Abstract
Identification of microstructural evolution of nanoscale conducting phase, such as conducting filament (CF), in many resistance switching (RS) devices is a crucial factor to unambiguously understand the electrical behaviours of the RS-based electronic devices. Among the diverse RS material systems, oxide-based redox system comprises the major category of these intriguing electronic devices, where the local, along both lateral and vertical directions of thin films, changes in oxygen chemistry has been suggested to be the main RS mechanism. However, there are systems which involve distinctive crystallographic phases as CF; the Magnéli phase in TiO2 is one of the very well-known examples. The current research reports the possible presence of distinctive local conducting phase in atomic layer deposited SrTiO3 RS thin film. The conducting phase was identified through extensive transmission electron microscopy studies, which indicated that oxygen-deficient Sr2Ti6O13 or Sr1Ti11O20 phase was presumably present mainly along the grain boundaries of SrTiO3 after the unipolar set switching in Pt/TiN/SrTiO3/Pt structure. A detailed electrical characterization revealed that the samples showed typical bipolar and complementary RS after the memory cell was unipolar reset.
Highlights
Identification of microstructural evolution of nanoscale conducting phase, such as conducting filament (CF), in many resistance switching (RS) devices is a crucial factor to unambiguously understand the electrical behaviours of the RS-based electronic devices
The lack of crystalline diffraction peaks, except for those from the substrate materials, from the as-deposited state suggested that the STO film was amorphous, which is consistent with the fact that this atomic layer deposition (ALD) STO film was formed through a two-step growth process for in-situ crystallization
The rapid thermal annealing (RTA) certainly crystallized the film into the perovskite structure as can be understood from the emergence of STO (110) peak near 2θ value of 32.5o and increase in the peak intensity near 2θ value of 46.5o which corresponded to STO (200) (and Pt (200))
Summary
Identification of microstructural evolution of nanoscale conducting phase, such as conducting filament (CF), in many resistance switching (RS) devices is a crucial factor to unambiguously understand the electrical behaviours of the RS-based electronic devices. In order to further improve the success rate of such trials, a highly reliable film deposition process, atomic layer deposition (ALD), was adopted which resulted in an extremely uniform and reliable electrical characteristics, facilitating this tough task affordable Such HRTEM work suffers from the scarcity of possible CFs in the memory cell structure, so extensive and dedicated TEM studies were necessary to identify the Sr2Ti6O13 or Sr1Ti11O20 phases as the conducting second phase in this work. The electrical properties of the STO films, which were differently heat-treated to change the crystallographic structure, were examined after the memory cell was URS reset This can provide a detailed understanding on the possible redox reaction at the region where the presumable Sr2Ti6O13 or Sr1Ti11O20 phase CF’s are ruptured
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