Ab initiocalculation of electron affinities of diamond surfaces

Abstract

The electron affinity ͑EA͒ of various terminations of diamond surfaces has been calculated by the ab initio pseudopotential method. The bare, reconstructed ͑100͒ and ͑111͒ surfaces are found to have positive EA's of 0.5 and 0.35 eV, respectively. The hydrogen-terminated surfaces 1ϫ1(100):2H, 2ϫ1 (100):H, and ͑111͒:H have sizable negative EA's of order Ϫ2.4, Ϫ2.0, and Ϫ2.0 eV, respectively. A symmetrical canting was found to be the most stable geometry for the 1ϫ1(100):2H surface. The oxygen-terminated surfaces have positive affinities of ϩ2.6 eV for the more stable ether configuration, while the OH termination has a negative EA. The various values can be understood in terms of the surface dipole of the terminating bond.

NEA peak of the differently terminated and oriented diamond surfaces

“…Agreement between −4.55 eV in order to satisfy the energy and k || -conservation. However, for the (111) surface, our measurements and the calculations by Rutter and Robertson [35] is not found for the absolute x is above −4.55 eV, and therefore the electrons are totally internally reflected at the diamond-NEA values, but is found for the electron affinity change between the H-saturated and H-free tervacuum interface. We have calculated this constraint for the (111) and (110) surfaces and found mination as well as for the electron affinity difference between H-and OH-termination.…”

“…We have calculated this constraint for the (111) and (110) surfaces and found mination as well as for the electron affinity difference between H-and OH-termination. For the Hthat x must be less than −4.32 eV and less than −0.68 eV, respectively, in order to satisfy the and OH-terminated (100) surfaces, the calculated values are −2.05 and −2.13 eV [35], while the energy and k || -conservation in photoemission. Indeed, for the (110)-(1×1):H surface, x is less measurements from Fig.…”

Light Metals on Oxygen-Terminated Diamond (100): Structure and Electronic Properties

“…refs [29,30]), there is tentative agreement in the literature that this structure is the lowest-energy ideal C(100)-(1x1):O structure and is therefore the appropriate energetic ground state. 22,[31][32][33][34] The adsorption energy per atom is then given by: (1) where E T is the total energy of the supercell, E 0 is the total energy of the bare oxygen-terminated surface supercell, N ads is the number of adsorbates in the supercell and E iso is the energy of an isolated adsorbate atom. The computed values of E T , E O and E iso are negative, thus the sign convention in this work is that exothermic adsorption energies are negative.…”

Nitrogen Doping of Amorphous Carbon Surfaces

“…With higher nitrogen concentration electron emission decreases, which they address to the fact that nitrogen tends to decrease the sp 3 content in a-C [5]. The negative electron affinity (i.e., the electrons in conduction band escape spontaneously to vacuum) of a hydrogen terminated diamond 100 surface has been shown to arise from a surface dipole [10], but until now no theoretical explanation has been given for the observed low electron affinity and especially for the role of nitrogen in it for a-C.…”

“…The electron affinity (the energy required to extract an electron from the bottom of the conduction band to vacuum) is not estimated here because the difficulties in determining the gap size (LDA deficiency) and the difficulties in defining the surface dipole of an amorphous layer. The electron affinities for diamond surfaces have been estimated by Rutter and Robertson [10].…”