In situ spectroscopic ellipsometry to monitor surface plasmon resonant group-III metals deposited by molecular beam epitaxy
Real-time spectra of Ga deposited on GaN collected every second for (a) , (b) , and (c) of the total deposition time. Note the redshifting, narrowing plasmon resonance, and the emergence of a second, high-energy mode for (c).
Comparison of equivalent thicknesses of 96 and 325 ML of Ga on GaN. The final spectra (a) reveal that the longitudinal mode of the 325 ML deposition is redshifted with respect to the 96 ML. A transverse mode is observed for the 325 ML sample. AFM images (b) and (c) reveal the redshifted plasmon modes correlate to increased average particle size of the equivalently thicker deposition. Histograms show single mode distribution of particle heights.
Oxidation of Ga particles redshifts the transverse mode while the longitudinal mode is relatively unaffected.
Final spectra of 276 and 187 ML equivalent thicknesses of In deposited on GaN (a). AFM images confirm that the larger average particle size (b) and (c) results in the redshifting of the resonance.
Kinetic spectra of Al deposited on GaN reveal a resonance feature which redshifts and narrows with increasing deposition time and gradually approaches Drude-like behavior (a). Tilted SEM image (b) measured at 45° reveals that the surface is a nearly fully coalesced thin Al film.
Reported values for the bulk plasma frequency and the 2D thin film surface plasmon resonance of Al, Ga, and In (Refs. 1, 2, 7, 14, and 26).
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