Relative stabilities of nitrogen-related defects in HfOx Ny have been extensively studied in terms of formation energies by using first-principles calculations. We have found that the two oxygen vacancies coupled with two substitutional nitrogen atoms at oxygen sites is the predominant defect in a low oxygen chemical potential (μO) with doubly positive [(NO) 2 (VO) 2] +2 and neutral [(NO) 2 (VO) 2] 0 forms for the p -type and n -type silicon substrates, respectively. On the other hand, the negatively charged substitutional nitrogen [(NO) 2] -2 predominates in a higher μO condition. A neutral defect, [(NO) 2 VO] 0, is found to be stabilized in the midregion of μO, which indicates that the oxygen partial pressure is an important factor to control fixed charges that cause malfunction in HfOx Ny -based devices. An electron counting concept is shown to be valid to predict the stable forms of the defects.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2008 Apr 25|
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics