Atomic-Scale Patterning of Arsenic in Silicon by Scanning Tunneling Microscopy

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Atomic-scale precision in silicon is crucial for advanced classical and quantum computing.
• Phosphorus has been the primary dopant used with scanning tunneling microscopy and hydrogen resist lithography.
• Alternative dopants compatible with these techniques remained largely unexplored.

Purpose of the Study:

• To demonstrate the fabrication of atomic-scale arsenic-in-silicon structures.
• To investigate the surface chemistry of arsine on silicon and compare it to phosphine.
• To evaluate the electrical properties and confinement of arsenic delta-layers.

Main Methods:

• Utilizing scanning tunneling microscopy (STM) to pattern a hydrogen mask on Si(001).
• Employing arsine (AsH3) as the precursor molecule for atomic arsenic placement.
• Encapsulating arsenic delta-layers with silicon using molecular beam epitaxy (MBE).

Main Results:

• Successful fabrication of atomic-scale arsenic structures in silicon.
• Elucidation of arsine surface chemistry, revealing differences from phosphine.
• Demonstrated enhanced surface immobilization and in-plane confinement of arsenic.
• Achieved dose-rate independent arsenic saturation density of 0.24 ± 0.04 monolayers.
• Obtained electrical characteristics competitive with phosphorus, including >80% carrier activation and low sheet resistance.

Conclusions:

• Arsine is a viable precursor for atomic-scale arsenic doping in silicon via hydrogen resist lithography.
• Arsenic delta-layers exhibit excellent electrical properties and confinement, comparable to phosphorus.
• This advancement expands the toolkit for atomic-scale dopant fabrication, particularly for 3D device architectures.