Influence of Precursor Density and Conversion Time on the Orientation of Vapor-Deposited ZIF-8

ZIF-8 was synthesized by subjecting ZnO thin films deposited via plasma-enhanced atomic layer deposition to a 2-methylimidazole vapor. The impact of the conversion time as well as the density and thickness of the ZnO precursor on the resulting ZIF-8 layers were investigated. Grazing Incidence X-ray diffraction reveals a preferred (100) or (111) orientation of the ZIF-8 crystals, depending on thickness and density of the precursor, and with a more prominent orientation at longer conversion times. The onset of crystallization occurs after 20 min of conversion for the less dense precursor, compared to 40 min for the denser one. The ZIF-8 thickness and roughness increase with conversion time. The final thickness of the ZIF-8 layer depends on the thickness and density of the precursor layer, and can be up to 15-fold higher than the precursor thickness

Aqueous Flow Reactor and Vapour-Assisted Synthesis of Aluminium Dicarboxylate Metal-Organic Frameworks with Tuneable Water Sorption Properties

Energy-efficient indoors temperature and humidity control can be realised by using the reversible adsorption and desorption of water in porous materials. Stable microporous aluminium-based metal-organic frameworks (MOFs) present promising water sorption properties for this goal. The development of synthesis routes that make use of available and affordable building blocks and avoid the use of organic solvents is crucial to advance this field. In this work, two scalable synthesis routes under mild reaction conditions were developed for aluminium-based MOFs: (1) in aqueous solutions using a continuous-flow reactor and (2) through the vapour-assisted conversion of solid precursors. Fumaric acid, its methylated analogue mesaconic acid, as well as mixtures of the two were used as linkers to obtain polymorph materials with tuneable water sorption properties. The synthesis conditions determine the crystal structure and either the MIL-53 or MIL-68 type structure with square-grid or kagome-grid topology, respectively, is formed. Fine-tuning resulted in new MOF materials thus far inaccessible through conventional synthesis routes. Furthermore, by varying the linker ratio, the water sorption properties can be continuously adjusted while retaining the sigmoidal isotherm shape advantageous for heat transformation and room climatisation applications

Integrated cleanroom process for the vapor-phase deposition of large-area zeolitic imidazolate framework thin films

Robust and scalable thin-film deposition methods are key to realize the potential of metal-organic frameworks (MOFs) in electronic devices. Here, we report the first integration of the chemical vapor deposition (CVD) of MOF coatings in a custom reactor within a cleanroom setting. As a test case, the MOF-CVD conditions for the zeolitic imidazolate framework-8 are optimized to enable smooth, pinhole-free, and uniform thin films on full 200 mm wafers under mild conditions. The single-chamber MOF-CVD process and the impact of the deposition parameters are elucidated via a combination of in situ monitoring and ex situ characterization. The resulting process guidelines will pave the way for new MOF-CVD formulations and a plethora of MOF-based devices

Molecular Layer Deposition of Zeolitic Imidazolate Framework‑8 Films [Dataset]

24 pages. -- Methods. -- Summary of some of the reported vapor-phase processes for the layer-by-layer deposition of MOFs6. -- Synchrotron GIXRD reciprocal space maps of direct ZIF-8 MLD show crystallinity even at a very low number of cycles. -- Vapor pressure determination of 2-methylimidazole (HmIM) via thermogravimetry: Knudsen effusion method. -- Direct ZIF-8 MLD linker exposure times. -- Direct ZIF-8 MLD films on Si are pinhole-free. -- AFM image of a MOF-CVD ZIF-8 “layer”, i.e., scattered crystallites. -- Photograph of a 200 mm wafer with 30 MLD ZIF-8 cycles and the corresponding 100-point ellipsometry thickness mapping. -- Film characterization of direct ZIF-8 MLD with a missing water pulse. -- Effect of no water pulses in direct ZIF-8 MLD. -- Direct ZIF-8 MLD with water completely or partially substituted by methanol. -- Humidified conditions HmIM post-deposition treatment of direct ZIF-8 MLD. -- HAXPES survey scans. -- HAXPES peak fitting. -- Study of aging effect due to exposure to atmospheric gasses. -- Direct ZIF-8 MLD on (100) oriented supercrystals. -- ZIF-67 crystals powder characterization. -- SEM images ZIF-67. -- Direct ZIF-8 MLD schematic representation of the protocol. -- Two-step ZIF-8 MLD schematic representation of the protocol. -- The optimized temperature gradient in the MOF-MLD reactor. -- MOF-MLD optimization of the temperature gradient. -- Ellipsometry of HmIM post-deposition treatment and activation in two-step ZIF-8 MLD. -- Ellipsometric porosimetry as a function of time. -- Supporting Information References.Vapor-phase film deposition of metal–organic frameworks (MOFs) would facilitate the integration of these materials into electronic devices. We studied the vapor-phase layer-by-layer deposition of zeolitic imidazolate framework 8 (ZIF-8) by consecutive, self-saturating reactions of diethyl zinc, water, and 2-methylimidazole on a substrate. Two approaches were compared: (1) Direct ZIF-8 “molecular layer deposition” (MLD), which enables a nanometer-resolution thickness control and employs only self-saturating reactions, resulting in smooth films that are crystalline as-deposited, and (2) two-step ZIF-8 MLD, in which crystallization occurs during a postdeposition treatment with additional linker vapor. The latter approach resulted in a reduced deposition time and an improved MOF quality, i.e., increased crystallinity and probe molecule uptake, although the smoothness and thickness control were partially lost. Both approaches were developed in a modified atomic layer deposition reactor to ensure cleanroom compatibility.Peer reviewe

Chemical Vapor Deposition and High-Resolution Patterning of a Highly Conductive Two-Dimensional Coordination Polymer Film

Crystalline coordination polymers with high electrical conductivities and charge carrier mobilities might open new opportunities for electronic devices. However, current solvent-based synthesis methods hinder compatibility with microfabrication standards. Here, we describe a solvent-free chemical vapor deposition method to prepare high-quality films of the two-dimensional conjugated coordination polymer Cu-BHT (BHT = benzenehexanothiolate). This approach involves the conversion of a metal oxide precursor into Cu-BHT nanofilms with a controllable thickness (20-85 nm) and low roughness (<10 nm) through exposure to the vaporized organic linker. Moreover, the restricted metal ion mobility during the vapor-solid reaction enables high-resolution patterning via both bottom-up lithography, including the fabrication of micron-sized Hall bar and electrode patterns to accurately evaluate the conductivity and mobility values of the Cu-BHT films

Integrated MLD supercycle for the direct deposition of zeolitic imidazolate framework films for integrated applications

status: publishe

From wet-lab to cleanroom: an integrated ALD-CVD process for the large-area deposition of ultrathin zeolitic imidazolate framework films

From wet-lab to cleanroom: an integrated ALD-CVD process for the large-area deposition of ultrathin zeolitic imidazolate framework films Alexander John Cruz*, Ivo Stassen*, Rob Ameloot Robust and scalable thin film deposition methods are key to realize the potential of the combined nanoporosity and hybrid organic-inorganic chemical modularity of metal-organic frameworks (MOFs) in electronic devices [1]. Here, we report the first fully integrated and highly-controllable vapor deposition process for MOFs (MOF-CVD) [2], as recently implemented in a 200 mm modified commercial ALD reactor. The process consists of two-steps: (1) atomic layer deposition for the metal oxide precursor, and (2) subsequent stop-flow reaction with the sublimated organic linker at elevated pressure and non-isothermal temperature conditions. As our selected test case, the optimized MOF-CVD process for ZIF-8 (zinc-2-methylimidazolate) showcases smooth, pinhole-free and large-area uniform ultrathin films that are highly nanoporous. Our process distinguishes itself from previous works as it permits single-chamber deposition, under mild conditions and without the need for a separate post-deposition crystallization steps; to the best of our knowledge, the only MOF thin film deposited via an integrated ALD-CVD method on large area substrates to date. Through its implementation in a single-chamber, the MOF-CVD reaction mechanism was studied using a combination of time-resolved in situ ellipsometry and QCM monitoring, and ex situ thin film characterization techniques. We will present the impact of relevant deposition parameters in the form of a MOF-CVD deposition-rate process chart. Our method shows great promise to ease the manufacturing of devices based on MOF thin films, as will demonstrated by a sneak preview of ongoing application projects. [1] Stassen, I., Ameloot R., et al. An updated roadmap for the integration of metal–organic frameworks with electronic devices and chemical sensors. Chem Soc Rev 46, 3185–3241 (2017). [2] Stassen, I., Ameloot R., et al. Chemical vapour deposition of zeolitic imidazolate framework thin films. Nat. Mater. 15, 304–310 (2016).status: Published onlin

Nanoporous Metal-Organic Framework Thin Films Prepared Directly from Gaseous Precursors by Atomic and Molecular Layer Deposition: Implications for Microelectronics

Atomic/molecular layer deposition (ALD/MLD) allows for the direct gas-phase synthesis of crystalline metal-organic framework (MOF) thin films. Here, we show for the first time using krypton and methanol physisorption measurements that ALD/MLD-fabricated copper 1,4-benzenedicarboxylate (Cu-BDC) ultrathin films possess accessible porosity matching that of the corresponding bulk MOF

Patterned growth of zeolitic imidazolate frameworks by solvent-free transformation of preprinted metal oxide patterns

status: publishe