Interface Structures and Electronic States of Epitaxial Tetraazanaphthacene on Single-Crystal Pentacene

The structural and electronic properties of interfaces composed of donor and acceptor molecules play important roles in the development of organic opto-electronic devices. Epitaxial growth of organic semiconductor molecules offers a possibility to control the interfacial structures and to explore precise properties at the intermolecular contacts. 5,6,11,12-tetraazanaphthacene (TANC) is an acceptor molecule with a molecular structure similar to that of pentacene, a representative donor material, and thus, good compatibility with pentacene is expected. In this study, the physicochemical properties of the molecular interface between TANC and pentacene single crystal (PnSC) substrates were analyzed by atomic force microscopy, grazing-incidence X-ray diffraction (GIXD), and photoelectron spectroscopy. GIXD revealed that TANC molecules assemble into epitaxial overlayers of the (010) oriented crystallites by aligning an axis where the side edges of the molecules face each other along the [1¯10] direction of the PnSC. No apparent interface dipole was found, and the energy level offset between the highest occupied molecular orbitals of TANC and the PnSC was determined to be 1.75 eV, which led to a charge transfer gap width of 0.7 eV at the interface.

Challenges and Solutions of Replacement Metal Gate Patterning to Enable Gate-all-Around Device Scaling

This paper addresses challenges and solutions of replacement metal gate of gate-all-around nanosheet devices. The unit process and integration solutions for the metal gate patterning as well as interface dipole patterning to offer multiple threshold voltage have been developed. The challenges of long channel device integration are also discussed.