Tip influence on plasmon excitations in single gold particles in an STM

Abstract

Photon-emission spectra have been measured for individual titania-supported gold particles excited by the electron current from an STM tip. Depending on the interaction strength between tip and cluster, the emission behavior changes from excitations with Mie-plasmon character at 2.3 eV to modes of tip-induced plasmons at 1.8 eV. The strong tip influence on plasmon excitations in Au particles results from the almost constant dielectric function of gold between 1.8 and 2.3 eV, making the plasmon resonance sensitive to small changes in the electromagnetic environment. The lifetime of collective modes, derived from homogeneous linewidths, is governed by dielectric losses in gold, in particular, by gold interband transitions.

Engineering the emission of light from a scanning tunneling microscope using the plasmonic modes of a nanoparticle

“…Due to nanometer size of the junction, we use a classical picture where the inelastic tunneling current is represented as a point electric dipole p placed in the junction and radiating at the transition frequency ω. The dipole amplitude is given by the transition matrix elements [13,[15][16][17][18]20,[22][23][24][25]46] or, according to recent theory, by the corresponding spectral components of the quantum noise [47]. This dipole p is located above the NP surface at position r d which is typically set at the middle of the junction, and is oriented along the direction of the tunneling current, i.e., parallel to the tip axis (z axis) when the tip is on the horizontal upper NP face.…”

“…Moreover, the plasmonic response of optical nanoantennas coupled to a tunnel junction has been recently used to control the emitted light [5,6]. This IET effect has been widely studied, especially since the invention of the scanning tunneling microscope (STM) [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] (see also Ref. [26] and references therein).…”

“…However, using metallic nanostructures with tunneling gaps as nanosources of light has been hampered by a lack of control of the emission properties. In most experiments, the emitted light is completely dominated by the resonance of the gap plasmon mode induced by the strong tip-sample interaction when both the tip and the sample are made of plasmonic materials such as gold or silver [22,25,27]. The * eric.le-moal@u-psud.fr † andrei.borissov@u-psud.fr extreme spatial confinement of the gap plasmon inside the junction makes it exceedingly sensitive to very slight yet unavoidable and unpredictable changes in the morphology of the tip apex [28,29].…”

High-resolution scanning force microscopy of gold nanoclusters on the KBr (001) surface

“…15 The most recent results suggest that primarily the low-coordinated atoms are bonding sites for CO and O 2 , 9,[16][17][18][19] and that the interaction with the substrate 14,20 or charge transfer could also play a role in the catalysis by gold clusters. 12,13 Scanning probe microscopy offers an excellent possibility for in situ studies of the properties of nanoclusters, and scanning tunneling microscopy ͑STM͒ has been applied to several model systems, [21][22][23][24][25][26] but the requirement of a conducting sample has restricted the STM's access to the important class of insulating surfaces. In principle dynamic scanning force microscopy ͑dynamic SFM͒ [27][28][29] offers the capability of imaging both the adsorbed metal clusters and the insulating surface in atomic resolution, hence providing unprecedented information about the cluster structural properties.…”

Properties of oxide thin films and their adsorption behavior studied by scanning tunneling microscopy and conductance spectroscopy

“…2.12 for single Au particles on a TiO 2 bulk support. 135,136 The injection of tip electrons with 5 eV energy into the particle centre produces a characteristic emission peak at 550 nm that can be assigned to a Mie-plasmon excitation in the hemispherical Au particle. The emission intensity starts to decline when the tip is moved towards the particle edge and completely vanishes for electron injection into the oxide support.…”