DC to GHz measurements of a near-ideal 2D material: P+ monolayers

P+ monolayers in Si are of great scientific and technological interest, both intrinsically as a material in the “ideal vacuum” of crystalline Si and because they are showing great promise as qubits of electron and nuclear spin. The GHz complex conductivity σ(ω) can allow one to elucidate basic physical properties and is also important for fast devices, but measuring σ(ω) in 2D materials has not been easy. We report on such measurements, including showing (i) qualitatively a lack of any resonances up to 5 GHz (indicating no energy splittings below about 0.02 meV); and (ii) the quantitatively ideal Drude behavior of this novel material up to 5 GHz, showing a lower bound on the scattering rate of about 2 × 1010 s−1. We also discuss deconvolving the confounding effect of the distributed resistance and capacitance of the monolayer.