Atomic layer deposition of nanoparticles on self-assembled monolayer modified silicon substrate
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Atomic layer deposition of nanoparticles on self-assembled monolayer modified silicon substrate 1 1 Kun Cao , Zhilong Ren , Shengmei Xiang1, Bin Shan1, and Rong Chen2* 1 State Key Laboratory of Material Processing and Die & Mould Technology, School of Materials Science and Engineering, 2 State Key Laboratory of Digital Manufacturing Equipment and Technology, School of Mechanical Science and Engineering, Huazhong University of Science and Technology, 1037 Luoyu Road, Wuhan, Hubei PR China 430074 *Corresponding author: [email protected] ABSTRACT Atomic layer deposition has attracted much attention recently in fabricating noble metal nanoparticles for a wide range of applications. We have explored synthesizing palladium nanoparticles via atomic layer deposition on self-assembled monolayers modified silicon substrate. Using alkyltrichlorosilanes as the passivating agents, our results show the method is capable of fabricating Pd nanoparticles with well controlled density and particle diameter on the modified silicon substrate. INTRODUCTION Noble metal nanoparticles (NPs) catalysts such as Ru, Pt and Pd play an important role in many catalytic applications due to their outstanding performance and great stability[1]. Palladium is one of the most widely used noble metal catalysts in fuel cells, automotive exhaust gas system, and so on[2-3]. Synthesizing Pd NPs with well-controlled particle size and distribution density is of great importance to optimizing their reactivity[4]. However, nanoparticles synthesized through conventional wet chemistry usually have a broad distribution of size and density, which are hard to purify[5-6]. Synthesis methods to achieve controlled size and density are urgently needed. Atomic layer deposition (ALD) is a rapidly developing thin film deposition technique based on surface saturated chemical reactions[7-8]. Due to the self-limiting nature of half-reactions, each ALD cycle forms a single atomic layer on the substrate. This enables sub-nanometer thickness control in the vertical direction[9]. However, ALD usually could not control materials growth in the lateral direction, which is disadvantageous to nanoparticle synthesis. Through adjusting the ALD process and suitable modification of the substrates, it is possible to overcome this drawback. Recent works have shown that noble metal nanoparticles, such as Ru, Pt, Pd and their alloys have been successfully synthesized on non-flat surfaces via ALD methods[10-11]. Self-assembled monolayers (SAMs) are widely used to modify the surface properties on flat substrates include Si wafer, glass, gold and so on[12]. In previous study, it was found that the pinhole free octadecyltrichlorosilane can perfectly block the ALD growth of oxide and noble metal such as HfO2 and Pt[13-14]. By appropriately modifying the substrate with SAMs and making use of the pinholes and defect sites on SAMs, it is possible to obtain nanoparticles with controlled size and density. In
this paper, we show that Pd NPs with controlled size and density can be obtained throu
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