The energy barrier at noble metal/TiO2 junctions

Abstract

Nobel metal/TiO2 structures are used as catalysts in chemical reactors, active components in TiO2-based electronic devices, and connections between such devices and the outside circuitry. Here, we investigate the energy barrier at the junctions between vacuum-deposited Ag, Au, and Pt thin films and TiO2 layers by recording their electrical current vs. voltage diagrams and spectra of optical responses. Deposited Au/, Pt/, and Ag/TiO2 behave like contacts with zero junction energy barriers, but the thermal annealing of the reverse-biased devices for an hour at 523 K in air converts them to Schottky diodes with high junction energy barriers, decreasing their reverse electric currents up to 106 times. Similar thermal processing in vacuum or pure argon proved ineffective. The highest energy barrier and the lowest reverse current among the devices examined belong to the annealed Ag/TiO2 contacts. The observed electronic features are described based on the physicochemical parameters of the constituting materials. The formation of higher junction barriers with rutile than with anatase is demonstrated.

Electronic Conduction in Ti/Poly-TiO2/Ti Structures

“…2d ) is attributed to the uneven IOV distribution within the oxide layer. (This asymmetric I–V is distinctly different from the I–V asymmetry observed in Schottky type metal/semiconductor junctions 26 28 51 ). In all biasing conditions, the IOVs close to the positively biased electrode play a more constructive role in the filament formation.…”

“…The thickness of the grown oxide layers is in the 350 nm to 550 nm range. According to the obtained XRD patterns (see Supplementary, Section 1 ), the grown oxide layers are of rutile phase dominantly consisting of {110}-faceted grains; those grown at 500 °C are mixtures of rutile and anatase 26 . The micrographs given in Fig.…”

“…The structures considered are mostly of the M′/MO/M″ type, where MO is a nanometer-sized metal oxide crystallite sandwiched between M′and M″ metal electrodes 5 15 . The most widely studied oxide for resistance switching is TiO 2 connected to noble metal electrodes, such as platinum 16 17 18 19 20 , silver 21 22 23 or gold 24 25 , which usually add to the complexity of the device performance by forming Schottky energy barriers at their junctions with TiO 2 26 27 28 , and introduce at least one additional mobile cation to the structure 23 .…”

Electrical characteristics of interfacial barriers at metal—TiO2 contacts

“…In addition, the role of the TE (evaporated through a shadow mask) on a metalTiO 2 (nonrectifyingPt) memory cell, evaluated with a readout voltage of ±1 V, was correlated to the formation free energy for the top metal electrode oxide [39]. Moreover, the symmetry or asymmetry of metalTiO 2 (nonrectifyingAl) current-voltage characteristics was also attributed to the top metal fabrication details, such as the thermal annealing [40]. More recently, the source and drain electrodes of TiO 2 based TFTs were found to play a major role on performance param eters such as the on/off ratio and the field effect mobility [19].…”

Enhanced effect of a plasma‐irradiated titanium substrate on the photocatalytic activity of a TiO2 film

“…Much work has been carried out to resolve the issue by doping metals such as Pt, Pd, Cu, Ag, and Au onto TiO 2 in order to bring the metal into contact with TiO 2 , where a metal‐semiconductor junction forms that promotes charge carrier separation and therefore showed improved performance . However, few works studied photocatalytic performance of TiO 2 /Ti system with plasma‐irradiated Ti substrate, despite the fact that they form an ohmic junction which facilitates better charge transfer than does a Schottky junction formed by most noble metals with TiO 2 . In particular, to the best of our knowledge, the effect of crystal structure change of plasma‐irradiated Ti substrate on photocurrent and photocatalytic activity has not yet been reported.…”