Project's information

Project's title Development of computational models for Scanning Tunneling Microscope (STM) and Scanning Gate Microscope (SGM) in studying the electronic and local transmission properties of two-dimensional materials devices
Project’s code GUST.STS.ĐT2020-VL01
Research hosting institution Graduate University of Science and Technology
Project leader’s name PhD. Nguyen Mai Chung
Project duration 01/06/2020 - 15/11/2022
Project’s budget 408 million VND
Classify Fair
Goal and objectives of the project

The development of experimental measurements requires computational techniques that simulate local electronic and transmission properties in real devices in order to compare experimental and theoretical results. The advent of graphene and other two-dimensional materials and their heterostructures has opened a new direction in the development of electronic devices to replace traditional silicon materials. With two-dimensional materials, STM (Scanning Tunneling Microscope) and SGM (Scanning Gate Microscope) are ideal tools for studying the properties of electronics. The project “Development of computational models for Scanning Tunneling Microscope (STM) and Scanning Gate Microscope (SGM) in studying the electronic and local transmission properties of two-dimensional materials devices” has the main objective of building and develop theoretical calculation and simulation tools for analyzing physical pictures leading to experimental results of STM/SGM measurements. These tools also allow theoretical research on new structures to guide experimental research.

Main results

Theoretical results:
- First, the topic has built a computational model to simulate the behavior of the charge carriers using the Tight binding model, and the transmission characteristics based on the non-equilibrium Green’s function technique applied to the material channel. Graphene and two-dimensional materials (2D structures likes graphene) have large sizes, the size of micrometers, as in the experiment. Numerical coding programs are set up and optimized and parallelized on the high-performance computer system of the Institute of Physics and the center for computing and computing VAST.
- Next, we investigated the local electronic and transmission properties of electronic devices using graphene material as the conducting channel. Specifically, the project has studied the characteristic transmission quantities such as conductivity and the picture of the local-state density of electrons of the graphene bubble channels. Here, we has focused on studying bubbles with the radius R from 30 nm to 100 nm and the height h0 from 2.5 nm to 5.0 nm, respectively. These characteristic sizes of the proposed channel are consistent with the experimental study of Jia's group, which is published in the journal of nature communications. The results show that the conductivity in the graphene bubble channel tends to decrease compared to the normal graphene channel because the bubble region limits the transmission. In particular, we observed the appearance of resonance peaks in the low energy domain.
- Final, we has studied the characteristic transmission quantities of the stacked channel graphene nanoribbons. Specifically, a two-layer system of graphene nanoribbons with different sizes is studied under the effect of an external electric field. The results show the fluctuation of conductivity according to Fermi energy with the appearance of peaks and valleys. Furthermore, the project investigated the local state density picture to clarify the transmission picture of electrons. The obtained results demonstrate the quantum interference of electrons (similar to the famous Fabry-Pérot interferometer for light waves) when electrons travel along the channel in the proposed structure. Then, we investigated the dependence of quantum interference on characteristic parameters such as the strength of electric field and the width of active domain (cavity domain) of the channel.

Novelty and actuality and scientific meaningfulness of the results

- The project has successfully built and optimized the computational model for the large-sized channel system in accordance with the experimental fabrication.
- The quantum interference of electrons (similar to light waves) is observed under the influence of an external electric field. In general, interference phenomena are observed under the effect of an external magnetic field.

Products of the project

•    01 paper on national journal
Mai-Chung Nguyen et al, “Electron transport through experimentally controllable parabolic bubbles on graphene nanoribbons”, Communications in Physics, Vol. 32, No. 3 (2022), pp. 265-273. DOI: https://doi.org/10.15625/0868-3166/16763
•    01 paper on international journal
Mai-Chung Nguyen et al, “Quantum interference of electrons through electric-field-induced edge states in stacked graphene nanoribbons”, Physica Scripta, Vol. 97, No. 11 (2022), pp. 115814. DOI: https://doi.org/10.1088/1402-4896/ac9934

Images of project
1675304431833-207.png