A General Framework of Scanning Tunneling Microscopy Based on Bardeen's Approximation for Isolated Molecules

Area of Science:

• Surface science
• Computational chemistry
• Scanning Probe Microscopy

Background:

• Current theoretical Scanning Tunneling Microscopy (STM) implementations often rely on approximations like periodic boundary conditions and the Tersoff-Hamann method.
• These methods have limitations in exploring diverse tip states beyond s-wave and accurately simulating charged molecules, which are common in chemical studies.

Purpose of the Study:

• To develop a generalized theoretical framework for Scanning Tunneling Microscopy (STM) image simulations.
• To overcome the limitations of existing theoretical models in handling various tip states and charged molecular systems.

Main Methods:

• Established a theoretical framework for STM image simulations using Bardeen's approximation and cluster boundary conditions.
• Developed an analytic algorithm for precise evaluation of the transfer Hamiltonian matrix, accounting for tip state asymptotic behaviors.

Main Results:

• Successfully simulated molecular images under various STM tip states and mapping modes with quantitative accuracy.
• The framework correctly addresses the asymptotic behaviors of tip states, enhancing simulation fidelity.

Conclusions:

• The developed framework provides a versatile tool for accurate STM image simulations of both neutral and charged molecules.
• This advancement facilitates conclusive investigations into the ground state electronic structures of molecular systems.