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SUMMARY:Electrical contacts between three-dimensional metals and two-dimen
 sional semiconductors - Prof. Manish Chhowalla\, Goldsmiths' Professor of 
 Materials Science\, University of Cambridge
DTSTART:20181019T133000Z
DTEND:20181019T143000Z
UID:TALK113002@talks.cam.ac.uk
CONTACT:Kayleigh Dunn
DESCRIPTION:As the dimensions of semiconducting channels in field effect t
 ransistors (FETs) decrease\, the contact resistance of metal-semiconductor
  interface at the source and drain electrodes dominates the performance. T
 wo dimensional (2D) transitional metal dichalcogenides (TMDs) such as moly
 bdenum disulfide (MoS2) have been demonstrated to be excellent semi-conduc
 tors for ultra-thin FETs. However\, unusually high contact resistance has 
 been observed across the metal-2D TMD interface. We have shown that it is 
 possible to reduce the contact resistance by forming lateral junctions bet
 ween metallic and semiconducting phases of 2D materials. Recent studies ha
 ve shown that van der Waals (vdW) contacts formed by graphene on 2D TMDs p
 rovide lowest contact resistance. However\, vdW contacts between evaporate
 d three-dimensional metal and 2D TMDs have yet to be demonstrated. Here\, 
 we report the realization of ultra-clean vdW contacts between 3D metals an
 d single layer MoS2. Using scanning transmission electron microscopy (STEM
 ) imaging\, we show that the 3D metal and 2D MoS2 interface is atomically 
 sharp with no detectable chemical interaction\, suggesting van-der-Waals-t
 ype bonding between the metal and MoS2. We show that the contact resistanc
 e of indium electrodes is ~ 800 Ω-μm – amongst the lowest observed for
  metal electrodes on MoS2 and is translated into high performance FETs wit
 h mobility in excess of 160 cm2-V-s-1 at room temperature without encapsul
 ation. We also demonstrate low contact resistance of 220 Ω-μm on 2D NbS2
  and near ideal band offsets\, indicative of defect free interfaces\, in W
 S2 and WSe2. I will introduce 2D TMDs and their properties and then descri
 be our efforts on making good contacts on 2D semiconductors. \n\n
LOCATION:Small Lecture Theatre\, Bragg Building\, Cavendish Laboratory (Ph
 ysics Department)
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