Field electron emission study of nitrogen adsorbed on individual tungsten planes

The adsorption of nitrogen on 211, 111, 100 and 110 tungsten planes has been studied by means of the probe-hole emission technique over a wide range of temperatures. The field emission tube was attached to a molecular beam system. This technique enabled deposition of strictly controlled doses of nitrogen. It has been found that on the 211 plane three states of nitrogen γ, α and β exist. In the γ state molecules of opposite polarity are present. These correspond to the γ⁺ and γ^?. The α state undergoes transformation at about 300 K to a more stable β state. β nitrogen leaves the 211 plane through surface diffusion in the temperature region 600–700K. Results obtained on the 111 plane in the low temperature region confirm previous findings on the existence of γ and α states. At higher temperatures the concentration of nitrogen in the β state increases as a result of migration from the 211 plane. There is some evidence as to the existence of two high energetic states of nitrogen on the 111 and 100 planes. On the 110 plane only partial results were obtained due to field desorption.