The Lightest 2D Nanomaterial: Freestanding Ultrathin Li Nanosheets by in-situ Electron Microscopy

TL;DR

This study demonstrates the controlled growth of ultrathin 2D lithium nanosheets using in-situ TEM, revealing their growth mechanism, plasmonic properties, and potential for lightweight nanomaterials.

Contribution

First demonstration of 2D ultrathin lithium nanosheets growth via in-situ TEM, with insights into their formation mechanism and optical properties.

Findings

Li nanosheets have large lateral size and nanometer thickness

Growth is kinetically controlled by surface oxidation in trace oxygen

Li nanosheets exhibit broadband plasmonic emission

Abstract

Lithium (Li) is the simplest metal and the lightest solid element. Here we report the first demonstration of controlled growth of two-dimensional (2D) ultrathin Li nanosheets with large lateral dimensions up to several hundreds of nanometres and thickness limited to just a few nanometres by in-situ transmission electron microscopy (TEM). The nanoscale dynamics of nanosheets growth were unravelled by real-time TEM imaging, which, in combination with density function theory (DFT) calculations indicates that the growth of bcc structured Li into 2D nanosheets is a consequence of kinetic control as mediated by preferential oxidization of the (111) surfaces due to the trace amount of O2 (~10-6 Pa) within TEM chamber. The plasmonic optical properties of the as-grown Li nanosheets were probed by cathodoluminescence (CL) spectroscopy equipped within TEM, and a broadband visible emission was observed that contains contributions of both in-plane and out-of-plane plasmon resonance modes.