Functionalization of SiO2 Surfaces for Si Monolayer Doping with Minimal Carbon Contamination

Maart van Druenen; Gillian Collins; Colm Glynn; Colm O'Dwyer; Justin D Holmes

doi:10.1021/acsami.7b16950

Functionalization of SiO₂ Surfaces for Si Monolayer Doping with Minimal Carbon Contamination

ACS Appl Mater Interfaces. 2018 Jan 17;10(2):2191-2201. doi: 10.1021/acsami.7b16950. Epub 2018 Jan 4.

Authors

Maart van Druenen^{1

2}, Gillian Collins^{1

2}, Colm Glynn¹, Colm O'Dwyer¹, Justin D Holmes^{1

2}

Affiliations

¹ School of Chemistry, and Tyndall National Institute, University College Cork , Cork, T12 YN60 Ireland.
² CRANN@AMBER, Trinity College Dublin , Dublin 2, Ireland.

PMID: 29240397
DOI: 10.1021/acsami.7b16950

Abstract

Monolayer doping (MLD) involves the functionalization of semiconductor surfaces followed by an annealing step to diffuse the dopant into the substrate. We report an alternative doping method, oxide-MLD, where ultrathin SiO₂ overlayers are functionalized with phosphonic acids for doping Si. Similar peak carrier concentrations were achieved when compared with hydrosilylated surfaces (∼2 × 10²⁰ atoms/cm³). Oxide-MLD offers several advantages over conventional MLD, such as ease of sample processing, superior ambient stability, and minimal carbon contamination. The incorporation of an oxide layer minimizes carbon contamination by facilitating attachment of carbon-free precursors or by impeding carbon diffusion. The oxide-MLD strategy allows selection of many inexpensive precursors and therefore allows application to both p- and n-doping. The phosphonic acid-functionalized SiO₂ surfaces were investigated using X-ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy, whereas doping was assessed using electrochemical capacitance voltage and Hall measurements.

Keywords: X-ray photoelectron spectroscopy; carbon contamination; covalent functionalization; doping; monolayer; phosphonic acids; silicon; stability.