Plasmon-Enhanced Electron Harvesting in Robust Titanium Nitride Nanostructures

Abstract

Titanium nitride (TiN) continues to prove itself as an inexpensive, robust, and efficient alternative to gold in plasmonic applications. Notably, TiN has improved hot electron harvesting and photocatalytic abilities compared to gold systems, which we recently attributed to the role of oxygen in TiN and its native semiconducting TiO2-x surface layer. Here, we explore the role of localized surface plasmon resonances (LSPRs) on electron harvesting across the TiN/TiO2-x interface and probe the resilience of TiN nanoparticles under high-power laser illumination. To investigate this, we fabricate titanium nitride strips where the lateral confinement allows for polarization-selective excitation of the LSPR. Using ultrafast pumpprobe spectroscopy, optical characterization and Raman vibrational spectroscopy we relate differences and changes observed in the electron behaviour to specific material properties. We observe plasmon-enhanced electron harvesting beyond what is expected resulting from the enhanced absorption of the plasmonic mode. We accredit this to the surface oxide damping the plasmon resonance providing additional nonradiative loss channels. Subsequently, we show that low-power annealing of the surface oxide layer reduces the trap density at the interface and increases the initial harvested electron concentration. The unique properties of TiN make it important in the future development of plasmonic electron harvesting applications.

Broadband Ultrafast Dynamics of Refractory Metals: TiN and ZrN

“…[ 1–9 ] Titanium nitride (TiN), zirconium nitride (ZrN), and other plasmonic nitrides such as hafnium nitride (HfN) and tantalum nitride (TaN) are particularly attractive due to their high melting points that bolster stability at higher ambient temperatures [ 10–12 ] and/or under higher laser irradiation intensities, [ 13–16 ] in addition to their mechanical hardness [ 17,18 ] and complementary metal‐oxide‐semiconductor compatibility. [ 19–21 ] Recent work has demonstrated that TiN shows strong local heating compared to Au, [ 22–24 ] which may be exploited for photothermal therapy, [ 25,26 ] shape‐memory effects, [ 27 ] thermochromic windows, [ 28 ] photoreactions, [ 29–32 ] heat transducers or thermophotovoltaic materials, [ 22,33–37 ] or photodetection. [ 38 ] Implicit in these observations and devices are very different optical responses of metallic nitrides compared to gold—the most similar classical plasmonic material—particularly with regard to the dissipation of heat.…”

Hot carrier optoelectronics with titanium nitride

“…In this work, we compare the electron extraction efficiency across Au/TiO2 and titanium oxynitride/TiO2-x interfaces, where in the latter case the spontaneously forming oxide layer (TiO2-x) creates a metal-semiconductor contact. Time-resolved pump-probe spectroscopy is used to study the electron recombination rates in both cases [12,13]. Unlike the nanosecond recombination lifetimes in Au/TiO2, we find a bottleneck in the electron relaxation in the TiON system, which we explain using a trap-mediated recombination model.…”

Titanium Nitride-Supported Platinum with Metal–Support Interaction for Boosting Photocatalytic H2 Evolution of Indium Sulfide

“…53 After loading of Pt nanoparticles, all TiN peaks exhibit blue shift indicating that the nitride lattice is marginally perturbed due to the bonding with surface Pt atoms. [54][55] Besides, two new characteristic peaks at 174 and 721 cm -1 , which belong to Pt-Pt stretching vibrations and Pt-O vibrations in Pt nanoparticles. [56][57][58] and Pt 4f 5/2 , respectively.…”