In situstudies of morphology, strain, and growth modes of a molecular organic thin film

Abstract

We use grazing incidence x-ray scattering to study the molecular structure and morphology of thin ͑Ͻ70 ML͒ crystalline films of 3,4,9,10-perylenetetracarboxylic dianhydride ͑PTCDA͒ on Au͑111͒ surfaces as a function of film thickness, substrate temperature, and growth rate. Although the first two PTCDA monolayers grow in a layer-by-layer fashion, the film evolution beyond the second monolayer depends strongly upon the growth conditions resulting in low-temperature ͓i.e., nonequilibrium ͑NEQ͔͒ and high-temperature ͓equilibrium ͑EQ͔͒ growth regimes. In the NEQ regime, the films roughen monotonically with increasing film thickness, but retain a well-defined film thickness. Furthermore, we find that these films have a lattice strain which is independent of film thickness. In the EQ regime, the film acquires a three-dimensional morphology for thicknesses Ͼ2 ML, and the lattice strain decreases rapidly with increasing thickness. We also show that the transition between the NEQ and EQ regimes is sharp and depends upon the balance between the growth rate and substrate temperature. These results suggest that the PTCDA/Au͑111͒ system is thermodynamically described by incomplete wetting, and that strain and kinetics play an important role in determining molecular organic film characteristics.

Exciton emission in PTCDA films andPTCDA∕Alq3multilayers

“…Compared to the PL obtained from single PTCDA crystals, 21,22 the PTCDA film shows a very similar PL structure; however, the whole emission is shifted to lower energies by approximately 20 meV. A possible explanation for this redshift might be different strain within the film 40 and in the single crystals. Furthermore, the PTCDA film reveals a more pronounced highenergy band at 1.95 eV compared to the PTCDA crystals.…”

Theoretical study of PTCDA adsorbed on the coinage metal surfaces, Ag(111), Au(111) and Cu(111)

“…For the Au(111) surface, it has been found that the molecule does not form monolayers commensurate with the substrate but rather exhibits a point-on-line growth on the (22 × √ 3) reconstructed surface [27]- [30]. Inclusion of these effects in the present calculations is hampered by the excessive computational effort arising from the required huge supercells.…”

Exploring the bonding of large hydrocarbons on noble metals: Diindoperylene on Cu(111), Ag(111), and Au(111)

“…[12][13][14] With respect to its chemical structure, DIP is a relatively simple, planar hydrocarbon without heteroatoms. In contrast to the intensely studied perylene derivative [15][16][17][18][19][20] 3,4,9,10-perylene tetracarboxylic dianhydrid (PTCDA, C 32 H 8 O 6 ) with its four keto groups, the DIP-substrate interaction is not complicated by polar side groups, and the influence of intermolecular interactions is expected to be smaller than for PTCDA. 21 Here, we present a systematic study with high-precision experimental data and state-of-the-art calculations of DIP adsorbed on Cu(111), Ag(111), and Au(111).…”