(a) Schematic diagram of Si junction photodiode device structure, colloidal Au nanoparticles deposited from solution, and geometry employed for photocurrent response measurements. (b) Scanning electron micrograph of Au nanoparticles deposited on photodiode surface.
Schematic diagram of simulation geometry employed. The volume simulated explicitly consisted of the box shown in the figure, with the boundary conditions specified leading the simulations to correspond to an infinite square array of spheres atop a Si substrate.
(a) Measured photocurrent response spectrum of a Si junction photodiode, , without Au nanoparticles. (b) Ratio of the photocurrent response of a Si junction photodiode upon which Au nanoparticles have been deposited, , to that of the same device prior to nanoparticle deposition, .
Grey-scale images of electric field magnitude , obtained from finite-element numerical simulations, for an electromagnetic plane wave with wavelength 550 nm incident on (a) a Si semiconductor substrate and (b) a Si semiconductor substrate with a 100 nm diameter Au nanoparticle positioned 2 nm above the Si surface.
(Color online) Simulated electric field amplitude squared, , integrated over the semiconductor volume for electromagnetic plane waves incident on Si with Au nanoparticles 50, 80, and 100 nm in diameter placed atop the Si surface. All integrated quantities are normalized to the integral of for a Si substrate in the absence of any Au nanoparticles, .
Simulated component of the electric field, , in the Si semiconductor region of a structure consisting of a 100 nm diameter Au nanoparticle atop the Si region, separated into components corresponding to transmission across the air-Si interface (lower right quadrants), and scattering from the Au nanoparticle (lower left quadrants), for incident electromagnetic radiation at wavelengths of (a) 500 and (b) 575 nm.
Magnitude and phase of the polarizability of a spherical Au particle, normalized to the particle volume , as functions of wavelength.
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