Spatial molecular layer deposition of polyamide thin films on flexible polymer substrates using a rotating cylinder reactor

Abstract

Polyamide thin films were rapidly grown using spatial molecular layer deposition (MLD) in a rotating cylinder reactor. The polyamide MLD films were coated on flexible metalized polyethylene terephthalate substrates using sequential exposures of trimesoyl chloride (TMC) and m-phenylenediamine (mPD). The rotating cylinder reactor was housed in a custom oven enclosure that maintained a constant temperature of 115 °C. One MLD cycle (TMC/mPD) was performed per rotation of the cylinder. Polyamide growth rates of 4.5 Å/cycle or 90 Å/min were observed at a slow rotation speed of 20 revolutions per minute (RPM) at a substrate speed of 0.33 m/s. Growth rates of 2.27 Å/cycle or 477 Å/min were measured at higher rotation speeds of 210 RPM at substrate speeds of 3.5 m/s. The polyamide film thicknesses were uniform over the substrate widths as large as ∼16.5 cm. The polyamide MLD surface chemistry was also self-limiting. Constant polyamide growth rate per cycle was measured at larger TMC and mPD exposures. In addition, infrared analysis and thermal annealing studies confirmed the chemical identity of the polyamide films. With four MLD cycles per rotation of the rotating cylinder, spatial MLD should be able to obtain polymer growth rates of >1900 Å/min at a rotation speed of 210 RPM. These rapid growth rates are much higher than the growth rates that can be obtained in temporal MLD reactors. The spatial MLD of polyamide films has many possible applications including the deposition of ultrathin reverse osmosis membranes for water desalination.

Speeding up the unique assets of atomic layer deposition

“…The same applies to organic and hybrid materials deposited by MLD, with encouraging initial results by spatial MLD, as discussed above. [67] Secondly, and as has been shown above, in some cases the use of plasma activation can contribute to an increase in the deposition rate and film quality. While atmospheric plasma has already been implemented for the deposition of oxides and metals with SALD, [68,143,150,[169][170][171] scaling up to large substrates will remain a technical challenge.…”

“…To date, SALD has been extensively used for encapsulation, to protect devices or to fabricate gas diffusion barriers, both in rigid and flexible substrates, including paper, as detailed below. [44,48,64,[66][67][68][69][70][71][72][73] Choi et al have demonstrated Al2O3 deposition rates as high as 7 nm/min (0.12 nm/s) at temperatures below 100 °C. The SALD system they have developed is coupled to a glove box and can coat substrates of industrial size (370 x 470 mm 2 ).…”

“…Using a SALD system, authors claimed polymer growth rate > 1900 Å/min at a rotation speed of 210 RPM. [67] Another group has recently proposed to make a hybrid [PVA/Al2O3 (R2R-SALD)] (Table 2). [70] In that case, however, the PVA polymer was done using a spray derivative technique, not MLD, but taking advantage of the open air processing offered by SALD to combine it with other atmospheric deposition techniques in a sequential (or in-line) mode (Fig.…”

Spatial Molecular Layer Deposition of Ultrathin Polyamide To Stabilize Silicon Anodes in Lithium-Ion Batteries

“…A detailed report on the spatial reactor used in these depositions was previously reported. 22 The coating was deposited directly onto the as-prepared electrodes. Because of the nanoscale features and high aspect ratio in the electrodes, long precursor exposure times were needed to deposit a conformal coating on all surfaces within the electrode.…”

“…Deposition was performed in a custom-built spatial MLD system enclosed within a convection oven. The operation 22 and design 23 of this rotary drum system were previously described. The nitrogen purge gas (99.998%, Airgas) separating precursor dosing zones had a flow rate of 1000 sccm.…”