Nanoscale Depth Profiling of Optoelectronic Devices Using Deep-UV LIBS.

Accurate elemental nanoscale depth profiling is vital for semiconductor junctions, optical coatings, and thin-film photonic devices. While Secondary Ion Mass Spectrometry (SIMS) is capable of providing nanoscale elemental depth profiling, it requires bulky and complex instrumentation and is not portable for real-time process monitoring. Alternatively, the technique of Laser-Induced Breakdown Spectroscopy (LIBS) has been shown to provide sensitive detection of elements; however, its depth resolution is limited to approximately μm, hindering nanoscale profiling. Here, we demonstrate nanoscale elemental depth profiling (∼10s of nm) using deep UV LIBS under ambient conditions. Using a fiber-coupled 266 nm wavelength (UV-C) pulsed laser, the system achieves an ablation depth as low as ∼20-25 nm per pulse, enabling high-resolution profiling, while maintaining an elemental detection sensitivity in the parts-per-million range. Depth profiling of a silicon photovoltaic device's diffused silicon PN junction reveals a clear boron dopant profile signal within ∼650 nm, aligning with expected emitter diffusion depths. Similarly, the depth profiling of a dielectric mirror reveals the nanoscale alternating layers of optical coatings of Ta