First-principles calculations of Li-doped diamond in hydrogen-rich environment

A study on Li-doped diamond reveals that interstitial Li atom doping acts as an n-type impurity, while substitutional Li serves as an acceptor impurity. Due to the high binding energy between Li impurity atoms, Li atoms tend to aggregate easily, exhibiting acceptor characteristics. Diamond grown via CVD (Chemical vapor deposition) occurs in a hydrogen-rich environment, where H atoms exist as interstitials in the diamond. During the growth process, a large number of vacancies are present in diamond, which readily capture H atoms, forming H-vacancy complex defects. These complex defects possess negative defect formation energy, allowing them to form spontaneously and exhibit acceptor characteristics. When Li is doped into diamond in a hydrogen-rich environment, the formation energy of co-doping involving substitutional Li and other defects is lower than that of co-doping with interstitial Li and other defects. The presence of vacancies significantly reduces the defect formation energy and increases the binding energy, making the co-doping configuration of substitutional Li and H-vacancy complex defects energetically more stable. The H-vacancy complex defects in diamond compensate for donor impurities, making n-type doping in diamond more difficult to achieve. • Li atoms tend to aggregate easily, exhibiting acceptor characteristics. • Interstitial H atoms are readily captured by vacancy to forming H-vacancy complex defects. • H-vacancy complex defects compensate for donor impurities in diamond.