Nano-Laminated Metal Oxides/Polyamide Stretchable Moisture- and Gas-Barrier Films by Integrated Atomic/Molecular Layer Deposition

Abstract

Stretchable barrier films capable of maintaining high levels of moisture- and gas-barrier performance under significant mechanical strains are a critical component for wearable/flexible electronics and other devices, but realization of stretchable moisture-barrier films has not been possible due to the inevitable issues of strain-induced rupturing compounded with moisture-induced swelling of a stretched barrier film. This study demonstrates nanolaminated polymer/metal oxide stretchable moisture-barrier films fabricated by a novel molecular layer deposition (MLD) process of polyamide-2,3 (PA-2,3) integrated with atomic layer deposition (ALD) metal oxide processes and an in situ surface-functionalization technique. The PA-2,3 surface upon in situ functionalization with H2O2 vapor offers adequate surface chemisorption sites for rapid nucleation of ALD oxides, minimizing defects at the PA-2,3/oxide interfaces in the nanolaminates. The integrated ALD/MLD process enables facile deposition and precise structural control of many-layered oxide/PA-2,3 nanolaminates, where the large number of PA-2,3 nanolayers provide high tolerance against mechanical stretching and flexing thanks to their defect-decoupling and stress-buffering functions, while the large number of oxide nanolayers shield against swelling by moisture. Specifically, a nanolaminate with 72 pairs of alternating 2 nm (5 cycles) PA-2,3 and 0.5 nm HfO2 (five cycles) maintains its water vapor transmission rate (WVTR) at the 10–6 g/m2 day level upon 10% tensile stretching and 2 mm-radius bending, a significant breakthrough for the wearable/flexible electronics technologies.

Atomic/Molecular Layer Deposition for Designer's Functional Metal–Organic Materials

“…245 [259] Bdy 1,4-Butynediol 50 [258] 4,4′-BPDC 4,4′-Biphenyldicarboxylic acid 250 [106] Aconitic acid 114 [234] 1,3-BDC 1,3-Benzenedicarboxylic acid 212 [114] EA Ethanolamine 80 [260,261] 1,3,5-BTC 1,3,5-Benzenetricarboxylic acid 245 [205] MC Malonyl chloride RT, [262] 28 [261] AZO 4,4′-Azobenzenedicarboxylic acid 310 [134,263] Lactic acid 115 [264] Cur Curcumin 260 [135,265] Pimelic acid 139 [221] 1,4-NDC 1,4-Naphthalenedicarboxylic acid 200 [266] DEG Diethylene glycol 100 [267] ADA 9,10-Anthracenedicarboxylic acid 240 [266] HD 1,6-Hexanediol 85 [125] Qz Quinizarin 130 [268] DD 1,10-Decanediol 120 [269] BDS 1,4-Benzenedisulfonic acid 190 [121] H 4 Pe Pentaerythritol 160 [268] DHTP 2,5-Dihydroxyterephthalic acid 190 [270] PD 1,3-Propanediol 100 [271] PMDA 1,2,4,5-Benzenetetracarboxylic anhydride 150 [209] l-Cys l-Cysteine [217,272] Abbreviation Full name (ring-opening) Source temperature [°C] l-Ala l-Alanine [217] Phenol 80 [273,274] l-Lys l-Lysine [217] 3F 3-(Trifluoromethyl)phenol 80 [273,274] Malonic acid 125 [221] 4F 2-Fluoro-4-(trifluoromethyl)benzaldehyde 60 [273,274] l-aspartic acid 225 [210] GLY Glycidol 60 [275,…”

“…Zirconium-based ALD/MLD films have been deposited from ZrCl 4 , [106,122,204,224,416] and also from tetrakis(dimethylamido) (TDMA)- [65] and tetra-tert-butoxide (ZTB)- [126,230,[417][418][419] based precursors together with a variety of different organic precursors. Likewise, Hf-based films have been deposited from TDMAH, [230,262,324,420] HfCl 4 , [122] and TEMAH [367] together with various organics. In the few additional studies involving the 4d or 5d transition metals, Nb-based films have been deposited from Nb(OEt) 5 in combination with HQ, [421] Mo-based films from molybdenum hexacarbonyl together with 1,2-ethanedithiol (EDT), [242,243] 1,4-butanedithiol, and BDT, [243] and In-based films from bis(trimethylsilyl)amidodiethylindium (INCA-1) and HQ.…”

“…[ 31,32,39–44,176,181–200 ] In recent years, the organic precursor library has been rapidly expanding. We have collected in Table 1 the organic precursors so far used in ALD/MLD processes, together with the heating temperatures employed for their evaporation in the corresponding process conditions; [ 17,18,32,40,46,51,57–59,61,63,64,66,81,105–108,114,118,119,121,122,125,129,134–136,139,141,142,156,164,168,189,201–284 ...…”

“…[ 111,231,287–332 ] However, TMA works very well with many other organics as well. [ 40,46,54,108,109,114,125,148,211–213,218,219,221,226,228,230,234,240,244,245,249,252,255,256,258,260,262,264,267–269,273–277,279–284,325,333–369 ] The bulkier dimethyl aluminum isopropoxide precursor has been successfully used with EG as well. [ 323 ] Different TMA + organic processes have been investigated, e.g., to elucidate the effect of the organic backbone length, i.e., long (1,10‐decanediol) or short (1,6‐hexanediol), on the mechanical properties; indeed, as expected, with the increasing chain length, the stretchability was enhanced.…”

Complete stress release in monolayer ALD-Al2O3 films based on mechanical equilibrium homeostasis to realize a bending radius of 1 mm

“…If the ALD-Al 2 O 3 monolayer film has better flexibility to achieve independent flexible encapsulation performances, it would undoubtedly reduce the preparation process and realize ultra-flexible optoelectronic devices. 25–27…”