Templating effect of single-layer graphene supported by an insulating substrate on the molecular orientation of lead phthalocyanine

• Published in: Beilstein journal of nanotechnology Vol. 11; no. 1; pp. 814 - 820
• Main Authors: Madhuri, K Priya, Sagade, Abhay A, Santra, Pralay K, John, Neena S
• Format: Journal Article
• Language: English
• Published: Frankfurt am Main Beilstein-Institut zur Föerderung der Chemischen Wissenschaften 19-05-2020; Beilstein-Institut
• Subjects: Atomic force microscopy; Charge transfer; Chemical vapor deposition; conducting atomic force microscopy (c-afm); Crystallites; Electrical properties; Full Research Paper; Graphene; Lead phthalocyanine; lead phthalocyanine (pbpc); molecular orientation; Nanoscience; Nanotechnology; Polymers; Resistance; Silicon dioxide; single-layer graphene; Spectrum analysis; substrate effect; Substrates; two-dimensional grazing incidence x-ray diffraction (2d-gixrd); Van der Waals forces
• ISSN: 2190-4286; 2190-4286
• DOI: 10.3762/bjnano.11.66

The influence of single-layer graphene on top of a SiO
2
/Si surface on the orientation of nonplanar lead phthalocyanine (PbPc) molecules is studied using two-dimensional grazing incidence X-ray diffraction. The studies indicate the formation of a mixture of polymorphs, i.e., monoclinic and triclinic forms of PbPc with face-on (lying down) and edge-on (standing up) PbPc orientations, respectively. The formation of monoclinic fractions is attributed to the presence of the graphene layer directing the π interactions between the highly delocalized macrocycles. The competing interfacial van der Waals forces and molecule–molecule interactions lead to the formation of a small fraction of triclinic moieties. The nanoscale electrical characterization of the thin PbPc layer on graphene by means of conducting atomic force microscopy shows enhanced vertical conductance with interconnected conducting domains consisting of ordered monoclinic crystallites through which the charge transfer occurs via tunneling. These results show the importance of a templating layer to induce the formation of a required phase of PbPc suitable for specific device applications.