Structure, Oxygen Content and Electric Properties of Titanium Nitride Electrodes in TiNx/La:HfO2/TiNx Stacks Grown by PEALD on SiO2/Si.

This work reports experimental results of the quantitative determination of oxygen and band gap measurement in the TiNx electrodes in planar TiNx top/La:HfO2/TiNx bottom MIM stacks obtained by plasma enhanced atomic layer deposition on SiO2. Methodological aspects of extracting structural and chemical information from (scanning) transmission electron microscopy imaging (bright field and high angular annular dark field), energy dispersive X-ray spectrometry and electron energy loss spectroscopy are thoroughly considered. The study shows that the oxygen concentration is higher in the TiNxOy bottom electrode (about 14.2 ± 0.1 at. %) compared to the TiNxOy top electrode (about 11.4 ± 0.5 at. %). The following average stoichiometric formulas are TiN0.52O0.20 top and TiN0.54O0.26 bottom for top and bottom electrodes, respectively. The amount of oxygen incorporated into TiNx during PEALD because of oxygen impurities in the plasma is minor compared to that because of diffusion from SiO2 and HfO2. This asymmetry, together with results on a sample grown on a Si substrate, shows that incorporating oxygen impurity from the plasma itself is a minor part compared to diffusion from the SiO2 substrate and HfO2 dielectric during the PEALD growth. We observe the presence of TiO2 at the interface between the Hf oxide layer and the Ti nitride electrodes as well as at the SiO2 interface. EELS analysis led to a band gap ranging from 2.2 to 2.5 eV for the bottom TiNxOy and 1.7-2.2 eV for the top TiNxOy, which is in fair agreement with results obtained on the top TiNx electrode (1.6 ± 01 eV) using optical absorption spectra. Measurement of sheet resistance, resistivity and temperature coefficient of resistance by a four-point probe on the top TiNxOy electrode from 20 to 100 °C corresponds to the typical values for semiconductors.

Uniform arrays of gold nanoelectrodes with tuneable recess depth.

Nanoelectrode arrays are much in demand in electroanalytical chemistry, electrocatalysis, and bioelectrochemistry. One of the promising approaches for the preparation of such systems is templated electrodeposition. In the present study, porous anodic alumina templates are used to prepare Au nanoelectrode arrays. Multistage electrodeposition is proposed for the formation of recessed electrodes with the ability to tune the distance between the surface of the porous template and the top surface of the nanoelectrodes. A set of complementary techniques, including chronoamperometry, coulometry, and scanning electron microscopy, are used to characterize the nanoelectrode arrays. The number of active nanoelectrodes is experimentally measured. The pathways to further improve the recessed nanoelectrode arrays based on anodic alumina templates are discussed.