Layered memristive and memcapacitive switches for printable electronics
1 like3,423 views
The document discusses advances in memristive and memcapacitive switches for printable electronics, specifically focusing on solution-processed MoOx/MoS2 and WxO/Ws2 heterostructures. It details the device characteristics, including the photonic flash oxidation technique used for forming ultrathin transition metal oxide layers, and presents experimental data on their resistive switching properties and endurance tests. The findings indicate significant potential for these layered materials in the development of active components for flexible and printable electronic applications.
Layered memristive and memcapacitive switches for printable electronics
- 1. SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135 NATURE MATERIALS | www.nature.com/naturematerials 1 1 Layered memristive and memcapacitive switches for printable electronics Alexander A. Bessonov1 , Marina N. Kirikova1 , Dmitrii I. Petukhov1,2 , Mark Allen3 , Tapani Ryhänen3 , Marc J.A. Bailey1 1 Nokia Labs Skolkovo, Nokia Technologies, Moscow region 143025, Russia 2 Department of Chemistry, Lomonosov Moscow State University, Moscow 119991, Russia 3 Sensor Systems, Nokia Technologies, Cambridge CB3 0FA, United Kingdom Figure S1. Solution-processed MoOx/MoS2 memristors. Figure S2. XPS analysis of MoOx/MoS2 heterostructures. Figure S3. Photonic flash oxidation of transition metal dichalcohenides (TMDs). Figure S4. I-V characteristics of layered switching devices. Figure S5. Memristive and memcapacitive effects. Figure S6. Multilevel operation and endurance test. © 2014 Macmillan Publishers Limited. All rights reserved.
- 2. 2 NATURE MATERIALS | www.nature.com/naturematerials SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135 2 Figure S1 | Solution-processed MoOx/MoS2 memristors. a, Top-view optical image of a cross-point area (~130×170 m2 ) with inkjet printed bottom electrode (BE) and screen printed top electrode (TE). b, Cross-section SEM image of the AgNW/MoOx/MoS2 switching device with both BE and TE fabricated by screen printing; insets show a top-view image of the MoOx/MoS2 film on printed silver (top) and a cross-section of the MoOx/MoS2 film conformally covering the Ag BE (bottom). c, UV-vis transmittance spectra of MoOx/MoS2 and WOx/WS2 films on the 50 m thick PEN substrate. Thermal oxidation is performed at 200°C for 3 h. The transmittance at 565 nm is 51% for MoS2 and 68% for WS2. 400 500 600 700 800 Wavelength (nm) 0 20 40 60 80 100 Transmittance(%) MoOx /MoS2 WOx /WS2 1 m 500 nm MoOx/MoS2 Ag BE AgNW PEN 1 m b Inkjet-printed silver BE Screen-printed silver TE 100 m MoOx/MoS2 filma c © 2014 Macmillan Publishers Limited. All rights reserved.
- 3. NATURE MATERIALS | www.nature.com/naturematerials 3 SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4135 3 Figure S2 | XPS analysis of MoOx/MoS2 heterostructures. a, Evolution of Mo 3d core levels with depth profiling for layered MoOx/MoS2 films obtained by 200°C / 3 h oxidation. The intensities are normalized for visual clarity. The features at 228.8 and 231.9 eV are associated with Mo4+ 3d5/2 and 3d3/2 core levels in MoS2, respectively, while S 2s appears at 225.9 eV. The peak at 229.7 and 232.8 eV could be attributed to the Mo5+ 3d core level in MoOxSy. The features at 232.4 and 235.5 eV indicate the presence of Mo6+ (MoO3) on the surface of the film. With oxidation progression the oxide components are seen to increase in intensity. The MoOx thickness of < 3 nm is confirmed, which is consistent with previous data1,2 . In addition, we observe a shift of the Mo 3d peaks from the inner disulfide to the top oxide layer towards the higher binding energy values that can be attributed to a stronger n-doping process at the MoOx/MoS2 interface due to more electronegative oxygen, indicating a relative shift of the Fermi level towards the conductive band edge3 . However, it should be noted that the interfacial MoOx layer is assumed to reveal p-type semiconductivity because of heavily chemisorbed oxygen, as discussed in the main text of paper. b, Mo6+ and Mo5+ oxidation-state XPS profiles of the MoOx/MoS2 sample oxidized at various conditions; the sputtering rate is approximately 0.1 nm/s. We note that the oxidation at 150°C for 3 h reveals a larger Mo5+ /Mo6+ ratio and thus a more pronounced MoOxSy content with depth showing a less distinct MoOx/MoS2 interface compared to annealing at higher temperatures (180°C and 200°C for 3 h) and photonic flash oxidation for 600 s, which is probably caused by a greater oxygen diffusion through the poorly oxidized top layers. 0 30 60 90 120 150 0 20 40 Sputtering time (s) Relativepeakarea(%) Mo5+ (MoOx Sy ) 10 20 30 150o C 180o C 200o C xenon flash lamp Mo6+ (MoO3 ) 224226228230232234236238240242 Mo5+ 3d (MoOx Sy ) S 2s Mo6+ 3d (MoO3 ) Mo4+ 3d3/2 (MoS2 ) Mo4+ 3d5/2 (MoS2 ) Normalizedintensity 10 nm depth 3 nm depth surface Binding energy (eV) ba © 2014 Macmillan Publishers Limited. All rights reserved.
- 4. 4 NATURE MATERIALS | www.nature.com/naturematerials SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135 4 Figure S3 | Photonic flash oxidation of transition metal dichalcohenides (TMDs). a, Schematics of the oxidation of TMD film on PEN using a xenon flash lamp tool (UIS-100, Aeromed LLC). As a result, an ultrathin transition metal oxide (TMO) layer forms on the top of TMD film. The technique is fast and works at low bulk temperatures making it preferable in high-volume roll-to-roll manufacturing4,5,6 . The apparatus consists of a power supply, discharge unit, controller, and lamp housing. A linear xenon flash lamp with an emission spectrum ranging from 200 to 900 nm is placed in the elliptical reflector (reflectivity of > 98%). A forced air cooling of the lamp and the sample can be applied in the case of high power operation. The reflector projects an image on the substrate with an illumination area of 20 × 250 mm. An adjustable table for samples allows tuning the focus line width and thus changing the light intensity. The setup has an average electric power consumption of ~1000 W with a pulsed peak power of approximately 2.2 MW. A pulse energy is adjustable in the range of 12 – 108 J, a pulse frequency can be varied from 1 to 50 Hz, and a pulse duration is 50 s. b, Few-layer MoS2 and WS2 materials absorb the light in the UV-visual range where the xenon flash lamp emits. The photonic exposure in air causes a local heating of the TMD film facilitating rapid oxidation of the topmost layers and finally resulting in TMO/TMD heterostructures. 200 400 600 800 1000 MoS2 WS2 Xenon flash lamp Normalizedabsorbance/emittance Wavelength (nm) PEN TMD PEN TMO Xenon flash lamp Elliptic reflector Focus line ba © 2014 Macmillan Publishers Limited. All rights reserved.
- 5. NATURE MATERIALS | www.nature.com/naturematerials 5 SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4135 5 Figure S4 | I-V characteristics of layered switching devices. a, b, The MoOx/MoS2 and WOx/WS2 heterostructures sandwiched between two screen-printed silver electrodes show a typical bipolar resistive switching in contrast to a linear I-V curve of non-oxidized MoS2 device (in forward direction the TE is negatively charged, the sweep rate is 16.5 mV/s, the compliance current is 1 mA). Being structural analogues and having similar electronic properties, MoOx/MoS2 and WOx/WS2 exhibit an almost identical I-V behavior. Thus, we show that few-layer TMD-based systems can be used as a viable way for active materials to enable printable resistive switches. An observed rectifying I-V orientation suggests an important role of a Schottky junction at the interface of TMO and Ag TE, which blocks the current in the OFF state (IOFF). A compositional gradient (Mo6+ to Mo4+ ) built into the switching layer supports a resistance memory effect via oxygen vacancy migration under applied voltage, similar to that previously observed in WO3 devices7,8 . Pre-electroforming is not required since the insulating oxygen-saturated MoOx interfacial layer with the thickness of less than 3 nm is located on the oxygen-deficient area with anion vacancies ready to move towards the negatively biased TE. When a large fraction of applied voltage drops on the resistive Ag/MoOx interface, a virtual anode naturally propagates towards the cathode along defects and structural imperfections supported by the low-dimensional nature9 . c, Temperature effect on the AgNW/MoOx/MoS2 resistive switching performance. The activation energy (EA) of 0.36 ± 0.04 eV extracted from temperature-dependent measurements of the reverse IOFF at -0.2 V appears to be slightly higher than EA = 0.30 ± 0.02 eV obtained for MoOx/MoS2 memristors lacking an intermediate AgNW layer (Fig. 2e). -0.2 -0.1 0.0 0.1 0.2 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 25o C 40o C 60o C 80o C Current(A) Voltage (V) 32 34 36 38 40 -28 -27 -26 -25 ln(IR /T2 ) 1/kT (eV-1 ) EA=0.36 eV -0.1 0.1-0.2 0.0 0.2 10-11 10-10 10-9 10-8 10-7 10-6 10-5 10-4 10-3 10-2 Current(A) Voltage (V) WOx /WS2 -0.2 -0.1 0.0 0.1 0.2 -1.0 -0.5 0.0 0.5 1.0 Reset Set OFF Current(mA) Voltage (V) MoS2 MoOx /MoS2 WOx /WS2 ON c a b © 2014 Macmillan Publishers Limited. All rights reserved.
- 6. 6 NATURE MATERIALS | www.nature.com/naturematerials SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135 6 Figure S5 | Memristive and memcapacitive effects. a, Resistive (RM) and capacitive (CM) components of the MoOx/MoS2 as a function of AC 10 mV signal frequency in the ON (after +0.2 V bias) and OFF (after -0.2 V bias) states. Inset shows the Nyquist plot in the OFF state. The equivalent circuit is represented as a parallel combination of a resistor and a capacitor. b, AgNW/MoOx/MoS2 switches concurrently support memristive and memcapacitive behavior with the same state variables, which is consistent with previous observations10 . The CM-V and RM-V profiles are extracted from the impedance measurements with 10 mV 0.5 kHz AC signal superimposed on a continuous DC bias sweep. Capacitive and resistive switching ratios appear to be 103 and 106 , respectively. 1 10 100 1k 10k 100k 1M 100 1k 10k 100k 1M 10M MoOx /MoS2 RM (ON) Resistance() Frequency (Hz) RM (OFF) CM (OFF) CM (ON) 1p 10p 100p 1n 10n Capacitance(F) 0 1 2 3 0 1 2 3-Z"(M) Z' (M) 1p 10p 100p 1n 10n -0.1 0.1-0.2 0.0 0.2 10 1k 100k 10M dwewdwed deeededed dedede de xd CM (F) AgNW/MoOx /MoS2 CM RM RM () Voltage (V) ba © 2014 Macmillan Publishers Limited. All rights reserved.
- 7. NATURE MATERIALS | www.nature.com/naturematerials 7 SUPPLEMENTARY INFORMATIONDOI: 10.1038/NMAT4135 7 Figure S6 | Multilevel operation and endurance test. a, Multiple states of the resistance recorded after three pulses of 0.3 V for 10 s with varied compliance currents (IC). The read voltage is 0.01 V. The resistance values are calculated by Ohm’s law at 1000 s. The AgNW/MoOx/MoS2 device under investigation is obtained by heat-assisted oxidation at 200⁰C for 10 h. The range of possible resistance states depends on the Schottky junction height; when the depletion width becomes narrow electron tunneling occurs reducing the contact resistance. b, Cycling endurance of the AgNW/MoOx/MoS2 switch. ON/OFF switching is programmed by alternating pulses of +0.3 V for 0.6 s and -0.1 V for 1.8 s (IC = 1 mA). 0 200 400 600 800 1000 10-9 10-8 10-5 10-4 10-3 Ic =10 mA Ic =1 mA Ic =100 A Ic =10 A Ic =5 A Ic =1 A Current(A) Time (s) 25.5 123 614 1.51 k 3.09 M 13.1 M 0 10000 20000 30000 10-11 10-9 10-7 10-5 10-3 10-1 OFF ON Current(A) Number of cycles -0.1 V +0.3 V 0 ba © 2014 Macmillan Publishers Limited. All rights reserved.
- 8. 8 NATURE MATERIALS | www.nature.com/naturematerials SUPPLEMENTARY INFORMATION DOI: 10.1038/NMAT4135 8 References 1. Lince, J. R., Hilton, M. R. & Bommannavar, A. S. EXAFS of sputter-deposited MoS2 films. Thin Solid Films 264, 120–134 (1995). 2. Tagawa, M., Yokota, K., Matsumoto, K., Suzuki, M. & Teraoka, Y. Space environmental effects on MoS2 and diamond-like carbon lubricating films: Atomic oxygen-induced erosion and its effect on tribological properties. Surf. Coat. Technol. 202, 1003–1010 (2007). 3. Fang, H., et al. Degenerate n-doping of few-layer transition metal dichalcogenides by potassium. Nano Letters 13, 1991–1995 (2013). 4. Abbel, R., et al. Photonic flash sintering of silver nanoparticle inks: a fast and convenient method for the preparation of highly conductive structures on foil. MRS Communications 2, 145–150 (2012). 5. Niittynen, J., et al. Alternative sintering methods compared to conventional thermal sintering for inkjet printed silver nanoparticle ink. Thin Solid Films 556, 452–459 (2014). 6. Perelaer, J., et al. Roll-to-Roll compatible sintering of inkjet printed features by photonic and microwave exposure: from non-conductive ink to 40% bulk silver conductivity in less than 15 seconds. Adv. Mater. 24, 2620–2625 (2012). 7. Yang., R., et al. On-demand nanodevice with electrical and neuromorphic multifunction realized by local ion migration. ACS Nano 6, 9515–9521 (2012). 8. Guo, J., et al. Reconfigurable resistive switching devices based on individual tungsten trioxide nanowires. AIP Advances 3, 042137 (2013). 9. McDonnell, S., Addou, R., Buie, C., Wallace, R. M. & Hinkle, C. L. Defect-dominated doping and contact resistance in MoS2. ACS Nano 8, 2880–2888 (2014). 10. Qingjiang, L., et al. Memory impedance in TiO2 based metal-insulator-metal devices. Sci. Rep. 4, 4522 (2014). © 2014 Macmillan Publishers Limited. All rights reserved.