Why metallic thin films show higher resistivity that their b

Why metallic thin films show higher resistivity that their bulk samples? Explain why higher temperature increases resistivity in metallic materials but decreases the same for semiconductors. Write factors that will influence conductivity in metallic materials?

Solution

Metallic Fim shows higher resistivity than bulk sample : The reasons for this change is due to increased surface interactions as well as absorption (Absorption of conduction electron hence less will be available) and scattering effects (because the mean free path of conduction electrons is reduced due to increased scattering effects) .

Metallic and Semiconductor have different mechanism of conduction thats why resistivity behaves differently with increasing temperature.

Metals : Lets first understand why metals conduct electricity. Every atom has an outer band of electrons, known as the valence band. In metals, the electrons from this valence band are not confined to the atom and are free to move throughout the metal lattice. It is this \"sea of electrons\" which makes conduction possible.

At higher temperatures, the atoms are vibrating more and are more likely to be collide as the electrons go past. Hence higher resistivity.

Semi-conductors act as non-metals at low temperatures - the electrons are trapped within the atom. As the temperature of the semi-conductor is increased, the electrons in the valence band gain sufficient energy to escape from the confines of their atoms. As a result, in higher temperatures, a semi-conductor\'s valence electrons are free = conduction results, resistivity decreases.