Fabrication of Nanometer-Scale Si Field Emitters Using Self-Assembled Ge Nanomasks

Abstract

Large-area, nanometer-scale Si field emitters have been fabricated by selective chemical etching of self-assembled Ge islands on Si. Taking advantage of the relatively low etching rate, uniform Ge islands act as virtual nanomasks for the underlying Si substrate. During selective chemical etching, Ge nanomasks shrink into small Ge-core islands, which determine the apex sharpness of the resulting Si pyramidal tips. The results demonstrate that Si pyramidal tips exhibited improved antireflective and electron field emission characteristics compared to as-grown Ge islands. The high field enhancement factor can be attributed to high tip density, nanoscale apex, and well-controlled spacing between Si pyramidal tips. This work offers a low cost alternative for designing and fabricating high efficiency Si-based field emitters or nanodevices.

Strain Relaxation during Formation of Ge Nanolens Stacks

“…The Ge-rich area in the Ge dots exists as a core of the dots encapsulated by the Si-Ge intermixed phase. 17 Therefore, highly intermixed parts of Ge dots were easily etched out during the process, resulting in a smaller composition fluctuation within the Ge nanolens stacks. In addition, the small Ge dots in the as-grown sample may also be filtered out through the vertical alignment of Ge nanolenses during the etching process.…”

Formation Mechanism of Self-Assembled Ge∕Si∕Ge Composite Islands

“…Strain-induced self-organized semiconductor nanostructures have attracted considerable interest for the future nanoscale applications such as quantum computing and optoelectronic devices. [1][2][3] With an adjustable band structure and a moderate lattice mismatch, Ge/Si has emerged as a model system for the fabrication and investigation of nanoscale heteroepitaxy. 4,5 The self-assembly of Ge islands on Si is known to develop in Stranski-Krastanov growth mode; in which heteroepitaxial growth starts with the formation of a two-dimensional wetting layer followed by the nucleation of three-dimensional Ge islands.…”