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As the title said, does the photoelectric effect occurs only with metals?

I searched on Google about it and on the first result's webpage I read that :

In metal the electrons are in a loose connection to the metal's atoms

How's that ? What does it means ? I mean, what's the difference between atoms of a plate of Nickel and a piece of wood ?

How can we explain this using the terms "conduction band" and "valence band" ?

Thanks a lot in advance!

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  • $\begingroup$ Is your question about the photoelectric effect or about band structure? $\endgroup$ Feb 6, 2017 at 1:00
  • $\begingroup$ The photoelectric effect doesn't occur in metals - only in half metals. Metals are conductors, and for this effect we need semiconductors. $\endgroup$
    – Steeven
    Feb 6, 2017 at 1:03
  • $\begingroup$ I think we can make two questions from this post. The first being : "Does it occurs only on metals?" and the second : "Can it be explained with band structure ?" $\endgroup$
    – Lulzsec
    Feb 6, 2017 at 1:03
  • $\begingroup$ @Steeven why does it works for half metals only ? Why metals are conductors ? What do you mean by "and for this effect we need semiconductors" ? $\endgroup$
    – Lulzsec
    Feb 6, 2017 at 1:04
  • $\begingroup$ What exactly do you mean by 'the photoelectric effect'? If you mean something that's detected through current in a circuit, then you're going to have a problem hooking an insulator up as your cathode. If you mean light releasing electrons with a specific energy that depends on the wavelength, then yes, it happens much anywhere. $\endgroup$ Feb 6, 2017 at 1:55

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The photoelectric effect is a photon absorption with energy kept in balance by emission (from an atomic or molecular orbital) of a bound electron.

If electrons are ejected from an insulator, the remaining charges (positive) will attract any subsequent electrons: there will be, in observed emitted electrons, a diminution of current, until no electron has enough kinetic energy to escape the insulator and its positive (attractive) charge. So, for experimental purposes, a metal or semiconductor target and grounding wire are advantageous. That allows observation of electrons freed by the photoelectric effect.

Photoelectric rates of absorption are highest in materials with broad energy bands, because there are lots of electrons at a range of energies, rather than only at discrete (sharp) energy levels, as in a gas. Metals all have a broad energy band (the 'conduction band') which causes metallic (covalent) bonding. When a photon energy is within the band energy, it has an absorption-probability advantage over photons that, when absorbed, leave large amounts of leftover energy.

Photoelectric effect is seen in all material substances that contain electrons.

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