Conformal Ultrathin Film Metal–Organic Framework Analogues: Characterization of Growth, Porosity, and Electronic Transport

Abstract

Thin-film formation and transport properties of two copper-paddlewheel metal-organic framework (MOF) -based systems (MOF-14 and MOF-399) are investigated for their potential integration into electrochemical device architectures. Thin-film analogs of these two systems are fabricated by the sequential, alternating, solution-phase deposition of the inorganic and organic ligand precursors that result in conformal films via van der Merwe-like growth. Atomic force microscopy reveals smooth film morphologies with surface roughnesses determined by the underlying substrates and linear film growth of 1.4 and 2.2 nm per layer for the MOF-14 and MOF-399 systems, respectively. Electrochemical impedance spectroscopy is used to evaluate the electronic transport properties of the thin films, finding that the MOF-14 analog films demonstrate low electronic conductivity, while MOF-399 analog films are electronically insulating. The intrinsic porosities of these ultrathin MOF analog films are confirmed by cyclic voltammetry redox probe characterization using ferrocene. Larger peak currents are observed for MOF-399 analog films compared to MOF-14 analog films, which is consistent with the larger pores of MOF-399. The layer-by-layer deposition of these systems provides a promising route to incorporate MOFs as thin films with nanoscale thickness control and low surface roughness for electrochemical devices.

Tuning interfacial interactions for bottom‐up assembly of surface‐anchored metal‐organic frameworks to tailor film morphology and pattern surface features

“…Throughout 12 deposition cycles, the surMOF film thicknesses of the 0% and 25% ODTs were the same at a rate of 17 Å of film deposited per cycle, which is similar to previous findings for MOF‐14‐based films. [ 25 ] For the film deposited on the 25% ODT SAM, a conformal morphology similar to that of the 0% ODT sample was observed after the foundational first four deposition cycles. Subsequent film deposition on the 25% ODT SAM resulted in a changed film morphology that no longer displayed conformity with the underlying gold substrate.…”

“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25] To produce surface-anchored MOFs (surMOFs) with controlled thickness and surface coverage, films are commonly deposited by introducing the metal ion source and the organic linker in an alternating, sequential, solution-phase deposition process. [12][13][14][15][16][17][18][19][20][21][22][23][24][25] For the incorporation of nanostructured MOFs into device architectures, design rules must be developed that allow for the directed formation of surMOF film structures with regard to patterning features and tailoring morphological parameters, such as film roughness or grain size. Toward the development of these rules to control the structure of surMOF films, this study investigates the impact of modifying the chemical composition of the coating on the substrate that anchors the MOF and explores chemical patterning techniques to selectively direct film formation.…”

Integration of High‐Performance Cost‐Effective Copper‐Metal‐Organic‐Nanocluster‐based Gate Dielectric for Next‐Generation CMOS Applications

“…[ 30,31 ] The Cu 2+ metal node with open‐shell metal ion [ 29 ] , large radius, less electrical conductivity, high activation energy, charge density [ 31 ] , and single valency as compared with counterpart metal nodes provide large bandgap and excellent insulating properties to the Cu‐MOCs. [ 5,46,47 ] Small conjugated chains with a single COOH group attached to the benzene ring in m‐Toulic acid (MTA) organic linker [ 48 ] along with the presence of acetonitrile in small quantities as a guest solvent molecule aid in achieving the desired large bandgap and high dielectric constant in the Cu‐MOCs. [ 32,49 ] Also, without any intentional metal substitution as well as ligand functionalization in Cu‐MOCs, it displays its inherent large bandgap, which is imperative for high‐performance gate dielectric material for transistor applications.…”

“…On top of this, the measured crystal size of Cu‐MOCs nanocluster ≈1.6 nm as shown in Figure 3a confirms the existence of the highly compact nanocrystals arrangement and highly dense copper nanoclusters with nanosize pores location. The tight packing or minimal voids of nanoclusters leaves negligible space for guest molecules in slender pores’ location providing very low conduction [ 48 ] and high dielectric constant. [ 33 ] In the present case, the small amount of guest acetonitrile solvent molecule may be present in the Cu‐MOCs system during the low‐temperature drying process in the air.…”

Chemical Lift-Off Lithography of Metal and Semiconductor Surfaces

“…Accordingly, ultrathin monolayers fabricated from other metal and semiconductor surfaces may have chemical and physical properties that can be differentially exploited compared to bulk materials (e.g., magnetism, Ni, semiconductor, Ge) . Furthermore, functional metal monolayers could be used as supports for additional structural growth, enabling patterning of a diverse range of materials (e.g., nanoparticles, , surface-tethered metal-organic frameworks and multilayers, − and metal–organic chalcogenolate assemblies) on flexible and transparent substrates. Capabilities to create bimetallic and multimetallic layers and monolayers with CLL add an additional level of control to the generation and tailoring of supported metal monolayers with designed properties.…”