Gas Phase Electrodeposition: A Programmable Multimaterial Deposition Method for Combinatorial Nanostructured Device Discovery

Abstract

This article reports and applies a recently discovered programmable multimaterial deposition process to the formation and combinatorial improvement of 3D nanostructured devices. The gas-phase deposition process produces charged <5 nm particles of silver, tungsten, and platinum and uses externally biased electrodes to control the material flux and to turn deposition ON/OFF in selected domains. Domains host nanostructured dielectrics to define arrays of electrodynamic 10× nanolenses to further control the flux to form <100 nm resolution deposits. The unique feature of the process is that material type, amount, and sequence can be altered from one domain to the next leading to different types of nanostructures including multimaterial bridges, interconnects, or nanowire arrays with 20 nm positional accuracy. These features enable combinatorial nanostructured materials and device discovery. As a first demonstration, we produce and identify in a combinatorial way 3D nanostructured electrode designs that improve light scattering, absorption, and minority carrier extraction of bulk heterojunction photovoltaic cells. Photovoltaic cells from domains with long and dense nanowire arrays improve the relative power conversion efficiency by 47% when compared to flat domains on the same substrate.

Approaching Gas Phase Electrodeposition: Process and Optimization to Enable the Self‐Aligned Growth of 3D Nanobridge‐Based Interconnects

“…Some previously reported structures are shown. [ 15,16 ] Taking a closer look at the basic process, it becomes clear that gas phase electrodeposition shares some of the characteristics of electrodeposition in the liquid phase. However, it is a gas phase process with a much larger mean free path of the particles.…”

“…For example, it was used to grow straight metallic nanowire arrays whose height and density were adjusted to vary across the substrate which in turn were used as contacts in photo voltaic devices. [ 16 ] Others have used this technique to fabricate metallic nanostructures for surface enhanced Raman spectroscopy (SERS). [ 20,21 ] In any event, charged material continues to deposit into locations where charge dissipation can occur, leading to a growth of extended structures much like what is observed in the liquid phase based electrodeposition/plating.…”

“…No continued buildup of material on the insulating resist was reported as a result: b 2 ) SEM image where the process was used to prepare a planar (2D) patterned metallic layer containing Au nanoparticles; [ 15 ] b 3 ) SEM image where the process was used to prepare 2.5 D rod-like deposit containing Pt nanoparticles. [ 16 ] The introduced carrier gas appears to play an important role in determining the nanoparticle size and affects the uniformity of the growing structures. Experimentally, we fi nd that the use of a carrier gas leads to the production of smaller particles, which will be discussed later.…”

“…Different from prior implementations, [ 16 ] we used a carrier gas (N 2 ) in the current reactor. Experimentally, we fi nd that the use of a carrier gas leads to the production of smaller particles and growing structures that have an increased density and improved electrical conductivity.…”

“…Prior structures which contained larger particle had a lower packing density and had poor electrical and mechanical properties. [ 16 ] However, there is still room for improvement. The theoretical limit is 0.56 Ω (calculated using R = ρ l / A with l = 5 µm, crosssection A = π(0.25 µm) 2 , and ρ Au = 2.2 × 10 −8 Ω m).…”