Physicists shine light on solid way to extend excitons' life
Dr. Anton Malko’s Optics and Ultrafast Spectroscopy Laboratory focuses on the science and engineering of excitonic processes in various novel nanomaterials and hybrid structures. Malko and fellow researchers tested ultrathin semiconductors made with a method called laser-assisted synthesis technique in a recent study. Credit: University of Texas at Dallas

The University of Texas at Dallas has shown for the first time that a new method for manufacturing ultrathin semiconductors yields material in which excitons survive up to 100 times longer than before.

The findings show that excitons can be used in a wide range of applications.

A paper written by a professor of physics in the School of Natural Sciences and Mathematics has been published online. New quantum physics is shown in the findings.

Semiconductors have an electrical conductivity that is 888-609- 888-609- 888-609- 888-609- 888-609- The diodes and transistors that underpin all modern electronic technology are made up of this conductivity.

Two-dimensional transition metal dichalcogenide are a novel type of ultrathin Semiconductor consisting of a transition metal and a chalcogen element arranged in one atomic layer The 2D form that Malko examined has advantages over the 10 year old form.

The methodLAST is very pure. Malko said to evaporate them under intense laser light The two-dimensional TMD layer is less than 1 nanometer thick thanks to the distribution of those atoms.

The behavior of excitons determines the optical properties of a material.

A negatively charged electron and a positive hole are created when a photon is absorbed by a Semiconductor. They are the exciton. Malko said that the two parts are still interacting with one another.

Malko and his team were surprised to find that excitons in LAST-produced TMDs were 100 times longer than those in other materials.

He said that the 2D samples behaved differently from any they had seen before. It's dependent on growth conditions and not a one-off.

Malko thinks that these longer lifetimes are caused by indirect excitons.

The excitons are used to feed the excitons.

According to the lead study author, Dr. Navendu Mondal, there is an abnormal amount of strain between the monolayers.

Mondal said that strain controlling is an important tool to tailor their optoelectronic properties. The electronic band-structure is very sensitive to structure changes. Band-gap modifications cause formation of dark excitons that are not visible to the naked eye.

Malko said that the built-in strain is comparable to what would be caused by pressing on the material with pillars.

He said that the strain is important for creating excitons. The optical response is gone if the strain is removed.

A path to the development of new optoelectronic devices can be opened by Malko's statement.

He said that the increased lifespan has interesting applications. There isn't time to use an exciton when it has a lifespan of less than 100 seconds. In this material, we can create a lot of inactive excitons that live a long time. You can do many things with this.

The results of the research are important proof of concept for quantum-scale devices.

He said that it was the first time anyone had ever made such a fundamental observation of long-lived excitations in materials. We now know why these lifetimes are so long.

The researchers will try to manipulate excitons with an electric field in order to create quantum level logic elements.

Before quantum effects change the game completely, classical semiconductors have already been shrunken down to the doorstep. It's a huge step if you can show that 2D material will work in electronic devices. The material's atomic monolayer is 10 times smaller than the one in Silicon. Can you make logic elements that big? We need to know that.

More information: Navendu Mondal et al, Photoexcitation Dynamics and Long‐Lived Excitons in Strain‐Engineered Transition Metal Dichalcogenides, Advanced Materials (2022). DOI: 10.1002/adma.202110568 Journal information: Advanced Materials