Precise control of the atomic defects in diamond and two-dimensional materials
by
Zoom
Recorded seminar: https://stanford.zoom.us/rec/share/zd-N-m4eLJ5bLEQ-AA6rTUnAZT1lDtX318qF3p0r5rkQw-BlkOTZTOUI1KdtJ6jp.VTeyDIuhrxct5l-R
Abstract:
“Nothing is perfect.” This law applies both to people and to materials. In practice, a material with a perfectly regular arrangement of atoms does not exist, and the defects in materials are inevitable. Although the word defect usually carries a negative connotation, the defects in diamond or two-dimensional (2D) materials will offer a new properties and performance in quantum emitter and battery applications. In my talk, I will present two research directions: (I) improvement of silicon-vacancy (SiV) centers in diamond via sub-µs pulsed annealing treatment; and (II) Angstrom-pores interlayer towards the suppression of lithium dendrites growth and polysulfide shuttle for lithium-metal-sulfur batteries.
(I) Lattice defects that form optical impurity centers are ubiquitous in all kinds of crystalline materials, among which diamond-based color centers have emerged for a variety of applications in quantum communication, quantum photonics, and biological sciences. While diamond has been shown to host hundreds of impurity color centers, very few such color centers have been well-characterized. The most studied color centers in diamond are the nitrogen-vacancy (NV) and SiV defects which have drastically different optical properties. Compared with the well-known NV, SiV is the lack of fundamental understanding on the physical and chemical properties limits the implementation of this defect in real applications. However, the high-temperature annealing treatment that is required to create SiV centers in diamond also determines the brightness of its photoluminescence. This is the first time that a ultra-fast pulsed annealing treatment has been demonstrated to improve the efficiency of the creation of SiV centers in diamond, which can open up new frontiers for fundamental materials science and overcome material limits for quantum photonics or devices.
(II) Rechargeable lithium-ion batteries are the most practical and widely-employed power sources for portable electronics and electric vehicles. Lithium-ion batteries present many advantages over competing technology, including possessing higher energy density, lower rates of self-discharge, and less maintenance. Since sulfur was rich reserve, innocuousness, and low cost, the high-density energy storage of Li-metal-sulfur batteries have attracted considerable attention to be an ideal alternative to Li-ion batteries in the future. Over the last decade, Li-S batteries research made a lot of progress, but they are still faced with polysulfides (molecules of multiple sulfur atoms) migrating to the anode and lithium dendrite formation on the anode side of the battery. Therefore, 2D materials, which include hexagonal boron-nitride (hBN) and graphene, with atomic defects building an Angstrom-pores interlayer onto the electrodes and separators can be a straightforward method to selectively allow Li+ ions to pass while not only blocking polysulfides but also suppressing the Li-metal dendrite formation. I believe that this thin and lightweight Angstrom-pores interlayer, with extraordinary mechanical property, electronic insulator, chemical stability, and physical barrier for polysulfide migration/diffusion, will enable to be new interlayer for the next-generation Li-metal-sulfur batteries.