Mechanical properties of boron-nitride nanotubes after intense femtosecond-laser excitation

Abstract

A femtosecond-laser pulse constitutes an unconventional tool to manipulate solids and nanostructures, for it may excite materials in a transient nonthermal state with hot electrons and atoms close to their initial temperature. Here we study the Young's modulus and the electronic band gap of a (5, 0) zigzag boron-nitride nanotube (BNNT) after an ultrashort laser pulse excitation using density functional theory, where the effect of a femtosecond-laser pulse is modelled by an instantaneous rise of the electronic temperature. At room temperature, before the laser pulse, we obtain a Young's modulus of 763 GPa, which decreases with increasing electronic temperature. For the band gap we find a value of 2.26 eV at room temperature, which increases with increasing electronic temperature and equals 3.28 eV at 28 420 K. We note that conventional means decrease the band gap of BNNTs and that a femtosecond-laser pulse is, to the best of our knowledge, the first tool that increases it. For comparison, we also present results for a (9, 0) zigzag BNNT.

Charged Carbon Nanomaterials: Redox Chemistries of Fullerenes, Carbon Nanotubes, and Graphenes

“…Boron nitride (BN) nanomaterials are structurally analogous to the carbon nanomaterials forming graphene-like hexagonal lattices (h-BN) and nanotubes (BNNTs). In stark contrast to the carbon nanomaterials (and most TMDs), the band gaps of BN nanomaterials are large (5.2 eV for h-BN, 4 eV for BNNTs with diameters ≥1.2 nm), leading to electrically insulating materials less susceptible to direct doping. Intercalation of h-BN with potassium and lithium is possible; however, charge transfer from the metal to the BN is negligible.…”

Controlling Three Laser-Excited Coherent Phonon Modes in Boron Nitride Nanotubes To Produce Ultrashort Shaped Terahertz Pulses: Implications for Memory Devices

“…We calculated the ionic forces immediately following ultrashort laser excitation using the concept of a laser-excited potential energy surface, on which the atoms move . In the generalized Born–Oppenheimer approximation this surface is given by the electronic free energy, which we computed in the framework of electronic-temperature-dependent DFT using our in-house Code for Highly excIted Valence Electron Systems (CHIVES). , More details of our method are given in ref .…”

“…A further characteristic property of BNNTs is the appearance of buckling, which is directly related to the binary nature of these nanostructures . In a previous work, we have found that their static mechanical properties, particularly their Young moduli, are strongly affected by femtosecond laser excitations …”