Toward Scalable Fabrication of Atomic Wires in Silicon by Nanopatterning Self-Assembled Molecular Monolayers Chufan Zhang, † Meng Peng, ‡ Weida Hu, ‡ and Yaping Dan* ,† † University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China ‡ State Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China * S Supporting Information ABSTRACT: Developing a scalable method to fabricate atomic wires is an important step for building solid-state semiconductor quantum computers. In this work, we developed a selective doping strategy by patterning the self- assembled monolayer to a few nanometers using standard nanofabrication processes, which significantly improves the lateral doping resolution of monolayer doping from microscale to nanoscale. Using this method, we further explore the possibility to fabricate phosphorus wires in silicon by patterning self-assembled diethyl vinylphosphonate mono- layers into lines with a width ranging from 500 to 10 nm. The phosphorus dopants are driven into silicon by rapid thermal annealing, forming dopant wires. Four-probe and Hall effect measurements are employed to characterize the dopant wires. The results show that the conductance is linear with the width for the wires, showing the success of the monolayer patterning process to nanoscale. To fabricate atomic wires made of one or a few lines of phosphorus atoms, we need to significantly shorten the thermal diffusion length and increase the dopant incorporation rate at the same time. Pulsed laser annealing may be a promising solution. The present work provides a promising pathway for mass fabrication of atomic wires in silicon that may find important applications in quantum computing. KEYWORDS: monolayer doping, nanoelectronics, semiconductors, atomic wires, self-assembled monolayers ■ INTRODUCTION The successful development of complementary metal-oxide- semiconductor (CMOS) technology in the past decades is mainly driven by the constant down-scaling of CMOS transistor sizes. 1 However, the down-scaling has become increasingly difficult as the size of the transistors approaches the physical limit of single atoms. 2,3 Interestingly, Kane proposed in 1998 a new quantum computing device based on the spin coupling of two phosphorus dopant atoms in silicon. 4 A sophisticated quantum computer based on this sort of device requires the precise control of phosphorus atoms at large scale. Simmons et al. 5-8 have demonstrated a scanning tunneling microscopic technique to successfully fabricate atomic wires and single atom transistors in silicon. A Japanese group reported in 2005 a technique to implant single dopant ions into silicon at a spatial resolution of 20 nm. 9 However, these techniques are time- consuming serial processes in which dopants are placed one by one. A parallel process for control of individual dopants at large scale is required if the solid-state semiconductor quantum computing in the coming decades is expected to replicate the success of CMOS technology in the past half-century. In recent years, self-assembled molecular monolayer doping (MLD) has attracted intensive research interests due to its capability of facilitating mass production, flexibility in doping nonplanar structures, and forming ultrashallow junctions with atomic precision. 10-20 MLD is believed to have a great potential in controllable dopant manipulation at sub-10 nm scale. 13,14,21 However, there is still no general method for effectively patterning a dopant-containing monolayer at nanoscale. In this work, we first demonstrated a selective doping strategy by patterning self-assembled monolayers (SAMs) to a few nanometers using standard nanofabrication processes, which improves the lateral doping resolution of MLD from micro- scale 14,16,17 to nanoscale. Using this method, we further explore the possibility of fabricating dopant wires in silicon at large scale. We first grafted a monolayer of diethyl vinylphosphonate (DVP) molecules on intrinsic Si wafer via hydrosilylation. Hydrogen silsesquioxane (HSQ) was used as a negative electron beam resist to pattern the DVP monolayer, forming an array of dopant wires with width from 500 nm down to 10 nm after the phosphorus dopants were thermally driven into silicon by rapid thermal processing (RTP). Four-probe and Hall effect measure- ments are employed to characterize the dopant wires. The results show that the conductance is linear with the width for the wires, showing the success of the monolayer patterning process to nanoscale. To fabricate atomic wires made of one or a few Received: November 8, 2019 Accepted: December 16, 2019 Published: December 16, 2019 Article pubs.acs.org/acsaelm Cite This: ACS Appl. Electron. Mater. 2020, 2, 275-281 © 2019 American Chemical Society 275 DOI: 10.1021/acsaelm.9b00749 ACS Appl. Electron. Mater. 2020, 2, 275-281 This article is made available for a limited time sponsored by ACS under the ACS Free to Read License, which permits copying and redistribution of the article for non-commercial scholarly purposes. Downloaded via 54.163.42.124 on July 23, 2020 at 23:25:58 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.