TY - JOUR AU - Memarzadeh, Sarvenaz AU - Palm, Kevin J. AU - Murphy, Thomas E. AU - Leite, Marina S. AU - Munday, Jeremy N. TI - Control of hot-carrier relaxation time in Au-Ag thin films through alloying JO - Optics Express J2 - Opt. Express VL - 28 IS - 22 SP - 33528 PY - 2020 DO - 10.1364/OE.406093 AB - 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. UR - http://www.opticsexpress.org/abstract.cfm?URI=oe-28-22-33528 KW - Optical measurement Photodetectors Surface plasmon resonance Surface plasmons Thin films Visible light LB - Memarzadeh_OE_28_33528_2020 ER -