Graphene Conductivity: Testing the Resistance

AI Thread Summary
A user tested a homemade graphene sample on cardboard and polyethylene, finding that the cardboard was nonconductive while the polyethylene exhibited negative resistance. They speculated that this could be due to a capacitive effect or static discharge, suggesting that grounding the sample might eliminate faulty readings. The discussion highlighted that graphene may demonstrate negative differential resistance, where increased current leads to a drop in voltage, a phenomenon being explored for high-speed applications in graphene transistors. The user plans to experiment further, including using foil to create a shorted capacitor effect. The exploration of graphene's unique conductivity properties continues to generate interest for potential applications.
Matthew Travers
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Hi
I've made what I think is graphene. I first put the solution on cardboard and then I put some on polyethylene.
When they had dried, I tested conductivity with a digital multimeter with the scale set on megaohms.
The cardboard was nonconducting, but the sample on poly to my astonishment showed a negative resistance.
I touched the 2 probes together and they read zero, touched them back to the poly sample and again got anegative resistance. Since I am confident that thermodynamic laws are fully universal on all scales governing all energy interactions from solar concentrators to theoretical maxwell demons involving measuring quantum states, there has to be a conservative explanation. Is it some sort of capacitive effect?
 
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Negative resistance? You're discharging static charge on the polyethylene.
 
Thanks for that. So if I connected the sample to Earth first, that would eliminate the faulty reading?
 
Sample and meter leads (and probably your hands) to the same ground should take care of it.
 
Hang on, just caught up to you...earth everything to discharge and then measure after disconnecting earth.
Will try that and a couple of other ideas like putting foil on the other side of the polyethylene and connecting that to the sample so it acts like a shorted cap. Cheers mate
 
What I found was perhaps not electrostatic discharge. Apparently graphene demonstrates negative resistance or negative differential resistance where an increase of current through the material counter intuitively leads to a drop in voltage. Researchers intographene transistors are seeking to exploit the effect as they predict switching speeds over 400Ghz. It certainly explains why I was unable to detect any significqnt electrstatic charge with the hypersensitive e-field meter I have( its not a DMM). Going to look into this effect more and see if I can come up with anymore uses for it.
I'll keep you posted. Many thanks for the feedback
 

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