[Paper Review] Correlating 3D atomic defects and electronic properties of 2D materials with picometer precision

Xuezeng Tian, Dennis Kim+11 more|arXiv (Cornell University)|Jan 3, 2019

Electronic and Structural Properties of OxidesMaterials Science53 references3 citations

TL;DR

This study introduces scanning atomic electron tomography (sAET) to map 3D atomic defects in 2D materials with picometer precision, enabling direct correlation between atomic structure and electronic properties. By using experimentally determined 3D atomic coordinates in density functional theory (DFT), the authors achieve more accurate electronic band structures than conventional DFT, validated by photoluminescence measurements in Re-doped MoS2.

ABSTRACT

The exceptional electronic, optical and chemical properties of two-dimensional materials strongly depend on the 3D atomic structure and crystal defects. Using Re-doped MoS2 as a model, here we develop scanning atomic electron tomography (sAET) to determine the 3D atomic positions and crystal defects such as dopants, vacancies and ripples with a precision down to 4 picometers. We measure the 3D bond distortion and local strain tensor induced by single dopants for the first time. By directly providing experimental 3D atomic coordinates to density functional theory (DFT), we obtain more truthful electronic band structures than those derived from conventional DFT calculations relying on relaxed 3D atomic models, which is confirmed by photoluminescence measurements. We anticipate that sAET is not only generally applicable to the determination of the 3D atomic coordinates of 2D materials, heterostructures and thin films, but also could transform ab initio calculations by using experimental 3D atomic coordinates as direct input to better predict and discover new physical, chemical and electronic properties.

Motivation & Objective

• To achieve picometer-precision 3D atomic structure determination of 2D materials, including defects like dopants, vacancies, and ripples.
• To directly correlate atomic-scale 3D defects with electronic properties using experimental data.
• To improve the accuracy of ab initio electronic structure calculations by replacing relaxed theoretical models with experimentally measured 3D atomic coordinates.
• To validate the enhanced DFT predictions through experimental photoluminescence measurements.
• To demonstrate the general applicability of sAET for 2D materials, heterostructures, and thin films.

Proposed method

• The authors developed scanning atomic electron tomography (sAET), a technique combining electron tomography with atomic-resolution scanning transmission electron microscopy (STEM).
• sAET reconstructs 3D atomic positions from a series of 2D projections acquired at different tilt angles with sub-angstrom resolution.
• The method achieves a spatial precision of 4 picometers, enabling detection of atomic displacements and bond distortions from single dopants.
• Experimental 3D atomic coordinates from sAET are directly input into density functional theory (DFT) calculations to compute electronic band structures.
• The resulting DFT predictions are compared with photoluminescence measurements to validate accuracy.
• The approach is applied to Re-doped MoS2 to study strain and electronic effects from individual dopants.

Experimental results

Research questions

• RQ1 Can 3D atomic positions and defects in 2D materials be mapped with picometer precision?
• RQ2 How do single dopants induce local strain and bond distortions in 2D materials?
• RQ3 Can experimentally measured 3D atomic coordinates improve the accuracy of ab initio electronic structure calculations?
• RQ4 How does the electronic band structure derived from experimental 3D coordinates compare to conventional DFT using relaxed models?
• RQ5 To what extent do photoluminescence measurements confirm the enhanced accuracy of sAET-informed DFT?

Key findings

• The sAET technique achieves a spatial resolution of 4 picometers, enabling precise mapping of atomic positions and defects in 2D materials.
• The method directly measures 3D bond distortions and local strain tensors induced by single Re dopants in MoS2 for the first time.
• DFT calculations using experimentally derived 3D atomic coordinates yield more accurate electronic band structures than those from conventional DFT with relaxed models.
• The improved DFT predictions are experimentally validated through photoluminescence measurements, confirming enhanced accuracy.
• The study demonstrates that sAET is generally applicable to 2D materials, heterostructures, and thin films for high-precision defect and property correlation.
• The approach paves the way for transforming ab initio calculations by using real experimental 3D atomic data as input.