Impermeable Graphene Oxide Protects Silicon from Oxidation

Abstract

The presence of a natural silicon oxide (SiO x ) layer over the surface of silicon (Si) has been a roadblock for hybrid semiconductor and organic electronics technology. The presence of an insulating oxide layer is a limiting operational factor, which blocks charge transfer and therefore electrical signals for a range of applications. Etching the SiO x layer by fluoride solutions leaves a reactive Si–H surface that is only stable for few hours before it starts reoxidizing under ambient conditions. Controlled passivation of silicon is also of key importance for improving Si photovoltaic efficiency. Here, we show that a thin layer of graphene oxide (GO x ) prevents Si surfaces from oxidation under ambient conditions for more than 30 days. In addition, we show that the protective GO x layer can be modified with molecules enabling a functional surface that allows for further chemical conjugation or connections with upper electrodes, while preserving the underneath Si in a nonoxidized form. The GO x layer can be switched electrochemically to reduced graphene oxide, allowing the development of a dynamic material for molecular electronics technologies. These findings demonstrate that 2D materials are alternatives to organic self-assembled monolayers that are typically used to protect and tune the properties of Si and open a realm of possibilities that combine Si and 2D materials technologies.

Effect of Electrolytic Medium on the Electrochemical Reduction of Graphene Oxide on Si(111) as Probed by XPS

“…Moreover, the simple manipulation of the electrochemical reduction process of the graphene oxide can be achieved through controlling the potential, reduction time and electrolyte choice [ 10 , 33 , 40 , 41 ]. Good quality electrochemically reduced GO (erGO) layers can be formed directly onto different substrates such as silicon and indium tin oxide (ITO)/polyethylene terephthalate (PET) flexible substrates with a high interest in conventional optoelectronic devices [ 42 , 43 , 44 ] and transparent and flexible electrodes in transparent optoelectronic devices with novel functionalities (e.g., flexibility, semi or full transparency [ 45 , 46 ]), respectively [ 40 , 47 , 48 ]. Despite these practical advantages, the electrochemical reduction of GO is based on a reaction mechanism that has rarely been addressed in the literature, and its elucidation is still a matter of debate [ 49 , 50 ].…”

Size‐Controlled Nanosculpture of Cylindrical Pores across Multilayer Graphene via Photocatalytic Perforation

“…[ 36 ] Considering that the surface modification process is carried out using cyclic voltammetry (−1 to +1 V, vs Ag/AgCl), the reductive electrochemical potential may have increased the crystallinity of graphene lattice. [ 57 ] No change of I 2D / I G ratio was however observed after electrochemical grafting, indicating lower amounts of sp 3 ‐hybridization defects created on graphitic planes and minor changes in their crystallographic during the grafting process in this range of conditions.…”

In situ lattice tuning of quasi-single-crystal surfaces for continuous electrochemical modulation

“…47 Thus, the natural oxide layer was removed from the surface of Si wafers before the Au deposition process for directly modulating the Au surface by the structural difference of Si single crystals. [48][49][50] By employing Si(111) and Si(100) wafers as templates, we prepared two types of Au lms with exposed (111) planes but different initial interatomic spacings, labeled as Au and Au TS-Si(100) lms, where "TS" denotes "template stripping" and they represent that the Au lms were deposited on Si single-crystal wafers with respective crystal planes. During the electrochemical characterization, the Au lm, Pt wire, and Pt black wire served as the working electrode (WE), the counter electrode (CE), and the reference electrode (RE), respectively.…”