Photon Emission Spectroscopy of Individual Oxide-Supported Silver Clusters in a Scanning Tunneling Microscope

Abstract

Photon emission spectra of individual alumina-supported silver clusters have been measured for the first time. The light emission stimulated by electron injection from the tip of a scanning tunneling microscope can be assigned to the (1,0) mode of the Mie-plasmon resonance in small silver particles. As cluster sizes decrease, the resonance position shifts to higher energies and the linewidth increases. In the size range examined (1.5-12 nm), intrinsic size effects are discussed as possible origins for the observed size dependence of the Mie resonance.

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

“…23,55 Photon emission spectroscopy with the STM, where local optical modes are excited by electron/hole injection from the tip, offers the required spatial resolution. The potential of this technique has already been demonstrated with experiments performed on single molecules, 124,125 metal particles 119,134 and quantum dots, 121 while comparable studies on the oxide materials are still scarce. 51,82,119 Photon emission spectroscopy with the STM will however develop into a versatile tool to explore the local optical properties and their interrelation with the photo-catalytic performance of oxide materials.…”

“…The potential of this technique has already been demonstrated with experiments performed on single molecules, 124,125 metal particles 119,134 and quantum dots, 121 while comparable studies on the oxide materials are still scarce. 51,82,119 Photon emission spectroscopy with the STM will however develop into a versatile tool to explore the local optical properties and their interrelation with the photo-catalytic performance of oxide materials. In general, the exploitation of the spectroscopic capabilities of the STM to investigate oxide surfaces at the atomic level is only at the beginning and substantial progress in this direction can be expected in the near future.…”

“…Further experiments have been performed for Ag and Ag-Au alloy particles on alumina thin films, putting special emphasis on the interrelation between the plasmon-mediated emission behavior and the geometry and chemical composition of the individual particles. 119,137 For Ag clusters, for example, a blue-shift of the plasmon resonance was revealed with decreasing particle diameter, 119 reflecting the diminishing influence of the Ag d-electrons on the plasmon energy in aggregates with large surface-to-volume ratio. STM-induced light emission has also been observed for individual Zn-Etiol molecules deposited on alumina/NiAl(110), as shown in .2.13.…”

“…An increase in spatial resolution can however be achieved, when a narrow-gap oxide is used for optical studies that requires lower excitation energies for the excitons. In contrast to bare oxide surfaces, photon emission spectroscopy with the STM has been widely employed to investigate the optical response of single metal particles 119,134 and molecules on oxide supports. 124,125 In the case of metal particles, the emission mechanism is governed by the excitation of collective electronic modes in the particle electron gas (so called Mie plasmons) followed by their radiative decay.…”

Influence of size, shape and core–shell interface on surface plasmon resonance in Ag and Ag@MgO nanoparticle films deposited on Si/SiOx

“…Plasmon-enhanced performance can also be achieved in organic solar cells by incorporating Ag NPs on surface-modified transparent electrodes [8], and in LEDs by increasing their external quantum efficiency [6]. On the other hand, a number of studies on the optical properties of noble metal NPs on different surfaces have been performed [10,11], revealing the drastic dependence of the SPR oscillator strength and energy position on the NP size [12][13][14], geometrical shape [14][15][16], surface density [15][16][17] and the type of substrate [18]. In most of these works, NPs were realized by metal evaporation on a substrate, where islands were formed by the Vollmer-Weber growth mode [15,16].…”