Investigation of the spin-dependent properties of electron doped cobalt–CuPc interfaces

We have grown metal–organic interfaces by in-situ deposition of ultrathin copper phthalocyanine (CuPc) films on a thin cobalt film on Cu(0 0 1). Evidence for layer-by-layer growth is found. The spin-dependent electronic properties of the Co–CuPc interface and their modification under caesium doping are investigated by spin-resolved photoemission spectroscopy. We observe a doping-induced shift of the highest occupied molecular orbital (HOMO) of CuPc away from the Fermi level (EF), accompanied by the formation of an unpolarised gap-state at 0.7 eV below EF in the high doping regime. Such features are reflected in the behaviour of the detected interfacial spin-polarisation.