Study of the Effects of Chemical Etchants on the Quality of Silver Nanowires Cultivated on Periodically Poled Lithium Niobate

Jade Cyan Snow

Abstract


Silver nanowires are promising microstructures for various applications such as substrates for surface-enhanced Raman spectroscopy of biomolecules like DNA, and as interconnects in integrated circuits. Ferroelectric lithography is used to prepare such wires on periodically poled lithium niobate (PPLN) crystals, but imperfections in the crystal surface cause unwanted interstitial silver deposition and irregularities in the wires. In this work, an interdisciplinary collaboration with University of North Carolina Asheville's Department of Physics, several chemical treatments were used to attempt to etch the z-face of the PPLN crystals to an atomically smooth state. HF/HNO3 preferentially etched the poled domains creating an uneven surface and KOH caused irregular pitting of the surface. However, as confirmed through scanning electron microscopy and energy dispersive x-ray spectroscopy, aqua regia was hypothesized to etch the PPLN surface evenly and laterally, repairing preexisting surface flaws as well as those caused by KOH treatment, improving the quality and size of wires prepared, and reducing interstitial silver deposition. Further investigation is necessary to optimize the treatment parameters of aqua regia exposure time, temperature and other variables to the point of highest possible wire quality. Aqua regia treatment will be investigated in tandem with physical polishing methods, as preliminary tests suggest that ideal results may be achieved via complementary aqua regia treatment and physical polishing methods. Once treatment parameters are optimized, this combination treatment method could be used to prepare newly manufactured wafers for silver deposition, as well as repair for re-use damaged wafers which would previously have been considered waste. If continued research confirms this possibility, then a reliable and efficient new method of synthesizing silver nanowires of usable quality will have been discovered.

 


Keywords


Ferroelectric Lithography; Periodically Poled Lithium Niobate; Silver Nanostructures

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