Published/Posted: October 26, 2020

Authors: Memarzadeh, S.; Palm, K. J.; Murphy, T. E.; M. S. Leite; Munday, J. N.

DOI: 10.1364/OE.406093

Abstract: The plasmon resonance of a structure is primarily dictated by its optical properties and geometry, which can be modified to enable hot-carrier photodetectors with superior performance. Recently, metal alloys have played a prominent role in tuning the resonance of plasmonic structures through chemical composition engineering. However, it has been unclear how alloying modifies the time dynamics of the generated hot-carriers. In this work, we elucidate the role of chemical composition on the relaxation time of hot-carriers for the archetypal Au(x)Ag(1-x) thin film system. Through time-resolved optical spectroscopy measurements in the visible wavelength range, we measure composition-dependent relaxation times that vary up to 8x for constant pump fluency. Surprisingly, we find that the addition of 2% of Ag into Au films can increase the hot-carrier lifetime by approximately 35% under fixed fluence, as a result of a decrease in optical loss. Further, the relaxation time is found to be inversely proportional to the imaginary part of the permittivity. Our results indicate that alloying is a promising approach to effectively control hot-carrier relaxation time in metals.

S. Memarzadeh, K. J. Palm, T. E. Murphy, M. S. Leite and J. N. Munday, "Control of hot-carrier relaxation time in Au-Ag thin films through alloying", Opt. Express 28(22) 33528-33537 (2020)
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Manuscript: Memarzadeh_OE_28_33528_2020.pdf

Control of hot-carrier relaxation time in Au-Ag thin films through alloying