Controlled Electroless Deposition of Noble Metal Nanoparticle Films on Germanium Surfaces

Abstract

Thin noble metal films have been prepared as a result of the immersion of germanium substrates into dilute, aqueous solutions of AuCl 4-, PdCl 4 2-, or PtCl 4 2-, respectively. Deposition proceeds via galvanic displacement in the absence of fluoride, pH adjusters, complexing agents, or external reducing agents. This manner of metal deposition serves as a cost-effective, high-throughput methodology with control over surface morphology and deposition rate by modulation of plating parameters such as concentration, temperature, and immersion time.Recent progress toward metallization on the diminishing size regimes dictated by the feverishly evolving disciplines of nanotechnology has imposed increasingly stringent demands upon thin film preparation methodologies.1 Ultra large scale integration (ULSI) device fabrication, nanoelectromechanical systems (NEMS), and arrayed nanosensors will require unparalleled control of metal film surface morphology, deposition rate, and substrate adhesion without sacrificing throughput or cost effectiveness. Furthermore, noble metal films of this type are important for fundamental investigations aimed at elucidating the intricate nature of interfacial topics ranging from self-assembled monolayers (SAMs) to sensing and heterogeneous catalysis. [2][3][4][5][6][7][8] In contrast to complex and expensive vacuum methods of metallization, research in our laboratory has focused on the preparation of noble metal thin films on semiconductor substrates via electroless deposition. Herein we describe the implementation of this facile methodology to prepare nanostructured, high surface area noble metal films with control over surface morphology and deposition rate. Moreover, metal films prepared in this manner exhibit excellent adhesion to the underlying semiconductor substrate."Electroless" plating is a term coined by Brenner and Riddell 9 to describe the spontaneous reduction of metal ions to metallic particles and films in the absence of an external source of electric current. 10 This method has attracted great interest due to simplicity of operation, cost effectiveness, high throughput, and lack of elaborate equipment. [10][11][12] Electroless deposition is applicable to a wide range of metal/ substrate combinations, including metal-on-metal, metal-onsemiconductor, and metal-on-insulator. This is particularly important with regard to metal deposition on electronically isolated substrate regions, such as those on a circuit board, for example. The literature commonly utilizes the term "electroless deposition" interchangeably to describe three fundamentally different plating mechanisms (Figure 1). 11These include autocatalytic, substrate catalyzed, and galvanic displacement (immersion) processes. Autocatalytic plating baths are commonly employed in electronics fabrication and typically contain a metal salt, pH adjuster, complexing agent, reducing agent, and other various additives.12 Once initiated, the reduced metal species serves to catalyze subsequent metal * Corresponding author. E-ma...

Enhanced Fluorescence from Fluorophores on Fractal Silver Surfaces

“…Metal particles can be generated with light [28][29][30] and by electroless deposition via galvanic displacement. 31 Additionally, the fractal silver surfaces result in a partial elimination of selfquenching. As a result it may now be possible to use proteins and DNA, which are heavily overlabeled with fluorophores, as ultrabright reagents themselves for immunoassays or DNA arrays.…”

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“…Metal particles can be generated with light [24][25][26] and by the electroless deposition via galvanic displacement [27]. Additionally, the fractal silver surfaces result in a partial elimination of self-quenching.…”

X-ray induced reduction of Au and Pt ions on silicon substrates

“…The conventional routes utilize methods involving deposition of vaporized atoms from the gas phase, or reduction of their salts using electrochemical and/or electroless wet chemical methods. Other unconventional techniques utilizing lasers, ion-beams and Xrays have also been investigated for incorporating metal clusters on to the substrates in the desired chemical and morphological state(s) [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Use of energetic particle beams and X-rays are particularly attractive since clean lithographic techniques can also be introduced for direct-writing purposes.…”