Preparation of 1T′- and 2H–MoTe2 films and investigation of their photoelectric properties and ultrafast photocarrier dynamics

Abstract

1T′- and 2H–MoTe2 are metallic and semiconducting two-dimensional transition metal dichalcogenides, respectively, due to their different atomic structure. It is a pretty attractive work to control the synthesis of MoTe2 with different phases and study on their different physical properties. In this work, large-area 1T′- and 2H–MoTe2 films with nanometer thicknesses were successfully prepared. XRD, Raman spectra and SAED pattern all indicate that the two films have different atomic structures. The photoelectric properties and ultrafast photocarrier dynamics were further investigated. The results show that 1T′-MoTe2 has a higher conductivity than 2H–MoTe2 by four orders of magnitude, while 2H–MoTe2 has better photoelectric response with a responsivity of 0.016 A/W at a Vds of 1 V for 532 nm light. Transient absorption spectra reveal that the intraband relaxation time (τ1) of 1T′-MoTe2 is ∼6 ps while it is ∼100 ps in 2H–MoTe2. The interband electron-hole recombination time (τ2) in 2H–MoTe2 is longer than that in 1T’ phase. Our findings contribute to a deeper understanding of the physical properties of MoTe2 films with different phases and provide important basis for the applications of 1T′- and 2H–MoTe2 in various electrical, photoelectric and ultrafast optical devices.