Magnetic penetration depth of Aluminum thin films

We present a study of the superconducting penetration depth $\lambda$ 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 $\lambda =163.3\pm 0.4\mathrm{n}\mathrm{m}$ for the thinnest $20\mathrm{n}\mathrm{m}$ samples down to $\lambda =53.6\pm 0.4\mathrm{n}\mathrm{m}$ for the $200\mathrm{n}\mathrm{m}$-thick ones. In order to accurately determine $\lambda$, 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 $\lambda$ in aluminum in the relevant range for applications in fields such as quantum computing and microwave radiation detector technologies.