What Are Good Low Work Function Materials for Photoelectric Effect Experiments?

[Lambduh]

Hi Guys,

I wanted to do an experiment testing the photoelectric effect but am having trouble getting light with energy higher than ~4 eV(300nm) through my window into vacuum as it's made of BK7 instead of something like fused silica. Does anyone know of a good material to use with a work function lower than that so i can see some electrons

Thanks!

 

[Bob S]

Are you interested in photomultipliers that have a high quantum efficiency at 400 nm? The Hamamatsu photocathodes have a low work function. See
http://jp.hamamatsu.com/resources/products/etd/pdf/UBA_SBA_TPMH1305E03.pdf

 

[Lambduh]

Sorry i wasn't very clear. I have a Monochromater source with xenon/deuterium lamps. I want to shine light into a vacuum cell with a sample in it and then collect them at a positively biased cathode then read the current with a picoammeter. However the window on my vacuum cell doesn't transmit light below ~350nm so I'm trying to find a material that i can hit with ~3.5 eV photons and eject some electrons.

I can't seem to find a relatively stable compound with a low enough work function to use. I guess that makes sense because all of the stable compounds want to hold on to those electrons:) So any suggestions would be awesome.

Thanks again!:)

Mark

 

[ZapperZ]

Magnesium has a work function of around 3.7 eV. That is lower than your photon energy.

Zz.

 

[Lambduh]

Hmm i'll definitely try it thanks! I'm curious though... because magnesium forms an oxide layer(which seems to be hard to remove) won't that affect the work function? Depending on the material I've read that even a monolayer of adsorbates can change the work function by up to ~1eV.

Thanks again:)

 

[ZapperZ]

Hmm i'll definitely try it thanks! I'm curious though... because magnesium forms an oxide layer(which seems to be hard to remove) won't that affect the work function? Depending on the material I've read that even a monolayer of adsorbates can change the work function by up to ~1eV.

Thanks again:)

Then you will have to do some form of cleaning, such as e-beam polishing, in situ in vaccum.

Zz.

 

[Lambduh]

Cool. Thanks for the info Zz.