Organic diodes consisting of molecular nano-pyramid structures sandwiched between metal and strained nano-membrane electrodes are created. The robust and smooth contacts provided by self-curled metal layers render the molecular nano-pyramids efficent channels for detecting nitrogen dioxide airflow.

Iron phthalocyanine (FePc) is a molecular semiconductor whose building blocks are 1D ferromagnetic chains. It is shown that its optical and magnetic properties are controlled by the growth strategy, obtaining extremely high coercivities of over 1 T and modulating the exchange constant between 15 and 29 K through switching from thin films with controlled orientations, to ultralong nanowires. Magnetization measurements are analyzed using concepts and formulas with broad applicability to all 1D ferromagnetic chains. They show that FePc is best described by a xy model with moments preferentially lying in the molecular planes. The chain Hamiltonian is very similar to that for the classic inorganic magnet CsNiF 3 , but with ferromagnetic rather than antiferromagnetic interchain interactions. The dominant degrees of freedom are topological excitations called solitons, namely moving 1D magnetic domain walls, and at low temperatures and fields a "super-Curie-Weiss" law characteristic of nearly 1D xy and Heisenberg ferromagnets, where susceptibility scales as 1/(T 2 -θ 2 ), is observed. The ability to control the molecular orientation and ferromagnetism of FePc systems, and produce them on flexible substrates, together with excellent transistor characteristics reported previously for phthalocyanine analogues, makes them potentially useful for magneto-optical and spintronic devices.

† Electronic supplementary information (ESI) available: Maldi-ToF spectrum of [TbPc2] 0 (Fig. S1). UV/vis/nIR spectrum of [TbPc2] 0 (Fig. S2). MOKE spectrum of a blank Si substrate (Fig. S3). VASE spectra of one sample and the model fit (Fig. S4), and in-plane components (Fig. S5), as well as the out-of-plane components of the dielectric tensor (Fig. S6) of the TbPc2 films grown on SiO2/Si. Complex refractive index of TbPc2/PTCDA (Fig. S7). Complex refractive index of TbPc2/Co (Fig. S8). Ligand field parameters of TbPc2 powder and film (Table S1).In this work, we investigated the magneto-optical response of thin films of TbPc2 on substrates which are relevant for (spin) organic field effect transistors (SiO2) or vertical spin valves (Co) in order to explore the possibility of implementing TbPc2 in magneto-electronic devices, the functionality of which includes optical reading. The optical and magneto-optical properties of TbPc2 thin films prepared by organic molecular beam deposition (OMBD) on silicon substrates covered with native oxide were investigated by variable angle spectroscopic ellipsometry (VASE) and magneto-optical Kerr effect (MOKE) spectroscopy at room temperature. The magneto-optical activity of the TbPc2 films can be significantly enhanced by one to two orders of magnitude when changing the molecular orientation (from nearly standing molecules on SiO2/Si substrates to nearly lying molecules on perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) templated SiO2/Si substrates) or by using metallic ferromagnetic substrates (Co).

This work investigates the evolution of structure and morphology of pure and co-evaporated thin films, as a function of pentacene concentration in a solid host of p-terphenyl.

In the present work, the templating effect of thin layers of perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) on the growth of cobalt tetrakis(thiadiazole)porphyrazine (CoTTDPz) thin films was examined.X-ray diffraction and optical absorption spectra indicate that while CoTTDPz forms amorphous thin films on the bare substrates, it forms crystalline thin films on the PTCDA templates, in which the molecular planes of CoTTDPz are considered to be parallel to the substrates. Magnetic measurements reveal a significantly enhanced antiferromagnetic interaction of CoTTDPz in the templated thin films, with values reaching over 13 K. The ability to generate crystalline films and to control their orientation using molecular templates is an important strategy in the fields of organic electronics and spintronics in order to tailor the physical properties of organic thin films to suit their intended application.

SummaryThe optical and electrical properties of terbium(III) bis(phthalocyanine) (TbPc2) films on cobalt substrates were studied using variable angle spectroscopic ellipsometry (VASE) and current sensing atomic force microscopy (cs-AFM). Thin films of TbPc2 with a thickness between 18 nm and 87 nm were prepared by organic molecular beam deposition onto a cobalt layer grown by electron beam evaporation. The molecular orientation of the molecules on the metallic film was estimated from the analysis of the spectroscopic ellipsometry data. A detailed analysis of the AFM topography shows that the TbPc2 films consist of islands which increase in size with the thickness of the organic film. Furthermore, the cs-AFM technique allows local variations of the organic film topography to be correlated with electrical transport properties. Local current mapping as well as local I–V spectroscopy shows that despite the granular structure of the films, the electrical transport is uniform through the organic films on the microscale. The AFM-based electrical measurements allow the local charge carrier mobility of the TbPc2 thin films to be quantified with nanoscale resolution.

Metallocenes are a promising candidate for future spintronic devices due to their versatile and tunable magnetic properties. However, single metallocenes, e.g., ferrocene, sublimate below room temperature, and therefore the implementation for future applications is challenging. Here, a method to prepare biferrocene thin films using organic molecular beam deposition (OMBD) is presented, and the effect of substrate and deposition rate on the film structure and morphology as well as its chemical and magnetic properties is investigated. On Kapton and Si substrates, biferrocene interacts only weakly with the substrate, and distinct grains scattered over the surface are observed. By incorporating a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) seeding layer and depositing biferrocene at high deposition rates of 1.0 Å s–1, it is possible to achieve a well-ordered densely packed film. With spintronic applications in mind, the magnetic properties of the thin films are characterized using superconducting quantum interference device (SQUID) magnetometry. Whereas initial SQUID measurements show weak ferromagnetic behavior up to room temperature due to oxidized molecule fragments, measurements of biferrocene on PTCDA capped with LiF show the diamagnetic behavior expected of biferrocene. Through the successful deposition of biferrocene thin films and the ability to control the spin state, these results demonstrate a first step toward metallocene-based spintronics.

We report on a new approach for the fabrication of ferromagnetic molecular thin films. Co-evaporated films of manganese phthalocyanine (MnPc) and tetracyanoquinodimethane (TCNQ) have been produced by organic molecular beam deposition (OMBD) on rigid (glass, silicon) and flexible (Kapton) substrates kept at room temperature. The MnPc:TCNQ films are found to be entirely amorphous due to the size mismatch of the molecules. However, by annealing while covering the samples highly crystalline MnPc films in the β-polymorph can be obtained at 60 °C lower than when starting with pure MnPc films. The resulting films exhibit substantial coercivity (13 mT) at 2 K and a Curie temperature of 11.5 K.