Drop-on-demand inkjet printing of functional inks has received a great deal of attention for realizing printed electronics, rapidly prototyped structures, and large-area systems. Although this method of printing promises high processing speeds and minimal substrate contamination, the performance of this process is often limited by the rheological parameters of the ink itself. Effective ink design must address a myriad of issues, including suppression of the coffee-ring effect, proper drop pinning on the substrate, long-term ink reliability, and, most importantly, stable droplet formation, or jettability. In this work, by simultaneously considering optimal jetting conditions and ink rheology, we develop and experimentally validate a jettability window within the capillary number−Weber number space. Furthermore, we demonstrate the exploitation of this window to adjust nanoparticle-based ink rheology predictively to realize a jettable ink. Finally, we investigate the influence of mass loading on jettability to establish additional practical limitations on nanoparticle ink design.
Low-temperature, plasma-free atomic layer etching (ALE) of Pd 0 is explored. A vacuum ultraviolet (VUV) light source (115 < λ < 400 nm) is used in conjunction with a controlled O 2 gas exposure to produce PdO x at 100 °C. The amount of PdO x that forms is dependent on the duration of coexposure of O 2 at 1 Torr and VUV irradiation. A minimum coexposure time of 1 min is required to partially oxidize 2 nm Pd while 3 min is required for 20 nm Pd films, which is verified in situ using X-ray photoelectron spectroscopy (XPS). Formic acid vapor is used to complete the etch cycle, which does not etch Pd 0 and only removes the PdO x that forms. Repeated etch cycles on a ∼20 nm Pd thin film yield an etch rate of 2.81 Å/cycle, which is characterized in situ using XPS and ex situ using X-ray reflectivity. The morphology of the Pd 0 surface does not change appreciably with etching. The only observed effect of repeated ALE cycles is a reduction in the roughness of the Pd film, which is measured using atomic force microscopy.
The
high-voltage, cobalt-free spinel cathode LiNi0.5Mn1.5O4 (LNMO) is receiving extensive attention
for lithium-ion batteries due to its low cost, high operating voltage
and energy density, superior power density, and good thermal stability.
However, its high operating voltage hampers its stability with commercial
electrolytes and makes its practical viability challenging. We present
here a Mn-rich LNMO cathode to encourage the disordering of Mn and
Ni in the lattice and the incorporation of a small dose of Fe into
Mn-rich LNMO (Fe-LNMO) to improve the cycling stability. The introduction
of Fe further increases the cation disorder between Mn and Ni, thus
enabling a better rate capability. Electron energy loss spectroscopy
analysis indicates that Fe is concentrated on the surface, and X-ray
photoelectron spectroscopy analysis shows that Fe-LNMO alleviates
the aggressive reaction between the cathode surface and the electrolyte,
thus stabilizing the interface and cycle life. Furthermore, a full
cell assembled with a graphite anode with an areal capacity of 3 mA
h cm–2 displays a capacity retention of 90% over
300 cycles. The present work demonstrates an effective way to promote
cation disordering and lower the surface reactivity of LNMO with the
electrolyte, thereby enhancing the conductivity, stabilizing the cathode–electrolyte
interphase, and making LNMO promising for practical applications.
The authors report the deposition of 4.5-nm-thick cobalt (II) oxide on SiO2/Si(001) and MgO(001) substrates at 180–270 °C by atomic layer deposition using bis(N-tert-butyl-N′-ethylpropionamidinato) cobalt (II) and water as coreactants. The resulting CoO film is smooth and carbon-free. CoO can be reduced to Co metal using hydrogen or deuterium gas at 400–500 °C in a vacuum furnace, but the high temperature processing causes dewetting, leading to discontinuous Co metal islands rather than continuous films. Two low temperature (∼200 °C) reduction methods are reported: deuterium atom reduction and the use of an O-scavenging Al metal film. The low temperature methods can suppress dewetting to a large extent, and the resulting metallic cobalt film is smooth and continuous.
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