Single Nanoparticle-Based Heteronanojunction as a Plasmon Ruler for Measuring Dielectric Thin Films.
Nondestructive, noninvasive and accurate measurement of thin film thicknesses on dielectric substrates is challenging. In this work a ruler for measuring thin film thicknesses utilizes the heteronanojunction construct formed between a plasmonic nanoparticle and a high refractive index nonplasmonic substrate. The high near-field sensitivity in the nanojunction renders it suitable for measuring the thickness of intervening dielectric thin films. We demonstrate this by controlling the thickness of dielectric spacer layers created by overgrowing SiO2 thin films on commercially available silicon substrates. While Rayleigh (using dark-field) scattering measurements show that the spectral response is well correlated to the thickness of SiO2 spacer layers the distance-dependence is much steeper with surface-enhanced Raman scattering (SERS). Good agreement between 3D simulations and experimental results confirm the plasmon ruler construct's sensitivity to the dielectric thin film spacing. Thus, we postulate that this single nanoparticle based heteronanojunction configuration can serve as a convenient and simple ruler in metrology of thin films as well as a platform for SERS-based detection even in cases where plasmonically active films are not a suitable substrate.
†School of Chemistry and Molecular Engineering, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China.|‡Institute for Life Sciences and Department of Chemistry, Highfield Campus, University of Southampton, Southampton SO17 1BJ, U.K.
Li
L
Li
§Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, U.K.
Tanya
T
Hutter
∥Key Laboratory of Polar Materials and Devices, Ministry of Education, Department of Electronic Engineering, East China Normal University, 500 Dongchuan Road, Shanghai 200241, China.
Wenwu
W
Li
‡Institute for Life Sciences and Department of Chemistry, Highfield Campus, University of Southampton, Southampton SO17 1BJ, U.K.
Sumeet
S
Mahajan
D006046:Gold / Q000737:chemistry; D053768:Metal Nanoparticles / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D013059:Spectrum Analysis, Raman
D006046:Gold; D012822:Silicon Dioxide
Plasmon ruler; dark-field scattering; gold; silica; surface-enhanced Raman scattering