Phosphorous (P)-doped CVD diamonds are expected to be good n-type semiconductor diamonds. However, the resistivity of P-doped intrinsic diamonds is very high due to a large ionization energy of impurity phosphorus. When phosphorus is doped in a large amount (≥∼10²⁰cm⁻³), the resistivity reduces with a pseudo-n-type conductivity at temperatures above 400 K. These intrinsic n-type and pseudo-n-type P-doped diamond single crystal surfaces have been studied recently by electron spectroscopic methods. The surface electronic energy states of both intrinsic n-type and pseudo-n-type diamond surfaces have been examined by electron spectroscopic methods. The mechanism of field emission from the pseudo-n-type diamond surface has been elucidated.