Question

5) Zn1+xO, Ti1+xO, Cu2S1+x, CuI1+x and ZnO1+x are semiconductors. What type of semiconductors are they (n- or p-type)?

Answer 1

Zn1+xO, Ti1+xO, and ZnO1+x ------------------> n -type semi conductors

explanation : these are all metal excess defects in a crystal. here majority of carriers electrons . this can be explanained by this way

Metal excess defect due to the presence of extra cations at interstitial sites: In this case, there are extra positive ions occupying interstitial sites and the electrons in another interstitial sites to maintain electrical neutrality. The defect may be visualised as the loss of non-metal atoms which leave their electrons behind. The excess metal ions occupy interstitial positions.

The common example is Zinc Oxide. Zinc oxide is white in colour at room temperature. On heating it loses oxygen and turns yellow.

ZnO —-> Zn²⁺ + ½ O₂ +2e^–

Now there is excess of zinc in the crystal and its formula becomes Zn_1+xO. The excess Zn²⁺ ions move to interstitial sites and the electrons to neighbouring interstitial sites.

Cu2S1+x CuI1+x---------------------> p -type semi conductors