Formation of Surface Silver Nano-network Structures through Hot Electron Regulated Diffusion-limited Aggregation

Abstract

A surface Ag nano-network pattern is formed by first depositing Ag nanoparticles (NPs) on a conductive template, which has a certain defect structure, and then illuminating the Ag NPs with ultraviolet (UV) light in a moist environment. Such an Ag nano-network pattern consists of multiple connected Brownian trees (BTs), which are produced through the diffusion-limited aggregation (DLA) process. In the DLA process, diffuse Ag + ions, which are generated by UV light illumination and dissolved by a thin adsorbed water layer on the surfaces of the Ag NPs and used GaN template, settle to form a BT through the combination with excited hot electrons migrating into the template from the Ag NPs. The lateral transport of hot electrons in the template is regulated by the distributions of threading dislocation and point defect cluster in the template, which eventually become the centers of BTs. The structure of a surface Ag nano-network can potentially serve as a transparent conductor.

Surface Plasmon Resonance-Induced Diffusion-Limited Aggregation in the Formation of Ag/AgOx Nanonetworks as Broad-Spectrum Transparent Conductors

“…Further study should also lead to the application to flexible optoelectronics. Different from our previous work, in which all the original Ag NPs were reorganized, either dissolved, merged, or enlarged, to form an NNW structure, the composition of AgO x in an NNW structure of the current study results in the advantage of high thermal stability. The coverage of AgO x on an NNW structure can also help in the resistance to sulfidation, further oxidation, and other corrosion effects.…”

“…Such an NNW structure could be formed at room temperature and had the potential for the application to flexible optoelectronics. The fabrication of such an NNW structure required the following conditions: (1) UV light (>360 nm in wavelength) illumination onto the surface Ag NPs for generating hot electrons through intraband-related absorption, (2) Ag NPs on a slightly conductive template for hot electron migration, and (3) ambient moisture to produce a condensed surface water layer (a couple nm in thickness) for dissolving Ag + ions such that DLA can occur. − The sheet resistance and transparency of such a surface Ag NNW structure depended on the deposited Ag thickness at the beginning of fabrication . Usually, a thicker (thinner) Ag deposition led to lower (higher) sheet resistance and lower (higher) transparency.…”

“…Targeting at this application demand, recently this research team has demonstrated the formation of a transparent conductive surface Ag nano-network (NNW) structure directly on a template. 19 The formation of such an NNW structure was based on the generation and migration of hot electrons and the diffusion-limited aggregation (DLA) of Ag + ions induced by the intraband-related absorption of surface Ag NPs with ambient moisture. 20 DLA is a clustering process of diffuse particles to form an aggregation network.…”

“…26−28 The sheet resistance and transparency of such a surface Ag NNW structure depended on the deposited Ag thickness at the beginning of fabrication. 19 Usually, a thicker (thinner) Ag deposition led to lower (higher) sheet resistance and lower (higher) transparency. Under the condition of illuminating the Ag NPs of 1.6 nm in the deposition thickness on a GaN template with a 395 nm LED, the transmittance could be higher than 80%.…”

Formation Mechanism of a Surface Silver Nanonetwork and Its Electrical and Optical Properties

“…4 However, a Ag nanonetwork (NNW) with multiple connected Brownian trees (BTs) shows high transparency in these spectral ranges. 4 It has been reported that a Ag-nanowire (NW)-based NNW transparent conductor can be fabricated by piling up Ag NWs and welding their intersections to form a network structure. 5,6 Thus, the Ag NNWs have a potential application in flexible optoelectronics fields as a transparent conductor with low sheet resistance and high transparency.…”