Talk:Work function

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This is a question about work fonction for a glass surface:

How does the work function change when the glass surface is 'wet' i.e. it is covered with few monolayers of water?

How doe the work function change when the glass surface is covered by some deposits? How does this change depends on the composition of these depostits?

Will be very grateful for any information or for suggestions how to make such measurements..

Adam Para, para@fnal.gov

The question is 4 years old now, but an answer anyway - Yes, the work function can change, for example when a charge transfer from adsorbate to the surface occurs. One can reason that, when adsorbate electrons are transferred the surface, the work function will decrease, and vice versa. In the case of water adsorption this effect might be smaller then compared to ion adsorption, when the dipole of the surface will not be changed too much by the presence of the water.
See for example the paper concerning water and alkali metal ions on graphite is given in J. Chem. Phys. 125, 014708 (2006)
-- Mipmip 11:27, 27 November 2006 (UTC)

doing some research:

"defines characteristics of contact between two materials featuring different work function; for conductor-semiconductor contact determines whether contact is ohmic or rectifying."

Actually the ionization potential and work function of any metal is the same, but it is different for semiconductors or insulators. In fact work function is defined as the energy required to remove an electron from Fermi level to Vacuum level(energy level differences), but ionization potential is the energy required to remove the electron from the bottom of the conduction band to vaccuum level. I hope that I have clearly written to you, if not pleaze advice me.

http://arxiv.org/PS_cache/physics/pdf/0207/0207116.pdf

does the work function depend on the charge of the material? i would imagine it does. - Omegatron 20:45, May 20, 2005 (UTC)

looks like it does: "The same process will charge a spacecraft orbiting in the sunlight positively, to a few volts. Sunlight knocks out electrons from the surface and a few manage to escape, leaving the spacecraft positively charged; the situation then stabilizes, because the positive charge prevents any more electrons from leaving." - Omegatron 21:46, May 20, 2005 (UTC)

the equation needs to have all the terms defined. - Omegatron 20:45, May 20, 2005 (UTC)

Contents

[edit] changed 'metal' to 'conductor' in definition

Semiconductors for example have an associated work function so 'metal' in the definition is not strictly correct. I have changed it to 'conductor' which I believe to be more accurate. Andrew Gray Edinburgh University

[edit] Define the terms on the formula

This comment was left on the page:

You need to say what "N" is. You need to identify explicitly "V". From your definition I do not think it is the vacuum level. Also the fermi energy and the chemical potential (neither of which you define and assume the reader knows) aren't always the same thing. This is a place where people come to find out things they don't know. Define all your terms. A derivation would be nice.

I am postint it here, where it belongs -- Marco ✉ 16:45, 8 October 2005 (UTC)

[edit] Surface effect is important for work function

I changed the definition and gave a new formula for work function because the original one did not take surface effect into account, which is important. Work function is not simply negative Fermi energy due to the "double charge layer" on the conductor surface. There is a very good description in Ashcroft's text book concerning this.

[edit] origin of term

does anyone have any idea where this term comes from? it kind of stands out relative to the names of other material properties.

[edit] caesium

how come caesium is quoted as two different work function 1.9 eV in text and 2.14 eV in the table. which is correct? --Liamstone (talk) 06:38, 9 May 2008 (UTC)

according to http://symp15.nist.gov/pdf/p563.pdf, it is approximately 1.95eV

the CRC value of 2.14eV apparently refers to work done in 1969; an old AIP handbook lists both values and refers to work done in 1964. It looks to me like the CRC table is based on a 1977 JAppliedP paper by Michaelson (48, 4729) Tkirkman (talk) —Preceding comment was added at 17:45, 24 May 2008 (UTC)

[edit] delete?

"A saturation state of the filament current is reached, where a minor change in the filament current does not affect the beam current. The electron gun is then operated with the filament current very near the potential to overcome the work function (W)(Goldstein, 2003)"

For any normal material (and certainly for W as the data of Jones & Langmuir showed long ago) more filament current results in higher temperature (say, T \propto \sqrt{I} )...so I always affects T

"filament current..near..potential" amps cannot be volts!

"When an electron gains energy, it jumps from one energy level to another in "quantum leaps." This process is called exciting an electron, and the higher energy levels are called "excited states" while the bottom level is called "ground state.""

true, but not really relevant as ejection is to a continuum of states..perhaps just a link to Electron excitation Tkirkman (talk) —Preceding comment was added at 17:32, 10 May 2008 (UTC)

I checked the cited source (Goldstein, 2003) out of our library and have determined that the cited material relates to the electron gun of an electron microscope. It is referring to the complex interaction of the Wehneit cylinder (or grid cap) and bias resistor that is used to focus the electron beam from the heated filament; it is not a fundamental part of thermionic emission or the work function. I am therefore going to edit the document to delete this material. Tkirkman (talk) —Preceding comment was added at 14:49, 9 June 2008 (UTC)