Localized Electroless Deposition of Gold Nanoparticles Using Scanning Electrochemical Microscopy

Abstract

The aim of this study is to locally deposit nanoparticles on an unbiased surface by electroless deposition ͑ED͒ using scanning electrochemical microscopy ͑SECM͒. We have developed an ED process that is based on the reduction of gold ions by hydroquinone ͑H 2 Q͒ and catalyzed by a metallic surface, such as palladium. One of the advantages of this system is the ability to drive the ED at pH 1-7. The metal ions were electrogenerated in a solution consisting of H 2 Q and KCl by anodic dissolution of a gold microelectrode. AuCl 4 − reacted with H 2 Q at the electrolyte/metallic interface to form benzoquinone and gold deposit. The ED has been studied initially in bulk solution containing KCl, H 2 Q, and HAuCl 4 , and then by SECM. We found that the pH had a significant effect on the nature of the deposited gold and could be correlated with the kinetics of gold ions reduction by H 2 Q. Hence, either nanoparticles or much larger crystals could be formed, depending on the pH of the deposition solution. Time of deposition and H 2 Q concentration also affected the shape and density of the deposition.Since the introduction of electroless deposition ͑ED͒ as a plating method for semiconductors and circuit boards by Bell Laboratories, 1 ED has been widely used in the microelectronics industry. 2,3 In this surface catalyzed process, metal ions are reduced by a reducing agent and deposited onto a catalytic substrate without applying an external electric current. A kinetic barrier, which prevents the reduction of the metal ions in the solution, is an essential feature of ED. Over the past 40 years, ED has been used for the deposition of various metals, such as Cu, 4-6 Ag, 7,8 Pt, 9 and Au, 10,11 on unbiased metals and on insulators. Gold plating is relevant in a number of fields because of its high conductivity and chemical stability. Gold ED offers several advantages, including simplicity, processability at low temperature, and coating uniformity. Several studies focusing on Au ED have been reported using different deposition baths. The first autocatalytic gold ED bath consisted of KAu͑CN͒ 2 as the source of gold and KBH 4 or dimethylammine borane ͑DMAB͒, 10 as the reducing agent in a basic solution. 12 Additional baths have been developed based on other reducing agents. For example, Iacovangelo 13 reported a bath for gold plating on nickel using DMAB and hydrazine as reducing agents. Hypophosphite, thiourea, and ascorbic acid have also been employed. 14 All these baths involve basic solutions that are required to increase the thermodynamic driving force of the reducing agents as well as to avoid the evolution of hydrogen cyanide. Therefore, alternative systems using different gold salts ͑e.g., ͓Au͑S 2 O 3 ͒ 2 ͔ 3− ͒ have been developed. 10,11,15,16 Interestingly and in spite of the large number of patents and studies on gold ED, there are only a few reports on the localized ED of gold. Martin and Menon 17 for example produced arrays of gold nanoelectrodes by ED techniques. In their work, a polycarbonate filter membrane ͑10-30 nm...

Control of locally deposited gold nanoparticle on polyaniline films

“…This allows electroless deposition of metals on conducting and insulating surfaces [35,36]. Here we report on locally depositing gold nanoparticles on unbiased PAN films by anodically dissolving a gold microelectrode [37,38].…”

Scanning Electrochemical Microscopy versus Scanning Ion Conductance Microscopy for Surface Patterning

“…The formation of a ring structure due to Pd deposition by SECM has been previously reported [18] although in a different system in which the Pd(II) ions were embedded in a polymeric matrix on the substrate. The formation of an inhomogeneous disc and preferred deposition in the periphery can be attributed to the dependence on chloride diffusion towards the Pd tip.…”

“…Scanning electrochemical microscopy (SECM), a scanning probe technique with high spatial resolution was evolved as a means of imaging, studying interfacial processes or modifying surfaces. [14][15][16][17] Indeed, SECM has been used to form metallic patterns of Au, [18][19][20][21] Ag, [22] Co [23] and other metals on various surfaces using different modes, e. g. feedback and generation/ collection. [24] Other approaches, including scanning probe microscopy, [25] chemical etching, [26] laser irradiation [27] and electrochemistry using masks [28] have been reported to achieve micrometer resolution through local deposition followed by electroless metal deposition on different substrates.…”

Remote Control Electrodeposition: Principles for Bipolar Patterning of Substrates without an Electrical Connection

“…[19][20][21][22][23][24] Initial applications of the SBC used an electrically-floating copper metal substrate as the electron donor and cupric ion containing electrolytes as the electron acceptor for the bipolar pair. As the copper substrate was oxidized in the far-field, electrons were donated to the equal and opposite local reduction of cupric ion (to copper) beneath the microjet.…”