Triple phase boundary induced self-catalyzed growth of Ge-graphite core-shell nanowires: field electron emission and surface wettability

摘要

We report a simple method to fabricate Ge-graphite core-shell nanowires on a large scale using a CVD (Chemical Vapor Deposition) system free of catalyst and complicated precursors, which demonstrates interesting V-L-S (vapor-liquid-solid) boundary induced self-catalyzed growth. The novel catalystfree VLS (vapor liquid solid) mechanism is expected to be generalized for the design of other 1D (one dimensional) metal-graphite hybrids in a controlled manner, based on the fact that tunable shell thickness was achieved on Ge-graphite and a 1D Cu-graphite core-shell was realized in the same way. The Ge-graphite core-shell nanowires deliver very good field emission properties with a threshold field of about 5.33 V mu m(-1) and a turn-on field of 2.58 V mu m-1. The surface wetting measurement confirms the superhydrophobicity of the sample with a WCA (Water Contact Angle) of about 150.8 degrees +/- 2 degrees, which decreased to 84.7 degrees after 300 degrees C (3 h) treatment under vacuum (10(-3) Torr). Moreover, the wettability behavior is robust against 365 nm UV (ultraviolet) radiation with the WCA unchanged, indicating stable superhydrophobicity in a UV-rich environment. We hope that this study contributes to the design of 1D metal-graphite nanostructures with the aim to explore more novel functionalities.