Negative electron affinity surfaces on silicon using a rubidium/oxygen dipole layer

Rubidium/oxygen dipole layers have been used to generate negative electron affinity (NEA) surfaces on Si (100). Rb/O layers behave exactly as Cs/O layers with respect to the activation schedule and to the electron emission characteristics. Rb/O layers show the same crystallographic anisotropy as Cs/O layers in that only the Si (100) surface activates to NEA. The spectral photoresponse curves for each layer are identical. The characteristics of the Si/Cs/O and Si/Rb/O surfaces are compared to III-V NEA emitters and to conventional emitters for which an Rb/O surface layer produces a less efficient emitting surface. These results are explained by the fact that the dipole layer on NEA Si (100) is very well ordered with specific sites for the anions and the cations. The geometrical arrangement of the dipole layers most strongly determines their characteristics, as opposed to the chemical nature of the Cs/O or Rb/O compounds. Among other possible substitutes for Cs and O, neither Cs/I, Cs/F, and Cs/S layers nor Na/O and K/O layers produced NEA on Si (100).