1. Exploration of Nanoelectronics
Built with Novel Materials Systems
December 2014
Jeong Seuk Kang
Materials Science and Engineering
Electrical Engineering & Computer Sciences
University of California, Berkeley

2. 2
Jeong Seuk (Louis) Kang
UC Berkeley Senior majoring in
Ø Materials Science and Engineering
Ø Electrical Engineering & Computer Sciences
8 co-author publications &
1 first-author publication submitted
on two-dimensional semiconductor materials
Graduate Fellowship
Ø Samsung Scholarship (covering both tuition and stipend throughout my entire PhD)
Research Experience
Ø Novel electronics design and fabrication with Prof. Ali Javey (UC Berkley EECS)
Ø Characterization of low-dimensional materials with Prof. Junqiao Wu (UC Berkeley MSE)
Ø Li-ion battery pack design for electric vehicles with Prof. Dennis Lieu (UC Berkeley Mech. E)
Ø Cost-benefit analysis on solar industry in developing countries with Prof. Daniel Kammen
(UC Berkeley Energy and Resources Group)

3. 3
Motivation
Device scaling needs:
LG : gate length
T : channel length
T < ~ 2/3 LG T < ~ 1/3 LG
Device miniaturization at extreme (For LG <5 nm, T ~ 2 nm)
Ø This demands materials control at unprecedented level – atomic perfection needed
Ø Ultimate scaling: the channel and the gate dielectric should be only a monolayer thick

4. 4
Motivation
Layered Chalcogenides: atomic level uniformity and new opportunities
c/2
X
M
EC
EV
-2
-3
-4
-5
-6
-7
-8
-9
E relative to Evac (eV)
…
Ø New library of semiconductors, scalable down to a monolayer
Ø Lack surface dangling bonds; no native oxide
Ø Uniform thickness down at the atomic level
sharp band edges!

5. 5
Stable Doping
Ø p-Doping via Covalent Functionalization w/ NO2
P. Zhao, D. Kiriya, A. Azcatl, C. Zhang, M. Tosun, Y.-S. Liu, M. Hettick, J. S. Kang, S. McDonnell, S. KC, J. Guo, K. Cho, R. M Wallace, A. Javey. "Air Stable
p-Doping of WSe2 by Covalent Functionalization", ACS Nano (2014)
Ø n-Doping via Charge Transfer from Benzyl Viologen
D. Kiriya, M. Tosun, P. Zhao, J. S. Kang, A. Javey. "Air-stable surface charge transfer doping of MoS2 by benzyl viologen ”, JACS (2014)

6. 6
Strain Engineering
Ø Strain-induced Indirect-to-Direct Transition in WSe2
S. B. Desai, G. Seol, J. S. Kang, H. Fang, C. Battaglia, R. Kapadia, J. W. Ager, J. Guo, and A. Javey. "Strain-Induced Indirect to Direct Bandgap Transition in
Multilayer WSe2", Nano Letters, (2014)

7. 7
Contact Engineering
Ø MoOx p-Type Contacts for MoS2 PFETs
S. Chuang, C. Battaglia, A. Azcatl, S. McDonnell, J. S. Kang, X. Yin, M. Tosun, R. Kapadia, H. Fang, R. M. Wallace, A. Javey, "MoS2 P-type Transistors and
Diodes Enabled by High Workfunction MoOx Contacts", Nano Letters, (2014)

8. 8
Heterostructures
Ø Interlayer Coupling between TMDC monolayers
H. Fang, C Battaglia, C. Carraro, S. Nemsak, B. Ozdol, J. S. Kang, H. A. Bechtel, S. B. Desai, F. Kronast, A. A. Unal, G. Conti, C. Conlon, G. K. Palsson, M.
C. Martin, A. M. Minor, C. S. Fadley, E. Yablonovitch, R. Maboudian, A. Javey. "Strong interlayer coupling in van der Waals heterostructures built from single-layer
chalcogenides”, PNAS, (2014)
Ø FET built from all 2D components
T. Roy, M. Tosun, J. S. Kang, A. B. Sachid, S. B. Desai, M. Hettick, C. C. Hu, and A. Javey. "Field-Effect Transistors Built from All Two-Dimensional Material
Components”, ACS, (2014)

9. 9
Materials Characterization
Ø Defects Activated Photoluminescence (PL) in TMDCs
Sefaattin Tongay, Joonki Suh, Can Ataca, Fan Wen, Alexander Luce, J. S. Kang, Jonathan Liu, Changhyun Ko, Jian Zhou, Jingbo Li, Jeffrey C. Grossman and
Junqiao Wu, Defects activated photoluminescence in two-dimensional semiconductors: interplay between bound, charged, and free excitons, Sci. Rep. (2013)
Ø PL Engineering via Physisorption Gating
Sefaattin Tongay, Jian Zhou, Can Ataca, Jonathan Liu, J. S. Kang, Tyler S. Matthews, Long You, Jingbo Li, Jeffrey C. Grossman and Junqiao Wu, Broad-range
modulation of light emission in two-dimensional semiconductors by molecular physi-sorption gating, Nano Lett, (2013)

10. 10
Current Projects
Ø Light Outcoupling Engineering in 2D materials (submitted)
D. Lien*, J. S. Kang*, M. Amani, K. Chen, M. Tosun, H. Wang, T. Roy, M. Eggleston1, M. Wu, S. Lee, J. He, A. Javey.
Engineering Light Outcoupling in 2D Materials, in preparation. (*These authors contributed euqally to this work)
Ø Deterministic Nucleation and Growth of Ultralarge grain (>100 μm) III-V
Thin-Films on Nonepitaxial Substrates using the Thin-Film Vapor-Liquid-
Solid Growth Mode