Rice Researchers Uncover Defects Threatening Advanced Electronics

Researchers at Rice University have identified a type of defect in hexagonal boron nitride (hBN), a widely used two-dimensional insulator, that can trap electrical charges and reduce the material's structural integrity. These findings, published in Nano Letters, indicate that such defects can lead to premature device failure by weakening the material's insulating properties.

Hae Yeon Lee, an assistant professor of materials science and nanoengineering at Rice, stated that the ability to detect these defects can enhance the reliability and reproducibility of future electronic devices.

Understanding hBN's Critical Role

hBN is a critical component in advanced ultrathin electronics, including transistors, photodetectors, and quantum devices, due to its atomically flat and chemically stable properties.

The Hidden Flaw: Stacking Faults

The identified defects are termed "stacking faults," which are long, narrow misalignments within the material's atomic arrangement. These faults can form easily during routine material handling, such as transferring hBN flakes onto wafers, and are difficult to detect using standard optical or atomic force microscopes.

Unmasking Defects with Cathodoluminescence

To identify these hidden flaws, the research team utilized cathodoluminescence spectroscopy at Rice's Shared Equipment Authority. This technique, which scans a material with an electron beam and analyzes the emitted light, revealed bright, narrow stacking faults through hBN's deep ultraviolet light emission map. The study observed that these faults were more prevalent in thicker hBN flakes.

Impact on Device Performance

Functionally, these defects act as tiny charge pockets, compromising the material's insulation. This means that hBN can begin to leak electricity at much lower voltages along these defect lines compared to defect-free areas, potentially causing performance variations between devices built identically.

A Practical Detection Method

The researchers developed a practical detection method by combining electron microscopy, cathodoluminescence mapping, and force-based measurements. This approach allows for the identification of these defects before they negatively impact device performance and can be adapted for other layered materials.

Funding and Support

The research received funding from entities including the U.S. Army Research Office, the Japan Society for the Promotion of Science, the Japan Science and Technology Agency, and Japan's MEXT Scholarship.