ISSN:1071-1023    

DOI:10.1116/1.583553

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

The initial stages of interface formation between CaF2and Si(111) have been studied with both core‐level and angle‐resolved valence band photoemission spectroscopy. Both the Si 2pand Ca 3pcore levels indicate that a Si–Ca bond is present at the CaF2–Si(111) interface. Annealing of thin CaF2films at 700–800 °C results in preferential evaporation of F, and the surface undergoes a number of reconstructions until a stable Si(111):Ca 3×1 reconstruction is obtained on which there is calcium, but no fluorine. This surface exhibits a surface state with an upward dispersion of 0.4 eV towards theK̄ point of the 1×1 surface Brillouin zone. Our results show that the CaF2molecule can be dissociated on the Si(111) surface at typical epitaxial growth temperatures, with the Ca being more strongly adsorbed to the Si than is the F.

ISSN:1071-1023    

DOI:10.1116/1.583554

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

ISSN:1071-1023    

DOI:10.1116/1.583555

出版商:American Vacuum Society    

年代:1986

数据来源: AIP

摘要:

The energy location for the interface state densityNssminimum of the insulator–semiconductor (I–S) interface and the Fermi‐level pinning position at the metal–semiconductor (M–S) interface are shown to coincide and to lie at the same position of 5.0 eV from the vacuum level for major tetrahedral semiconductors. Neither the unified defect model nor the metal induced gap state model can explain the novel striking correlation between the I–S and M–S interfaces. The correlation as well as the observed peculiar photoionization behavior of the I–S interface are explained by the novel unified disorder induced gap state (DIGS) model where DIGS pin or restrict the movement of the surface Fermi level. The above characteristic energy,EHO, is shown to be the Fermi energy of the DIGS spectrum which is given by the hybrid orbital energy of thesp3bond of the host. The DIGS model explains remarkably well the behavior of the M–S interface formed on the bare or oxide covered semiconductor surface as well as the various features ofNssdistribution of the I–S interface. The correlation between the DIGS‐free heterojunction (S–S) interface and M–S/I–S interface is explained by the fact thatEHOis a universal reference energy level of the host which is invariant under any off‐diagonal interactions, as is evidenced by the alignment of transition metal deep levels, DX centers and EL2 with respect toEHO. Band offset at the S–S interface is proposed to be determined by the alignment ofEHOwhich inevitably involves formation of interface dipole when twoEHOlevels lie at different positions from the vacuum level.

ISSN:1071-1023    

DOI:10.1116/1.583556

出版商:American Vacuum Society    

年代:1986

数据来源: AIP