Imperfections, such as missing atoms, in near perfect structures are key to the useful properties of many materials. We use precision-engineered materials every day—for example, the introduction of very small quantities of other elements into nearly pure silicon gives rise to the properties that make this doped silicon useful in LEDs. Indeed, it is the defects in hexagonal boron nitride (hBN), a material made up of sheets of interlinked hexagons of alternating boron and nitrogen atoms, that make this material interesting to material scientists. Imperfections in the structure of hBN give rise to color centers—tiny spots in the material that emit photons of a particular wavelength upon irradiation with light or an electron beam—that have unprecedented brightness. These photons can carry information, a property that has potential uses in next generation quantum computers.
Scaling up manufacture of hBN for use in applications has unfortunately been difficult—controlling the number and placement of the color centers is challenging and their brightness can vary depending on the manufacturing method. However, recent research conducted at Lawrence Berkeley National Lab and UC Berkeley has found that stacking sheets of hBN with a twist angle between the layers can greatly improve the brightness of the color centers, which is highly desirable. The team then demonstrated that treating the sheets with an electron beam controlled where defects, and therefore color centers, would form. Interestingly, they also discovered that applying a voltage across the hBN would turn the color centers on, and tuning the voltage could brighten and dim the spots. Now that the problems of both controlling the placement and brightness of the color centers have been solved, manufacturing and using hBN in materials applications should be easier. It’s looking like a very bright future for hBN!
This article is part of the Spring 2023 issue.
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