Nickel Nanofilms Electrolessly Deposited on Organosilane Nanorings and Characterized by Contact Mode AFM Combined with Magnetic Sample Modulation

Abstract

Surface structures of magnetic nanorings were made using electroless deposition of Ni onto patterned templates of an amine-functionalized organosilane. Samples were prepared by chemical approaches based on colloidal lithography employing a surface mask of size-sorted, monodisperse silica spheres. Surface changes were evaluated after key points of the reactions using imaging modes of atomic force microscopy (AFM). Nanopatterns of 3-aminopropyltriethoxysilane (APTES) were prepared on Si(111) by applying a heated vapor to a surface mask of silica spheres. After rinsing, the particle mask was removed to reveal ring-shaped nanopatterns presenting amine groups at the interface. Organosilane nanopatterns were then immersed in a solution of Pd catalyst followed by treatment in a Ni plating bath. Changes in surface morphology after each reaction step were characterized ex situ using tapping-mode AFM to follow the time course of nanofabrication. Images of the Ni nanorings acquired with AFM were compared with SEM micrographs to further elucidate the morphology of the metal coatings. The magnetic character of the nanostructures was investigated with magnetic sample modulation (MSM-AFM), which is a hybrid of contact mode AFM combined with magnetic actuation of samples. Surface maps of the vibration of diamagnetic Pd and magnetic Ni nanorings were obtained with MSM-AFM, providing insight on processes of electroless plating. Fine details of the surface corrugation and grain structure of the Ni coated areas of the sample detected with SEM were sensitively resolved with MSM-AFM that were not apparent in AFM topography frames. Chemistry-based steps with electroless deposition (ELD) of metal and colloidal lithography provide a practical route for reproducible nanofabrication of highly regular geometries with high-throughput.

Controlled Electroless Deposition of Noble Metals on Silicon Substrates Using Self-Assembled Monolayers as Molecular Resists To Generate Nanopatterned Surfaces for Electronics and Plasmonics

“…The OTS monolayer started showing signs of metal deposition at rather high concentrations of NH 4 F and metal ions or at longer plating durations under conditions used (see Figures S4–S6). While this is promising for fundamental understanding of the nature of plating solution components at smaller concentrations and their microscopic effects toward electroless metal deposition, there is ample room for more investigation toward fabricating hybrid surfaces using techniques such as AFM nanoshaving, , nanosphere lithography, , and photolithography …”

Electroless Plating of Metal Nanomaterials

“…[133] (ii) The aforementioned reaction steps can also be inverted: Metal ions can first be attached to a substrate and then reduced either in the plating bath, a separate solution, [121,124] or with alternative methods such as photoreduction. [137] Anchoring groups for surface complexes can be established, e. g., through molecular self-assembly, [138] polyelectrolyte coatings, [120] or organic functionalization. [124] Alternatively, precursors can be infiltrated into the substrate (e. g., polyimide can be loaded with Pd(acac) 2 in supercritical CO 2 [139] or hydrolyzed and ion-exchanged with Ag(I)).…”

Fabrication and Growth Control of Metal Nanostructures through Exploration of Atomic Force Microscopy-Based Patterning and Electroless Deposition Conditions

“…This showed good selectivity and control of the deposition of these metals in a regular nanoscale array. The ELD process could be applied to a wide range of metals including Pd, , Pt, Ni, , and Co , as the process is controlled by the difference in reduction potential between Si and the metal ions in the solution.…”