Periodic Arrays of Dopants in Silicon by Ultralow Energy Implantation of Phosphorus Ions through a Block Copolymer Thin Film

Abstract

In this work, block copolymer lithography and ultralow energy ion implantation are combined to obtain nanovolumes with high concentrations of phosphorus atoms periodically disposed over a macroscopic area in a p-type silicon substrate. The high dose of implanted dopants grants a local amorphization of the silicon substrate. In this condition, phosphorus is activated by solid phase epitaxial regrowth (SPER) of the implanted region with a relatively low temperature thermal treatment preventing diffusion of phosphorus atoms and preserving their spatial localization. Surface morphology of the sample (AFM, SEM), crystallinity of the silicon substrate (UV Raman), and position of the phosphorus atoms (STEM-EDX, ToF-SIMS) are monitored during the process. Electrostatic potential (KPFM) and the conductivity (C-AFM) maps of the sample surface upon dopant activation are compatible with simulated I−V characteristics, suggesting the presence of an array of not ideal but working p− n nanojunctions. The proposed approach paves the way for further investigations on the possibility to modulate the dopant distribution within a silicon substrate at the nanoscale by changing the characteristic dimension of the self-assembled BCP film.

Diblock and Triblock Copolymers as Nanostructured Precursors to Functional Nanoporous Materials: From Design to Application

“…During the past decade, different research groups have rapidly expanded the scope of nanoporous polymers arising from block copolymers to design advanced materials for various high added value applications, including supports for heterogeneous catalysis, ,, responsive (biocatalytic) (ultra)­filtration membranes, ,− nanopatterns, ,, semiconductors and electrode materials, and materials for electrical energy storage …”

Assembling Vertical Block Copolymer Nanopores via Solvent Vapor Annealing on Homopolymer-Functionalized Substrates

“…High-aspect ratio vertical nanopore arrays synthesized through the spontaneous self-assembly of block copolymer (BCP) thin films have attracted intense interest for applications in nanolithography, − membrane separations, − Li battery anode protection, and templating nanomaterial synthesis . A majority of BCP nanopatterning applications have utilized polystyrene- block -poly­(methyl methacrylate) (PS- b -PMMA) based on the near-equal surface energies of the two blocks at elevated temperatures (>200 °C) at the air–polymer interface.…”