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2D Semiconductors

Transition metal dichalcogenides have garnered increased attenition for their applications in transparent, flexible, and low-cost electronics and highly scaled logic transistors. There has been particularly widespread interest in molybdenum disulfide (MoS2) which has a non-zero band gap,  relatively high mobility (~200 cm^2/V-s),  and can be obtained from geological samples.

We have demonstrated large-area chemical vapor depostion (CVD) growth of MoS2 that utilizes high temperature sulfurization of sputter deposited Mo metal to produce MoS2 with (0001) orientation. The Raman and X-ray diffraction (XRD) spectra of our MoS2 demonstrate that it is comparable to geological samples typically used for  micromechanical exfoliation and single crystal. We have demonstrated in situ p-doping of MoS2 utilizing Nb as the dopant with hole mobility of 8.5 cm^2/V-s with a charge concentration of 3.1 x 10^20 cm^-3. 

2D Semiconductors 


1) Masihhur R. Laskar, Lu Ma, ShanthaKumar K, Pil Sung Park, Sriram Krishnamoorthy, Digbijoy N. Nath, Wu Lu, Yiying Wu, Siddharth Rajan, "Large Area Single Crystal (0001) Oriented MoS2 Thin Films", Applied Physics Letters, 102, 252108, (2013).

2) Masihhur R. Laskar, Digbijoy N. Nath, Lu Ma, Edwin W. Lee II, Choong Hee Lee, Thomas Kent, Zihao Yang, Rohan Mishra, Manuel A. Roldan, Juan-Carlos Idrobo, Sokrates T. Pantelides, Stephen J. Pennycook, Roberto Myers, Yiying Wu, Siddharth Rajan, “p-type doping in CVD grown MoS2 using Nb”,  Applied Physics Letters 104, 092104, (2014).

3) Lu Ma, Digbijoy N. Nath, Edwin W. Lee II, Choong Hee Lee, Mingzhe Yu, Aaron R. Arehart, Siddharth Rajan, Yiying Wu, "Epitaxial growth of large area single-crystalline few-layer MoS2 with high space charge mobility of 192 cm^2V^-1s^-1", Applied Physics Letters 105, 072105, (2014).

4) Edwin W. Lee II, Lu Ma, Digbijoy N. Nath, Choong Hee Lee, Aaron R. Arehart, Yiying Wu, Siddharth Rajan, "Growth and electrical characterization of two-dimensional layered MoS2/SiC heterojunctions", Applied Physics Letters 105, 203504, (2014).

5) Edwin W. Lee II, Choong Hee Lee, Pran K. Paul, Lu Ma, William D. McCulloch, Sriram Krishnamoorthy, Yiying Wu, Aaron R. Arehart, Siddharth Rajan, "Layer-transferred MoS2/GaN PN diodes", Applied Physics Letters 107, 103505, (2015).

6) Choong Hee Lee, William McCulloch, Edwin W. Lee II, Lu Ma, Sriram Krishnamoorthy, Jinwoo Hwang, Yiying Wu, and Siddharth Rajan, "Transferred large area single crystal MoS2 field effect transistors", Applied Physics Letters 107, 193503 (2015).