Order on disorder: Copper phthalocyanine thin films on technical substrates

Abstract

We have studied the molecular orientation of the commonly used organic semiconductor copper phthalocyanine (CuPC) grown as thin films on the technically relevant substrates indium tin oxide, oxidized Si, and polycrystalline gold using polarization-dependent x-ray absorption spectroscopy, and compare the results with those obtained from single crystalline substrates [Au(110) and GeS(001)]. Surprisingly, the 20–50 nm thick CuPC films on the technical substrates are as highly ordered as on the single crystals. Importantly, however, the molecular orientation in the two cases is radically different: the CuPC molecules stand on the technical substrates and lie on the single crystalline substrates. The reasons for this and its consequences for our understanding of the behavior of CuPC films in devices are discussed.

Different approaches to adjusting band offsets at intermolecular interfaces

“…Therefore, molecules lying well out of the plane of the surface are expected to have molecular orbitals with strong Cu and N weight suppressed in a highly surface sensitive spectroscopy like inverse photoemission while molecular orbitals with stronger ligand weight would not be so strongly suppressed, as observed in Figure 4. This is consistent with the fact that CuPc tends to lie flat on metal substrates and stand on oxide surfaces [43]. Regrettably, photoemission features alone are not an effective means of determining orientation and crystal packing of CuPc, although this has been attempted [24], so further measurements such as light incident angle dependent near edge X-ray absorption fine structure measurements are indicated, but as yet, have not been carried out.…”

Ammonia adsorption on iron phthalocyanine on Au(111): Influence on adsorbate–substrate coupling and molecular spin

“…On solid supports, phthalocyanines and phthalocyanine derivatives form ordered monolayer structures. [2][3][4][5][6][7] Such monolayers are promising candidates for novel catalytic [8][9][10][11][12] and gas sensing applications. [13][14][15][16][17][18][19][20][21][22][23][24][25][26] Their function will depend critically on the molecular electronic structure, which for phthalocyanines containing certain transition metals (such as Cr, Mn, Fe, Co) is quite complex with an open shell structure of the d orbitals and a number of energetically close-lying electronic states.…”

Molecular Orientation and Ordering during Initial Growth of Copper Phthalocyanine on Si(111)

“…Thick ordered phthalocyanine films have been grown on various substrates [14][15][16][17] and the adsorption behaviors of CuPc molecules on Si(111) and Si(100) 18,19 have been previously studied by scanning tunneling microscopy (STM). In this study, we report the in situ nucleation of CuPc on Si(111)-(7x7) by angular-dependent XAS, with particular attention to the evolution of molecular orientation and order in the first few layers.…”

“…The interactions, especially molecule-substrate interaction, play an important role in the initial growth of the CuPc film 14 . To understand the phase transitions in the 8 CuPc/Si(111) system, we studied the interactions at a CuPc coverage of one monolayer by core level photoemission spectroscopy, which is a surface sensitive tool for determining the interactions between molecule and surface 23 .…”