MOCVD Routes to 2D Crystals Joan M. Redwing Department of Materials - - PowerPoint PPT Presentation
MATERIALS RESEARCH INSTITUTE MOCVD Routes to 2D Crystals Joan M. Redwing Department of Materials Science & Engineering Materials Research Institute Center for Two-Dimensional and Layered Materials (2DLM) The Pennsylvania State University
MATERIALS RESEARCH INSTITUTE
Joan M. Redwing Department of Materials Science & Engineering Materials Research Institute Center for Two-Dimensional and Layered Materials (2DLM) The Pennsylvania State University University Park, PA 16802 USA
MATERIALS RESEARCH INSTITUTE 2D at Penn State
Mauricio Terrones Joshua Robinson
Director Assoc.Director
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20+ Faculty and 45+ Students/Post-docs
Michael Abraham Amin Azizi Zakaria Al Balushi Ganesh Bhimanapati Donna D. Deng Anna Domask Haila Al Dosari
Simin Feng Robert Fraleigh Jarod Gagnon Yiyang Gong Corey T. Janisch Ethan Kahn Nina Kovtyukhova Chia-Hui (Candace) Lee Yu-Chuan Lin Minh An Nguyen Lavish Pabbi Nestor Perea Lakshmy Rajukumar Chris Rotella Dr Eduardo Cruz Silva Ivan Skachko Yifan Sun Youjian Tang Timothy Walter Junjie Wang Yuanxi Wang Zefang Wang Xiaoxiang Xi Kehao Zhang Xiaotian Zhang Liang Zhao Rui Zhao Chanjing Zhou Zhong Lin Debangshu Mukherjee Roger Walker Shruti Subramanian
Nasim Alem Vincent Crespi Ismaila Dabo Suman Datta Aman Haque Eric Hudson Tom Jackson Ying Liu Zhiwen Liu Kin Fai Mak Tom Mallouk Theresa Mayer Suzanne Mohney Joan Redwing Joshua Robinson Nitin Samarth Jie Shan Jorge Sofo Mauricio Terrones Sulin Zhang Jun Zhu
Faculty Students/Post-docs
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Q.H. Huang, et al. Nature Nanotech. 7 (2012) p. 699
insulators, semiconductors, semi-metals, superconductors
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Annual Review of Materials Research, 45 , 1-27 (2015) 4
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W:Se ratio
850 oC 900 oC 600 Torr 500 Torr 700 Torr
INCREASING DOMAIN SIZE
800 oC
T = 750oC P = 700 Torr
500 nm 500 nm 500 nm 500 nm 500 nm
0 nm 10 nm
50 nm
WSe2 SiO2 SiC
W-rich WSe2
S.M. Eichfeld, J.M. Redwing, J.A. Robinson, et al., ACS Nano, 2015, 9 (2), pp 2080–2087
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sites in 2D materials.
chalcogen (S,Se,Te) vacancies.
Wallace Group (UT Dallas)
WSe2 Se:W Ratio: 400 Se:W Ratio: 800 Se:W Ratio: 170 Se:W Ratio: 14000
Temp (°C) Time (min) Pre- Anneal Pressure (Torr)
800 30 500C, 15min 700
Se:W ratio has significant impact on domain size, shape, and “defect” formation
0.0 2.0x10
4
1.0x10
51.5x10 5
1 2 3 4
WSe2/Sapphire WSe2/EG
Domain size (m)
Se to W ratio
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After MOCVD Growth As Prepared
van der Waals heterostructures
with graphene
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(a) HAADF-STEM image of monolayer and multilayer WSe2
HAADF-STEM images of (b) monolayer WSe2 and (c) edge region showing W-termination d) TEM image showing nucleation near grain boundary in graphene
(a) TEM image and (b) SAD pattern showing
epitaxial relationship between WSe2 and graphene (c) Structural model showing alignment of W atoms in WSe2 and C atoms in graphene (circled in red)
MATERIALS RESEARCH INSTITUTE Pulsed MOCVD growth of GaN 9
SiC Substrate Epitaxial Graphene Cross-section TEM of GaN growing between graphene and SiC substrate Ke Wang, PSU MCL
2 nm
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Pathways for Ga intercalation:
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Two structurally different 2D layers of GaN at interface:
ABF STEM image near the [𝟐𝟐𝟑 𝟏] zone axis Inverted image Ke Wang, PSU MCL
1 nm
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Predicted bandgap energies:
Low buckled GaN Eg=4.96 eV High buckled GaN Eg=4.24 eV Composite structure Eg=2.02 eV
Ram Krishna Ghosh and Suman Datta
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Graduate Students Xiaotian Zhang Zakaria Al Balushi Nathan Martin Mel Hainey Jr. Postdoctoral Scholars Chen Chen Jarod Gagnon Tanushree Choudhury PSU Collaborators
Financial support provided by:
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Wurtzite Bulk Structure of GaN
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Stabilized Structure Indirect bandgap 4.12 eV direct bandgap 5.28 eV
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Polarization-induced Topological insulators for memory and quantum computing Single-photon emitters for quantum optics and communication Nano Lett. 14, 982–986 (2014)