Structural, electrical, and optical properties of NiO films for surface-enhanced Raman spectroscopy applications

Area of Science:

• Materials Science
• Nanotechnology
• Surface Science

Background:

• Nickel oxide (NiO) is a promising semiconductor material.
• Thin film deposition techniques are crucial for tailoring material properties.
• Surface-Enhanced Raman Spectroscopy (SERS) requires highly active substrates.

Purpose of the Study:

• To investigate the impact of oxygen concentration on NiO thin film properties.
• To optimize NiO films for enhanced SERS performance.
• To elucidate the mechanism behind SERS enhancement in NiO films.

Main Methods:

• DC sputtering deposition of NiO thin films with varying Ar/O2 ratios.
• Energy-dispersive X-ray (EDX) for elemental analysis and defect identification.
• Electrical (I-V measurements) and optical characterization.
• SERS measurements using Rhodamine 6G as a probe molecule.

Main Results:

• Increased oxygen concentration led to higher Ni vacancies and Ni3+ ions.
• Resistivity decreased, and crystal quality slightly reduced with higher O2 content.
• The NiO-50 film showed optimal crystallinity, surface roughness, and hole concentration for SERS.
• A remarkable SERS enhancement factor of 9.6 × 10⁸ was achieved for NiO/Si.

Conclusions:

• NiO film properties can be tuned by controlling oxygen concentration during sputtering.
• NiO-50 demonstrates superior SERS activity, driven by electron transition mechanisms.
• These findings highlight NiO as a highly effective SERS-active material for advanced sensing.