Adsorption of Metal Phthalocyanines on Ag(100)

Abstract

Since its invention STM has been widely used to study molecules on surfaces. It proved an ideal tool for this purpose, giving access to both the real space adsorption geometry and electronic structure of molecular adsorbates. CuPc on polycrystalline Silver were among the first molecules studied as early as 1987 [1–3]. Today many more MePc molecules on different metal surfaces have been investigated (Me = Cu [1, 3–6], Co [6–8], Fe [9–16], Ni [12], Pd [17], Zn [18], Mn [19, 20], Sn [21]). In general, single MePc molecules adsorb flat on the surface, and their four isoindole groups (see Fig. 4.1) are imaged as a four lobed cross shape in STM topography. Depending on the character of the filled d states of the metal ion, the center appears either as a dip or as a protrusion [6, 12]. The interplay between molecule-substrate and molecule–molecule interactions leads to the self assembly of MePc into highly ordered clusters or layers. The substrate symmetry in relation to the four fold symmetry of the molecules can lead to ordered molecular domains [9]. Multilayer films show a growth structure with the molecular plane parallel [22] or tilted with respect to the surface plane [9, 10]. Many growth studies on noble metal (111) surfaces have been undertaken on Ag(111): CuPc monolayers [23], FePc up to multilayer [10], FePc sub-monolayer [24, 25], single SnPc to multilayer [21]; on Au(111): MnPc and FePc sub-monolayer [19], CoPc multilayers [26], SnPc multilayers [27], single FePc to monolayer [16] and on Cu(111) single CoPc [8, 28] and up to monolayer structures [29]. For the (100) surface studies are more scarce, to our best knowledge only CoPc [30] and NiPc/CuPc monolayers [31] on Cu(100) have been investigated.