Fig. 1
From: Anisotropy of impact ionization in WSe2 field effect transistors
Device structures and sample characterization. a Left panel: schematic of the lateral WSe2 FET. Right panel: SEM image of the lateral WSe2 FET, with the channel length indicated. b Left panel: schematic of the vertical WSe2 FET employing a WSe2/graphene heterostructure. Right panel: OM image of the vertical WSe2 FET. c Corresponding HR-TEM image and AFM data indicating the thickness of the WSe2/graphene heterostructure (the thickness of the WSe2 used in the lateral FET is also same as 90 nm). The stacked structure consists of bi-layer graphene, bulk WSe2, and an Au electrode as the drain. d Raman spectra of mechanically exfoliated WSe2 and bi-layer graphene used for in the fabrication of devices