A New Synthetic Method for HfS₂ Thin Films Using MOCVD.

Area of Science:

• Materials Science
• Nanotechnology
• Semiconductor Physics

Background:

• Hafnium disulfide (HfS2) shows promise as a 2D semiconductor, potentially outperforming MoS2 and WS2.
• Its native oxide, HfO2, is a well-established high-k dielectric, offering synergistic advantages.
• Existing synthesis methods like MOCVD have not been successfully applied to HfS2 due to precursor limitations.

Purpose of the Study:

• To develop the first metal-organic chemical vapor deposition (MOCVD) method for synthesizing high-quality HfS2.
• To introduce and evaluate novel nitrogen-coordinated hafnium precursors for HfS2 deposition.
• To investigate the oxidation pathways and electrical properties of MOCVD-grown HfS2 films.

Main Methods:

• Synthesis of two novel nitrogen-coordinated hafnium precursors: [Hf(TMSAEDMA)(NMe2)3] (1) and [Hf(TMSAEDMA)(NEtMe)3] (2).
• Deposition of HfS2 films using MOCVD with precursor 1 under moderate, H2S-free conditions.
• Characterization using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrical conductivity measurements.

Main Results:

• Successful MOCVD growth of crystalline HfS2 using precursor 1.
• Observation of rapid native oxidation to HfO2 and HfOxSy, forming heterostructures.
• Electrical conductivity was preserved in HfS2 films with native oxide and after ZnS capping.

Conclusions:

• This study establishes the first MOCVD route for high-quality HfS2.
• Precursor 1 is identified as a versatile tool for chalcogenide growth.
• The findings highlight HfS2's potential for advanced semiconductor applications due to its properties and oxidation behavior.