Nature of electrical conduction in MoS 2 films deposited by laser physical vapor deposition

Molybdenum disulfide (MoS 2 ) films with n- and p-type conductivity are considered to be important for potential use in next generation devices. Laser physical vapor deposition is used in the present work to deposit undoped, niobium (Nb)-doped and tungsten (W)-doped films on sapphire (Al 2 O 3 ), silicon oxide (SiO 2 )-n-Si and silicon oxide (SiO 2 )-p-Si substrates maintained at 600 °C. The films are characterized for the nature of charge carriers, composition, lattice orientation and phonon signature. Results from Seebeck and Hall measurements corroborate to show that all films on sapphire and SiO 2 -n-Si are n-type whereas films on SiO 2 -p-Si are p-type with a higher activation energy for conduction. The reasons for the difference in nature of conductivity in the films are investigated. Sulfur deficient films are predominantly n-type; however, the presence of adsorbed oxygen and molybdenum trioxide (MoO 3 ) in the films on SiO 2 -p-Si is found to be responsible for p-type conductivity.