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

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.