For 10  points, name these materials which have a resistivity between that of conductors and insulators.
The first of these type of materials was discovered by Michael Faraday in 1833 when he was studying the properties of silver sulfide. Frenkel excitons generally form in these materials when they are exposed to photons that have energies in or near the visible range of the spectrum. These materials observe an increase in resistivity when they are cooled, unlike metals such as copper. Graphite behaves like one of these because of its extensive pi-delocalization, allowing access to conduction bands. Conductivity of these materials is modified by doping. For 10  points, name these materials which have a resistivity between that of conductors and insulators.
The first of these type of materials was discovered by Michael Faraday in 1833 when he was studying the properties of silver sulfide.
semiconductors