Atomic Layer Deposition of Ruthenium Films from (Ethylcyclopentadienyl)(pyrrolyl)ruthenium and Oxygen
Ru films were grown by atomic layer deposition in the temperature range of 275―350°C using (ethylcyclopentadienyl)(pyrrolyl)ruthenium and air or oxygen as precursors on HF-etched Si, SiO 2 , ZrO 2 , and TiN substrates. Conformal growth was examined on three-dimensional silicon substrates with 20:1 aspect ratio. ZrO 2 promoted the nucleation of Ru most efficiently compared to other substrates, but the films roughened quickly on ZrO 2 with increasing film thickness. The minimum number of cycles required to form continuous and conductive metal layers could be decreased by increasing the length of the oxygen pulse. In order to obtain well-conducting Ru films growth to thicknesses of at least 8―…
Suppression of Forward Electron Injection from Ru(dcbpy)2(NCS)2 to Nanocrystalline TiO2 Film As a Result of an Interfacial Al2O3 Barrier Layer Prepared with Atomic Layer Deposition
Subnanometer-thick Al2O3 barrier layers on nanocrystalline TiO2 film were prepared with atomic layer deposition (ALD). The method allowed variation of barrier thicknesses at atomic resolution also deep in nanoporous structures, which makes it a superior method as compared to, e.g., sol−gel techniques. In this letter we present results on the effect of Al2O3 barriers of various thicknesses on forward electron injection in dye-sensitized solar cells. A decrease in the amplitude of the oxidized Ru(dcbpy)2(NCS)2 dye absorption signal due to singlet injection was observed already after one deposition cycle that produces a discontinuous layer with nominal thickness of 1 A. More than two layer coa…
Investigation of ZrO[sub 2]–Gd[sub 2]O[sub 3] Based High-k Materials as Capacitor Dielectrics
Atomic layer deposition (ALD) of ZrO 2 ―Gd 2 O 3 nanolaminates and mixtures was investigated for the preparation of a high permittivity dielectric material. Variation in the relative number of ALD cycles for constituent oxides allowed one to obtain films with controlled composition. Pure ZrO 2 films possessed monoclinic and higher permittivity cubic or tetragonal phases, whereas the inclusion of Gd 2 O 3 resulted in the disappearance of the monoclinic phase. Changes in phase composition were accompanied with increased permittivity of mixtures and laminates with low Gd content. Further increase in the lower permittivity Gd 2 O 3 content above 3.4 cat. % resulted in the decreased permittivity…
Atomic Layer Deposition and Characterization of Erbium Oxide-Doped Zirconium Oxide Thin Films
ZrO 2 films doped with Er 2 O 3 were grown by atomic layer deposition from tris(2,2,6,6-tetramethyl-3,5-heptanedionato)erbium, bis(methylcyclopentadienyl)methoxymethylzirconium, and ozone as precursors at 350°C. The erbium content was 1―5 cation %. The films were uniform in thickness. The ZrO 2 :Er 2 O 3 films were crystallized already in the as-deposited state. Upon annealing at 650°C, they were stabilized in the form of cubic or tetragonal polymorph of ZrO 2 . Enhancement in capacitance required intense crystallization that was observed when the film thickness exceeded 4.4 nm. The permittivity of the ZrO 2 :Er 2 O 3 films could reach 31. The capacitors based on the doped ZrO 2 possessed l…
Carbocatalytic Oxidative Dehydrogenative Couplings of (Hetero)Aryls by Oxidized Multi‐Walled Carbon Nanotubes in Liquid Phase
HNO3-oxidized carbon nanotubes catalyze oxidative dehydrogenative (ODH) carbon-carbon bond formation between electron-rich (hetero)aryls with O-2 as a terminal oxidant. The recyclable carbocatalytic method provides a convenient and an operationally easy synthetic protocol for accessing various benzofused homodimers, biaryls, triphenylenes, and related benzofused heteroaryls that are highly useful frameworks for material chemistry applications. Carbonyls/quinones are the catalytically active site of the carbocatalyst as indicated by model compounds and titration experiments. Further investigations of the reaction mechanism with a combination of experimental and DFT methods support the compet…
Plasma-Enhanced Atomic Layer Deposition of Silver Thin Films
Thermal properties of various silver precursors known in the literature were evaluated in order to discover which precursor is the most suitable one for plasma-enhanced atomic layer deposition (PEALD) of silver thin films. Ag(fod)(PEt3) (fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluorooctane-3,5-dionato) was found to be the best choice. Using Ag(fod)(PEt3) together with plasma-activated hydrogen, silver thin films were deposited at growth temperatures of 120–150 °C, and ALD-type saturative growth was achieved at 120–140 °C. At 120 °C, the growth rate was 0.03 nm per cycle. The plasma exposure time had also an effect on the growth rate: with shorter exposure times, the growth rate was lower over…