Afifi Ahmed S, Weerasinghe Janith, Prasad Karthika, Levchenko Igor, Alexander Katia
School of Engineering, College of Systems and Society, The Australian National University, Canberra, ACT 2601, Australia.
Plasma Sources and Application Centre, NIE, Nanyang Technological University, Singapore 637616, Singapore.
Nanomaterials (Basel). 2025 Jun 21;15(13):961. doi: 10.3390/nano15130961.
Erosion detection in materials exposed to plasma-generated species, such as those used for space propulsion systems, is critical for ensuring their reliability and longevity. This study introduces an efficient image processing technique to monitor the evolution of the erosion depth in boron nitride (BN) subjected to multiple cycles of iodine plasma exposure. Utilising atomic force microscopy (AFM) images from both untreated and treated BN samples, the technique uses a modified semi-automated image registration method that accurately aligns surface profiles-even after substantial erosion-and overcomes challenges related to changes in the eroded surface features. The registered images are then processed through frequency-domain subtraction to visualise and quantify erosion depth. Our technique tracks changes across the BN surface at multiple spatial locations and generates erosion maps at exposure durations of 24, 48, 72 and 84 min using both one-stage and multi-stage registration methods. These maps not only reveal localised material loss (up to 5.5 μm after 84 min) and assess its uniformity but also indicate potential re-deposition of etched material and redistribution across the surface through mechanisms such as diffusion. By analysing areas with higher elevations and observing plasma-treated samples over time, we notice that these elevated regions-initially the most affected-gradually decrease in size and height, while overall erosion depth increases. Progressive surface smoothing is observed with increasing iodine plasma exposure, as quantified by AFM-based erosion mapping. Notably, up to 89.3% of surface heights were concentrated near the mean after 72-84 min of plasma treatment, indicating a more even distribution of surface features compared to the untreated surface. Iodine plasma was compared to argon plasma to distinguish material loss during degradation between these two mechanisms. Iodine plasma causes more aggressive and spatially selective erosion, strongly influenced by initial surface morphology, whereas argon plasma results in milder and more uniform surface changes. Additional scale-dependent slope and curvature analyses confirm that iodine rapidly smooths fine features, whereas argon better preserves surface sharpness over time. Tracking such sharpness is critical for maintaining the fine structures essential to the fabrication of modern semiconductor components. Overall, this image processing tool offers a powerful and adaptable method for accurately assessing surface degradation and morphological changes in materials used in plasma-facing and space propulsion environments.
对于暴露于等离子体产生的物质（如用于太空推进系统的物质）中的材料，侵蚀检测对于确保其可靠性和寿命至关重要。本研究引入了一种高效的图像处理技术，以监测氮化硼（BN）在多次碘等离子体暴露循环下侵蚀深度的演变。该技术利用未经处理和经处理的BN样品的原子力显微镜（AFM）图像，采用一种改进的半自动图像配准方法，即使在大量侵蚀后也能准确对齐表面轮廓，并克服了与侵蚀表面特征变化相关的挑战。然后，通过频域减法对配准后的图像进行处理，以可视化和量化侵蚀深度。我们的技术在多个空间位置跟踪BN表面的变化，并使用单阶段和多阶段配准方法在24、48、72和84分钟的暴露持续时间生成侵蚀图。这些图不仅揭示了局部材料损失（84分钟后高达5.5μm）并评估其均匀性，还表明了蚀刻材料的潜在再沉积以及通过扩散等机制在表面的重新分布。通过分析海拔较高的区域并随时间观察经等离子体处理的样品，我们注意到这些最初受影响最大的升高区域的尺寸和高度逐渐减小，而总体侵蚀深度增加。随着碘等离子体暴露的增加，观察到表面逐渐平滑，这通过基于AFM的侵蚀映射进行了量化。值得注意的是，在等离子体处理72 - 84分钟后，高达89.3%的表面高度集中在平均值附近，这表明与未处理的表面相比，表面特征分布更均匀。将碘等离子体与氩等离子体进行比较，以区分这两种机制在降解过程中的材料损失。碘等离子体导致更具侵蚀性和空间选择性的侵蚀，受初始表面形态的强烈影响，而氩等离子体导致更温和、更均匀的表面变化。额外的尺度相关斜率和曲率分析证实，碘能迅速平滑精细特征，而氩随着时间推移能更好地保留表面锐度。跟踪这种锐度对于维持现代半导体组件制造所必需的精细结构至关重要。总体而言，这种图像处理工具为准确评估面向等离子体和太空推进环境中使用的材料的表面降解和形态变化提供了一种强大且适应性强的方法。
