Molecular layer deposition of photoactive metal-naphthalene hybrid thin films

Conformal Zn-Benzene Dithiol Thin Films for Temperature-Sensitive Electronics Grown via Industry-Feasible Atomic/Molecular Layer Deposition Technique

The atomic/molecular layer deposition (ALD/MLD) technique combining both inorganic and organic precursors is strongly emerging as a unique tool to design exciting new functional metal-organic thin-film materials. Here, this method is demonstrated to work even at low deposition temperatures and can produce highly stable and conformal thin films, fulfilling the indispensable prerequisites of today's 3D microelectronics and other potential industrial applications. This new ALD/MLD process is developed for Zn-organic thin films grown from non-pyrophoric bis-3-(N,N-dimethylamino)propyl zinc [Zn(DMP)2] and 1,4-benzene dithiol (BDT) precursors. This process yields air-stable Zn-BDT films with appreciably high growth per cycle (GPC) of 4.5 Å at 60 °C. The Zn/S ratio is determined at 0.5 with Rutherford backscattering spectrometry (RBS), in line with the anticipated (Zn─S─C6H6─S─)n bonding scheme. The high degree of conformality is shown using lateral high-aspect-ratio (LHAR) test substrates; scanning electron microscopy (SEM) analysis shows that the film penetration depth (PD) into the LHAR structure with cavity height of 500 nm is over 200 µm (i.e., aspect-ratio of 400). It is anticipated that the electrically insulating metal-organic Zn-BDT thin films grown via the solvent-free ALD/MLD technique, can be excellent barrier layers for temperature-sensitive and flexible electronic devices.

Excitation Wavelength Engineering through Organic Linker Choice in Luminescent Atomic/Molecular Layer Deposited Lanthanide-Organic Thin Films

We demonstrate multiple roles for the organic linker in luminescent lanthanide-organic thin films grown with the strongly emerging atomic/molecular layer deposition technique. Besides rendering the hybrid thin film mechanically flexible and keeping the lanthanide nodes at a distance adequate to avoid concentration quenching, the organic moieties can act as efficient sensitizers for the lanthanide luminescence. We investigate six different aromatic organic precursors in combination with Eu3+ ions to reveal that by introducing different nitrogen species within the aromatic ring, it is possible to extend the excitation wavelength area from the UV range to the visible range. This opens new horizons for the application space of these efficiently photoluminescent thin-film materials.

Aromatic sensitizers in luminescent hybrid films

Atomic layer deposition offers a unique set of design possibilities due to the vast range of metal and organic precursors that can be used and combined. In this work, we have combined lanthanides with aromatic aids as strongly absorbing sensitizers to form highly luminescent thin films. Terephthalic acid is used as a base sensitizer, absorbing shorter wavelengths than 300 nm. The absorption range is extended towards the near-UV and blue range by increasing the aromatic system and adding functional groups that have strong red-shifting effects. While terbium and europium provide green and red emission, yttrium allows emission from the sensitizer itself spanning the whole color range from purple, blue and green to red. Many organic dye molecules show very high luminescence quantum yields and several of the molecules and materials investigated in this work show bright luminescence.

Photoactive Zr-aromatic hybrid thin films made by molecular layer deposition

The principle of antimicrobial photodynamic therapy (PDT) is appealing because it can be controlled by an external light source and possibly the use of durable materials. However, to utilise such surfaces requires a process for their production that allows for coating on even complex geometries. We have therefore explored the ability of the emerging molecular layer deposition (MLD) technique to produce and tune PDT active materials. This study demonstrates how the type of aromatic ligand influences the optical and antimicrobial properties of photoactive Zr-organic hybrid thin films made by MLD. The three aromatic dicarboxylic acids: 2,5-dihydroxy-1,4-benzenedicarboxylic acid, 2-amino-1,4-benzenedicarboxylic acid and 2,6-naphthalenedicarboxylic acid have been combined with ZrCl₄ to produce hybrid coatings. The first system has not been previously described by MLD and is therefore more thoroughly investigated using in situ quartz crystal microbalance (QCM), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. The antibacterial phototoxic effects of Zr-organic hybrids have been explored in the Staphylococcus aureus bacteria model using a UVA/blue light source. Films based on the 2,6-naphthalenedicarboxylic acid linker significantly reduced the number of viable bacteria by 99.9%, while no apparent activity was observed for the two other photoactive systems. Our work thus provides evidence that the MLD technique is a suitable tool to produce high-quality novel materials for possible applications in antimicrobial PDT, however it requires a careful selection of aromatic ligands used to construct photoactive materials.

Photoactive organic–inorganic hybrid thin films for potential use in antimicrobial photodynamic therapy (PDT) were fabricated based on Zr clusters and three different aromatic dicarboxylic acid linkers using the molecular layer deposition (MLD) technique.

Low-temperature ALD/MLD growth of alucone and zincone thin films from non-pyrophoric precursors

The combined atomic/molecular layer deposition (ALD/MLD) technique is emerging as a state-of-the-art synthesis route for new metal-organic thin-film materials with a multitude of properties by combining those of the inorganic...