Measurement of Lateral Resolution in Confocal Raman Spectroscopy Using Indium Arsenide Nanowires

Lateral resolution is a key figure of merit for spectroscopy across all applications. Confocal Raman spectroscopy is able to provide chemical and structural information with submicrometre resolution, resulting in widespread use across multiple disciplines of science and technology. However, the lack of agreed-upon measurement standards and appropriate reference samples has hindered uptake. Here, we report the development and demonstration of a reference sample based on indium arsenide (InAs) semiconducting nanowires for measuring the lateral resolution of confocal Raman spectroscopy with a pathway for traceability to the International System of Units (SI). An interlaboratory comparison involving 15 participants from 11 countries has been conducted to rigorously test and demonstrate the suitability of the sample and the method. The study identified required revisions to the measurement protocol to improve the consistency of data analysis and that the long-term operational stability of the reference sample requires further improvement. Based on a revised data analysis protocol, the method delivered consistent results at the 95% confidence level for eight of the nine participants who returned full datasets. Outcomes from this study have contributed to the publication of a new international standard (ISO 23124:2024).