Hall Effect Measurements of Surface Conductive Layer on Undoped Diamond Films in NO₂ and NH₃ Atmospheres

In order to clarify the mechanism of change in resistance of the surface conductive layer exposed to oxidizing and reducing gases, the Hall effect measurements of the surface conductive layer on as-grown undoped diamond films in NO 2 and NH 3 gas atmospheres were carried out. It was found that holes were generated in the surface conductive layer by the adsorption of NO 2 gas, and the adsorption of NH 3 gas resulted in the disappearance of the holes. Morever, the dependences of gas concentration on the sheet resistivity, carrier density per unit area and Hall mobility were observed. The mechanism of change in resistance of the surface conductive layer in gas atmospheres could be explained by the proposed model based on the experimental results.