Plasmonic structures have a wide variety of sensing applications because of their high field localization effect that leads to high sensitivity at lower powers. Specifically, plasmonic nanohole arrays are attractive platforms for sensing because of their easy alignment and measurement. In terms of fabricating these sensors, usually an adhesion layer is needed to ensure firm contact between the plasmonic metal layer and the substrate. Most fabrication efforts rely on titanium or chromium based metallic adhesion layers. However, the presence of the adhesion layer may hinder the plasmonic resonance by broadening the resonance and reducing the plasmonic field enhancement. This leads to degradation of sensing capabilities. We investigate the effect of tantalum, chromium, and titanium adhesion layers on plasmonic sensors made of nanohole arrays. Using the bulk refractive index data for metallic adhesion layers, we show that tantalum has the potential to show less damping effect compared to commonly used chromium and titanium. However, it still causes significant damping because of its high absorption, which becomes even larger for tantalum thin film according to our ellipsometry measurement results. We also propose here to use MgO dielectric adhesion layers to avoid the damping effect. Our investigation on MgO adhesion layers shows strong adhesion properties without scarifying sensor performance. Moreover, we will present an alternate sensor geometry that is less prone to damping by the adhesion layer and that can enhance the plasmonic resonance even if there is a metallic adhesion layer.
Scintillating dyes in polymer blends is a common tool used in radiation detection and its modifiability is a desirable attribute for different applications. Through nanocomposite loading, nanocrystals are generally employed to enhance scintillation either through radiative or non-radiative energy transfer. In this work similar methods are pursued with focus in the UV region through UV emitting nanocluster such as ZnO and CdS. A wide range of UV emission nanocrystals are selected and combined with different polymer and dyes demonstrating both quenching and enhancement. Preliminary results show not only dependency of the wavelength but also the polymer medium indicating different energy transfer paths. Compared to samples without nanocrystal the light yield was increased throughout different combinations.
Plasmonic nanostructures are highly used for sensing purposes since they support plasmonic modes
which make them highly sensitive to the refractive index change of their surrounding medium.
Therefore, they can also be used to detect changes in optical properties of ultrathin layer films in a
multilayer plasmonic structure. Here, we investigate the changes in optical properties of ultrathin
films of macro structures consisting of STT-RAM layers. Among the highest sensitive plasmonic
structures, nanohole array has attracted many research interest because of its ease of fabrication,
small footprint, and simplified optical alignment. Hence it is more suitable for defect detection in
STT-RAM geometries. Moreover, the periodic nanohole pattern in the nanohole array structure
makes it possible to couple the light to the surface plasmon polariton (SPP) mode supported by the
structure. To assess the radiation damages and defects in STT-RAM cells we have designed a
multilayer nanohole array based on the layers used in STT-RAM structure, consisting 4nm-
Ta/1.5nm-CoFeB/2nm-MgO/1.5nm-CoFeB/4nm-Ta layers, all on a 300nm silver layer on top of a
PEC boundary. The nanoholes go through all the layers and become closed by the PEC boundary on
one side. The dimensions of the designed nanoholes are 313nm depth, 350nm diameter, and 700nm
period. Here, we consider the normal incidence of light and investigate zeroth-order reflection
coefficient to observe the resonance. Our simulation results show that a 10% change in refractive
index of the 2nm-thick MgO layer leads to about 122GHz shift in SPP resonance in reflection
pattern.
Plastic scintillators such as Polyvinyl Toluene (PVT) are used for radiation detection but due to their poor performance they are not widely implemented. In order to circumnavigate this, dopants are added to enhance scintillation by energy transfer otherwise lost through non-radiative processes. In this work, we exploit the effects of energy transfer through the use of short wavelength emission Cadmium Sulfide Quantum Dots (QD) as the transfer stimulant. Scintillation enhancement was observed as Cadmium Sulfide QD with scintillating dyes are embedded in PVT polymer matrix for beta and gamma radiation. Energy transfer was observed between Quantum Dots, scintillating dye, and the host polymer. Different concentrations of QD and 2,5-diphenyloxazole (PPO) dye are investigated to characterize the energy transfer.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.