What Does Hydrogen Passivation Mean?
Hydrogen passivation refers to the stabilization of silicon material surfaces from chemical reactions through the creation of hydrogen silicon bonds. Recently manufactured silicon-based materials may contain reactive dangling bonds on their silicon atoms. These dangling bonds can affect the band gap energies of the material, affecting its properties as a semiconductor. In addition, reactive dangling bonds are sensitive to air; passivating these positions with hydrogen can increase the material's stability and longevity.
Hydrogen passivation is achieved with a variety of hydrogen sources:
- Molecular H2
- Atomic H generated in plasma
- Firing of hydrogenated Si nitride solids (SiN:H)
- Hydrogen fluoride
The importance and effects of hydrogen passivation are relevant in the electronics industry for semiconductors and for energy-related applications such as solar energy devices. The complicated nature of the underlying chemistry has seeded much scientific research.
Corrosionpedia Explains Hydrogen Passivation
Silicon-based materials contain silicon atoms on their surface that are unsaturated, meaning they have three paired bonds and a dangling bond with an unpaired electron. In accordance with the chemical principle of the octet rule, these silicon atoms with dangling bonds are reactive. Reactions with other molecules can change the properties of the material or cause damage. Hydrogen passivation is one such reaction, where the dangling bond (Si•) reacts with hydrogen to produce a stable Si-H bond. Basic mechanistic understanding involves the following reactions:
Si• + H2 -> Si-H + H•, or
Si• + H• -> Si-H
depending on the hydrogen source. The true mechanistic details are complicated still debated in theoretical scientific research.
The dangling bonds are considered to be defects within the silicon material because they generate defect states within the material's bandgap. Such defects can reduce device quality. Although passivation typically refers to stabilizing a material from damage, hydrogen passivation typically enhances the electronic properties of the material. Scientific research aims to optimize these enhancements by using various hydrogen sources and application conditions such as temperature, duration and pressure.