Question

Is graphite a semiconductor?

Answer 1

Hint: Recall that a semiconducting material selectively conducts current depending on the configuration of its terminals with respect to the battery. Also recall that semiconductors do not have as many free electrons and semiconductors use electrons and holes as charge carriers. We know that graphite is made up of graphene, which is nothing but layers of carbon atoms stacked in a hexagonal structure. But this arrangement makes room for graphite to possess delocalized or free electrons in its structure capable of carrying charge. In such a case, determine how you would classify graphite, given that it is essentially a semi-metal.

Complete answer:
We know that solids can be broadly classified into conductors, semiconductors or insulators based on their conductive properties. Both conductors and semiconductors conduct electricity. So let is comprehensively deduce the distinction between conductors and semiconductors and understand to which category graphite belongs to, keeping in mind that graphite, though an allotrope of carbon which is a non-metal, consists of delocalized (free) electrons which possess the ability to move freely from one atom to the next.
Now, conductors always allow current to flow through, whereas semiconductors conditionally allow current to flow through, depending upon their structural and circuital configuration. Conductors usually have a large number of free electrons and their conductivity is based on their motion whereas semiconductors have a low number of free electrons and their conductivity is thus based on the motion of electrons and holes. The resistivity of a conductor increases with increase in temperature whereas the resistivity of a semiconductor decreases with an increase in temperature.
We empirically know that graphite has a large number of free (delocalized) electrons that are capable of carrying out unimpeded conduction irrespective of its configuration in a circuit. It is essentially a semimetal for that reason, but it has better conducting abilities than semiconductors since it conducts unconditionally. The conduction of current through graphite is entirely due to these electrons and does not depend on the creation or flow of holes. We can thus conclude that graphite is more of a conductor than a semiconductor.

Note:
It is important to understand that graphite is fully composed of layers of graphene
arranged in a hexagonal structure. Graphene is a perfect electrical and thermal conductor due to the presence of delocalized electrons and lends the same properties to graphite due to which graphite is also classified as a good conductor. Note that graphite has been classified as a semiconductor but only in the ultrafast time scales (in the scale of femtoseconds ($10^{-15}\;s$)) during which it was seen to exhibit semi-conductor-like properties, by virtue of which it might find appropriate applications in future carbon-based electronic devices.