Efficient Gate-tunable light-emitting device made of defective boron nitride nanotubes: from ultraviolet to the visible

Scientific Reports 3, 2698 (2013)

Efficient Gate-tunable light-emitting device made of defective boron nitride nanotubes: from ultraviolet to the visible

Claudio Attaccalite, Ludger Wirtz, Andrea Marini, Angel Rubio

Boron nitride is a promising material for nanotechnology applications due to its two-dimensional graphene-like insulating and highly-resistant structure. It has been widely studied in the past but it has recently received a lot of attention as a substrate to grow and isolate graphene as well as for its intrinsic UV lasing response. Similar to carbon, one-dimensional boron nitride nanotubes (BNNTs) have been theoretically predicted and later synthesised with diameters of few nanometers. They have been shown to possess a large band gap regardless of chirality, diameter, multi-wall or single-wall structure and dimensionality. Their optical spectra is dominated by a single Frenkel-like exciton that concentrates most of the oscillator strength and responsible for the efficient lasing response. In this context, the application of an external electric field has been shown to continuously reduce of the band-gap as the field intensity increases. Here we use first principles simulations to unambiguously demonstrate that i) the nanotubes inherit the highly efficient UV luminescence of hexagonal BN; ii) the application of an external perpendicular field does indeed close the electronic gap keeping the UV lasing with lower yield; iii) the defects in BNNTS are responsible for tunable light emission from the UV to the visible controlled by an external transverse electric field. The highly efficient lasing response of hex-BN in the UV is not deteriorated and transported from the UV to the visible. The new mechanism for controlling the light-emission frequency identified here is mediated by defects that are either in the as-grown material or introduced after synthesis as a simple post-processing technique that does not require advanced synthetic schemes as the imperfect BN nanotubes perform best in light emission. Our present findings pave the road towards optoelectronic applications of BN-nanotube-based devices that are simple to implement and build because they do not require any special doping or complex growth on particular substrates. Our devices can also be applied to converting electron kinetic energy into light in a specific frequency range.

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