Wafer-scale synthesis of a morphologically controllable silicon ordered array as a platform and its SERS performance

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Single crystal silicon wafers possess distinct physical and chemical properties based on their crystal orientation.
• Anisotropic etching rates of different silicon crystal planes are crucial for surface structuring.
• Surface-enhanced Raman spectroscopy (SERS) requires precisely engineered substrates for optimal performance.

Purpose of the Study:

• To fabricate four distinct nanostructures on silicon wafers with varying crystal orientations.
• To investigate the formation mechanisms of these structures using reactive ion etching (RIE) and KOH etching.
• To evaluate and compare the SERS performance of the fabricated silicon nanostructures.

Main Methods:

• Fabrication of nanostructures using reactive ion etching (RIE) in O2 and O2/SF6 atmospheres.
• Anisotropic wet etching with KOH to modify silicon wafer surfaces with different crystal orientations ((110) and (100)).
• Characterization of surface morphology and SERS performance of the resulting structures.

Main Results:

• Four unique structures were successfully fabricated: hexagonal holes ((110) Si, O2 RIE), inverted pyramids ((100) Si, O2 RIE), diamond-based pyramids ((110) Si, O2/SF6 RIE), and 'straw hat' columns ((100) Si, O2/SF6 RIE).
• The formation mechanisms for each structure were elucidated based on etching conditions and crystal orientation.
• Comparative SERS characterization revealed differences in performance among the four structures.

Conclusions:

• Tailoring silicon crystal orientation and etching processes (RIE, KOH) enables the fabrication of diverse nanostructures.
• The generated silicon nanostructures exhibit varying SERS capabilities, highlighting the importance of structural design.
• These findings contribute to the development of advanced SERS substrates for sensitive chemical detection.