Charge density waves in exfoliated films of van der Waals materials: evolution of Raman spectrum in TiSe2.

Goli, Pradyumna; Khan, Javed; Wickramaratne, Darshana; Lake, Roger K; Balandin, Alexander A · Nano Lett · 2012

basic_science · Level V

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Abstract

A number of the charge-density-wave materials reveal a transition to the macroscopic quantum state around 200 K. We used graphene-like mechanical exfoliation of TiSe(2) crystals to prepare a set of films with different thicknesses. The transition temperature to the charge-density-wave state was determined via modification of Raman spectra of TiSe(2) films. It was established that the transition temperature can increase from its bulk value to ~240 K as the thickness of the van der Waals films reduces to the nanometer range. The obtained results are important for the proposed applications of such materials in the collective-state information processing, which require room-temperature operation.