Surface-bound states and zero-point motion effect in nanodiamonds and diamondoids

The positive electron affinity of bulk diamond becomes negative for hydrogen passivated nanodiamonds and leads to a type-II offset with a vacuum level at nearly midgap. We use ab initio density functional theory and a screened configuration interaction approach to show [1] that in this case and with three further conditions: (i) a surface dipole
with positive charge on the outside layer, (ii) a spherical symmetry, and (iii) a dielectric mismatch at the surface,
a peculiar type of surface emerges, localized just outside the nanodiamond. These
“surface-bound states” have consequently a strong environmental sensitivity. We contrast these findings with results from
“conventional” silicon quantum dots. For a set of diamondoids, we calculate the renormalization of the electronic structure
induced by coupling to nuclear vibrations [2]. We obtain an energy gap reduction between 0.1 and 0.3 eV across nine different
diamondoids.

[1] P. Han, D. Antonov, J. Wrachtrup, G. Bester, Phys. Rev. B. 95, 733 (2017)
[2] P. Han, G. Bester, New. J. Phys. 18, 113052 (2016)