Vangelista Silvia, Piagge Rossella, Ek Satu, Lamperti Alessio
CNR-IMM, Unit of Agrate Brianza, Via C. Olivetti 2, Agrate Brianza (MB) I-20864 Italy.
STMicroelectronics, Via C. Olivetti 2, Agrate Brianza (MB) I-20864 Italy.
Beilstein J Nanotechnol. 2018 Mar 15;9:890-899. doi: 10.3762/bjnano.9.83. eCollection 2018.
In this work, we investigate the effect of thermal treatment on CeO films fabricated by using atomic layer deposition (ALD) on titanium nitride (TiN) or on silicon (Si) substrates. In particular, we report on the structural, chemical and morphological properties of 25 nm thick ceria oxide with particular attention to the interface with the substrate. The annealing treatments have been performed in situ during the acquisition of X-Ray diffraction patterns to monitor the structural changes in the film. We find that ceria film is thermally stable up to annealing temperatures of 900 °C required for the complete crystallization. When ceria is deposited on TiN, the temperature has to be limited to 600 °C due to the thermal instability of the underlying TiN substrate with a broadening of the interface, while there are no changes detected inside the CeO films. As-deposited CeO films show a cubic fluorite polycrystalline structure with texturing. Further, after annealing at 900 °C an increase of grain dimensions and an enhanced preferential (200) orientation are evidenced. These findings are a strong indication that the texturing is an intrinsic property of the system more than a metastable condition due to the ALD deposition process. This result is interpreted in the light of the contributions of different energy components (surface energy and elastic modulus) which act dependently on the substrate properties, such as its nature and structure.
在本工作中，我们研究了热处理对通过原子层沉积（ALD）在氮化钛（TiN）或硅（Si）衬底上制备的CeO薄膜的影响。特别地，我们报告了25nm厚氧化铈的结构、化学和形态特性，尤其关注其与衬底的界面。在获取X射线衍射图谱的过程中进行了原位退火处理，以监测薄膜的结构变化。我们发现，在达到完全结晶所需的900°C退火温度之前，氧化铈薄膜具有热稳定性。当氧化铈沉积在TiN上时，由于底层TiN衬底的热不稳定性以及界面变宽，温度必须限制在600°C，而在CeO薄膜内部未检测到变化。沉积态的CeO薄膜呈现出具有织构的立方萤石多晶结构。此外，在900°C退火后，晶粒尺寸增大且择优（200）取向增强。这些发现有力地表明，织构是该系统的固有特性，而非由于ALD沉积过程导致的亚稳态条件。根据不同能量成分（表面能和弹性模量）的贡献对这一结果进行了解释，这些能量成分的作用取决于衬底的性质，如其本质和结构。
