Reduction of the Low-Energy Electron Reflectivity of Ag(100) upon Adsorption of Cobalt Phthalocyanine Molecules

Abstract

Using the retarding field diode method for detection of the work function changes, we explore the low-energy electron (0 to 3 eV) reflectivity of Ag(100) covered with a layer of CoPc molecules. The molecular layer significantly reduces the electron reflectivity from the sample surface. The maximum of the sample current, which is associated with minimum of electron reflectivity is observed for 1 ML of CoPc. The reflectivity is diminished from above 50% for the clean sample to almost 20% for the coverage of 1 ML. Additionally, we show that the large change in reflectivity greatly influences the determination of changes in work function (Δϕ) when the retarding field diode method is used without normalization to the saturation currents of each I–V diode curve.

Revealing the Presence of Mobile Molecules on the Surface

“…We observe the diffusive noise on the surface for coverages in the range of 0.4 to 0.8 ML. The coverage has to be smaller than 1 monolayer (ML) because the Pc molecules are known, from low electron energy diffraction (LEED) and STM investigations, to be arranged in ordered stable structures at 1 ML. , …”

“…This confirms that the creation of islands is related to a modification of the molecules underneath the tip, which, in turn, influences their mobility. Indeed, a sensitivity of the CoPc molecule to electron bombardment was shown by recording LEED patterns after various lengths of electron beam exposition in ref .…”

“…The coverage has to be smaller than 1 monolayer (ML) because the Pc molecules are known, from low electron energy diffraction (LEED) and STM investigations, to be arranged in ordered stable structures at 1 ML. 35,36 3.2. Phthalocyanines on Ag(100) -Effect of Voltage Pulses during the Presence of a Pc Gas.…”

Ordering of Zn-centered porphyrin and phthalocyanine on TiO2(011): STM studies

“…In general, they depend not only on the characteristics of the individual building blocks, but are also sensitive to the organic–inorganic interface and the molecule orientation [4–5]. In this context, metal containing phthalocyanines and porphyrins are very often used for microscopic studies with the aim to understand molecule–molecule and molecule–substrate interactions [6–8]. The strength and physicochemical character of such interactions determine the system geometrical structure and electronic properties; hence, detailed knowledge is necessary for optimization of the optoelectronic device functionality.…”

Attenuation of Photoelectron Emission by a Single Organic Layer

“…Therefore, the minimum of ΔW obtained from the Anderson method should also correspond to a coverage of 0.8 ML. Note that in the previous work of Sabik et al, 11,12 the minimum of ΔW was assigned to a full monolayer (1 ML) of CoPc, whereas with the revised definition, we find that 1 ML corresponds to the minimum of the low-energy electron reflectivity, R(Θ) (see Figure S1 in the Supporting Information).…”