A new instrumentation for in situ characterization of the charge transport and crystallographic properties in co-evaporated organic thin film transistor

Abstract

ABSTRACTA new instrumentation was developed to study the in situ electrical and crystallographic properties of organic thin film transistor during vacuum deposition. We characterized pentacene (PEN) and perfluoro-pentacene (PFP) co-deposited organic thin film transistor with various mixing ratio using this equipment. Lattice parameters and crystal orientations of PEN and PFP alloyed phases (named σ-phase and λ-phase) were determined using an in situ two-dimensional grazing incidence X-ray diffraction (2D-GIXD) measurement. The observed 2D-GIXD patterns clarified that the σ-phase is in triclinic unit cell with the following lattice parameters: a = 0.67 nm, b = 0.75 nm, c = 1.58 nm, α = 95.7° β = 94.2° and γ = 84.0°. The c plane of σ-phase crystal is parallel to the substrate surface. The λ-phase is also in triclinic with the following lattice parameters: a = 0.66 nm, b = 0.69 nm, c = 1.56 nm, α = 109.5° β = 113.0° and γ = 81.5°. The a plane of λ-phase crystal was parallel to the substrate surface. It was also found the best symmetric hole and electron mobility (μh = 5.5 × 10−4 cm2V−1s−1 and μe = 5.1 × 10−4 cm2V−1s−1) were obtained at PEN: PFP = 1:1.