Ab-initio Guided Shaping of Semiconductor Nanowires

In recent years, one dimensional (1D) nanomaterials such as carbon nanotubes and semiconductor nanowires/nanotubes have been intensively explored as potential building blocks for multiple electronic, optoelectronic and biosensing applications. Extensive efforts have been devoted to the synthesis of semiconductor nanowires with controlled chemical and physical properties such as: dimension, chemical composition, doping and crystal structure.  However, and despite the great synthetic advances achieved, the ability to control nanowire’s geometry has been significantly limited. To fully exploit their full potential, new semiconductor nanowires building blocks with ab-initio controlled shapes are desired.

Here, we demonstrate a simple and robust method that enables to pre-design not only the chemical and physical attributes of the synthesized nanowires, but also allows a perfect unlimited control over their geometry. Our method allows the synthesis of semiconductor nanowires, via the vapor-liquid-solid (VLS) mechanism, in a wide variety of two dimensional shapes such as any kinked (different turning angles), sinusoidal, linear and spiral shapes, so that practically any desired geometry can be defined. The approach also allows for a fine control over the density and number of nanowires synthesized. The shape-controlled nanowires can be grown on almost any substrate such as silicon wafer, quartz and glass slides and even on plastic substrates (e.g. Kapton HN).

Writing with Nanowires

Nanowires with a wide variety of two-dimensional shapes

Nanowires with a wide variety of two-dimensional shapes

[a]-[e] SEM images of multiply-kinked two-dimensional Si nanowires with different turning angles from 120˚ to 80˚. The green arrow [a] highlights the growth direction of the nanowires. The black arrow [c] highlights the position of the nanocluster catalyst. The clearly visible gold catalyst at the nanowire tip indicates that growth proceeds by means of the nanocluster catalyzed VLS process throughout the entire synthesis.

[f]-[h] SEM images of sinusoidal shape two-dimensional silicon nanowires with different periods.

[i] SEM image of a two-dimensional spiral shape Si nanowire. [j] Back secondary electron image of the wire from figure [i]. The black arrow highlights the position of the nanocluster catalyst.