Liquid Atomic Layer Deposition Research Articles

Liquid atomic layer deposition as emergent technology for the fabrication of thin films.

Atomic layer deposition (ALD) is widely recognized as a unique chemical vapor deposition technique for the fabrication of thin films with high conformality and precise thickness control down to the Ångstrom level, thereby allowing surface and interface nanoengineering. However, several challenges such as the availability of chemical precursors for ALD and the use of vacuum conditions have hampered its widespread adoption and scalability for mass production. In recent years, the liquid phase homolog of ALD, liquid atomic layer deposition (LALD), has emerged as a much simpler and versatile strategy to overcome some of the current constraints of ALD. This perspective describes the different strategies that have been explored to achieve conformality and sub-nanometer thickness control with LALD, as well as the current challenges it faces to become a part of the thin-film community toolbox, in particular its automation and compatibility with different types of substrates. In this regard, the important role of LALD as complementary technology to ALD is emphasized by comparing the different pathways to deposit the same material and the precursors used to do so.

Fabrication and photoelectrochemical properties of silicon nanowires/g-C3N4 core/shell arrays

A photoelectrochemical (PEC) cell made of metal-free carbon nitride (g-C3N4) @siliconnanowire(Si NW) arrays (denoted as Si NWs/g-C3N4) is presented in this work. The as-prepared photoelectrodes with different mass contents of g-C3N4 have been synthesized via a metal-catalyzed electroless etching (MCEE), liquid atomic layer deposition (LALD) and annealing methods. The amount of g-C3N4 on the Si NW arrays can be controlled by tuning the concentration of the cyanamide solution used in the LALD procedure. The dense and vertically aligned Si NWs/g-C3N4 core/shell nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). In comparison with FTO/g-C3N4 and Si NW samples, the Si NWs/g-C3N4 samples showed significantly enhanced photocurrents over the entire potential sweep range. Electrochemical impedance spectroscopy (EIS) was conducted to investigate the properties of the charge transfer process, and the results indicated that the enhanced PEC performance may be due to the increased photo-generated interfacial charge transfer between the Si NWs and g-C3N4. The photocurrent density reached 45μA/cm2 under 100mW/cm2 (AM 1.5G) illumination at 0V (vs. Pt) in neutral Na2SO4 solution (pH∼7.62). Finally, a systematical PEC mechanism of the Si NWs/g-C3N4 was proposed.

Band structure and decay channels of thorium‐229 low‐lying isomeric state for ensemble of thorium atoms adsorbed on calcium fluoride

AbstractThe results are presented on the study of the electronic structure of thorium atoms adsorbed by the liquid atomic layer deposition from aqueous solution of thorium nitrate on the surface of CaF2. The chemical state of the atoms and the change of the band structure in the surface layers of Th/CaF2 system on CaF2 substrate were investigated by XPS and REELS techniques. It was found that REELS spectra for Th/CaF2 system include peaks in the region of low energy losses (3‐7 eV) which are missing in the similar spectra for pure CaF2. It is concluded that the presence of the observed features in the REELS spectra is associated with the chemical state of thorium atoms and is caused by the presence of uncompensated chemical bonds at the Th/CaF2 interface, and, therefore, by the presence of unbound 6d‐ and 7s‐electrons of thorium atoms. Assuming the equivalence of the electronic configuration of thorium‐229 and thorium‐232 atoms, an estimate was made on the time decay of the excited state of thorium‐229 nuclei through the channel of the electron conversion. It was found that the relaxation time is about 40 μs for 6d‐electrons, and about 1 μs for 7s‐electrons. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)