CAJ | 학술논문

采用基于MS(Materials Studio)软件和密度泛函理论的第一性原理方法,研究了HfO2俘获层的电荷俘获式存储器(Charge Trapping Memory, CTM)中电荷的保持特性以及耐擦写性.在对单斜晶HfO2中四配位氧空位(VO4)缺陷和VO4与Al替位Hf掺杂的共存缺陷体(Al+VO4)两种超晶胞模型进行优化之后,分别计算了其相互作用能、形成能、Bader电荷、态密度以及缺陷俘获能.相互作用能和形成能的计算结果表明共存缺陷体中当两种缺陷之间的距离为2.216?时,结构最稳定、缺陷最容易形成；俘获能计算结果表明,共存缺陷体为双性俘获,且与VO4缺陷相比,俘获能显著增大； Bader电荷分析表明共存缺陷体更有利于电荷保持；态密度的结果说明共存缺陷体对空穴的局域能影响较强；计算两种模型擦写电子前后的能量变化表明共存缺陷体的耐擦写性明显得到了改善.因此在HfO2俘获层中可以通过加入Al杂质来改善存储器的保持特性和耐擦写性.本文的研究可为改善CTM数据保持特性和耐擦写性提供一定的理论指导.
채용기우MS(Materials Studio)연건화밀도범함이론적제일성원리방법,연구료HfO2부획층적전하부획식존저기(Charge Trapping Memory, CTM)중전하적보지특성이급내찰사성.재대단사정HfO2중사배위양공위(VO4)결함화VO4여Al체위Hf참잡적공존결함체(Al+VO4)량충초정포모형진행우화지후,분별계산료기상호작용능、형성능、Bader전하、태밀도이급결함부획능.상호작용능화형성능적계산결과표명공존결함체중당량충결함지간적거리위2.216?시,결구최은정、결함최용역형성；부획능계산결과표명,공존결함체위쌍성부획,차여VO4결함상비,부획능현저증대； Bader전하분석표명공존결함체경유리우전하보지；태밀도적결과설명공존결함체대공혈적국역능영향교강；계산량충모형찰사전자전후적능량변화표명공존결함체적내찰사성명현득도료개선.인차재HfO2부획층중가이통과가입Al잡질래개선존저기적보지특성화내찰사성.본문적연구가위개선CTM수거보지특성화내찰사성제공일정적이론지도.
In this work, the first-principles method based on materials studio(a soft ware) and the density functional theory is used to invesigate the properties of charge retention and charge endurance in HfO2 as a trapping layer in charge trapping memory (CTM). Two supercell models are optimized for the monoclinic HfO2, separately. One contains a four-fold-coordinated O vacancy defect (VO4), and the other is a co-doped composite defect consisting of a VO4 and an Al atom. Interaction energies, formation energies, Bader charge, density of states and trapping energy are calculated for the two models. According to the calculated results of interaction energies and formation energies, it is found that the structure is the most stable and the defect is the most easily formed when the distance between the two kinds of defects is of 2.216 ? in the co-doped composite defect system. The trapping energy results show that the co-doped composite defect system can trap both electrons and holes. Moreover, the trapping ability of the co-doped composite defect is enhanced significantly as compared with the VO4 defect. Bader charge analysis shows that the co-doped composite defect system provides a more preferable site for the charge retention. Calculations of the density of states show that the co-doped composite defect system has a strong effect on the trapping energy of holes. Calculated energy changes after program/erase cycles show that the endurance is improved obviously in the co-doped composite defect system. In conclusion, the date retention and endurance in the trapping layer of monoclinic HfO2 can be improved by doping of the substitutional impurity Al. This work may provide a theoretical guidance for performance improvement with respect to the date retention and endurance of CTM.