1. Graphene Liquid Metal RF Detector
Team Lead: Kaleo Norman
Participants: Matthew Chan, Alex Li, Michelle Masutani, Keanu Robles, Austin Tasato
With mentor, Richard C. Ordonez and advisor, Dr. David Garmire
University of Hawaiʻi at Mānoa, Dept. of Electrical Engineering, In collaboration with the Space and Naval Warfare Systems Center Pacific
.
Fabrication Methods
Intergrate the LM rails with Differential Amplifier. This will reduce noise
during experimentation and amplify any measured signal on the surface of
graphene
RF test: Expose the device to RF wavelengths
Our setup includes a graphene sheet stacked on top of four conducting rails
made out of liquid metal. The rails are shaped with polyimide tape and
enclosed in PDMS. Liquid metal (galinstan) is inserted in the cavities to make
contact with graphene
Background
Objective
In Spring 2014 on my 296 project, I was learning how to
understand graphene’s electrical properties and how to
manipulate those properties to implement graphene into a RF
detector. The device consisted of a differential amplifier
configured for low-powered operation and corresponding metal
rails to detect e-h generation on the surface of graphene
The previous design we learned that because we were
measured the graphene surface response via capacitive
coupling (no physical connection to graphene) to the input
terminals of differential amplifier, the signal measured was
VERY WEAK.
GOAL of 496: Improve previous graphene RF detector
design by making physical contact to graphene by using
liquid metal with isolation of PDMS.
Measure Current: We are trying to measure photocurrent by using a
picoammeter.. This will tell us whether the RF energy is generating electron
– hole pairs that can be electronically registered by the differential
Amplifier. The picoammeter is ran through a software called ExceLINX.
The previous design did not make physical contact to the graphene materials.
We believe the signal was weak because the charges genertaed on graphene
could not be drained from the graphene surface. In this embodiement we used
Galinstan is a liquid metal alloy that contains gallium, indium, and tin.
Desirable Properties of galinstan
1 thermal conductivity 16.5
𝑊
𝑚∗𝐾
2 melting -19°C
3 viscosity 0.0024 Pa*s
Due to galinstan’s liquid properties, we were able to make good contact with
graphene. However, we needed to encapusluate galinstan in polyimide and
PDMS to stop the alloy from oxidizing with air .
Differential Amplifier Isolated Differential
Amplifier
Galinstan (Wikipedia)
Galinstan Design Layout
KE6485 Picoammeter
ExceLINX
Next Steps
References
• T. Winzer, A. Knorr, E. Malic, “Carrier multiplication in graphene,” Nano
Letters, vol. 10, no. 12, pp. 4839-4843, 2010.
• J. Liu, S. Safavi-Naeini, D. Ban, “Fabrication and measurement of
graphene p-n junction with two top gates”, Electronics Letters, vol. 50,
no. 23, pp. 1724-1726, 2014.