be exfoliated down to a single layer. Through extensive characterization of the two morphologies, differences in the electronic properties are found and attributed to a higher density of sulphur vacancies in nanosheets, which, according to density functional theory calculations, leads to an n-type doping.

TiS3 Transistors with Tailored Morphology and Electrical Properties

Recent results (some previously unpublished) on the physics of charge density waves (CDWs) are reviewed. The synthesis conditions and unique properties of the quasi-one- dimensional compound NbS3, with highly coherent room tem- perature CDWs, are described. A peculiar type of 'quantiza- tion' is discussed, which is observed in micro- and nanosamples of K0:3MoO3 and NbSe3 due to the discrete nature of CDW wave vector values. The electric-field-induced torsional strain (TS) in quasi-one-dimensional conductors is considered. Re- search results on the TS of a noise character induced by sliding CDWs are presented, along with those on the inverse effect, the modulation of the voltage induced by externally driven TS. ResultsonthenonlinearconductionofTiS3,aquasi-one-dimen- sional compound not belonging to the family of classical Peierls conductors, are also described.

https://iopscience.iop.org/article/10.3367/UFNe.0183.201301b.0033/pdf

High-frequency, 'quantum' and electromechanical effects in quasi-one-dimensional charge density wave conductors

This work was supported by the Netherlands Organization for Scientific Research (NWO/FOM). AJM-M acknowledges the financial support of MINISTERIO DE CIENCIA E INNOVACION (MICINN) (Spain) through the scholarship BES2012–057346. R.D’A and RB acknowledge financial support by the DYN-XC-TRANS (Grant No. FIS2013-43130-P), NanoTHERM (Grant No. CSD2010-
00044), and SElecT-DFT (FIS2016-79464-P) of the Ministerio de Economia y Competitividad (MINECO), and Grupo Consolidado UPV/EHU del Gobierno
Basco (Grant No. IT578-13). RB acknowledges the financial support of the Ministerio de Educacion, Cultura y Deporte (Grant No. FPU12/01576). AC-G
acknowledges financial support from the European Commission under the Graphene Flagship, contract CNECTICT-604391, from the MINECO (Ramon y
Cajal 2014 program, RYC-2014-01406) and from the MICINN (MAT2014-58399-JIN). MIRE Group thanks MINECO (MAT2015-65203R) for financial support. E Flores also acknowledges the Mexican National Council for Science and Technology (CONACyT).

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Pei-Ling Hsieh

Papers

Disorder effects in the linear chain compound TiS3