Contrast Enhancement of SEM Image Using Photoelectric Effect Under UV LED Irradiation

Scanning electron microscopy (SEM) is widely used for nanoscale imaging and the study of surface fine structure. However, its image quality is often limited by low secondary electron (SE) yield and surface charging, especially on insulating or micro-structured materials. In this study, we introduce a non-destructive technique that significantly improves SEM image acquisition by irradiating the specimen surface with ultraviolet (UV) light during observation. This approach leverages the photoelectric effect to enhance SE emission, resulting in a higher signal-to-noise ratio and improved image contrast in SEM imaging. Experiments were conducted using an in situ UV irradiation module on three representative samples: a 1 µm thick gold film (Au) deposited on a 525 µm thick silicon (Si) substrate, a black silicon (b-Si) sample, and a GaN substrate. The results demonstrate clear SE signal enhancement and effective charge mitigation under UV illumination. This UV-assisted SEM technique offers a simple and practical approach to improving electron-beam-based imaging and is expected to expand capabilities for high-contrast observation of nanoscale materials.