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.

Transition metal chalcogenides have raised a huge interest in the nanoscience and material science communities. [1][2][3] The possibility of isolating ultrathin layers of these materials opens the door to new applications and phenomena derived from the reduced dimensionality.Among the large family of semiconducting chalcogenides, Mo-and W-based dichalcogenides are the most studied materials because of their electronic and optical properties which could make them complementary materials to graphene in applications requiring optically active semiconducting materials. [4][5][6][7][8][9][10][11][12][13][14] Nonetheless, there are many other semiconducting chalcogenide materials where electronic properties, in atomically thin form, are thus far unexplored. TiS 3 , for instance, is one of the semiconducting members of the trichalcogenides family with a bulk optical bandgap of ≈ 1 eV. 15 It has a structure, shown in Figure 1(a), composed of parallel sheets of one dimensional chains of stacked triangular prisms (TiS 3 ). 16 The sheets are held together by van der Waals forces and might be exfoliated in the same manner as This is the post-peer reviewed version of the following article: J.O. Island et al. "Ultrahigh photoresponse of few-layer TiS 3 nanoribbon transistors".

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The isolation of graphene and transition metal dichalcongenides has opened a veritable world to a great number of layered materials which can be exfoliated, manipulated, and stacked or combined at will. With continued explorations expanding to include other layered materials with unique attributes, it is becoming clear that no one material will fill all the post-silicon era requirements. Here we review the properties and applications of layered, quasi-one dimensional transition metal trichalcogenides (TMTCs) as novel materials for next generation electronics and optoelectronics. The TMTCs present a unique chain-like structure which gives the materials their quasi-one dimensional properties such as high anisotropy ratios in conductivity and linear dichroism. The range of band gaps spanned by this class of materials (0.2 eV-2 eV) makes them suitable for a wide variety of applications including field-effect transistors, infrared, visible and ultraviolet photodetectors, and unique applications related to their anisotropic properties which opens another degree of freedom in the development of next generation electronics. In this review we survey the historical development of these remarkable materials with an emphasis on the recent activity generated by the isolation and characterization of atomically thin titanium trisulfide (TiS3).

We present characterizations of few-layer titanium trisulfide (TiS3) flakes which, due to their reduced in-plane structural symmetry, display strong anisotropy in their electrical and optical properties. Exfoliated few-layer flakes show marked anisotropy of their in-plane mobilities reaching ratios as high as 7.6 at low temperatures. Based on the preferential growth axis of TiS3 nanoribbons, we develop a simple method to identify the in-plane crystalline axes of exfoliated few-layer flakes through angle resolved polarization Raman spectroscopy. Optical transmission measurements show that TiS3 flakes display strong linear dichroism with a magnitude (transmission ratios up to 30) much greater than that observed for other anisotropic two-dimensional (2D) materials. Finally, we calculate the absorption and transmittance spectra of TiS3 in the random-phase-approximation (RPA) and find that the calculations are in qualitative agreement with the observed experimental optical transmittance.

The potential of bulk black-phosphorus, a layered semiconducting material with a direct band gap of ∼0.3 eV, for thermoelectric applications has been experimentally studied. The Seebeck Coefficient (S) has been measured in the temperature range from 300 K to 385 K, finding a value of S = +335 ± 10 μV/K at room temperature (indicating a naturally occurring p-type conductivity). S increases with temperature, as expected for p-type semiconductors, which can be attributed to an increase of the charge carrier density. The electrical resistance drops up to a 40% while heating in the studied temperature range. As a consequence, the power factor at 385 K is 2.7 times higher than that at room temperature. This work indicates the prospective use of black-phosphorus in thermoelectric applications such as thermal energy scavenging, which typically require devices with high performance at temperatures near room temperatureAuthors from MIRE Group acknowledge the support of the Ministry of Economy and Competitiveness (MINECO) for this research (Contract No. MAT2011-22780). They also thank technical support from Mr. F. Moreno. E. Flores acknowledges to the Mexican National Council for Science and Technology (CONACyT) for providing the funding necessary to complete his PhD. A.C.-G. acknowledges financial support through the FP7-Marie Curie Project PIEF-GA-2011-300802 (“STRENGTHNANO”) and the Fundación BBVA through the grant “I Convocatoria de Ayudas Fundación BBVA a Investigadores, Innovadores y Creadores Culturales” (“Semiconductores ultradelgados: hacia la optoelectrónica flexible”

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