Chemically addressed switching measurements in graphene electrode memristive devices using: In situ XPS

Itir Köymen, Pinar Aydoǧan Göktürk, Coşkun Kocabaş, Şefik Süzer

Research output: Contribution to journalArticlepeer-review

Abstract

The memristor has been the topic of heated research activity since the Pt/TiO 2 /TiO x /Pt structure was reported by Hewlett-Packard Labs. The characteristics of memristors such as the pinched hysteresis loops and time and input signal-dependent memristance are due to the drift of positively charged oxygen vacancies in the TiO x layer. While different modes of switching behaviour have been characterized, observing the switching as it happens with in situ measurements using X-ray photoelectron spectroscopy (XPS) can allow a better understanding of the device operation. The setup used in this work enables the application of voltage signals of different frequencies and amplitudes and observing the hysteresis seen in the I-V plane through chemical addressing. The measurements were conducted on Pt/TiO 2 /TiO x /graphene structures. The single layer graphene, utilized as a top electrode, effectively acts as a transparent electrode in that the layer beneath it can be observed to a depth of ∼10 nm in XPS. This allows for the observation of the changes in the binding energies of C 1s, Ti 2p and O 1s. By comparing the variation in the binding energy of Ti 2p to that of C 1s, and observing how the variation changes for different excitation signals (at different frequency and amplitudes), it is possible to inspect the effect of the oxygen vacancy drift. We employed a variety of input signals with varying frequency and amplitudes in order to test the memristive devices thoroughly: sine wave, triangular wave and DC bias. Graphene has been attracting attention due to its intriguing optoelectronic properties. This study utilizes graphene as a transparent top electrode for in situ measurements in XPS to observe chemically-addressed memristive hysteresis while an excitation signal is being applied to the device.

Original languageEnglish
Pages (from-to)231-244
Number of pages14
JournalFaraday Discussions
Volume213
Early online date6 Aug 2018
DOIs
Publication statusPublished - 1 Jan 2019

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