Magnetic penetration depth of Aluminum thin films
We present a study of the superconducting penetration depth $λ$ in aluminum thin films of varying thickness. The range of thicknesses chosen spans from the thin-film regime to the regime approaching bulk behavior. The penetration depths observed range from $λ= 163.3\pm0.4~\rm{nm}$ for the thinnest $20~\rm{nm}$ samples down to $λ= 53.6\pm0.4~\rm{nm}$ for the $200~\rm{nm}$-thick ones. In order to accurately determine $λ$, we performed complementary measurements using the frequency of superconducting $LC$ resonators as well as the resistance of normal-state meanders. Both methods yield comparable results, providing a well-characterized set of values of $λ$ in aluminum in the relevant range for applications in fields such as quantum computing and microwave radiation detector technologies.