Characterization of colloidal nanoparticles: a comparison study among light scattering and atomizing instruments

Abstract

Controlling nanoparticle characteristics throughout the semiconductor manufacturing process is essential for reducing chip failure probability and enhancing production stability. To identify the properties of engineered nanoparticles, several advanced analytical tools—such as atomizers, scanning electron microscopy (SEM), dynamic light scattering (DLS), and nanoparticle tracking analysis (NTA)—have been utilized, each with its inherent limitations and boundary conditions. The manuscript highlights a newly developed methodology using ES-SMPS for characterizing colloidal nanoparticles and presents a detailed comparison of the aforementioned instruments, evaluating their relative advantages. In Chapter 1, we mainly present the development of a methodology for characterizing nanoparticles in low-concentration samples using the ES-SMPS, and then compare the performance of ES-SMPS with atomizer and NTA. To serve this purpose, we first conducted a parametric study to identify optimal conditions for separating the residue peak from the main particle peak. The findings indicate that to effectively separate the residue from the particle peak, the sample should have higher electrical conductivity and be pushed with a lower flow rate, while the system sheath flow rate should remain high. We then determined the range of detectable liquid concentrations measurable by the ES-SMPS, Atomizer, and NTA for comparison purposes. It was found that the operating range of the NTA (~10⁹ to ~10⁷ particles/mL) was narrower than that of the ES 3480 and Kanomax atomizer which can operate over a broader range of ~4 × 10¹² to ~10⁸ particles/mL and ~2 × 10¹² to ~10⁸ particles/mL respectively. Finally, we compared the sensitivity of precise particle counting across ES-SMPS models (ES 3480 and ES 3482), the Kanomax Atomizer, and NTA over a range of silica particle sizes from 23 to 200 nm. When it comes to particle size determination, atomizing instruments provide more accurate measurements than NTA. Unlike the NTA, which overestimated the particle concentration, the atomizing equipment provided a more accurate measurement. The findings of this research offer valuable insights for selecting suitable instruments for applications that require precise characterization of colloidal particles. In Chapter 2, we employed primarily three techniques electrospray-scanning mobility particle sizer (ES-SMPS), nanoparticle tracking analysis (NTA), and dynamic light scattering (DLS) to assess multimodal samples. In the case of monodisperse particles, both the ES-SMPS (all sizes) and NTA (particle size larger than 40 nm) accurately determined the mean size, while the DLS approach overestimated it. The ES-SMPS technique demonstrated precision in particle counting of multimodal samples with a standard deviation of around 2.5-4%. Conversely, the NTA's ability to count particles potentially leads to misinterpretation. The ES-SMPS approach could identify particle peaks in multimodal (bimodal, trimodal, and tetra-modal) samples, and show the relatively right position of the mode diameter. In contrast to ES-SMPS, DLS, and NTA have weaknesses in characterizing multimodal samples. While NTA’s performance depends on the optical properties of particles and it can’t measure silica particles smaller than 30-40 nm, ES-SMPS are independent of light scattering and can do the job even with a particle of ~13 nm. The ES-SMPS also excelled in separating particle peaks of bimodal sample with a size interval gap of 10 nm whereas NTA needs at least 20-50 nm depending on the particle type. To sum up, the ES-SMPS method performs better and gives an accurate measurement of characterizing multimodal samples as compared to NTA and DLS.