Matthias Treier

Porous graphenes: two-dimensional polymer synthesis with atomic precision.

We demonstrate, by surface-assisted coupling of specifically designed molecular building blocks, the fabrication of regular two-dimensional polyphenylene networks with single-atom wide pores and sub-nanometer periodicity.

Surface-assisted cyclodehydrogenation provides a synthetic route towards easily processable and chemically tailored nanographenes

Atomically thin sheets of sp(2)-hybridized carbon--graphene--have enormous potential for applications in future electronic devices. Particularly promising are nanostructured (sub)units of graphene, the electronic properties of which can be tuned by changing the spatial extent or the specific edge termination of the carbon network. Processability and precise tailoring of graphene-derived structures are, however, still major obstacles in developing applications; both bottom-up and top-down routes are presently under investigation in attempts to overcome this limitation. Here, we propose a surface chemical route that allows for the atomically precise fabrication of tailored nanographenes from polyphenylene precursors. The cyclodehydrogenation of a prototypical polyphenylene on Cu(111) is studied using scanning tunnelling microscopy and density functional theory. We find that the thermally induced cyclodehydrogenation proceeds via several intermediate steps, two of which can be stabilized on the surface, yielding unprecedented insight into a dehydrogenative intramolecular aryl-aryl coupling reaction.

Fabrication of surface-supported low-dimensional polyimide networks.

Interest in thermal and chemical stability of surface-supported organic networks has stimulated recent attempts to covalently interlink adsorbed molecular species into extended nanostructures. We show, using low-temperature scanning tunneling microscopy, that imidization of anhydrides and amines adsorbed on Au(111) can be thermally initiated under controlled ultrahigh vacuum conditions. Using two types of amine-functionalized polyphenyl molecules together with the organic semiconductor PTCDA, monolayer thick linear polymeric strands and a porous polymeric network with nanoscale dimensions are obtained.

Tuning the Photoresponse in Organic Field-Effect Transistors

We report on the fabrication of solution-processed organic phototransistors (OPTs) based on perylenebis(dicarboximide)s (PDIs). We found that the responsivity to the photoillumination depends on the transistors channel length and that it can be tuned by varying the device geometry. The analysis of different morphologies of the active semiconducting layer revealed that single PDI fibers exhibit the higher photoresponse when compared to more poorly organized films. The highest responsivity value of 4.08 ± 1.65 × 10(5) A/W was achieved on a multifiber-based OPT. These findings represent a step forward toward the use of organic based phototransistors as photosensors.

Tailoring Low-Dimensional Organic Semiconductor Nanostructures

The quest for miniaturization of organic nanostructures is fueled by their possible applications in future nanoscale electronic devices. Here we show how a range of nanostructures of reduced dimensionality of the organic semiconductor PTCDA can be realized on Au(111) by intermixing the latter with hydrogen bonding spacer molecules. The purpose of the spacers is to separate nanounits of pure PTCDA, using hydrogen bonds between the anhydride end of PTCDA and amine groups of the spacers. A highly regular array of potential quantum dots can be realized by this approach.

Ambipolar organic field-effect transistors with balanced mobilities through solvent–vapour annealing induced phase-separation of bi-component mixtures

Thin films of bi-component mixtures of two commonly used n- and p-type organic semiconductors are found to undergo spontaneous phase-separation with the formation of well-ordered nanoneedles/crystals upon solvent–vapour annealing. The de-mixing is used to fabricate ambipolar organic field-effect transistors where balanced mobilities were achieved by adjusting the relative amount of the constituent in solution.

Solid-solid transfer of organic semiconductors for field-effect transistor fabrication

We present a simple yet potentially universally applicable method for the solid–solid transfer of organic materials under ambient conditions for the fabrication of organic field-effect transistors. Thermal annealing of sprinkled powders of organic semiconductors on gold patterned SiOx surfaces yielded functional transistors with some of the characteristics comparable to those of solution-processed devices.