Role of Metal Contacts and Effect of Vacuum Annealing in High Performance 2D WSe2 FETs on Flexible Substrates
(Room Exhibit Hall A)
30 Apr 19
2:30 PM
-
4:00 PM
Among the two dimensional (2D) transitional metal dichalcogenides (TMDC), tungsten diselenide (WSe2) have recently attracted much attention owing to its potential in CMOS technology, optoelectronics and flexible electronics applications. In this work, the effect of mechanical stress on few layer WSe2, mechanically exfoliated on flexible polyethylene terephthalate (PET) substrates were studied by observing changes in Raman vibrational modes and band gap in WSe2 using Raman and Photoluminescence spectroscopy respectively. To analyze the role of different metal contacts, metals with a wide range of work functions ϕm such as Au (ϕm ~ 5.47), Mo (ϕm ~ 4.53) and Al (ϕm ~ 4.08) were used as top electrodes and WSe2 based FETs were fabricated using e-beam evaporation. It was found that the charge transport properties in WSe2 changed from p-type (Au/Ti), then to ambipolar (Mo) and finally to n-type (Al) as work functions of the metals changed from high to low. Additionally, the effect of post-fabrication vacuum annealing was also studied, and it was found that the channel resistance was greatly improved after vacuum annealing over 400 K due to the desorption of residues and adsorbates, which led to an enhanced device performance including a higher current injection efficiency and carrier mobility.