C. Krellner

Effects of polarized organosilane self-assembled monolayers on organic single-crystal field-effect transistors

The surface conductivity is measured by a four-probe technique for pentacene and rubrene single crystals laminated on polarized and nearly unpolarized molecular monolayers with application of perpendicular electric fields. The polarization of the self-assembled monolayers (SAMs) shifts the threshold gate voltage, while maintaining a very low subthreshold swing of the single-crystal devices (0.11 V∕decade). The results, excluding influences of parasitic contacts and grain boundaries, demonstrate SAM-induced nanoscale charge injection up to ∼1012cm−2 at the surface of the organic single crystals.

Determination of the interface trap density of rubrene single-crystal field-effect transistors and comparison to the bulk trap density

In order to gain further insight into the details of charge transport in organic semiconductor devices it is necessary to characterize the density of trap states at the semiconductor∕gate dielectric interface. Here we use the technique of gate bias stress to quantitatively determine the interface trap density in rubrene single-crystal field-effect transistors with two different types of interfaces. A reversible and reproducible shift of the I‐V characteristics is observed upon both negative and positive gate bias stress, whose physical origin is identified as charge trapping and detrapping at the crystal∕SiO2 insulator interface. We can thus quantify the density of interface traps that are alternately filled and emptied on a time scale of ≅1h in the energy range defined by the applied bias stress. For a typical rubrene∕SiO2 interface we extract a density of ∼2×1012cm−2 at a stress bias of ±50V, corresponding to a volume density of ≅1019∕(cm3eV). An octadecyltrichlorosilane treatment of the SiO2 dielectric...

Magnetic and structural transitions in layered iron arsenide systems: AFe2As2 versus RFeAsO

Resistivity, specific-heat, and magnetic-susceptibility measurements performed on

High-field phase diagram of the heavy-fermion metal YbRh2Si2

{\text{SrFe}}_{2}{\text{As}}_{2}

Density of bulk trap states in organic semiconductor crystals: Discrete levels induced by oxygen in rubrene

samples evidence a behavior very similar to that observed in LaFeAsO and

Emerging local Kondo screening and spatial coherence in the heavy-fermion metal YbRh2Si2

{\text{BaFe}}_{2}{\text{As}}_{2}

Strong coupling between magnetic and structural order parameters in SrFe2As2

, with the difference being that the formation of the spin-density wave and the lattice deformation occur in a pronounced first-order transition at

Fermi-surface collapse and dynamical scaling near a quantum-critical point

{T}_{0}=205\text{ }\text{K}

CeFePO: a heavy fermion metal with ferromagnetic correlations.

. Comparing further data evidences that the Fe magnetism is stronger in

CeRuPO: A rare example of a ferromagnetic Kondo lattice

{\text{SrFe}}_{2}{\text{As}}_{2}