Where physics meets chemistry: Thin film deposition from reactive plasmas

Abstract

Functionalising surfaces using polymeric thin films is an industrially important field. One technique for achieving nanoscale, controlled surface functionalization is plasma deposition. Plasma deposition has advantages over other surface engineering processes, including that it is solvent free, substrate and geometry independent, and the surface properties of the film can be designed by judicious choice of precursor and plasma conditions. Despite the utility of this method, the mechanisms of plasma polymer growth are generally unknown, and are usually described by chemical (i.e. radical) pathways. In this review, we aim to show that plasma physics drives the chemistry of the plasma phase, and surfaceplasma interactions. For example, we show that ionic species can react in the plasma to form larger ions, and also arrive at surfaces with energies greater than 1000 kJ mol-1 (>10 eV) and thus facilitate surface reactions that have not been taken into account previously. Thus, improving thin film deposition processes requires an understanding of both physical and chemical processes in plasma.

Mechanical properties of plasma polymer films: a review

“…Some of those applications will be detailed later in this review. As previously reported [27], the mechanical properties are one of the least explored characteristics of functionalized plasma depositions. However, as the interest in exploring other possible applications grows [9], the investigation of those properties for other organic precursors than organosilicons is also increasing.…”

“…A large number of reactions pathways are available during plasma excitation and the polymers formed in this environment are usually complex and highly crosslinked [5]. More details on plasma polymerization can be found on numerous reviews in the literature [5,17,26,27].…”

Controlling the flux of reactive species: a case study on thin film deposition in an aniline/argon plasma

“…gives a time averaged ion flux of about Γ i = 1.5 × 10 18 ions/(m 2 s). Assuming a mass density even as large as 2 g/ cm 3 for the deposited thin films and a sticking coefficient of 1 results in a -purely ion supported-growth rate of about 8 nm/min which is about 2 times higher than the measured growth rate. (A discussion about the sticking www.nature.com/scientificreports/ coefficient of positive ions can be found e.g.…”

Perspective on Plasma Polymers for Applied Biomaterials Nanoengineering and the Recent Rise of Oxazolines

“…Comparing our results and those of Zanini et al for 2-ethyl-2-oxazoline films deposited in two different plasma reactors and using different precursor flow rates, Figure 2d, we found film deposition rates of the same order of magnitude and comparable film wettability, in the range of approximately 60 to 70 depending on the nature of the precursor and deposition conditions, Figure 3a. It is worth noting, however, that the relationship between the film deposition rate and the power input (W/F) is complex and will be influenced by the plasma reactor geometry (e.g., deposition area and electron energy distribution function, ion density) despite the fact that the deposition conditions described in Zanini et al appear comparable to those used in our study [27,52,131,132]. As such, it is only meaningful here to compare the macroscopic attribute of the films as their intrinsic chemical nature may be quite different.…”

“…Plasma polymers prepared from non-synthetic monomers are a particularly hot topic because they combine desirable optical and physical properties with biocompatibility and environmental sustainability [50,51]. However, as the complexity of the monomer increases, so does the importance of carefully tuning the plasma deposition condition to tailor the amount of functionality retention to suit any specific application [52,53] and ensure that film reactivity can be maintained for relevant aging time [54].…”