1. in conjunction with
Two-Dimensional Mapping of Energy Transfer in Graphene/MoS2 Photodetectors
Michael Earle
Ossining High School, Ossining, NY
Stevens Institute of Technology, Hoboken, NJ
My name is Michael Earle, and the Title of my research is “Two Dimenisional Mapping of Energy Transfer in Graphene/MoS2 Photodetectors”. In my novel research, I fabricated, then studied the fundamental physics of a new kind of photodetector that’s revolutionizing nanotechnology. Instead of using silicon, I used single-atom thick crystals to create a devices that has the potential to be smaller, faster, and more efficient than today’s electronics.

2. Background Single Atom Thick Crystals
Used for next-generation electronics
Stacked into “Heterostructures” to create new electronics
Smaller
Faster
More Efficient
Flexible
Image 1: “Graphene”
Image 2: “Molybdenum Disulfide”

3. Graphene and MoS2 Graphene Molybdenum Disulfide
1. Zhang, Wenjing, et al. "Ultrahigh-Gain Photodetectors Based on Atomically Thin Graphene-MoS2 Heterostructures." Scientific reports 4 (2014).
2. Mueller, Thomas, Fengnian Xia, and Phaedon Avouris. "Graphene photodetectors for high-speed optical communications." Nature Photonics 4.5 (2010):

4. Purpose
Problem
Research has yet to uncover how structures of graphene and MoS2 work on an atomic scale
Goal
Use photoluminescence Mapping to understand the energy transfer in heterostructures of graphene and Molybdenum Disulfide
Images by the student researcher

5. Methods Sample Fabrication Van der Waals Forces Crystal Exfoliation
Images created by the student researcher

6. Methods Sample Fabrication Crystal Exfoliation Identification
100x magnification
Images created by the student researcher

7. Methods Sample Fabrication Crystal Exfoliation Identification Stamping
Dual Micromanipulators
Viscoelastic Stamp (Green)
Images created by the student researcher

8. Results Three-Layer Three-Layer MoS2 on top MoS2 on bottom
Images created by the student researcher

9. Two-Dimensional Mapping
LabVIEW
Images created by the student researcher

10. Two-Dimensional Mapping
LabVIEW
Images created by the student researcher

11. Two-Dimensional Mapping
LabVIEW
(This process takes
30 min. to 2 hours)
Images created by the student researcher

12. Review of Literature Photoluminescence
Photoluminescence is a measure of light absorbtion1-3
The less photoluminescence we see emitted, the more energy is being absorbed
Photons
MoS2 or other
semiconductor
Electron
Mueller, Thomas, Fengnian Xia, and Phaedon Avouris. "Graphene photodetectors for high-speed optical communications." Nature Photonics 4.5 (2010):
Mak, Kin Fai, et al. "Atomically thin MoS 2: a new direct-gap semiconductor." Physical Review Letters (2010):
Zhang, Wenjing, et al. "Ultrahigh-Gain Photodetectors Based on Atomically Thin Graphene-MoS2 Heterostructures." Scientific reports 4 (2014).

13. Results Photoluminescence Maps
Images created by the student researcher

14. Discussion Photoluminescence Maps
Graphene decreased MoS2’s PL by a factor of 27 and 35
Electrons are not allowed to recombine
Electrons are moving from MoS2 to graphene
27x Quenching
35x Quenching
Images created by the student researcher

15. Discussion Photoluminescence Maps
6x higher photoluminescence where graphene touches MoS2
This sample was studied over a year after fabrication
A new phenomenon is dominating the energy transfer in this structure
Images created by the student researcher

16. A new phenomenon is dominating the energy transfer in this structure
Discussion
Photoluminescence Maps
A new phenomenon is dominating the energy transfer in this structure
Clean Heterostructure
Graphene
MoS2
Pure Silicon Crystal
Images created by the student researcher

17. A new phenomenon is dominating the energy transfer in this structure
Discussion
Photoluminescence Maps
A new phenomenon is dominating the energy transfer in this structure
Oxidation creates an ion layer on top
Heterostructure exposed to air
Si becomes SiO2 with oxide ion layer
Oxide Layer
Graphene
MoS2
Oxide Layer
Pure Silicon Crystal
Images created by the student researcher

18. A new phenomenon is dominating the energy transfer in this structure
Discussion
Photoluminescence Maps
A new phenomenon is dominating the energy transfer in this structure
Heterostructure exposed to air
Oxide Layer
Graphene
MoS2
Oxide Layer
Pure Silicon Crystal
Images created by the student researcher

19. A new phenomenon is dominating the energy transfer in this structure
Discussion
Photoluminescence Maps
A new phenomenon is dominating the energy transfer in this structure
Heterostructure exposed to air
Oxide Layer
Graphene
MoS2
Oxide Layer
Pure Silicon Crystal
Images created by the student researcher

20. Discussion Photoluminescence Maps
A new phenomenon is dominating the energy transfer in this structure
Graphene protects MoS2 from environmental effects
Heterostructure exposed to air
Oxide Layer
Graphene
MoS2
Oxide Layer
Pure Silicon Crystal
Images created by the student researcher

21. Graphene can encapsulate MoS2 and preserve its electronic properties
Applications
Finding
Significance
Our research is the first to create a working model of how graphene and MoS2 interact
Establishing the groundwork principles of crystal interactions will enable the application of these crystals in new electronics
Graphene can encapsulate MoS2 and preserve its electronic properties
Preservation techniques will help bring these electronics out of the lab and into everyday life
Images created by the student researcher

22. in conjunction with
Two-Dimensional Mapping of Energy Transfer in Graphene/MoS2 Photodetectors
Michael Earle
Ossining High School, Ossining, NY
Stevens Institute of Technology, Hoboken, NJ
My name is Michael Earle, and the Title of my research is “Two Dimenisional Mapping of Energy Transfer in Graphene/MoS2 Photodetectors”. In my novel research, I fabricated, then studied the fundamental physics of a new kind of photodetector that’s revolutionizing nanotechnology. Instead of using silicon, I used single-atom thick crystals to create a devices that has the potential to be smaller, faster, and more efficient than today’s electronics.
The data and figures presented in this research were created entirely by the student researcher unless otherwise noted. All procedures were carried out by the student researcher.

23. Review of Literature Zhang et. al (2014)
Proof-of-concept for CVD-grown graphene/MoS2 devices
Used preliminary Raman Spectra to extrapolate charge carrier movement
Buscema et. al (2014)
Investigated the effect of substrate on the photoluminescence (PL) of MoS2
SiO2 ions reduced PL of MoS2
Zhang et. al (2014) did not investigate effect of substrate
Mueller, Thomas, Fengnian Xia, and Phaedon Avouris. "Graphene photodetectors for high-speed optical communications." Nature Photonics 4.5 (2010):
Zhang, Wenjing, et al. "Ultrahigh-Gain Photodetectors Based on Atomically Thin Graphene-MoS2 Heterostructures." Scientific reports 4 (2014).

24. Table of Contents