Copper surface protection by organothiol self-assembled monolayers
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Copper surface protection by organothiol self-assembled monolayers Sira Suren, Supattra Haokratoke, Soorathep Kheawhom Department of Chemical Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand ABSTRACT This work investigates the effects of concentration of organothiol molecules and temperature used during self-assembled monolayers (SAMs) formation on quality of the organothiol SAMs coating layer obtained in terms of wettability, corrosion inhibition efficiency and carbon to copper ratio. The organothiol SAMs were coated on copper substrates prepared by electro-polishing followed by oxygen plasma treatment for 15 s. Three types of organothiol SAMs including 1-octanethiol (OTT), 2-ethylhexanethiol (2-EHT) and 2-phenylethanethiol (2PET) were investigated. Concentration of organothiol molecules ranging from 0.005 to 0.02 M in isopropanol and forming temperature ranging from -15 to 50oC were studied. It was found that all organothiol SAMs of 0.01 M provided the SAMs coating layer with the highest quality. The SAMs formed at 40oC with OTT and 2-EHT, and at 0oC with 2-PET were the most favorable condition with the highest water contact angle of 124.79o, 130.66o and 120.58o at corrosion inhibition efficiencies of 96.24%, 99.37% and 98.90%, respectively. INTRODUCTION Using copper as conductive material in printed electronics has gained considerable attention in recent years due to its high electrical conductivity and low cost compared to other metals [1]. However, copper patterns printed are prone to oxidation and corrosion especially in environment containing chloride ion, and it affects the electrical properties of the copper patterns [2]. Organothiol self-assembled monolayers (SAMs) coating is one of effective methods to protect the copper patterns from corrosion and oxidation [3,4]. The condition used during SAMs formation affects quality of the organothiol SAMs coating layer obtained and hence corrosion protection efficiency. Only a few works have studied the effects of the condition used during SAMs formation on the properties of the SAMs coating layer obtained [5]. Therefore, the aim of this work is to investigate the effects of concentration of organothiol SAMs and temperature used during SAMs formation on the quality of the SAMs coating layer obtained. The organothiol SAMs were coated on copper substrates prepared by electro-polishing followed by oxygen plasma treatment for 15 s. Three types of organothiol molecules including 1-octanethiol (OTT), 2-ethylhexanethiol (2-EHT) and 2-phenylethanethiol (2-PET) were investigated. These chemicals are similar in terms of the number of carbon atoms but different in chemical structure. Concentration of organothiol SAMs ranging from 0.005 to 0.02 M in isopropanol alcohol and forming temperature ranging from -15 to 50oC were studied. EXPERIMENTAL DETAILS Materials A commercial copper sheet (99.9%) with thickness of 1 mm was used as the copper substrate. Silicon carbide sandpaper number 240, 600, 1000, 1500 and 2000 were used to polish the copp
