Semiconductor-to-metal transition in the bulk of WSe₂ upon potassium intercalation

We present electron energy-loss spectroscopic measurements of potassium (K) intercalated tungsten diselenide (WSe₂). After exposure of pristine WSe₂ films to potassium, we observe a charge carrier plasmon excitation at about 0.97 eV, which indicates a semiconductor-to-metal transition. Our data reveal the formation of one particular doped K-WSe₂ phase. A Kramers–Kronig analysis allows the determination of the dielectric function and the estimation of the composition of K_0.6WSe₂. Momentum dependent measurements reveal a substantial plasmon dispersion to higher energies. (paper)