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

Area of Science:

• Materials Science
• Analytical Chemistry
• Spectroscopy

Background:

• Accurate elemental nanoscale depth profiling is crucial for advanced materials like semiconductor junctions and optical coatings.
• Secondary Ion Mass Spectrometry (SIMS) offers nanoscale depth profiling but lacks portability and real-time monitoring capabilities.
• Laser-Induced Breakdown Spectroscopy (LIBS) provides sensitive elemental detection but typically has limited depth resolution (~μm).

Purpose of the Study:

• To demonstrate nanoscale elemental depth profiling using deep UV LIBS under ambient conditions.
• To develop a compact and portable LIBS instrument for real-time characterization.
• To achieve high depth resolution (~10s of nm) with parts-per-million elemental sensitivity.

Main Methods:

• Utilized a fiber-coupled 266 nm (UV-C) pulsed laser for deep UV LIBS.
• Achieved precise ablation depths of ~20-25 nm per pulse.
• Developed a compact optical head (3 × 2 × 1.5 cm³) with autofocusing and a custom ball lens.

Main Results:

• Demonstrated nanoscale depth profiling with ~10s of nm resolution.
• Achieved parts-per-million elemental detection sensitivity.
• Successfully profiled boron dopants in silicon PV devices (~650 nm), alternating Ta2O5/SiO2 layers in dielectric mirrors (~100-145 nm), and ~1-2 nm native oxide on silicon.

Conclusions:

• Deep UV LIBS enables high-resolution nanoscale elemental depth profiling under ambient conditions.
• The developed compact LIBS instrument is suitable for real-time, portable characterization of optical and electronic devices.
• This technique eliminates the need for vacuum or extensive sample preparation, offering an attractive alternative to traditional methods.