How to tell if its a metal or a semiconductor

[kini.Amith]

Given a material sample, what are the different experiments that one can perform on it to check if it's a conductor or a semiconductor. For eg, we can measure R at different temperatures. Anything else we can do?

 

[ZapperZ]

Please read this thread:

https://www.physicsforums.com/threads/what-makes-a-semiconducting-material-a-semiconductor.410165/

Zz.

 

[kini.Amith]

The thread you mentioned only talks about resistivity vs temp. I as wondering if there are other experiments. Is there any difference in how the resistance changes at different AC source frequencies?

 

[ZapperZ]

But how complicated do you want the experiment to be?

You can get single-crystal sources and then perform angle-resolved photoemission spectroscopy to see if there are bands crossing the Fermi level. Is this the type of experiments that you want and are able to comprehend?

Zz.

 

[kini.Amith]

I don't mind how complicated the experiment becomes practically. I just want to know how we can use our knowledge of conductors and semiconductors to construct experiments that will be at least able to tell the difference in theory. This is a question that is generally asked in Ph.D interviews here in India. Spectroscopy seems like a good option, i'll read more on it.
A friend of mine claims that the AC input frequency vs resistivity curve is different for conductors and Semiconductors, but I can't confirm it from anywhere else. Is this true?

 

[ZapperZ]

But you were already given the simplest example of temperature-dependent resistivity measurement. Why isn't that enough? It is certainly good enough for a Nature publication.

https://www.physicsforums.com/threads/metal-and-nonmetal-difference.312184/#post-2204169

So why are you asking for another one? How many do you need for such an interview?

Zz.

 

[Paradox101]

Semiconductors have 4 electrons in their valence shell.So,what usually is done is gating or perhaps doping to make it either a n-type or a p-type.SO,the material which responds to such techniques would have an increased conductivity.Moreover,why concentrate on the temperature? You do realize that certain semiconductors have excited electrons which relax by emitting light rather than heat(eg- the ones used in LEDs).

 

[ZapperZ]

Semiconductors have 4 electrons in their valence shell.So,what usually is done is gating or perhaps doping to make it either a n-type or a p-type.SO,the material which responds to such techniques would have an increased conductivity.Moreover,why concentrate on the temperature? You do realize that certain semiconductors have excited electrons which relax by emitting light rather than heat(eg- the ones used in LEDs).

This is puzzling. The question asked for an experiment that differentiate between a metal and a semiconductor. Why do you go into all that doping stuff?

Secondly, do you know that LEDs require that you form a PN junction? What does that have to do with the topic on hand? Can you cite a temperature-dependent resistivity measurement on a band semiconductor that actually does not show a semiconductor behavior as cited in that Nature paper?

Zz.