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

Abstract

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 mm À1 and a turn-on field of 2.58 V mm À1 . The surface wetting measurement confirms the superhydrophobicity of the sample with a WCA (Water Contact Angle) of about 150.8 AE 2 , which decreased to 84.7 after 300 C (3 h) treatment under vacuum (10 À3 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.

Ge-doped ZnO nanowire arrays as cold field emitters with excellent performance

“…Nanowires are natural one-dimensional electron transport channels with morphologies, dimensions and electronic properties that are tunable via various approaches. Currently, many nanowires composed of various materials, including carbon materials [1][2][3][4], oxides [5][6][7][8][9][10], carbides [11][12][13], silicide [14][15][16] and so on, can be synthesized on a large scale and exhibit fantastic FE emission performances. The discovery of new types of cold cathode emission materials and improving their performances are important tasks.…”

Compositional and structural engineering of inorganic nanowires toward advanced properties and applications

“…FET, field-effect transistor; NW, nanowire; HAADF, high-angle annular dark-field; SEM, scanning electron microscopy; STEM, scanning transmission electron microscopy result in improved FE performance via suppression of the screening effect of the electric field, thus increasing the field enhancement factor and the effective emission area. [67][68][69][70][71][72][73] However, among the numerous types of nanowires, there are a limited number intrinsically satisfying all the favorable factors, that is, low work function, high electron conductivity, Reproduced with permission. 78 Copyright 2011, American Chemical Society.…”

“…Benefiting from the facile growth of large‐scale (quasi‐) oriented NW arrays on planar substrates in a controllable manner (NW density, morphology, diameter, and length), diverse nanowires have been frequently investigated as field electron emitters in recent years, such as Si and silicide, B and boride, metal oxide, and carbide NWs . Rational design of the nanowire morphology and distribution can result in improved FE performance via suppression of the screening effect of the electric field, thus increasing the field enhancement factor and the effective emission area . However, among the numerous types of nanowires, there are a limited number intrinsically satisfying all the favorable factors, that is, low work function, high electron conductivity, outstanding thermal stability, and large field enhancement factor, which facilitate the achievement of a low turn‐on (threshold) electric field, large current emission, and stable long‐term emission.…”

Amorphous Ge/C Composite Sponges: Synthesis and Application in a High-Rate Anode for Lithium Ion Batteries

“…Kim et al synthesized amorphous Ge/GeO 2 /carbon that exhibited a high reversible capacity of 1631 mA h g –1 with superior capacity retention after 90 cycles at 0.5 A g –1 . The above-mentioned reports suggest that various types of nanostructures (e.g., nanoparticles, nanowires, thin films, nanotubes, and porous architectures) and the use of a conductive matrix such as carbonaceous materials can effectively reduce the degree of volume change and improve the cycling stability. ,,− However, the established synthesis process for Ge is usually rather complicated, tedious, and costly. For instance, Ge embedded in a conductive matrix such as carbon nanotubes or graphene is too costly to generate for large-scale practical applications.…”