One-dimensional germanium nanostructures—formation and their electron field emission properties

Abstract

Ge nanostructures were synthesized by reduction of GeO(2) in H(2) atmosphere at various temperatures. Entangled and straight Ge nanowires with oxide shells were grown at high temperatures. Ge nanowires with various numbers of nodules were obtained at low temperatures. Ge nanowires without nodules exhibited remarkable field emission properties with a turn-on field of 4.6 V µm(-1) and field enhancement factor of 1242.

Reliability Enhancement of Germanium Nanowires Using Graphene as a Protective Layer: Aspect of Thermal Stability

“…35,41 The FEF of pure Ge NW FE devices significantly decreased, but that of the devices based on Ge@G NWs stayed around 2000, which is the highest value yet reported for Ge-based FE devices. 35,39,40 This may be due to the high aspect ratio of the NWs with a clumped and conductive graphene on the tip. Herein, the Ge@G NWs had an average length of 20 μm and an average diameter of 50− 70 nm, and thus, the aspect ratio is 300−400.…”

A Review of Self-Seeded Germanium Nanowires: Synthesis, Growth Mechanisms and Potential Applications

“…The crystallinity of the Ge nanowires produced can be tuned to be either amorphous, polycrystalline or single crystalline, by modifying the substrate temperature and/or evaporation rate. Wu et al [ 149 ] used the GeO 2 precursor to synthesise self-seeded Ge nanostructures under H 2 flow at a temperature of 1100 °C (727–627 °C in the deposition zone). Different 1D structure morphologies (such as straight nanowires, sphere-capped nanowires and tapered nanowires) were obtained along the substrate length, each corresponding to a different growth temperature (see Figure 3 c).…”

“…Within the group of vapour phase-grown self-seeded Ge nanowires, several mechanisms have been proposed. Among these, classical VS growth was proposed to be mainly responsible for self-seeded growth of Ge nanowires, as reported by Kim et al [ 138 ] in 2009 and Wu et al [ 149 ] in 2010. Kim et al achieved nanowire growth via a CVD setup using GeH 4 as a precursor [ 138 ].…”

“…Higher densities of nanowires were observed on activated regions of the substrate (see Figure 8 b). In another report, Wu et al [ 149 ] proposed mixtures of OAG and VS growth mechanisms using GeO 2 as a precursor for the self-seeded growth of Ge nanowires. In the coldest substrate reaction zone (645 °C), participation of both VS and OAG growth produced Ge nanowires at high densities [ 93 ], whereas in the hottest substrate zone (720 °C), nanowires were produced by OAG combined with self-catalytic VLS growth [ 220 ].…”

“…Comparison of the emission properties between different Ge nanowire samples is difficult due to their different morphologies, which affects the geometric enhancement factor β that describes how electric fields are affected by geometry and surface. Wu et al [ 149 ] reported VS-grown Ge nanowires (diameter of approximately 60 nm) with a turn-on field (applied field to draw an emission current density of 100 nA cm −2 ) of 4.6 V μm −1 . Li et al [ 134 ], instead, obtained a turn-on voltage of 8.5 V μm −1 for the Ge nanowires grown by OAG.…”