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Perfecting Defects Could Impact Semiconductors

Haixuan XuIn baking, cooks often start with a simple recipe of flour, baking powder, butter, sugar, and eggs. This basic list of ingredients will come together to make a base for a variety of different goods. From here, the addition of milk will turn that base into cake batter, while baking soda will make cookie dough. The use of different ingredients in the same base can lead to vastly different outcomes.

The same can be said of materials science and the study of low-dimensional materials. Haixuan Xu, assistant professor of materials science and engineering, and his JDRD team propose to expand the understanding of the effect of point defects and impurities on low-dimensional materials such as graphene.

“We are trying to see how we can control the creation of defects in low-dimensional materials,” said Xu. “A defect could be a hole or what you call a vacancy in the material system. Then we want to put something else in there. That’s called a dopant.”

Dopants, or impurities, are inserted into a substance to change its electrical or optical properties. This is often done with semiconductor materials currently of interest in the advancement of electronics and computing.

The ultimate aim of Xu’s work is to advance the science of quantum computing by contributing to the foundation of knowledge needed in order to move forward.

“The joint LDRD [Laboratory Directed Research and Development] and JDRD work is trying to see if we can precisely control the atomic and material environment used to prepare and maintain coherent superposition of quantum states, which is the heart of the challenge for quantum computing. But there are many steps in between,” said Xu.

Xu’s project will study these defects in an attempt to ascertain how the use of particular dopants can affect the base material, particularly with relation to the electronic structure of the system. In order to do this, his team must first determine how to create defects in a controlled manner, a task that is currently under way.

Xu’s ORNL partner, Stephen Jesse, will tackle the same problem from an experimental angle using the national lab’s scanning electron beam microscope and helium ion microscope. Xu’s team will be hammering away at the theoretical understanding through computer modeling, with the intention of bringing their results together to provide a more complete picture.

“There is nice synergy between the Oak Ridge and UT teams. We’re actually studying the same scientific problem from two different and complementary perspectives,” said Xu. “Hopefully we can get a better understanding of what’s really going on in the system.”

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