The electronic properties of organic semiconductors depend strongly on the nature of the molecules, their conjugation and conformation, their mutual distance and the orientation between adjacent molecules. Variations of intramolecular distances and conformation disturb the conjugation and perturb the delocalization of charges. As a result, the mobility considerably decreases compared to that of a covalently well-organized crystal. Here, we present electrical characterization of large single crystals made of the regioregular octamer of 3-hexyl-thiophene (3HT)8 using a conductive-atomic force microscope (C-AFM) in air. We find a large anisotropy in the conduction with charge mobility values depending on the crystallographic orientation of the single crystal. The smaller conduction is in the direction of π-π stacking (along the long axis of the single crystal) with a mobility value in the order of 10(-3) cm(2) V(-1) s(-1), and the larger one is along the molecular axis (in the direction normal to the single crystal surface) with a mobility value in the order of 0.5 cm(2) V(-1) s(-1). The measured current-voltage (I-V) curves showed that along the molecular axis, the current followed an exponential dependence corresponding to an injection mode. In the π-π stacking direction, the current exhibits a space charge limited current (SCLC) behavior, which allows us to estimate the charge carrier mobility.

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A study of the structural and electrical properties of amorphous LaAlO3 (LAO)/Si thin films fabricated by molecular beam deposition (MBD) is presented. Two substrate preparation procedures have been explored namely a high temperature substrate preparation technique—leading to a step and terraces surface morphology—and a chemical HF-based surface cleaning. The LAO deposition conditions were improved by introducing atomic plasma-prepared oxygen instead of classical molecular O2 in the chamber. An Au/Ni stack was used as the top electrode for its electrical characteristics. The physico-chemical properties (surface topography, thickness homogeneity, LAO/Si interface quality) and electrical performance (capacitance and current versus voltage and TunA current topography) of the samples were systematically evaluated. Deposition conditions (substrate temperature of 550 °C, oxygen partial pressure settled at 10−6 Torr, and 550 W of power applied to the O2 plasma) and post-depositions treatments were investigated to optimize the dielectric constant (κ) and leakage currents density (JGate at |VGate| = |VFB − 1|). In the best reproducible conditions, we obtained a LAO/Si layer with a dielectric constant of 16, an equivalent oxide thickness of 8.7 Å, and JGate ≈ 10−2A/cm2. This confirms the importance of LaAlO3 as an alternative high-κ for ITRS sub-22 nm technology node.