Probing surface plasmons in individual Ag nanoparticles in the ultra-violet spectral regime.
Previous investigations of surface plasmons in Ag largely focused on their excitations in the visible spectral regime. Using scanning transmission electron microscopy with an electron beam of 0.2 nm in conjunction with electron energy-loss spectroscopy, we spectrally and spatially probe the surface plasmons in individual Ag nanoparticles (approximately 30 nm), grown on Si, in the ultra-violet spectral regime. The nanomaterials show respective sharp and broad surface-plasmon resonances at approximately 3.5 eV (approximately 355 nm) and approximately 7.0 eV (approximately 177 nm), and the correlated spectral calculations established their multipolar characteristics. The near-field distributions of the surface plasmons on the nanoparticles were also mapped out, revealing the predominant dipolar nature of the 3.5 eV excitation with obvious near-field enhancements at one end of the nano-object. The unveiled near-field enhancements have potential applications in plasmonics and molecular sensing.
Chu
Ming-Wen
MW
Center for Condensed Matter Sciences, National Taiwan University, Taipei 106, Taiwan. chumingwen@ntu.edu.tw
Sharma
Pradeep
P
Chang
Ching-Pin
CP
Liou
Sz Chian
SC
Tsai
Kun-Tong
KT
Wang
Juen-Kai
JK
Wang
Yuh-Lin
YL
Chen
Cheng Hsuan
CH