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采用基于密度泛函理论和广义梯度近似的第一性原理研究了立方相LaAlO3中不同价态氧空位的电子性质。结果表明,氧空位的存在会在立方相LaAlO3的禁带中引入缺陷能级,在氧缺失的条件下,氧空位在立方相LaAlO3中是稳定存在的。随着费米能级位置的改变,具有0价和+2价的氧空位分别为最稳定的电荷状态。LaAlO3中的氧空位具有负U性质,当空位进入到氧化物中时,氧空位会俘获2个空位,达到稳定状态。因此,在LaAlO3高k栅介质中,氧空位为主要俘获电荷的陷阱。
The electronic properties of different valence oxygen vacancies in cubic phase LaAlO3 were investigated by first principles based on density functional theory and generalized gradient approximation. The results show that the presence of oxygen vacancies introduces a defect level in the forbidden band of the cubic phase LaAlO3. The oxygen vacancies are stable in the cubic phase LaAlO3 under the condition of oxygen deficiency. With the change of the Fermi level, oxygen vacancies with valences of 0 and +2, respectively, are the most stable charge states. Oxygen vacancies in LaAlO3 have a negative U-character. When the vacancies enter the oxide, oxygen vacancies will trap two vacancies to reach a steady state. Therefore, in the LaAlO3 high-k gate dielectric, oxygen vacancies are the predominant trap traps.