Defect-Tolerant Monolayer Transition Metal Dichalcogenides.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Crystal defects in semiconductors create localized electronic states within the band gap, negatively impacting optoelectronic properties.
• Defect-tolerant semiconductors exhibit a reduced tendency to form these detrimental deep gap states.
• Monolayer transition metal dichalcogenides (TMDs) are crucial for nanoscale optoelectronics.

Purpose of the Study:

• To systematically investigate defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs).
• To identify which TMDs are suitable for optoelectronic applications by assessing their response to defects.
• To develop a descriptor for quantifying defect tolerance based on electronic band structure.

Main Methods:

• First-principles calculations were employed to simulate defect formation in various TMDs.
• Chalcogen vacancies (S, Se, Te) were introduced to study their impact on electronic states.
• A descriptor was developed to quantify the similarity between valence and conduction band orbital compositions.

Main Results:

• TMDs based on group IV metals were predicted to be defect-tolerant, forming only shallow defect levels.
• TMDs based on group VI and X metals formed deep gap states due to chalcogen vacancies.
• A strong correlation was found between band gap orbital composition and defect sensitivity.

Conclusions:

• Group IV TMDs are promising for defect-tolerant nanoscale optoelectronics.
• The orbital composition of valence and conduction bands dictates defect sensitivity in TMDs.
• The developed descriptor effectively quantifies defect tolerance in TMDs and their nanoribbons.