Molecularly-induced roughness and oxidation in cobalt/organodithiol/cobalt nanolayers synthesized by sputter-deposition and molecular sublimation

Integrating interfacial molecular nanolayers (MNL) with inorganic nanolayers is of interest for understanding processing-structure/chemistry correlations in hybrid nanolaminates. Here, we report the synthesis of Co/biphenyldithiol (BPDT)/Co nanolayer sandwiches by metal sputter-deposition and molecular sublimation. The density and surface roughness of the Co layers deposited on the native oxide are invariant with the Ar pressure pAr during deposition. In contrast, the Co layer roughness rCo deposited on top of the BPDT MNL increases with pAr, and correlates with a higher degree of Co oxidation. Increased roughening is attributed to MNL-accentuated self-shadowing of low mobility Co atoms at high pAr, which consequently increases Co oxidation. These results indicating MNL-induced effects on the morphology and chemistry of the inorganic layers should be of importance for tailoring nanolayered hybrid interfaces and laminates.

Iron-Based Oxygen Scavengers on Mesoporous Silica Nanospheres

Iron-based materials are among the most commonly used oxygen scavengers. Here, we investigated the mesoporous silica nanosphere (MSN)-supported iron-based scavengers, such as FeO_x nanoparticles and different atomic layer deposition (ALD) coatings (FeO_x and Fe). We found that the scavenger performance is a result of a complex interplay between available Brunauer-Emmett-Teller surface area and the scavenger composition, with the combination of infiltrated nanoparticles and Fe-ALD coating resulting in the best performance. When the glucose-based treatment of MSN is used to further enhance oxygen scavenging capacity, Fe-ALD coating yields the best performance, with a high oxygen adsorption capacity of 126.8 mL/g. ALD deposition of Fe represents a versatile method to introduce Fe-based oxygen scavengers onto different supports, and it can facilitate the integration of scavengers with different types of packaging, as the deposition can be performed at a low temperature of 150 °C.

Tuning the Porosity of Piezoelectric Zinc Oxide Thin Films Obtained from Molecular Layer-Deposited "Zincones"

Porous zinc oxide (ZnO) thin films were synthesized via the calcination of molecular layer-deposited (MLD) "zincone" layers. The effect of the MLD process temperature (110 °C, 125 °C) and of the calcination temperature (340 °C, 400 °C, 500 °C) on the chemical, morphological, and crystallographic properties of the resulting ZnO was thoroughly investigated. Spectroscopic ellipsometry reveals that the thickness of the calcinated layers depends on the MLD temperature, resulting in 38-43% and 52-56% of remaining thickness for the 110 °C and 125 °C samples, respectively. Ellipsometric porosimetry shows that the open porosity of the ZnO thin films depends on the calcination temperature as well as on the MLD process temperature. The maximum open porosity of ZnO derived from zincone deposited at 110 °C ranges from 14.5% to 24%, rising with increasing calcination temperature. Compared with the 110 °C samples, the ZnO obtained from 125 °C zincone yields a higher porosity for low calcination temperatures, namely 18% for calcination at 340 °C; and up to 24% for calcination at 500 °C. Additionally, the porous ZnO thin films were subjected to piezoelectric measurements. The piezoelectric coefficient, d₃₃, was determined to be 2.8 pC/N, demonstrating the potential of the porous ZnO as an, e.g., piezoelectric sensor or energy harvester.

Atomic/molecular layer deposition of Ni-terephthalate thin films

Atomic/molecular layer deposition (ALD/MLD) is currently strongly emerging as an intriguing route for novel metal-organic thin-film materials. This approach already covers a variety of metal and organic components, and potential applications related to e.g. sustainable energy technologies. Among the 3d metal components, nickel has remained unexplored so far. Here we report a robust and efficient ALD/MLD process for the growth of high-quality nickel terephthalate thin films. The films are deposited from Ni(thd)₂ (thd: 2,2,6,6-tetramethyl-3,5-heptanedionate) and terephthalic acid (1,4-benzenedicarboxylic acid) precursors in the temperature range of 180-280 °C, with appreciably high growth rates up to 2.3 Å per cycle at 200 °C. The films are amorphous but the local structure and chemical state of the films are addressed based on XRR, FTIR and RIXS techniques.

Organic-Component Dependent Crystal Orientation and Electrical Transport Properties in ALD/MLD Grown ZnO-Organic Superlattices

Two series of ZnO-organic superlattice thin films are fabricated with systematically controlled frequencies of monomolecular hydroquinone (HQ) or terephthalic acid (TPA) based organic layers within the ZnO matrix using the atomic/molecular layer deposition (ALD/MLD) technique. The two different organic components turn the film orientation to different directions and affect the electrical transport properties differently. While the TPA layers enhance the c-axis orientation of the ZnO layers and act as electrical barriers depressing the electrical conductivity even in low concentrations, adding the HQ layers enhances the a-axis orientation and initially increases the carrier concentration, effective mass, and electrical conductivity. The work thus demonstrates the intriguing but little exploited role of the organic component in controlling the properties of the inorganic matrix in advanced layer-engineered inorganic-organic superlattices.

Flexible Thermoelectric Materials and Generators: Challenges and Innovations

The urgent need for ecofriendly, stable, long-lifetime power sources is driving the booming market for miniaturized and integrated electronics, including wearable and medical implantable devices. Flexible thermoelectric materials and devices are receiving increasing attention, due to their capability to convert heat into electricity directly by conformably attaching them onto heat sources. Polymer-based flexible thermoelectric materials are particularly fascinating because of their intrinsic flexibility, affordability, and low toxicity. There are other promising alternatives including inorganic-based flexible thermoelectrics that have high energy-conversion efficiency, large power output, and stability at relatively high temperature. Herein, the state-of-the-art in the development of flexible thermoelectric materials and devices is summarized, including exploring the fundamentals behind the performance of flexible thermoelectric materials and devices by relating materials chemistry and physics to properties. By taking insights from carrier and phonon transport, the limitations of high-performance flexible thermoelectric materials and the underlying mechanisms associated with each optimization strategy are highlighted. Finally, the remaining challenges in flexible thermoelectric materials are discussed in conclusion, and suggestions and a framework to guide future development are provided, which may pave the way for a bright future for flexible thermoelectric devices in the energy market.

On the transformation of "zincone"-like into porous ZnO thin films from sub-saturated plasma enhanced atomic layer deposition

The synthesis of nanoporous ZnO thin films is achieved through annealing of zinc-alkoxide ("zincone"-like) layers obtained by plasma-enhanced atomic layer deposition (PE-ALD). The zincone-like layers are deposited through sub-saturated PE-ALD adopting diethylzinc and O₂ plasma with doses below self-limiting values. Nanoporous ZnO thin films were subsequently obtained by calcination of the zincone-like layers between 100-600 °C. Spectroscopic ellipsometry (SE) and X-ray diffraction (XRD) were adopted in situ during calcination to investigate the removal of carbon impurities, development of controlled porosity, and formation and growth of ZnO crystallites. The layers developed controlled nanoporosity in the range of 1-5%, with pore sizes between 0.27 and 2.00 nm as measured with ellipsometric porosimetry (EP), as a function of the plasma dose and post-annealing temperature. Moreover, the crystallinity and crystallite orientation could be tuned, ranging from a powder-like to a (100) preferential growth in the out-of-plane direction, as measured by synchrotron-radiation grazing incidence XRD. Calcination temperature ranges were identified in which pore formation and subsequent crystal growth occurred, giving insights in the manufacturing of nanoporous ZnO from Zn-based hybrid materials.

Mesoporous ZnO thin films obtained from molecular layer deposited “zincones”

The synthesis of MLD-derived mesoporous ZnO with 20% of porosity is demonstrated and studied by advanced in situ characterization techniques.

Iron-Terephthalate Coordination Network Thin Films Through In-Situ Atomic/Molecular Layer Deposition

Iron terephthalate coordination network thin films can be fabricated using the state-of-the-art gas-phase atomic/molecular layer deposition (ALD/MLD) technique in a highly controlled manner. Iron is an Earth-abundant and nonhazardous transition metal, and with its rich variety of potential applications an interesting metal constituent for the inorganic-organic coordination network films. Our work underlines the role of the metal precursor used when aiming at in-situ ALD/MLD growth of crystalline inorganic-organic thin films. We obtain crystalline iron terephthalate films when FeCl₃ is employed as the iron source whereas depositions based on the bulkier Fe(acac)₃ precursor yield amorphous films. The chemical composition and structure of the films are investigated with GIXRD, XRR, FTIR and XPS.

Characterization of nano-porosity in molecular layer deposited films

A correlation was found between the MLD process conditions, the open-porosity relative content, and the degradation of metalcone layers.

Bioactive titaminates from molecular layer deposition

Gas phase deposited films with amino acids by molecular layer deposition prove suitable as surfaces for cell growth.

Atomic and molecular layer deposition: off the beaten track

ALD archetype and deviations from it.

ALD/MLD processes for Mn and Co based hybrid thin films

New types of transition metal–organic hybrid thin films are fabricated with the emerging atomic/molecular layer deposition (ALD/MLD) technique through sequential gas-surface reactions from Mn(thd)₃, Co(thd)₂, Co(acac)₃ and terephthalic acid (1,4-benzenedicarboxylic acid) precursors.

Substantially enhanced Raman signal for inorganic–organic nanocomposites by ALD-TiO2 capping

Atomic layer deposition (ALD) enables conformal coating of various surface architectures with high-quality ultrathin films.

ALD/MLD fabrication of luminescent Eu-organic hybrid thin films using different aromatic carboxylic acid components with N and O donors

Atomic/molecular layer deposition (ALD/MLD) processes based on Eu(thd)₃ and three different aromatic organic acids with O and N donors as precursors are systematically investigated for the growth of Eu-based inorganic–organic thin-film phosphors.