Nanoimaging of Organic Charge Retention Effects: Implications for Nonvolatile Memory, Neuromorphic Computing, and High Dielectric Breakdown Devices

While a large variety of organic and molecular materials have been found to exhibit charge memory effects, the underlying mechanism is not well-understood, which hinders rational device design. Here, we study the charge retention mechanism of a nanoscale memory system, an organic monolayer on a silicon substrate, with Au nanoparticles on top serving as the electrical contact. Combining scanning probe imaging/manipulation and density functional simulations, we observe stable charge retention effects in the system and attributed it to polaron effects at the amine functional groups. Our findings can pave the way for applications in nonvolatile memory, neuromorphic computing, and high dielectric breakdown devices

Atomic layer deposition of Ru/RuO2Thin films studied by in situ infrared spectroscopy

The deposition of ruthenium thin films is investigated using a newly synthesized precursor (cyclopentadienyl ethylruthenium dicarbonyl, Ru(Cp)(CO)2 Et) and O2 gas as reactants. The conditions to achieve self-terminated surface reactions (sample temperature, precursor pulse length and precursor gas pressure) are investigated and the resulting composition, conductivity, and surface morphology are determined during/after deposition on hydrogen-terminated silicon (111) surfaces using in situ FTIR, and ex situ Rutherford back scattering, X-ray photoelectron spectroscopy, and atomic force microscopy. Higher growth rates (∼1.5-3 A˚ ) are obtained compared to those typical of ALD of metals (∼0.5-1 A˚ ), under conditions of saturation, i.e., through self-terminated surface reactions. Infrared absorption measurements reveal that bridged CO formed by the self-reaction of Ru(Cp)(CO)2 Et leads to surface passivation, thus terminating the precursor self-reaction. They also show that, under these “saturation” growth conditions, metallic Ru develops during the early stage of deposition (1-5 cycles), and RuO2 is observed later in the growth. The deposition rate is linear with cycles after an initially slow nucleation stage and the film becomes metallic after∼22 cycles. Thick films (∼45 nm) grown with short pulses produce metallic polycrystalline ruthenium with hcp structure

Chemical Modification Mechanisms in Hybrid Hafnium Oxo-methacrylate Nanocluster Photoresists for Extreme Ultraviolet Patterning

The potential implementation of extreme ultraviolet (EUV) lithography into next generation device processing is bringing urgency to identify resist materials that optimize EUV lithographic performance. Inorganic/organic hybrid nanoparticles or clusters constitute a promising new class of materials, with high EUV sensitivity from the core and tunable chemistry through the coordinating ligands. Development of a thorough mechanistic understanding of the solubility switching reactions in these materials is an essential first step toward their implementation in patterning applications but remains challenging due to the complexity of their structures, limitations in EUV sources, and lack of rigorous in situ characterization. Here, we report a mechanistic investigation of the solubility switching reactions in hybrid clusters comprising a small HfOx core capped with a methacrylic acid ligand shell (HfMAA). We show that EUV-induced reactions can be studied by performing in situ infrared (IR) spectroscopy of electron-irradiated films using a variable energy electron gun. Combining additional ex situ metrology, we track the chemical evolution of the material at each stage of a typical resist processing sequence. For instance, we find that a cross-linking reaction initiated by decarboxylation of the methacrylate ligands under electron irradiation constitutes the main solubility switching mechanism, although there are also chemical changes imparted by a typical post application bake (PAB) step alone. Lastly, synchrotron-based IR microspectroscopy measurements of EUV-irradiated HfMAA films enable a comparison of reactions induced by EUV vs electron beam irradiation of the same resist material, yielding important insight into the use of electron beam irradiation as an experimental model for EUV exposure

Unusual infrared-absorption mechanism in thermally reduced graphene oxide

Infrared absorption of atomic and molecular vibrations in solids can be affected by electronic contributions through non-adiabatic interactions, such as the Fano effect. Typically, the infrared-absorption lineshapes are modified, or infrared-forbidden modes are detectable as a modulation of the electronic absorption. In contrast to such known phenomena, we report here the observation of a giant-infrared-absorption band in reduced graphene oxide, arising from the coupling of electronic states to the asymmetric stretch mode of a yet-unreported structure, consisting of oxygen atoms aggregated at the edges of defects. Free electrons are induced by the displacement of the oxygen atoms, leading to a strong infrared absorption that is in phase with the phonon mode. This new phenomenon is only possible when all other oxygen-containing chemical species, including hydroxyl, carboxyl, epoxide and ketonic functional groups, are removed from the region adjacent to the edges, that is, clean graphene patches are presentclose19719