Atomic Layer Deposited Coatings on Nanowires for High Temperature Water Corrosion Protection

Sub-10 nm Nanolaminated Al2O3/HfO2 Coatings for Long-Term Stability of Cu Plasmonic Nanodisks in Physiological Environments

By supporting localized plasmon modes, metal-based plasmonic nanostructures can confine optical fields at deep-subwavelength scale in various applications, such as biological and chemical sensing, nanoscale light emission, and solar energy harvesting. While Cu is a low-cost complementary metal oxide semiconductor (CMOS) compatible material, its poor chemical stability limits the use of Cu plasmonic nanodevices in corrosive biochemical aqueous environments. In this paper, we demonstrate that sub-10 nm Al₂O₃/HfO₂ nanolaminated coatings can significantly extend the lifetime of Cu nanodisk arrays from ∼5 h to ∼180 days in the physiological environment of 1× phosphate-buffered saline (PBS) at 37 °C. Cu nanodisk arrays are fabricated using freestanding Au nanohole array films as the physical vapor deposition masks and sub-10 nm nanolaminated coatings composed of alternating Al₂O₃ and HfO₂ nanolayers are grown on Cu nanodisk arrays by atomic layer deposition (ALD). Time-dependent optical extinction measurements of Cu nanodisk arrays are conducted in 1× solutions at 37 °C to investigate the anticorrosion performance for different pure and nanolaminated ALD coatings. We observe a linear relationship between the lifetime of Cu nanodisk arrays in 1× PBS at 37 °C and the nanolaminated coating thickness, and ∼1.3 nm nanolaminated coatings of ∼10 ALD cycles can extend the lifetime of Cu plasmonics up to ∼20 days. Furthermore, we find that the anticorrosion performance of Al₂O₃/HfO₂ nanolaminated ALD coatings strongly depends on the processing and the geometric parameters, such as the annealing temperature and the nanolaminated backbone unit size.

Ultra-thin atom layer deposited alumina film enables the precise lifetime control of fully biodegradable electronic devices

Atomic layer deposited (ALD) ultra-thin alumina film is proposed to control the operational lifetimes of fully biodegradable (FB-) surface sensitive surface acoustic wave (SAW) devices. SAW devices encapsulated with conventional thick organic materials fail to function effectively, while devices with an ultra-thin alumina encapsulation layer (AEL) function normally with high performance. After being subjected to degradation in water, a FB-SAW device with no AEL starts to degrade immediately and fails within 8 h, due to dissolution of the tungsten electrode and piezoelectric material (ZnO). The coating of an ultra-thin AEL on the surfaces prevents SAW devices from undergoing degradation in water and enables SAW devices to perform normally before the AEL is dissolved. The stable operation lifetimes of SAW devices are linearly dependent on the AEL thickness, thus allowing for the design of devices with precisely controlled operational lifetimes and degradation times. The results show that all the materials used could be degraded; also, in vitro cytotoxicity tests indicate that the encapsulated FB-SAW devices are biocompatible, and cells can adhere and proliferate on them normally, demonstrating great potential for broader biodegradable electronic device applications.