In summary, we have synthesized a series of bistable hydrazone switches containing alkyl thiolate linkers (Cn HAT, n = 3, 8, 10, and 11) of various lengths, ranging from around 1 to 2 nm. The length effect of carbon chain linker on the photoisomerization of the hydrazone switches was systematically investigated in solution, in the solid state, and as a monolayer assembled on metal surfaces, using UV-vis spectroscopy, confocal Raman spectroscopy, and TERS. In solution, the conversion efficiency of Cn HATs upon irradiation at 415 nm or 340 nm was found to be independent of carbon chain length. We also monitored the conversion efficiency of Cn HAT SAMs on Au and Ag using UV-vis spectroscopy and TERS. Interestingly, we found that the Z-to-E conversion efficiency of Cn HAT SAMs on Au at PSS 415 increases as a function of the alkyl chain length and saturates after the carbon number of the alkyl chain reaches 8. A similar trend was found for the back isomerization. These results reflect the synergy between the metal surfaceinduced quenching and the previously proposed substrate-mediated photoisomerization mechanism. When the length of the carbon chain increases, quenching by the surface strongly decreases, as confirmed by DFT calculations. On the other hand, the proposed photoisomerization mechanism would stop working at a certain distance, since the electron transfer rate decays exponentially with donor-acceptor distance. Subsequently, direct light isomerization starts playing a larger role. Cn HAT SAMs, similar to C6 HAT, were found not to isomerize on Ag surfaces upon irradiation at 415 nm, but can isomerize upon irradiation at 280 nm, except for C3 HAT. Overall, these results confirm the previously proposed isomerization mechanism. Our study suggests that the isomerization of HAT monolayers assembled on metal surfaces is not only affected by the linker length, but also by the substrates. To increase the isomerization efficiency of photoswitches on surfaces, a rational design of their chemical structure and an appropriate choice of the substrate are of great importance. This understanding contributes to developing effective photocontrollable surfaces using molecular switches.