title: Strong enhancement of Raman scattering from a bulk-inactive vibrational mode in few-layer MoTe₂.
abstract: Two-dimensional layered crystals could show phonon properties that are markedly distinct from those of their bulk counterparts, because of the loss of periodicities along the c-axis directions. Here we investigate the phonon properties of bulk and atomically thin α-MoTe2 using Raman spectroscopy. The Raman spectrum of α-MoTe2 shows a prominent peak of the in-plane E(1)2g mode, with its frequency upshifting with decreasing thickness down to the atomic scale, similar to other dichalcogenides. Furthermore, we find large enhancement of the Raman scattering from the out-of-plane B(1)2g mode in the atomically thin layers. The B(1)2g mode is Raman inactive in the bulk, but is observed to become active in the few-layer films. The intensity ratio of the B(1)2g to E(1)2g peaks evolves significantly with decreasing thickness, in contrast with other dichalcogenides. Our observations point to strong effects of dimensionality on the phonon properties of MoTe2.
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , Tsukuba, Ibaraki 305-0044, Japan.
authors.forename: Mahito
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Sheng Tsung
authors.initials: ST
authors.lastname: Wang
authors.forename: Meiyan
authors.initials: M
authors.lastname: Ni
authors.forename: Yen-Fu
authors.initials: YF
authors.lastname: Lin
authors.forename: Song-Lin
authors.initials: SL
authors.lastname: Li
authors.forename: Shinya
authors.initials: S
authors.lastname: Aikawa
authors.forename: Wen-Bin
authors.initials: WB
authors.lastname: Jian
authors.forename: Keiji
authors.initials: K
authors.lastname: Ueno
authors.forename: Katsunori
authors.initials: K
authors.lastname: Wakabayashi
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Tsukagoshi