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He Buffer Gas for Moderating the Kinetic Energy of Pulsed Laser Deposition Plumes
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2021-07-28 , DOI: 10.1021/acs.cgd.1c00456 Ryota Takahashi 1, 2, 3 , Takahisa Yamamoto 4 , Mikk Lippmaa 3
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2021-07-28 , DOI: 10.1021/acs.cgd.1c00456 Ryota Takahashi 1, 2, 3 , Takahisa Yamamoto 4 , Mikk Lippmaa 3
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We have investigated the effect of helium buffer gas on the moderation of the kinetic energy of pulsed laser deposition (PLD) plumes during the growth of SrTiO3 thin films. Atomically smooth SrTiO3 thin films were grown by PLD using a neodymium yttrium aluminum garnet (Nd:YAG) laser for target ablation. The lattice parameters of the SrTiO3 thin films were found to be different from the cubic bulk value due to the presence of crystal defects, leading to the formation of a tetragonally distorted structure. One of the reasons for the presence of defects was found to be the high kinetic energy of the ablation plumes generated by the Nd:YAG laser operating at high energy densities. The kinetic energy of ionized species in the plume exceeded 100 eV, which means that adatoms arriving on the film surface had sufficient energy to resputter atoms from the surface of the deposited SrTiO3 film, creating point defects. A mixed atmosphere of He and O2 was used to moderate the plume kinetic energy without reducing the deposition rate. A nearly 10-fold reduction of the kinetic energy was obtained at a total pressure of 0.6 Torr, while the O2 pressure was kept at 10–5 Torr. Minimizing the plume kinetic energy and the associated film surface resputtering improved the crystallinity of SrTiO3 thin films. The helium gas pressure was found to be an important process parameter for tuning the functional properties of oxide films. We demonstrate the He moderator effect on two characteristics of SrTiO3 films, the appearance of a polar state and water permeability, both of which are sensitive to the presence of structural defects.
中文翻译：
用于调节脉冲激光沉积羽流动能的缓冲气体
我们研究了氦气缓冲气体对 SrTiO 3薄膜生长过程中脉冲激光沉积 (PLD) 羽流动能的调节作用。使用钕钇铝石榴石（Nd：YAG）激光器通过PLD生长原子光滑的SrTiO 3薄膜，用于目标烧蚀。SrTiO 3的晶格参数发现由于晶体缺陷的存在，薄膜与立方体值不同，导致形成四方扭曲结构。发现存在缺陷的原因之一是 Nd:YAG 激光器在高能量密度下运行时产生的烧蚀羽流的高动能。羽流中电离物种的动能超过 100 eV，这意味着到达薄膜表面的吸附原子有足够的能量从沉积的 SrTiO 3薄膜表面重新溅射原子，从而产生点缺陷。He 和 O 2 的混合气氛用于在不降低沉积速率的情况下调节羽流动能。在 0.6 Torr 的总压力下，动能降低了近 10 倍，而 O 2压力保持在 10 –5 Torr。最小化羽流动能和相关的薄膜表面再溅射提高了 SrTiO 3薄膜的结晶度。发现氦气压力是用于调节氧化膜功能特性的重要工艺参数。我们证明了 He 调节剂对 SrTiO 3薄膜的两个特性的影响，极性状态的出现和水渗透性，这两个特性对结构缺陷的存在都很敏感。
更新日期：2021-09-01
中文翻译：
用于调节脉冲激光沉积羽流动能的缓冲气体
我们研究了氦气缓冲气体对 SrTiO 3薄膜生长过程中脉冲激光沉积 (PLD) 羽流动能的调节作用。使用钕钇铝石榴石（Nd：YAG）激光器通过PLD生长原子光滑的SrTiO 3薄膜，用于目标烧蚀。SrTiO 3的晶格参数发现由于晶体缺陷的存在，薄膜与立方体值不同，导致形成四方扭曲结构。发现存在缺陷的原因之一是 Nd:YAG 激光器在高能量密度下运行时产生的烧蚀羽流的高动能。羽流中电离物种的动能超过 100 eV，这意味着到达薄膜表面的吸附原子有足够的能量从沉积的 SrTiO 3薄膜表面重新溅射原子，从而产生点缺陷。He 和 O 2 的混合气氛用于在不降低沉积速率的情况下调节羽流动能。在 0.6 Torr 的总压力下，动能降低了近 10 倍，而 O 2压力保持在 10 –5 Torr。最小化羽流动能和相关的薄膜表面再溅射提高了 SrTiO 3薄膜的结晶度。发现氦气压力是用于调节氧化膜功能特性的重要工艺参数。我们证明了 He 调节剂对 SrTiO 3薄膜的两个特性的影响，极性状态的出现和水渗透性，这两个特性对结构缺陷的存在都很敏感。
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