UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, Normandie Université, 76000 Rouen, France.
UNIROUEN, INSA Rouen, CNRS, Groupe de Physique des Matériaux, Normandie Université, 76000 Rouen, France.
Ultramicroscopy. 2018 Apr;187:126-134. doi: 10.1016/j.ultramic.2018.02.001. Epub 2018 Feb 6.
A systematic study of the biases occurring in the measurement of the composition of GaN by Atom Probe Tomography was carried out, in which the role of surface electric field and laser pulse intensity has been investigated. Our data confirm that the electric field is the main factor influencing the measured composition, which exhibits a deficiency of N at low field and a deficiency of Ga at high field. The deficiency of Ga at high field is interpreted in terms of preferential evaporation of Ga. The detailed analysis of multiple evaporation events reveals that the measured composition is not affected by pile-up phenomena occurring in detection system. The analysis of correlation histograms yields the signature of the production of neutral N due to the dissociation of GaN ions. However, the amount of N neutral molecules that can be detected cannot account for the N deficiency found at low field. Therefore, we propose that further mechanisms of neutral N evaporation could be represented by dissociation reactions such as GaN→ Ga+ N and GaN→ Ga+ N.
对原子探针层析术测量 GaN 组成时出现的偏差进行了系统研究，研究了表面电场和激光脉冲强度的作用。我们的数据证实，电场是影响测量成分的主要因素，在低场下表现为 N 的缺乏，在高场下表现为 Ga 的缺乏。高场下 Ga 的缺乏可以用 Ga 的优先蒸发来解释。对多次蒸发事件的详细分析表明，测量的组成不受检测系统中堆积现象的影响。相关直方图的分析产生了中性 N 产生的特征，这是由于 GaN 离子的离解。然而，检测到的中性 N 分子的数量不能解释在低场下发现的 N 缺乏。因此，我们提出，中性 N 蒸发的进一步机制可以由离解反应来表示，如 GaN→Ga+N 和 GaN→Ga+N。
