Microfluidic hydrothermal growth of ZnO nanowires over high aspect ratio microstructures

A hydrothermal synthesis of densely packed ZnO nanowires was realized in a confined space via forced circulation of the heated growth solution through microfluidic channels formed primarily by a set of high aspect ratio trenches in a Si substrate. A uniform and conformal seeding layer of ZnO was deposited to cover the entire surface of the trenches by means of atomic layer deposition (ALD). Densely packed ZnO nanowires were formed inside the trenches with particularly good coverage over the sidewalls, where they would not grow effectively through a conventional hydrothermal method. The strategy for controlled growth of densely packed ZnO nanowires over such high aspect ratio microstructures is deemed beneficial when these microstructures are employed as electrodes with high specific surface areas for devices such as supercapacitors or any other electrochemical devices.