Role of Defects and Growth Directions in the Formation of Periodically Twinned and Kinked Unseeded Germanium Nanowires

Abstract

Here we show the impact of preferred growth directions and defects in the formation of complex Ge nanowire (NW) structures grown by a simple organic medium based synthesis. Various types of NWs are examined including: straight defect free NWs; periodically bent NWs with precise angles between the NW segments; NWs with mutually exclusive lateral or longitudinal faults; and more complex "wormlike" structures. We show that choice of solvent and reaction temperature can be used to tune the morphology of the NWs formed. The various types of NWs were probed in depth using transmission electron microscopy (TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED), and dark field TEM (DFTEM).

Epitaxial Post-Implant Recrystallization in Germanium Nanowires

“…no lateral (111) stacking faults are formed. 58 However, for the <112> grown NW containing intrinsic (1 ത 11) longitudinal defects, extrinsic (1 ത 11) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 In summary, crystal recovery of grown and top-down fabricated Ge NWs studied using in-situ TEM has been presented. Using in-situ TEM data supported by MD calculations, we demonstrate that the recrystallization of the Ge NWs is complex and may result in structures having polycrystalline regions, large number of extended crystal defects such as stacking faults, and in some cases full crystal recovery.…”

High Density Germanium Nanowire Growth Directly from Copper Foil by Self-Induced Solid Seeding

“…Here, the NWs were viewed from near the edge of the copper, Interestingly, outliers with diameters > 25 nm were found to exhibit tortuosity (Supporting Information Figure S2) due to a diameter dependent increase in NW kinking caused by defect driven growth direction changes. 27 The XRD diffractogram shown in Figure 2, taken from a typical Ge NW covered Cu substrate, is indexed with the expected peaks of Cu, Ge. Interestingly, additional peaks were also observed consistent with Cu 3 Ge.…”

“…These faults result in a streaking in the inset FFT. 27 Figure 3f is a defect free NW with a <112> growth direction. Due to the scarcity of <112> NWs, we were unable to obtain a high resolution image of the NW seed, however, it is likely that the seed orientation is [200] seed / [112] NW due to the similarity in the d spacings of (400) and (224) Figure S5) showed that the formation of catalytic Cu 3 Ge leads to substantial roughening of the substrate.…”

Recent advances in the growth of germanium nanowires: synthesis, growth dynamics and morphology control

“…The transfer of crystallographic information from a seed particle to a nanowire opens up the possibility of engineering the structure of Ge nanowires and enabling the tuning of band structure via strain modulation. Kinking and defects in Ge nanowires were also investigated by Geaney et al who used a high boiling point (HBS) method to vary the synthesis temperature to produce straight nanowires consisting of stacking faults (longitudinal and transverse), kinked nanowires and tortuous nanowires 191 . While kinked nanowires may have limited applications outside of three-dimensional electronics 192 , the study of such architectures provides an understanding of how kinks are formed, thus enabling future generations of researchers to more accurately synthesise straight wires of uniform structural integrity.…”