Synthesis of Fluorene‐Type Thin Film Under Biphenyl/Methane Plasma Environment

Abstract

Fluorene‐type (C13H10) thin films were synthesized by using the mixture of biphenyl (C12H10) and methane (CH4) plasma. The reactor is a parallel plate installation; upper electrode is connected to 13.56 MHz rf power and lower electrode is grounded. The thin films were deposited by applying a negative bias potential between the substrate and the wall of reactor. The films were investigated by residual gas analysis (RGA), UV–vis spectroscopy, atomic force microscope (AFM) and ellipsometry. They had significant nanostructured properties which were suitable for photovoltaic applications. The conjugation was improved by iodine doping and the optical band gap energy dropped down up to 2.85 eV.

Wide Range Control of the Chemical Composition and Optical Properties of Propanethiol Plasma Polymer Films by Regulating the Deposition Temperature

“…Therefore, decreasing the deposition rate (i.e., substrate heating, cf. Figure a), increases the energy density of the ion bombardment, which leads to a higher crosslinking degree and a lower retention of the precursor structure . In this regards, it has been recently reported how the degree of crosslinking and the precursor fragmentation can be accurately controlled as a function of the deposition rate (in our case controlled by T S for a fixed plasma conditions), this being an effective strategy to regulate the preservation of the precursor integrity in remote plasma polymerized thin films …”

“…Equation and the influence of T S on R in Figure a). However this was reported to have a rather low impact on the atomic composition of PPFs . Therefore the evolution of the S sulfur content is also tentatively related to a dissimilar influence of T S over the adsorption/desorption kinetics of the plasma generated species on the growing films.…”

“…All these trends indicate a higher degree of crosslinking and a lower retention of precursor functionalities as T S increases. This behavior can be rationalized by considering the energy density dissipated during the growth of the film by ion bombardment ( ϵ surf ); which is given by Equation where Γ i and <E> are the ion flux impinging over the growing film and the mean ion energy, respectively. …”

“…Aiming to contribute to a better understanding of the growth mechanism of PPFs, numerous works have been published during the last years analyzing the chemical reactions occurring in the plasma phase and at the interfaces with the chamber walls (including the substrates) as a function of different working parameters; as well as the influence on the final deposit . Other works deal with the ion bombardment at which the growing films is exposed during the deposition; and how it affects the retention of target functionalities and the degree of crosslinking of the films . Despite of its importance, in caparison only a few works take into account and investigate the influence of the thermal conditions of the growing film on the surface physicochemical reactions involved during a plasma polymerization process.…”