Work function and electron affinity of the fluorine-terminated (100) diamond surface

Abstract

The work function and electron affinity of fluorine-terminated (100) diamond surfaces prepared by exposure to dissociated XeF2 have been determined using synchrotron-based photoemission. After vacuum annealing to 350 °C a clean, monofluoride terminated C(100):F surface was obtained for which an electron affinity of 2.56 eV was measured. This is the highest electron affinity reported for any diamond surface termination so far, and it exceeds the value predicted by recent density functional theory calculations by 0.43 eV. The work function of 7.24 eV measured for the same surface places the Fermi energy of 0.79 eV above the valence band maximum.

Role of exchange interaction in nitrogen vacancy center based magnetometry

“…For example, diamond with PEA oxygen-terminated surface can stabilize shallow NV − centers [60,68]. As discussed in previous section, PEA surfaces can be produced by terminating the surfaces with oxygen, chlorine or fluorine [50][51][52]. At the same time, as mentioned early, a high dose of nitrogen (n-dopant) implantation can increase the band bending and reduce the depletion width [49,60], thus shifting the crossing point of the Fermi level and the NV − level closer to the interface.…”

“…An alternative way to reduce the barrier height at the interface is to terminate the diamond surface with elements that induce a large positive electron affinity (PEA), since the Schottky barrier at the interface is roughly determined by the difference between the work function (Φ M ) of the metal and the electron affinity of diamond, i.e., Φ B = Φ M − χ e . For example, diamond with an oxygen-terminated surface has a PEA value of χ e = 2.13 eV [50], while that with a chlorine-terminated surface has χ e = 2.1 − 2.65 eV [51], and that with a fluorine-terminated surface has χ e = 2.56 eV [52]. With the above PEA values and typical work function value of metals Φ M = 5 eV, the barrier can be reduced to Φ B ∼ 2.5 eV.…”

Increased negatively charged nitrogen-vacancy centers in fluorinated diamond

“…Our experimental results indicate that more electronegative terminations lead to higher relative NV À concentration (Figure 4). Fluorine-termination could induce downward band-bending, 11 and the strength of the surface dipole can play a significant role in electron density at the surface, thus increasing the relative NV À signal. Additionally, it is important for the surface termination to have good coverage, since dangling bonds can be electron traps.…”

“…10 Recently, the fluorinated diamond electron affinity has been measured experimentally to be 2.56 eV, about 0.43 eV higher than for the oxygenterminated surface. 11 Various methods have been reported in the literature for fluorine-terminating diamond surfaces, including exposure to XeF 2 gas, 11,12 CF 4 plasma, 13 and CHF 3 plasma. 14 However, all prior work on diamond fluorination have been confined to surface chemistry, whereas this work studies the effect of surface fluorination on the charge states of NV centers in bulk diamond.…”

Nanoscale Sensing Using Point Defects in Single-Crystal Diamond: Recent Progress on Nitrogen Vacancy Center-Based Sensors

“…In contrast, fluorine (F)-terminated surfaces will lead to a downward bending of the diamond bands due to the large electron affinity of F [72]. In this case, the NV − population increases compared to H-terminated diamond [68] and also to oxygenated diamond [69].…”