Low Temperature Atomic Layer Deposition of (00l)-Oriented Elemental Bismuth

Area of Science:

• Materials Science
• Nanotechnology
• Thin Film Deposition

Background:

• Atomic Layer Deposition (ALD) is a crucial technique for fabricating thin films with atomic-level precision.
• Elemental bismuth (Bi) thin films have unique electronic and optical properties, but their synthesis via ALD is challenging.

Purpose of the Study:

• To demonstrate the first successful growth of elemental bismuth thin films using thermal atomic layer deposition.
• To investigate the growth mechanism, morphology, structural, and electrical properties of ALD-grown Bi films.

Main Methods:

• Thermal atomic layer deposition (ALD) using bismuth precursor Bi(NMe2)3 and co-reactant Sb(SiMe3)3.
• Deposition at 100°C with a growth per cycle (GPC) of 0.31-0.34 Å/cycle.
• Characterization using X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and temperature-dependent sheet resistance measurements.

Main Results:

• Achieved full surface coverage between 2000 and 2500 ALD cycles.
• Observed grain expansion and a preferential shift in growth orientation from (012) to (003) plane with increasing thickness.
• Confirmed metallic Bi with minimal oxidation via XPS and demonstrated semimetallic behavior with a room temperature resistivity of ~200 μΩcm.

Conclusions:

• Successfully established a thermal ALD process for growing high-quality elemental bismuth thin films.
• The ALD-grown Bi films exhibit controllable growth, desirable structural characteristics, and semimetallic properties with temperature-dependent carrier dominance.