Transparent and conducting copper nanowire networks with improved oxidation stability


Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2018

Öğrenci: SEVİM POLAT GENLİK

Danışman: HÜSNÜ EMRAH ÜNALAN

Özet:

Among all scalably synthesized metal nanowires, silver nanowires are the most widely studied and the first commercialized nanowire type. On the other hand, copper nanowires (Cu NWs) are not far behind the silver nanowires and hold great promise due to their lower cost in combination with comparable electrical conductivity in the network form. However, oxidation is the prominent barrier in front of the large scale utilization of Cu NWs. It is well known that bulk copper itself is also prone to oxidation, and numerous methods have been proposed to increase its resistance against oxidation. Inspired from bulk copper, in this thesis, benzotriazole (BTA) was utilized as an organic corrosion inhibitor to enhance the stability of Cu NW networks. High aspect ratio Cu NWs were synthesized by an environmentally benign hydrothermal method and highly transparent and conducting Cu NW networks (20 ohm/sq sheet resistance with a transmittance of 88% at a wavelength of 550 nm) were fabricated through spray deposition. The parameters affecting optoelectronic performance such as nanowire density, annealing temperature and time were studied in detail. Subsequent to the deposition of Cu NW networks, they were spin coated with a solution of BTA for passivation. Long term stability of the passivated networks under ambient and severe humidity conditions were systematically studied in comparison to that of bare control samples. It was found that BTA inhibits the formation of an oxide layer on Cu NWs for at least one year of storage under ambient atmospheric conditions. No significant change in sheet resistance of passivated Cu NW networks was observed (R/R0 < 1.1). High humidity conditions accelerated the degradation of bare Cu NW networks and they became insulating after 2 days under 75% RH condition, while they became insulating after a day under 90% RH. On the other hand, initial sheet resistance of BTA passivated networks was maintained up to 10 days under 75% RH condition, while it was maintained for 7 days under 90% RH. Moreover, attenuated total reflectance infrared spectroscopy (ATR-IR) was used to monitor the thermal stability of BTA for the protection of Cu NW networks and BTA was found to be thermally stable up to 125 °C. All in all, this highly effective and simple strategy to improve the stability of Cu NW networks without deteriorating the optoelectronic performance will certainly open new avenues for their large scale utilization in various optoelectronic devices.