Nanodroplet Hydrodynamic Transformation of Uniform Amorphous Bilayer into Highly Modulated Ge/Si Island-Chains

Abstract

Geometric and compositional modulations are the principal parameters of control to tailor the band profile in germanium/silicon (Ge/Si) heteronanowires (NWs). This has been achieved mainly by alternating the feeding precursors during a uniaxial growth of Ge/Si NWs. In this work, a self-automated growth of Ge/Si hetero island-chain nanowires (hiNWs), consisting of wider c-Ge islands connected by thinner c-Si chains, has been accomplished via an indium (In) droplet-mediated transformation of uniform amorphous a-Si/a-Ge bilayer thin films. The surface-running In droplet enforces a circulative hydrodynamics in the nanoscale droplet, which can modulate the absorption depth into the amorphous bilayer and enable a single-run growth of a superlattice-like hiNWs without the need for any external manipulation. Meanwhile, the separation and accumulation of electrons and holes in the phase-modulated Ge/Si superlattice leads to a modulated surface potential profile that can be directly resolved by Kelvin probe force microscopy. This simple self-assembly growth and modulation dynamics can help to establish a powerful new concept or strategy to tailor and program the geometric and compositional profiles of more complex hetero nanowire structures, as promising building blocks to develop advanced nanoelectronics or optoelectronics.

Ultra‐Confined Catalytic Growth Integration of Sub‐10 nm 3D Stacked Silicon Nanowires Via a Self‐Delimited Droplet Formation Strategy

“…An enlarged view of the 10th SiNW in Figure 2e reveals that there is still remnant a-Si layer (light-yellow) around the SiNW, implicating that the catalyst droplet consumes only a portion of the a-Si supply during the IPSLS growth. This partial a-Si absorption phenomenon has also been observed for the IPSLS growth of SiNWs on planar surface, [31,40] usually for the oversupply of a-Si for the relatively smaller catalyst droplets. Figure 2f presents the high resolution (HR)-TEM characterization of the 3 rd layer SiNW channel, revealing a monocrystalline core and elliptic shape, with H nw = 17 nm and W nw = 8 nm.…”

Highly stretchable graphene nanoribbon springs by programmable nanowire lithography

“…1a, the SiNW masks were firstly produced via an in-plane guided IPSLS growth. 38,39,41,43,45 The guiding edges are first etched in the wafer or glass substrates coated with a 500 -nm SiO 2 layer, by lithography and inductively coupled plasma (ICP) etching, as illustrated schematically in Fig. 1c, which is followed by the deposition of indium (In) stripes lying crossing to the guiding edge lines at the ends.…”

“…In this work, we propose and demonstrate a readily scalable and yet precise nanowire lithography (NWL) strategy, where ultra-long and orderly silicon nanowires (SiNWs), produced via a guided inplane solid-liquid-solid (IPSLS) growth, [37][38][39][40][41][42][43][44][45] are transferred onto the monolayer or few-layer graphene sheet to serve as nano shadow masks. By this way, very thin GNRs of D GNR~5 0 nm can be reliably patterned over the large area wafer or flexible polymer substrates, with a programmable layout and geometry.…”

In situ observation of droplet nanofluidics for yielding low-dimensional nanomaterials

“…[14] Substantial efforts have been made on the programmable manipulation of crawling catalytic droplets on substrate surfaces. For example, a wide group of metal droplets can be trapped along nanofacets, [15][16][17][18] guiding steps, [19,20] or nanochannels, [21] which facilitates the self-assembly of horizontal CNTs, [15] Si, [16], [19], [21] III-V, [17] III-N nanowires (NWs), [18] and Si/Ge island chains. [20] Moreover, gold droplets are reported to lead the growth of horizontal Ge nanocrawlers on graphene surface, thus realizing 1D/2D heterostructures.…”

“…For example, a wide group of metal droplets can be trapped along nanofacets, [15][16][17][18] guiding steps, [19,20] or nanochannels, [21] which facilitates the self-assembly of horizontal CNTs, [15] Si, [16], [19], [21] III-V, [17] III-N nanowires (NWs), [18] and Si/Ge island chains. [20] Moreover, gold droplets are reported to lead the growth of horizontal Ge nanocrawlers on graphene surface, thus realizing 1D/2D heterostructures. [22] Recently, VLS-grown MoS 2 nanoribbons have been realized by moving Na-Mo-O droplets, which avoids dry etching process to pattern the 2D sheets.…”