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. 2019 Sep 25;10(10):643.
doi: 10.3390/mi10100643.

Improved Memory Properties of Graphene Oxide-Based Organic Memory Transistors

Amjad Al-Shawi  1 , Maysoon Alias  2 , Paul Sayers  3 , Mohammed Fadhil Mabrook  4
Affiliations

Improved Memory Properties of Graphene Oxide-Based Organic Memory Transistors

Amjad Al-Shawi et al. Micromachines (Basel). .

Abstract

To investigate the behaviour of the organic memory transistors, graphene oxide (GO) was utilized as the floating gate in 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)-based organic memory transistors. A cross-linked, off-centre spin-coated and ozone-treated poly(methyl methacrylate) (cPMMA) was used as the insulating layer. High mobility and negligible hysteresis with very clear transistor behaviour were observed for the control transistors. On the other hand, memory transistors exhibited clear large hysteresis which is increased with increasing programming voltage. The shifts in the threshold voltage of the transfer characteristics as well as the hysteresis in the output characteristics were attributed to the charging and discharging of the floating gate. The counter-clockwise direction of hysteresis indicates that the process of charging and discharging the floating gate take place through the semiconductor/insulator interface. A clear shift in the threshold voltage was observed when different voltage pulses were applied to the gate. The non-volatile behaviour of the memory transistors was investigated in terms of charge retention. The memory transistors exhibited a large memory window (~30 V), and high charge density of (9.15 × 1011 cm-2).

Keywords: 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene); cross-linked poly(methyl methacrylate) PMMA; graphene oxide; organic memory transistors.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Scheme diagram of drop casting on a substrate with angle of 7°.
Figure 2
Figure 2
(a) Schematic configuration of graphene oxide-based organic memory transistor fabricated on a glass substrate; (b) optical microscopic image of the device and its channel; (c) the morphological quality and coverage for the cross-linked poly(methyl methacrylate) (cPMMA), graphene oxide, and 6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS)-pentacene layers.
Figure 3
Figure 3
Output and transfer characteristics of the organic thin film transistors (OTFTs) fabricated, (a) and (b) optimised devices using off-centre technique and (c) and (d) for devices with cPMMA fabricated using on-centre conventional deposition technique.
Figure 4
Figure 4
(a) Output and (b) transfer characteristics of the organic thin film memory transistors (OTFMT) with and without the floating gate.
Figure 5
Figure 5
(a) Transfer characteristics of the fabricated OTFMT after the application of positive and negative pulses of 10 V for 2 s. (b) Double sweep of transfer characteristics of OTFMT with different maximin gate voltages.
Figure 6
Figure 6
The effect of (a) negative and (b) positive pulses on transfer characteristics of OTFMT.
Figure 7
Figure 7
Programming characteristics of TIPS-pentacene based OTFMT. (a) The effect of the programming voltage (2 s pulses) on the threshold voltage shift(ΔVT), (b) write and erase processes by applying a negative and positive pulse voltage, respectively as a function of gate voltage and (c) charge retention characteristics of the OTFMT.
Figure 8
Figure 8
Endurance characteristic of OTFMT device with graphene oxide (GO) as the charge-storage layer.
Figure 9
Figure 9
Schematic diagram of the energy band for the OTFMT.
See this image and copyright information in PMC

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