We show that tris (8-hydroxyquinoline) aluminum (Alq3) thin films produced and characterized under ultrahigh vacuum conditions present a well-defined squared-law dependence of the injected current on the applied voltage at applied electric fields of the order of 0.25–1 MV/cm. From this, one derives an electric-field-independent electron mobility of the order of 10−7 cm2/(V s), with a variation between different samples of about one order of magnitude. Observations of current–voltage characteristics with clear indications of trap-filling and space-charge-limited conduction at high fields in Alq3 excludes the existence of traps with an exponential distribution of trap energies, as is commonly assumed in amorphous materials.

We report on electrical measurements of C60-based field-effect transistors (FETs) that were fabricated and characterized in an ultrahigh vacuum, and on how their properties are affected by progressive exposure to impurity gases. The in situ experiments demonstrated that oxygen-free devices have unipolar n-type characteristics with an electron field-effect mobility of up to 0.08cm2∕Vs immediately after fabrication, and up to 0.5cm2∕Vs after an annealing treatment in a high vacuum. Upon oxygen exposure, the effective electron mobility dramatically decreases in a way that depends on the diffusion time of oxygen into the C60 thin film. It is shown that contact with oxygen can lead to C60-FETs with ambipolar characteristics. The real-time measurement of the degradation of the devices subjected to oxygen allows us to derive the diffusion rate for oxygen molecules in C60 thin films, yielding a diffusion constant D=4×10−12cm2∕s.

Thin epitaxial films of the high-perovskite SrHfO 3 were grown by molecular beam epitaxy on Si(100) and investigated by ellipsometry and X-ray photoelectron spectroscopy to determine its band gap and valence band offset. Conducting AFM shows a good correlation between topography and current mapping, pointing to direct tunneling conduction. Long channels MOSFETs with low equivalent oxide thickness (EOT) were fabricated and their channel mobility measured. Mobility enhancement can be achieved by post processing annealing in various gases but at the cost of interfacial regrowth. An alternative approach to increase mobility without changing EOT is by electrically stressing the gate dielectric at ~150 o C.

For second‐order nonlinear optics, a supramolecularly ordered non‐centrosymmetric structure is required. Additionally, well‐ordered organic semiconducting thin films possess superior electronic properties compared to their amorphous counterparts. Herein, we firstly highlight that the design of nonlinear molecules and their functionalization for good molecular orientation (e.g., H‐bonding) is an important method in which to induce supramolecular ordering during subsequent growth. Secondly, we demonstrate a range of growth strategies (e.g., oblique‐incidence molecular beam deposition, hot‐wall deposition) for the growth of molecularly ordered thin films. Thirdly, we discuss various organic supramolecularly ordered material systems (4‐[trans(pyridin‐4‐ylvinyl)] benzoic acid, 5‐bromo‐5′‐formyl‐2,2′‐bithiophene‐4‐nitrophenyl hydrazone, tris(8‐hydroxyquinoline) aluminum) and observe the effects of molecular orientation on their nonlinear optical and optoelectronic properties.

No abstract