摘要
在激光分子束外延生长钛酸钡(BaTiO3,BTO)薄膜过程中,初期多粒子碰撞反应过程是薄膜形成的关键过程。本文采用密度泛函理论中的广义梯度近似(DFT/GGA),在PW91/DNP水平上研究了Ba、Ti、O、O2、BaO、TiO2以及BTO分子在真空中的优先反应形成与演化过程,计算研究了它们碰撞反应及其中间体的形成机理,获得了相应中间体的几何结构、过渡态及反应活化能,并运用前线轨道理论分析了BTO分子形成机理。对比BTO、SrTiO3(STO)原胞的计算,详细分析了BTO铁电薄膜钙钛矿结构形成的因素,结果表明,BaO、TiO2和BTO分子是激光分子束外延(LMBE)生长BTO薄膜初期的主要粒子形态,生长初期将以TiO2为中心,结合BaO成核生长,并经由类似于BTO单原胞中的钛酸钡分子结构形成大量的具有钙钛矿结构雏形的原胞。
Finding out the processes of the microcosmic reactions and particle states in the early growth of BaTiO3 （BTO） thin films is very important for the preparation and control of good structure in the growth of BTO thin films. The precedence reaction processes of Ba, Ti, and O atoms, the formation of BaO and TiOz molecules, and the microcosmic reaction mechanism underlying the formation of BTO have been investigated using a generalized gradient approximation of density functional theory （DFT） at the PW91/DNP level. The reaction intermediates, transition states （TS）, and activation energy have been calculated. The mechanisms of formation of BTO molecules have been explored using the highest occupied and lowest unoccupied molecular orbital theory. The reasons of formation of perovskite-structured BTO thin films have been investigated comparing with the formation of STO thin films. It was found that BaO, TiO2, and BTO molecules are the primary particle states in the early growth of BTO thin films. As it acts as a combining center, the TiO2 molecule is preferentially formed. Subsequently, BaO molecules combine with to the BTO unit cell, is constructed. Due to this center and BTO molecule, which is stable and somewhat similar the mechanisms, BTO thin films have been formed.
出处
《无机化学学报》
SCIE
CAS
CSCD
北大核心
2009年第8期1414-1419,共6页
Chinese Journal of Inorganic Chemistry
基金
国家重点实验室开放基金
国防973重大项目61363.3子项目
关键词
钛酸钡
铁电薄膜
反应机理
活化能
原胞形成
barium titanate
ferroelectric thin films
reaction mechanism
activation energy
the formations of unit cell
