Atomic/molecular layer deposition of Ni-terephthalate thin films

Chemical Bonding and Crystal Structure Schemes in Atomic/Molecular Layer Deposited Fe-Terephthalate Thin Films

Advanced deposition routes are vital for the growth of functional metal-organic thin films. The gas-phase atomic/molecular layer deposition (ALD/MLD) technique provides solvent-free and uniform nanoscale thin films with unprecedented thickness control and allows straightforward device integration. Most excitingly, the ALD/MLD technique can enable the in situ growth of novel crystalline metal-organic materials. An exquisite example is iron-terephthalate (Fe-BDC), which is one of the most appealing metal-organic framework (MOF) type materials and thus widely studied in bulk form owing to its attractive potential in photocatalysis, biomedicine, and beyond. Resolving the chemistry and structural features of new thin film materials requires an extended selection of characterization and modeling techniques. Here we demonstrate how the unique features of the ALD/MLD grown in situ crystalline Fe-BDC thin films, different from the bulk Fe-BDC MOFs, can be resolved through techniques such as synchrotron grazing-incidence X-ray diffraction (GIXRD), Mössbauer spectroscopy, and resonant inelastic X-ray scattering (RIXS) and crystal structure predictions. The investigations of the Fe-BDC thin films, containing both trivalent and divalent iron, converge toward a novel crystalline Fe(III)-BDC monoclinic phase with space group C2/c and an amorphous Fe(II)-BDC phase. Finally, we demonstrate the excellent thermal stability of our Fe-BDC 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.

ALD/MLD coating of patterned vertically aligned carbon nanotube micropillars with Fe-NH2TP hybrids

The creation of nanoscale organic-inorganic hybrid coatings with uniform architecture and high surface area, while maintaining their structural and morphological integrity, remains a significant challenge in the field. In this study, we present a novel solution, by utilizing Atomic/Molecular Layer Deposition (ALD/MLD) to coat patterned vertically aligned carbon nanotube micropillars with a conformal amorphous layer of Fe-NH₂TP, which is a trivalent iron complex complexed with 2-amino terephthalate. The effectiveness of the coating is verified through multiple analytical techniques, including high-resolution transmission electron microscopy, scanning transmission electron microscopy, grazing incidence X-ray diffraction, and Fourier transform infrared spectroscopy. The Fe-NH₂TP hybrid film exhibits hydrophobic properties, as confirmed by water contact angle measurements. Our findings contribute to advancing the understanding of how to grow high-quality one-dimensional materials using ALD/MLD and hold promise for future research in this area.