With the objective of applying laser-assisted atom probe tomography to compositional analysis within nanoscale InGaAs devices, experimental conditions that may provide an accurate composition estimate were sought by extensively studying an InGaAs blanket film. Overall, the determined arsenic atomic fraction was found to exhibit an electric field dependent deficiency, which was more pronounced at low field conditions. Although the determined group III site-fraction also showed a (weak) field-dependent deficiency at low field conditions, it remained invariant with analysis conditions and in close agreement with the nominal value at higher field. In this study, we investigate and discuss the mechanisms that could potentially contribute to As underestimation. Given the field dependence observed, the phenomena occurring between low and high field conditions are compared. At low field, the tendency of As to field evaporate in significant amounts as multiply charged cluster ions (Asni+ with n as large as 9 and i = 1,2,3) is shown to be a significant source of compositional inaccuracy. These clusters may lead to peak overlap in the mass spectrum (e.g. the peak at 150 Da may represent As42+ or As2+ or both), thereby creating an uncertainty in the quantification. Emitted clusters may also dissociate with the likelihood of neutral generation and multi-hit losses being non-negligible. Experimental studies and density functional theory calculations are presented to characterize cluster stability and its contribution to measurement uncertainty. Under high field conditions, although fewer clusters are detected and the composition appears more accurate, the emergence of two additional mechanisms, i.e., multi-hits and DC evaporation, may degrade the data quality. The challenges in evaluating the impact of all these loss mechanisms are examined in detail. Finally, we show that for InGaAs under UV illumination, due to the laser-tip interaction, the resulting asymmetric electric field distribution across the apex introduces local atomic fraction variations.

中文翻译：

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InxGa1-xAs 原子探针层析成像中成分不准确的潜在来源

为了将激光辅助原子探针层析成像应用于纳米级 InGaAs 器件内的成分分析，通过广泛研究 InGaAs 覆盖膜寻求可以提供准确成分估计的实验条件。总的来说，发现确定的砷原子分数表现出电场依赖性缺陷，这在低场条件下更为明显。尽管确定的第 III 组站点分数在低场条件下也显示出（弱）场依赖性缺陷，但它在分析条件下保持不变，并且与高场下的标称值非常一致。在这项研究中，我们调查并讨论了可能导致 As 低估的机制。鉴于观察到的场依赖性，比较了低场和高场条件之间发生的现象。在低电场下，As 倾向于作为多电荷簇离子（Asni+，n 大至 9，i = 1,2,3）大量蒸发，这被证明是成分不准确的重要来源。这些簇可能导致质谱中的峰重叠（例如，150 Da 处的峰可能代表 As42+ 或 As2+ 或两者），从而在量化中产生不确定性。发射的簇也可能与中性产生的可能性和不可忽略的多次命中损失无关。提出了实验研究和密度泛函理论计算来表征簇稳定性及其对测量不确定性的贡献。在高场条件下，尽管检测到的聚类较少并且组成看起来更准确，但两种额外机制（即多次命中和 DC 蒸发）的出现可能会降低数据质量。详细研究了评估所有这些损失机制的影响所面临的挑战。最后，我们表明，对于紫外线照射下的 InGaAs，由于激光尖端相互作用，在顶点上产生的不对称电场分布引入了局部原子分数变化。