Block Copolymer Templated Chemistry for the Formation of Metallic Nanoparticle Arrays on Semiconductor Surfaces

Abstract

Precise positioning of metallic nanostructures on semiconductor surfaces is important for applications such as photovoltaics, photoelectrocatalysis, metal interconnects, sensing platforms, and many others. In this paper, we demonstrate the utilization of self-assembling diblock copolymer monolayer films, made up of polystyrene-block-poly(2- or 4-vinylpyridine) (PS-b-P2VP or PS-b-P4VP), to spatially direct an aqueous metal reduction reaction on semiconductor surfaces, a process we call galvanic displacement. The diblock copolymer forms hexagonal arrays of spherical micelles consisting of a P2VP or P4VP core surrounded by a PS corona. Two approaches were developed, termed method 1 and method 2, to deliver metal ions to the semiconductor interface in a spatially defined manner utilizing the diblock template. In method 1, a metal complex preloaded into the P4VP cores is spontaneously reduced on the surface to form hexagonally ordered metallic nanoparticles whose structures mirror the parent polymer templates. This approach was employed to produce ordered Ag nanoparticles on Ge(100), InP(100), and GaAs(100) surfaces. Method 2, on the other hand, involves coating the semiconductor surface with an unloaded self-assembled block copolymer monolayer, followed by immersion in a solution of the metal ions and additional reagents, if required. Method 2 is particularly useful to pattern semiconductor surfaces that require the presence of hydrofluoric acid (HF) as an etchant to initiate the galvanic displacement, including Si(100). Using method 2, Cu, Au, Pt, and Pd nanoparticles were patterned on the semiconductor surfaces. In addition, the apparent order of the self-assembled monolayers is better as compared to that of the preloaded block copolymers (prepared via method 1). Since the self-assembling nanostructures of the PS-b-P2VP or PS-b-P4P diblock copolymers can be inverted to a PS core surrounded by a P2VP or P4VP corona (the so-called core−corona inversion) in the presence of HF, patterns of the resulting metallic structures are influenced by this morphological shift. The effects of polymer morphology on the galvanic displacement is described, and as an alternative approach, metal ion reduction and polymer removal with hydrogen/argon plasma is outlined.

Formation of silver nanoparticles created in situ in an amphiphilic block copolymer film

“…28 ATRP for the PS-b-PVP diblock copolymer was carried out with a procedure reported in the literature. 24,25 The first step, which produced PS-Br, involved the homopolymerization of styrene in bulk at 1108C for 5 h in the presence of MBP, CuCl, and HMTETA. The obtained polystyrene (PS) exhibited a narrow molecular distribution (polydispersity index 5 1.3) and a molecular weight of 14,000 g/mol, as determined by gel permeation chromatography.…”

Block Copolymer Nanostructures for Technology

“…This set of properties enables BCPs to be used as a general route for patterning a variety of materials into periodic structures. Transferring the self-assembled BCP pattern into the supporting substrate constitutes the most common example [4,5], while templating of magnetic materials [6], nanoparticles [7][8][9][10][11], and continuous thin metal films [12] have all been reported. and many separated charge carriers generated by solar illumination recombine before diffusing to the electrodes.…”

Controllable fabrication of carbon nanotubes on catalysts derived from PS-b-P2VP block copolymer template and in situ synthesis of carbon nanotubes/Au nanoparticles composite materials

“…A variety of metal salts can be selectively coordinated to the PVP blocks [27,28], here we added FeCl3 to the micellar solution for fabricating iron oxide nanoparticls, which can be used as an effective catalyst for CNTs growth. domain that was the isolated core of the micelles (Fig.…”