First-principles screening of surface-charge-transfer molecular dopants for n-type diamond.

Surface charge transfer doping (SCTD) is an alternative approach to achieving n-type doped diamond since the n-type bulk doping of diamond remains a challenge, but so far efficient diamond n-type SCTD has not been achieved. Here we provide a comprehensive study of the n-type SCTD of the diamond by using first-principles calculations based on the density functional theory. Taking the principle that ionization potentials of the dopants must be higher than those of the diamond, we screened a series of molecules that may be suitable for diamond n-type SCTD doping. Methyl viologen (MV) and benzyl viologen (BV) provide the largest amount of transfer electron among the common n-type SCTD dopants for the oxygen and fluorine terminated (100) surface diamond, with the electron areal densities of 2.60×1013cm-2 and 9.20×1012cm-2, respectively. It is indicated that the transferred electron amount is positively correlated with the difference between the ionization potentials of the dopants and the electron affinity of the diamond, while the density of dopants also has a positive impact with a decreasing trend. The present work provides a useful understanding of the physical mechanism for the n-type SCTD of diamond, and benefits the development of n-type SCTD diamond materials.&#xD.