Abstract Si nanocrystals (NCs) are synthesizable in low-pressure plasmas with narrow diameter distributions because of unipolar negative charging in the plasma. However, NCs must pass into a spatial afterglow, where NCs may decharge and aggregate. We use both low-pressure differential mobility analysis and quantitative TEM image analysis to examine Si NCs sampled from a 2 Torr Ar-SiH4 plasma reactor. We find that Si NCs are incorporated into aggregates largely composed of 20 and fewer primary particles with nearly equal concentrations of negatively and positively charged NCs. The projected areas of aggregates scale with aggregate volume in similar manner to the scaling observed for aggregates from atmospheric pressure systems. Higher aggregate concentration is observed with increasing flow rate, while larger aggregate size is found with increasing precursor concentration. Measurements show that the spatial afterglow has a significant influence on the charge and extent of NC aggregation.

中文翻译：

---

低压非热等离子体反应器中硅纳米晶聚集体的尺寸和结构表征

摘要 Si 纳米晶体 (NCs) 可在具有窄直径分布的低压等离子体中合成，因为等离子体中带有单极负电荷。然而，NCs必须进入空间余辉，在那里NCs可能会放电和聚集。我们使用低压差迁移率分析和定量 TEM 图像分析来检查从 2 Torr Ar-SiH4 等离子体反应器中取样的 Si NC。我们发现 Si NCs 被结合到主要由 20 个和更少的初级粒子组成的聚集体中，带负电荷和正电荷的 NCs 浓度几乎相等。聚集体的投影面积与聚集体体积成比例，其方式与从大气压力系统观察到的聚集体的比例相似。随着流速的增加，观察到更高的聚集体浓度，而随着前体浓度的增加，发现更大的聚集体尺寸。测量表明，空间余辉对NC聚集的电荷和程度有显着影响。