Micro-nanoscale metrology for reference material size from speckle pattern images

Abstract

Recently, the fabrication of micro- and nanoscale materials has become necessary in daily life. The sizes and compositions of those materials need to be explored, as the products will be used in other industries. Therefore, micro-nanoscale metrology is necessary for quality control, as some processes require the use of reference materials for comparing the size of industrial micro-nano-sized products. This study investigates the feasibility of using laser speckle imaging. Since the laser speckle setup is relatively inexpensive, the system is a good choice for installation in small factories. Combined with the Gray-level Co-occurrence Matrix (GLCM) analysis method, this technique has been used to compare the size of reference materials that are fabricated by the National Institute of Metrology of Thailand. Two sizes of reference materials, 100 nm and 1,000 nm, were of interest. The particles are composed of polystyrene, and their certified mean diameter and size distribution were determined using transmission electron microscopy (TEM), validated through international comparison, and served as the basis for testing the technique. Clear differences in GLCM contrast, dissimilarity, energy, and correlation were observed between the two particle sizes, reflecting their distinct scattering characteristics. The results demonstrate that speckle-based texture analysis provides a sensitive response to particle size variation, offering a promising pathway toward low-cost, non-invasive micro-nano metrology.