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Title: Impact of composition and crystallization behavior of atomic layer deposited strontium titanate films on the resistive switching of Pt/STO/TiN devices

The resistive switching (RS) properties of strontium titanate (Sr{sub 1+x}Ti{sub 1+y}O{sub 3+(x+2y)}, STO) based metal-oxide-metal structures prepared from industrial compatible processes have been investigated focusing on the effects of composition, microstructure, and device size. Metastable perovskite STO films were prepared on Pt-coated Si substrates utilizing plasma-assisted atomic layer deposition (ALD) from cyclopentadienyl-based metal precursors and oxygen plasma at 350 °C, and a subsequent annealing at 600 °C in nitrogen. Films of 15 nm and 12 nm thickness with three different compositions [Sr]/([Sr] + [Ti]) of 0.57 (Sr-rich STO), 0.50 (stoichiometric STO), and 0.46 (Ti-rich STO) were integrated into Pt/STO/TiN crossbar structures with sizes ranging from 100 μm{sup 2} to 0.01 μm{sup 2}. Nano-structural characterizations revealed a clear effect of the composition of the as-deposited STO films on their crystallization behavior and thus on the final microstructures. Local current maps obtained by local-conductivity atomic force microscopy were in good agreement with local changes of the films' microstructures. Correspondingly, also the initial leakage currents of the Pt/STO/TiN devices were affected by the STO compositions and by the films' microstructures. An electroforming process set the Pt/STO/TiN devices into the ON-state, while the forming voltage decreased with increasing initial leakage current. After a RESET process under opposite voltage has been performed, themore » Pt/STO/TiN devices showed a stable bipolar RS behavior with non-linear current-voltage characteristics for the high (HRS) and the low (LRS) resistance states. The obtained switching polarity and nearly area independent LRS values agree with a filamentary character of the RS behavior according to the valence change mechanism. The devices of 0.01 μm{sup 2} size with a 12 nm polycrystalline stoichiometric STO film were switched at a current compliance of 50 μA with voltages of about ±1.0 V between resistance states of about 40 kΩ (LRS) and 1 MΩ (HRS). After identification of the influences of the films' microstructures, i.e., grain boundaries and small cracks, the remaining RS properties could be ascribed to the effect of the [Sr]/([Sr] + [Ti]) composition of the ALD STO thin films.« less
Authors:
; ; ; ;  [1] ; ; ;  [2]
  1. Peter-Grünberg Institute (PGI-7), Forschungszentrum Jülich and JARA-FIT, 52425 Jülich (Germany)
  2. Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands)
Publication Date:
OSTI Identifier:
22314623
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 6; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ANNEALING; ATOMIC FORCE MICROSCOPY; CRYSTALLIZATION; DEPOSITS; ELECTRIC POTENTIAL; ELECTRODEPOSITION; GRAIN BOUNDARIES; LEAKAGE CURRENT; NITROGEN; OXIDES; OXYGEN; PEROVSKITE; PRECURSOR; STRONTIUM; SUBSTRATES; THIN FILMS; TITANATES; TITANIUM 46; TITANIUM NITRIDES; VALENCE