Temperature dependence of the electrical conductivity and hall coefficient in 2H‐MoS2, MoSe2, WSe2, and MoTe2

Abstract

The electrical conductivity and Hall coefficient perpendicular to the c‐axis of hexagonal MoS 2, MoSe 2, and WSe 2 are measured over the temperature ranges 120 to 1170 K and 140 to 820 K, respectively. The derived temperature‐dependent carrier densities are described by n ∼ exp (–E/kT) for temperatures less than 800 K indicating (thermal) energy gaps of 0.38 eV in n‐type MoS 2, 0.27 eV in n‐type MoSe 2, and 0.19 eV in p‐type WSe 2. Above room temperature the carrier mobilities are given by μ ∼ T−α, where α ≈ 1.5 in MoS 2, MoSe 2 and 2.7 in WSe 2. The high‐temperature (>800 K) thermal activation energies of conduction correspond to energy gaps of 1.27, 0.95, and 1.33 eV in MoS 2, MoSe 2, and WSe 2, respectively. Similar measurements on MoTe 2 crystals grown by bromine vapour transport demonstrate the effects of included bromine on the low‐temperature conduction processes.