Anderson's negative-U chemistry in amorphous silicon nitride: A complex system approach

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Chemistry

Background:

• The negative-U model describes electron-electron attraction in amorphous materials.
• Amorphous silicon nitride (a-SiNₓ) is crucial for charge storage applications.

Purpose of the Study:

• Investigate the chemical mechanisms behind charge trapping in a-SiNₓ.
• Explain the role of defects in the electronic properties of amorphous silicon nitride.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Structural sampling and quantum-chemical analysis.
• Analysis of coordination defects and bonding networks.

Main Results:

• Coordination defects in a-SiNₓ function as charge traps at high densities (10²¹ cm⁻³).
• Electron donor-acceptor interactions stabilize paired or empty states over singly occupied ones.
• Si-rich a-SiNₓ exhibits power-law distributed Si-Si bonds, correlating with trap depth.

Conclusions:

• Defect-mediated charge trapping explains the electronic behavior of a-SiNₓ.
• Reorganization of chemical bonds influences charge trapping dynamics.
• The findings elucidate a-SiNₓ's utility in charge trap flash memory.