Adsorption of Nanometer-Sized Palladium Particles on Si(100) Surfaces

Abstract

It is shown that polymer-stabilized Pd particles, adsorbed on Si, initiate the growth of electroless Ni. The influence of the polymer (poly(vinylpyrro1idone)) on the particle size and on the surface coverage is described. While Pd particles adsorb strongly on Si, almost no adsorption is observed on SiO2. Implications of this adsorption selectivity for the production of high-resolution metal patterns on Si are briefly discussed. IntroductionDarticles/cm2 for a Si(100) surface). The Pd deDosition The wet-chemical metalization of semiconductors is of considerable industrial importance. In practice, this is usually achieved by electroless plating. For electroless deposition of a metal layer (e.g. Nil, the substrate is immersed in a solution containing a reducing agent (hypophosphite) and metal ions (Ni2+). The reduction of Ni2+ by hypophosphite (eq 1) has a high activation energy and occurs at a significant rate only in the presence of a catalyst. If hypophosphite is used as the reducing agent, a small amount (9.8 w t % at pH 4) of phosphorus is incorporated during the deposition of an electroless Ni layer. The phosphorus concentration in the layer depends on the temperature and the pH ofthe electroless solution.2 In order to confine reaction 1 to the substrate to be plated, its surface has to be catalytically activated. Palladium has proven to be a good catalyst for the initiation of Ni3,4 and Cu5 deposition from an electroless solution.

Preparation and Characterization of Polymer-Stabilized Rhodium Sols. I. Factors Affecting Particle Size

“…Note that a large fraction of the metal surface has to be surrounded by the polymer to obtain sufficient stabilization. 30 Therefore, the low number of polymer strings per particle indicates that multiple adsorption 21,46 of the polymer on the metal surface is mandatory for sufficient stabilization.…”

“…Beginning with early reports of Turkevich et al the topic of controlled preparation of monodisperse nanoscale metal particles has maintained its fascination over the years (e.g., refs −12). The fundamental interest arises from the fact that the small metal particles in a sol show properties different from atomically dispersed and bulk metals. − Their electronic, magnetic, and optical properties can be fine-tuned. − Applications include such diverse fields as electroless metal deposition , and catalysis. − …”

“…[13][14][15][16] Their electronic, magnetic, and optical properties can be fine-tuned. [13][14][15][16][17][18][19] Applications include such diverse fields as electroless metal deposition 20, 21 and catalysis. [22][23][24][25][26][27][28][29] Generally, the sols can be stabilized via Coulombic forces (electrostatically stabilized colloids) or via steric protection (sterically stabilized colloids).…”

Shape-controlled preparation and catalytic activity of metal nanoparticles for hydrogenation of 2-butyne-1,4-diol and styrene oxide

“…Pd particles are considered to adsorb onto the polymer. At higher PVP/Pd ratios, beads on string-type of complexes may thus be formed, adsorbing multi-particle complexes [32], which is also one of the reasons for higher activity of nanoparticles at higher PVP concentration. The selectivity to B 2 D obtained was more than 98% for the Pd catalysts having PVP/Pd ratio in the range of 1-30.…”

Kinetic Control of Interparticle Spacing in Au Colloid-Based Surfaces: Rational Nanometer-Scale Architecture

“…As such, assembly of individual nanometer-scale particles into ensembles has recently become an important and widely-pursued objective. In many cases, the desired architecture consists of two-dimensional arrays of particles supported on a substrate. − However, little information exists on the factors that govern nanostructure within this geometry. In particular, the rates of particle-array formation, the significance of interparticle forces, and the approaches to controlling those forces have not been addressed.…”