Evaluation of Three Sample Introduction Systems for Impurity Analysis of an Ultrapure Reagent Using a Scanning Mobility Particle Sizer.

The semiconductor industry continues to shrink the device sizes while applying more complex shapes and using diverse materials, which requires parallel improvements in the quality of ultrapure reagents. The need for ultrapure reagents has led to ever-higher demands for the performance of analytical instruments used to detect ultratrace impurities. In this study, nonvolatile impurities in ultrapure reagents were quantified using a scanning mobility particle sizer (SMPS). The performances of three different sample introduction systems, i.e., an electrospray (ES), an aerosol generator with a heating chamber and a Nafion desolvation membrane (NB-II), and a MicroMist nebulizer with a heated cyclonic spray chamber and a three-stage Peltier-cooled desolvation system (MM-APEX), were evaluated for the lower limit of detection of a SMPS. The MM-APEX equipped with the SMPS was able to detect NaCl additives at a concentration of 100 parts per trillion (ppt, ng/L) in ultrapure water, which was approximately 104- and 102-fold lower than those of ES and NB-II, respectively. The practical application of MM-APEX with the SMPS for commercial isopropanol samples was also studied. The results clearly demonstrate that the impurity concentrations presented by the NaCl-equivalent concentrations among different sources of isopropanol were at the ppt to parts-to-billion (ppb) scale. The SMPS system equipped with MM-APEX is capable of recognizing impurities with concentrations ranging from tens ppt to thousands of parts per million (ppm), which is beneficial for an ultratrace analysis of nonvolatile impurities in semiconductor process chemicals.

Validated Analysis of Component Distribution Inside Perovskite Solar Cells and Its Utility in Unveiling Factors of Device Performance and Degradation.

Time-of-flight secondary-ion mass spectrometry (ToF-SIMS) has been used for gaining insights into perovskite solar cells (PSCs). However, the importance of selecting ion beam parameters to eliminate artifacts in the resulting depth profile is often overlooked. In this work, significant artifacts were identified with commonly applied sputter sources, i.e., an O2+ beam and an Ar-gas cluster ion beam (Ar-GCIB), which could lead to misinterpretation of the PSC structure. On the other hand, polyatomic C60+ and Ar+ ion beams were found to be able to produce depth profiles that properly reflect the distribution of the components. On the basis of this validated method, differences in component distribution, depending on the fabrication processes, were identified and discussed. The solvent-engineering process yielded a homogeneous film with higher device performance, but sequential deposition led to a perovskite layer sandwiched by methylammonium-deficient layers that impeded the performance. For device degradation, it was found that most components remained intact at their original position except for iodide. This result unambiguously indicated that iodide diffusion was one of the key factors governing the device lifetime. With the validated parameters provided, ToF-SIMS was demonstrated as a powerful tool to unveil the structure variation amid device performance and during degradation, which are crucial for the future development of PSCs.