Non-thermal light-assisted resistance collapse in a V2_2O3_3-based Mott-insulator device

The insulator-to-metal transition in Mott insulators is the key mechanism for a novel class of electronic devices, belonging to the Mottronics family. Intense research efforts are currently devoted to the development of specific control protocols, usually based on the application of voltage, strain, pressure and light excitation. The ultimate goal is to achieve the complete control of the electronic phase transformation, with dramatic impact on the performance, for example, of resistive switching devices. Here, we investigate the simultaneous effect of external voltage and excitation by ultrashort light pulses on a single Mottronic device based on a V$_2$O$_3$ epitaxial thin film. The experimental results, supported by finite-element simulations of the thermal problem, demonstrate that the combination of light excitation and external electrical bias drives a volatile resistivity drop which goes beyond the combined effect of laser and Joule heating. Our results impact on the development of protocols for the non-thermal control of the resistive switching transition in correlated materials

Experimental demonstration of a tunable transverse electric pass polarizer based on hybrid VO2/silicon technology

[EN] A tunable transverse electric (TE) pass polarizer is demonstrated based on hybrid vanadium dioxide/silicon (VO2/Si) technology. The 20-mu m-long TE pass polarizer exploits the phase transition of the active VO2 material to control the rejection of the unwanted transverse magnetic (TM) polarization. The device features insertion losses below 1 dB at static conditions and insertion losses of 5.5 dB and an attenuation of TM polarization of 19 dB in the active state for a wavelength range between 1540 nm and 1570 nm. To the best of our knowledge, this is the first time that tunable polarizers compatible with Si photonics are demonstrated. (C) 2018 Optical Society of AmericaMinisterio de Economia y Competitividad (MINECO) (TEC2016-76849); European Commission (EC) [PHRESCO (688579), SITOGA (619456)]; Universitat Politecnica de Valencia; Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT).Sánchez Diana, LD.; Olivares-Sánchez-Mellado, I.; Parra Gómez, J.; Menghini, M.; Homm, P.; Locquet, J.; Sanchis Kilders, P. (2018). Experimental demonstration of a tunable transverse electric pass polarizer based on hybrid VO2/silicon technology. Optics Letters. 43(15):3650-3653. https://doi.org/10.1364/OL.43.003650S365036534315Liu, L., Ding, Y., Yvind, K., & Hvam, J. M. (2011). Efficient and compact TE–TM polarization converter built on silicon-on-insulator platform with a simple fabrication process. Optics Letters, 36(7), 1059. doi:10.1364/ol.36.001059Alonso-Ramos, C., Halir, R., Ortega-Moñux, A., Cheben, P., Vivien, L., Molina-Fernández, Í., … Schmid, J. (2012). Highly tolerant tunable waveguide polarization rotator scheme. Optics Letters, 37(17), 3534. doi:10.1364/ol.37.003534Zhang, H., Das, S., Zhang, J., Huang, Y., Li, C., Chen, S., … Thong, J. T. L. (2012). Efficient and broadband polarization rotator using horizontal slot waveguide for silicon photonics. Applied Physics Letters, 101(2), 021105. doi:10.1063/1.4734640Azzam, S. I. H., Hameed, M. F. O., Areed, N. F. F., Abd-Elrazzak, M. M., El-Mikaty, H. A., & Obayya, S. S. A. (2014). Proposal of an Ultracompact CMOS-Compatible TE-/TM-Pass Polarizer Based on SoI Platform. IEEE Photonics Technology Letters, 26(16), 1633-1636. doi:10.1109/lpt.2014.2329416Dai, D., Wang, Z., Julian, N., & Bowers, J. E. (2010). Compact broadband polarizer based on shallowly-etched silicon-on-insulator ridge optical waveguides. Optics Express, 18(26), 27404. doi:10.1364/oe.18.027404Aamer, M., Gutierrez, A. M., Brimont, A., Vermeulen, D., Roelkens, G., Fedeli, J.-M., … Sanchis, P. (2012). CMOS Compatible Silicon-on-Insulator Polarization Rotator Based on Symmetry Breaking of the Waveguide Cross Section. IEEE Photonics Technology Letters, 24(22), 2031-2034. doi:10.1109/lpt.2012.2218593Xiong, Y., Xu, D.-X., Schmid, J. H., Cheben, P., & Ye, W. N. (2015). High Extinction Ratio and Broadband Silicon TE-Pass Polarizer Using Subwavelength Grating Index Engineering. IEEE Photonics Journal, 7(5), 1-7. doi:10.1109/jphot.2015.2483204Sánchez, L., & Sanchis, P. (2013). Broadband 8 μm long hybrid silicon-plasmonic transverse magnetic–transverse electric converter with losses below 2 dB. Optics Letters, 38(15), 2842. doi:10.1364/ol.38.002842Komatsu, M., Saitoh, K., & Koshiba, M. (2012). Compact Polarization Rotator Based on Surface Plasmon Polariton With Low Insertion Loss. IEEE Photonics Journal, 4(3), 707-714. doi:10.1109/jphot.2012.2195650Caspers, J. N., Alam, M. Z., & Mojahedi, M. (2012). Compact hybrid plasmonic polarization rotator. Optics Letters, 37(22), 4615. doi:10.1364/ol.37.004615Sun, X., Alam, M. Z., Wagner, S. J., Aitchison, J. S., & Mojahedi, M. (2012). Experimental demonstration of a hybrid plasmonic transverse electric pass polarizer for a silicon-on-insulator platform. Optics Letters, 37(23), 4814. doi:10.1364/ol.37.004814Alam, M. Z., Aitchison, J. S., & Mojahedi, M. (2011). Compact and silicon-on-insulator-compatible hybrid plasmonic TE-pass polarizer. Optics Letters, 37(1), 55. doi:10.1364/ol.37.000055Jin, L., Chen, Q., & Wen, L. (2014). Mode-coupling polarization rotator based on plasmonic waveguide. Optics Letters, 39(9), 2798. doi:10.1364/ol.39.002798Caspers, J. N., Aitchison, J. S., & Mojahedi, M. (2013). Experimental demonstration of an integrated hybrid plasmonic polarization rotator. Optics Letters, 38(20), 4054. doi:10.1364/ol.38.004054Briggs, R. M., Pryce, I. M., & Atwater, H. A. (2010). Compact silicon photonic waveguide modulator based on the vanadium dioxide metal-insulator phase transition. Optics Express, 18(11), 11192. doi:10.1364/oe.18.011192Ryckman, J. D., Hallman, K. A., Marvel, R. E., Haglund, R. F., & Weiss, S. M. (2013). Ultra-compact silicon photonic devices reconfigured by an optically induced semiconductor-to-metal transition. Optics Express, 21(9), 10753. doi:10.1364/oe.21.010753Markov, P., Marvel, R. E., Conley, H. J., Miller, K. J., Haglund, R. F., & Weiss, S. M. (2015). Optically Monitored Electrical Switching in VO2. ACS Photonics, 2(8), 1175-1182. doi:10.1021/acsphotonics.5b00244Joushaghani, A., Jeong, J., Paradis, S., Alain, D., Stewart Aitchison, J., & Poon, J. K. S. (2015). Wavelength-size hybrid Si-VO_2 waveguide electroabsorption optical switches and photodetectors. Optics Express, 23(3), 3657. doi:10.1364/oe.23.003657Sánchez, L., Lechago, S., & Sanchis, P. (2015). Ultra-compact TE and TM pass polarizers based on vanadium dioxide on silicon. Optics Letters, 40(7), 1452. doi:10.1364/ol.40.001452Sanchez, L., Lechago, S., Gutierrez, A., & Sanchis, P. (2016). Analysis and Design Optimization of a Hybrid VO2/Silicon2 $\times$ 2 Microring Switch. IEEE Photonics Journal, 8(2), 1-9. doi:10.1109/jphot.2016.2551463Miller, K. J., Hallman, K. A., Haglund, R. F., & Weiss, S. M. (2017). Silicon waveguide optical switch with embedded phase change material. Optics Express, 25(22), 26527. doi:10.1364/oe.25.026527Clark, J. K., Ho, Y.-L., Matsui, H., & Delaunay, J.-J. (2018). Optically Pumped Hybrid Plasmonic-Photonic Waveguide Modulator Using the VO2 Metal-Insulator Phase Transition. IEEE Photonics Journal, 10(1), 1-9. doi:10.1109/jphot.2017.2784429Ko, C., & Ramanathan, S. (2008). Observation of electric field-assisted phase transition in thin film vanadium oxide in a metal-oxide-semiconductor device geometry. Applied Physics Letters, 93(25), 252101. doi:10.1063/1.3050464Zimmers, A., Aigouy, L., Mortier, M., Sharoni, A., Wang, S., West, K. G., … Schuller, I. K. (2013). Role of Thermal Heating on the Voltage Induced Insulator-Metal Transition inVO2. Physical Review Letters, 110(5). doi:10.1103/physrevlett.110.056601Kats, M. A., Blanchard, R., Genevet, P., Yang, Z., Qazilbash, M. M., Basov, D. N., … Capasso, F. (2013). Thermal tuning of mid-infrared plasmonic antenna arrays using a phase change material. Optics Letters, 38(3), 368. doi:10.1364/ol.38.000368Chae, B.-G., Kim, H.-T., Youn, D.-H., & Kang, K.-Y. (2005). Abrupt metal–insulator transition observed in VO2 thin films induced by a switching voltage pulse. Physica B: Condensed Matter, 369(1-4), 76-80. doi:10.1016/j.physb.2005.07.032Ruzmetov, D., Gopalakrishnan, G., Deng, J., Narayanamurti, V., & Ramanathan, S. (2009). Electrical triggering of metal-insulator transition in nanoscale vanadium oxide junctions. Journal of Applied Physics, 106(8), 083702. doi:10.1063/1.3245338Lee, S. B., Kim, K., Oh, J. S., Kahng, B., & Lee, J. S. (2013). Origin of variation in switching voltages in threshold-switching phenomena of VO2 thin films. Applied Physics Letters, 102(6), 063501. doi:10.1063/1.4790842Joushaghani, A., Jeong, J., Paradis, S., Alain, D., Stewart Aitchison, J., & Poon, J. K. S. (2014). Voltage-controlled switching and thermal effects in VO2 nano-gap junctions. Applied Physics Letters, 104(22), 221904. doi:10.1063/1.4881155Yang, Z., Hart, S., Ko, C., Yacoby, A., & Ramanathan, S. (2011). Studies on electric triggering of the metal-insulator transition in VO2thin films between 77 K and 300 K. Journal of Applied Physics, 110(3), 033725. doi:10.1063/1.3619806Yoon, J., Lee, G., Park, C., Mun, B. S., & Ju, H. (2014). Investigation of length-dependent characteristics of the voltage-induced metal insulator transition in VO2 film devices. Applied Physics Letters, 105(8), 083503. doi:10.1063/1.4893783Sánchez, L., Rosa, A., Griol, A., Gutierrez, A., Homm, P., Van Bilzen, B., … Sanchis, P. (2017). Impact of the external resistance on the switching power consumption in VO2 nano gap junctions. Applied Physics Letters, 111(3), 031904. doi:10.1063/1.4994326Ryckman, J. D., Diez-Blanco, V., Nag, J., Marvel, R. E., Choi, B. K., Haglund, R. F., & Weiss, S. M. (2012). Photothermal optical modulation of ultra-compact hybrid Si-VO_2 ring resonators. Optics Express, 20(12), 13215. doi:10.1364/oe.20.013215Abreu, E., Gilbert Corder, S. N., Yun, S. J., Wang, S., Ramírez, J. G., West, K., … Averitt, R. D. (2017). Ultrafast electron-lattice coupling dynamics in VO2 and V2O3 thin films. Physical Review B, 96(9). doi:10.1103/physrevb.96.094309Van Bilzen, B., Homm, P., Dillemans, L., Su, C.-Y., Menghini, M., Sousa, M., … Locquet, J.-P. (2015). Production of VO2 thin films through post-deposition annealing of V2O3 and VOx films. Thin Solid Films, 591, 143-148. doi:10.1016/j.tsf.2015.08.036Olivares, I., Sánchez, L., Parra, J., Larrea, R., Griol, A., Menghini, M., … Sanchis, P. (2018). Optical switching in hybrid VO2/Si waveguides thermally triggered by lateral microheaters. Optics Express, 26(10), 12387. doi:10.1364/oe.26.012387Rosa, Á., Gutiérrez, A., Brimont, A., Griol, A., & Sanchis, P. (2016). High performace silicon 2x2 optical switch based on a thermo-optically tunable multimode interference coupler and efficient electrodes. Optics Express, 24(1), 191. doi:10.1364/oe.24.000191Shibuya, K., Kawasaki, M., & Tokura, Y. (2010). Metal-insulator transition in epitaxial V1−xWxO2(0≤x≤0.33) thin films. Applied Physics Letters, 96(2), 022102. doi:10.1063/1.3291053Ahuja, R., Granqvist, C. G., Hermansson, K., Niklasson, G. A., & Scheicher, R. H. (2012). Optical properties of Mg-doped VO2: Absorption measurements and hybrid functional calculations. Applied Physics Letters, 101(20), 201902. doi:10.1063/1.4766167Miyazaki, K., Shibuya, K., Suzuki, M., Wado, H., & Sawa, A. (2014). Correlation between thermal hysteresis width and broadening of metal–insulator transition in Cr- and Nb-doped VO2films. Japanese Journal of Applied Physics, 53(7), 071102. doi:10.7567/jjap.53.071102Niklasson, G. A., Granqvist, C. G., & Hunderi, O. (1981). Effective medium models for the optical properties of inhomogeneous materials. Applied Optics, 20(1), 26. doi:10.1364/ao.20.000026Jepsen, P. U., Fischer, B. M., Thoman, A., Helm, H., Suh, J. Y., Lopez, R., & Haglund, R. F. (2006). Metal-insulator phase transition in aVO2thin film observed with terahertz spectroscopy. Physical Review B, 74(20). doi:10.1103/physrevb.74.205103Fang, X., & Yang, L. (2017). Thermal effect analysis of silicon microring optical switch for on-chip interconnect. Journal of Semiconductors, 38(10), 104004. doi:10.1088/1674-4926/38/10/10400

Optical switching in hybrid VO2/Si waveguides thermally triggered by lateral microheaters

© 2018 Optical Society of America. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modifications of the content of this paper are prohibited"[EN] The performance of optical devices relying in vanadium dioxide (VO2) technology compatible with the silicon platform depends on the polarization of light and VO2 properties. In this work, optical switching in hybrid VO2/Si waveguides thermally triggered by lateral microheaters is achieved with insertion losses below 1 dB and extinction ratios above 20 dB in a broad bandwidth larger than 30 nm. The optical switching response has been optimized for TE and TM polarizations by using a homogeneous and a granular VO2 layer, respectively, with a small impact on the electrical power consumption. The stability and reversibility between switching states showing the possibility of bistable performance is also demonstrated. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.Funding from project TEC2016-76849 (MINECO/FEDER, UE) is acknowledged. The SOI samples were fabricated at IHP (we acknowledge Lars Zimmermann) in the framework of FP7-ICT-2013-11-619456 SITOGA project. Irene Olivares and Roberto Larrea also acknowledge respectively the Universitat Politecnica de Valencia and the Ecuadorian Government for funding their grant. P.H. acknowledges support from Becas Chile-CONICYT.Olivares-Sánchez-Mellado, I.; Sánchez Diana, LD.; Parra Gómez, J.; Larrea-Luzuriaga, RA.; Griol Barres, A.; Menghini, M.; Homm, P.... (2018). Optical switching in hybrid VO2/Si waveguides thermally triggered by lateral microheaters. Optics Express. 26(10):12387-12395. https://doi.org/10.1364/OE.26.012387S12387123952610Sorger, V. J., Lanzillotti-Kimura, N. D., Ma, R.-M., & Zhang, X. (2012). Ultra-compact silicon nanophotonic modulator with broadband response. Nanophotonics, 1(1), 17-22. doi:10.1515/nanoph-2012-0009Liang, H., Soref, R., Mu, J., Majumdar, A., Li, X., & Huang, W.-P. (2015). Simulations of Silicon-on-Insulator Channel-Waveguide Electrooptical 2 × 2 Switches and 1 × 1 Modulators Using a ${\bf Ge_2}{\bf Sb_2}{\bf Te_5}$ Self-Holding Layer. Journal of Lightwave Technology, 33(9), 1805-1813. doi:10.1109/jlt.2015.2393293Seo, G., Kim, B.-J., Ko, C., Cui, Y., Lee, Y. W., Shin, J.-H., … Kim, H.-T. (2011). Voltage-Pulse-Induced Switching Dynamics in $\hbox{VO}_{2}$ Thin-Film Devices on Silicon. IEEE Electron Device Letters, 32(11), 1582-1584. doi:10.1109/led.2011.2163922Yang, Z., Ko, C., & Ramanathan, S. (2011). Oxide Electronics Utilizing Ultrafast Metal-Insulator Transitions. Annual Review of Materials Research, 41(1), 337-367. doi:10.1146/annurev-matsci-062910-100347Vitale, W. A., Casu, E. A., Biswas, A., Rosca, T., Alper, C., Krammer, A., … Ionescu, A. M. (2017). A Steep-Slope Transistor Combining Phase-Change and Band-to-Band-Tunneling to Achieve a sub-Unity Body Factor. Scientific Reports, 7(1). doi:10.1038/s41598-017-00359-6Zimmers, A., Aigouy, L., Mortier, M., Sharoni, A., Wang, S., West, K. G., … Schuller, I. K. (2013). Role of Thermal Heating on the Voltage Induced Insulator-Metal Transition inVO2. Physical Review Letters, 110(5). doi:10.1103/physrevlett.110.056601Kats, M. A., Blanchard, R., Genevet, P., Yang, Z., Qazilbash, M. M., Basov, D. N., … Capasso, F. (2013). Thermal tuning of mid-infrared plasmonic antenna arrays using a phase change material. Optics Letters, 38(3), 368. doi:10.1364/ol.38.000368Chae, B.-G., Kim, H.-T., Youn, D.-H., & Kang, K.-Y. (2005). Abrupt metal–insulator transition observed in VO2 thin films induced by a switching voltage pulse. Physica B: Condensed Matter, 369(1-4), 76-80. doi:10.1016/j.physb.2005.07.032Ruzmetov, D., Gopalakrishnan, G., Deng, J., Narayanamurti, V., & Ramanathan, S. (2009). Electrical triggering of metal-insulator transition in nanoscale vanadium oxide junctions. Journal of Applied Physics, 106(8), 083702. doi:10.1063/1.3245338Joushaghani, A., Jeong, J., Paradis, S., Alain, D., Stewart Aitchison, J., & Poon, J. K. S. (2014). Voltage-controlled switching and thermal effects in VO2 nano-gap junctions. Applied Physics Letters, 104(22), 221904. doi:10.1063/1.4881155Markov, P., Marvel, R. E., Conley, H. J., Miller, K. J., Haglund, R. F., & Weiss, S. M. (2015). Optically Monitored Electrical Switching in VO2. ACS Photonics, 2(8), 1175-1182. doi:10.1021/acsphotonics.5b00244Yang, Z., Hart, S., Ko, C., Yacoby, A., & Ramanathan, S. (2011). Studies on electric triggering of the metal-insulator transition in VO2thin films between 77 K and 300 K. Journal of Applied Physics, 110(3), 033725. doi:10.1063/1.3619806Yoon, J., Lee, G., Park, C., Mun, B. S., & Ju, H. (2014). Investigation of length-dependent characteristics of the voltage-induced metal insulator transition in VO2 film devices. Applied Physics Letters, 105(8), 083503. doi:10.1063/1.4893783Sánchez, L., Rosa, A., Griol, A., Gutierrez, A., Homm, P., Van Bilzen, B., … Sanchis, P. (2017). Impact of the external resistance on the switching power consumption in VO2 nano gap junctions. Applied Physics Letters, 111(3), 031904. doi:10.1063/1.4994326Ryckman, J. D., Diez-Blanco, V., Nag, J., Marvel, R. E., Choi, B. K., Haglund, R. F., & Weiss, S. M. (2012). Photothermal optical modulation of ultra-compact hybrid Si-VO_2 ring resonators. Optics Express, 20(12), 13215. doi:10.1364/oe.20.013215Ryckman, J. D., Hallman, K. A., Marvel, R. E., Haglund, R. F., & Weiss, S. M. (2013). Ultra-compact silicon photonic devices reconfigured by an optically induced semiconductor-to-metal transition. Optics Express, 21(9), 10753. doi:10.1364/oe.21.010753Abreu, E., Gilbert Corder, S. N., Yun, S. J., Wang, S., Ramírez, J. G., West, K., … Averitt, R. D. (2017). Ultrafast electron-lattice coupling dynamics in VO2 and V2O3 thin films. Physical Review B, 96(9). doi:10.1103/physrevb.96.094309Sánchez, L., Lechago, S., & Sanchis, P. (2015). Ultra-compact TE and TM pass polarizers based on vanadium dioxide on silicon. Optics Letters, 40(7), 1452. doi:10.1364/ol.40.001452Joushaghani, A., Jeong, J., Paradis, S., Alain, D., Stewart Aitchison, J., & Poon, J. K. S. (2015). Wavelength-size hybrid Si-VO_2 waveguide electroabsorption optical switches and photodetectors. Optics Express, 23(3), 3657. doi:10.1364/oe.23.003657Diana, L. D. S., Juan, F. C., Escutia, A. R., & Kilders, P. S. (2017). Ultra-compact electro-absorption VO2–Si modulator with TM to TE conversion. Journal of Optics, 19(3), 035401. doi:10.1088/2040-8986/aa5c06Sanchez, L., Lechago, S., Gutierrez, A., & Sanchis, P. (2016). Analysis and Design Optimization of a Hybrid VO2/Silicon2 $\times$ 2 Microring Switch. IEEE Photonics Journal, 8(2), 1-9. doi:10.1109/jphot.2016.2551463Miller, K. J., Hallman, K. A., Haglund, R. F., & Weiss, S. M. (2017). Silicon waveguide optical switch with embedded phase change material. Optics Express, 25(22), 26527. doi:10.1364/oe.25.026527Clark, J. K., Ho, Y.-L., Matsui, H., & Delaunay, J.-J. (2018). Optically Pumped Hybrid Plasmonic-Photonic Waveguide Modulator Using the VO2 Metal-Insulator Phase Transition. IEEE Photonics Journal, 10(1), 1-9. doi:10.1109/jphot.2017.2784429Kumar, S., Pickett, M. D., Strachan, J. P., Gibson, G., Nishi, Y., & Williams, R. S. (2013). Local Temperature Redistribution and Structural Transition During Joule‐Heating‐Driven Conductance Switching in VO 2. Advanced Materials, 25(42), 6128-6132. doi:10.1002/adma.201302046Simon Mun, B., Yoon, J., Mo, S.-K., Chen, K., Tamura, N., Dejoie, C., … Ju, H. (2013). Role of joule heating effect and bulk-surface phases in voltage-driven metal-insulator transition in VO2 crystal. Applied Physics Letters, 103(6), 061902. doi:10.1063/1.4817727Freeman, E., Stone, G., Shukla, N., Paik, H., Moyer, J. A., Cai, Z., … Datta, S. (2013). Nanoscale structural evolution of electrically driven insulator to metal transition in vanadium dioxide. Applied Physics Letters, 103(26), 263109. doi:10.1063/1.4858468Gopalakrishnan, G., Ruzmetov, D., & Ramanathan, S. (2009). On the triggering mechanism for the metal–insulator transition in thin film VO2 devices: electric field versus thermal effects. Journal of Materials Science, 44(19), 5345-5353. doi:10.1007/s10853-009-3442-7Leroy, J., Crunteanu, A., Bessaudou, A., Cosset, F., Champeaux, C., & Orlianges, J.-C. (2012). High-speed metal-insulator transition in vanadium dioxide films induced by an electrical pulsed voltage over nano-gap electrodes. Applied Physics Letters, 100(21), 213507. doi:10.1063/1.4721520Xu, X., He, X., Wang, H., Gu, Q., Shi, S., Xing, H., … Chu, J. (2012). The extremely narrow hysteresis width of phase transition in nanocrystalline VO2 thin films with the flake grain structures. Applied Surface Science, 261, 83-87. doi:10.1016/j.apsusc.2012.07.098Kumar, S., Lenoble, D., Maury, F., & Bahlawane, N. (2015). Synthesis of vanadium oxide films with controlled morphologies: Impact on the metal-insulator transition behaviour. physica status solidi (a), 212(7), 1582-1587. doi:10.1002/pssa.201532325Guzman, G., Morineau, R., & Livage, J. (1994). Synthesis of vanadium dioxide thin films from vanadium alkoxides. Materials Research Bulletin, 29(5), 509-515. doi:10.1016/0025-5408(94)90039-6Gao, W., Wang, C. M., Wang, H. Q., Henrich, V. E., & Altman, E. I. (2004). Growth and surface structure of vanadium oxide on anatase (0 0 1). Surface Science, 559(2-3), 201-213. doi:10.1016/j.susc.2004.04.028Peter, A. P., Martens, K., Rampelberg, G., Toeller, M., Ablett, J. M., Meersschaut, J., … Radu, I. P. (2014). Metal-Insulator Transition in ALD VO2Ultrathin Films and Nanoparticles: Morphological Control. Advanced Functional Materials, 25(5), 679-686. doi:10.1002/adfm.201402687Rosa, Á., Gutiérrez, A., Brimont, A., Griol, A., & Sanchis, P. (2016). High performace silicon 2x2 optical switch based on a thermo-optically tunable multimode interference coupler and efficient electrodes. Optics Express, 24(1), 191. doi:10.1364/oe.24.000191Van Bilzen, B., Homm, P., Dillemans, L., Su, C.-Y., Menghini, M., Sousa, M., … Locquet, J.-P. (2015). Production of VO2 thin films through post-deposition annealing of V2O3 and VOx films. Thin Solid Films, 591, 143-148. doi:10.1016/j.tsf.2015.08.03

Impact of the external resistance on the switching power consumption in VO2 nano gap junctions

[EN] The influence of an external resistance on the performance of VO2 nanogap junctions is analyzed and experimentally characterized. The current-voltage response shows the reversible metal-insulator transition typical of VO2 based devices. When reaching the metallic state, the current through the VO2 junction is abruptly increased, which may result in electrical contact damage. Therefore, an external resistance in series with the VO2 junction is usually employed to limit the maximum current through the device. Our results indicate that the external resistance plays a key role in the switching power consumption showing an optimum value, which depends on the dimensions of the VO2 junction. In such a way, power consumption reductions up to 90% have been demonstrated by selecting the optimum external resistance value.This work was supported by the European Commission under Project No. FP7-ICT-2013-11-619456 SITOGA. Financial support from TEC2016-76849-C2-2-R and NANOMET Conselleria de Educacio, Cultura i Esport-PROMETEOII/2014 034 is also acknowledged. P.H. acknowledges support from Becas Chile-CONICYT.Sánchez Diana, LD.; Rosa Escutia, Á.; Griol Barres, A.; Gutierrez Campo, AM.; Homm, P.; Van Bilzen, B.; Menghini, M.... (2017). Impact of the external resistance on the switching power consumption in VO2 nano gap junctions. Applied Physics Letters. 111(3):1-4. https://doi.org/10.1063/1.4994326S14111

Nickel Nanopillar Arrays Electrodeposited on Silicon Substrates Using Porous Alumina Templates

Nickel nanopillar arrays were electrodeposited onto silicon substrates using porous alumina membranes as a template. The characterization of the samples was done by scanning electron microscopy, X-ray diffraction, and alternating force gradient magnetometry. Ni nanostructures were directly grown on Si by galvanostatic and potentiostatic electrodeposition techniques in three remarkable charge transfer configurations. Differences in the growth mechanisms of the nanopillars were observed, depending on the deposition method. A high correlation between the height of the nanopillars and the charge synthesis was observed irrespective of the electrochemical technique. The magnetization measurements demonstrated a main dependence with the height of the nanopillars. The synthesis of Ni nanosystems with a controllable aspect ratio provides an effective way to produce well-ordered networks for wide scientific applications

Magnetic orders and origin of exchange bias in Co clusters embedded oxide nanocomposite films

Magnetic nanoparticles embedded oxide semiconductors are interesting candidates for spintronics in view of combining ferromagnetic (FM) and semiconducting properties. In this work, Co-ZnO and Co-V2O3 nanocomposite thin films are synthesized by Co ion implantation in crystalline thin films. Magnetic orders vary with the implantation fluence in Co-ZnO, where superparamagnetic (SPM) order appears in the low-fluence films (2  ×  1016 and 4  ×  1016 ions cm-2) and FM order co-exists with the SPM phase in high-fluence films (1  ×  1017 ions cm-2). Exchange bias (EB) appears in the high-fluence films, with an EB field of about 100 Oe at 2 K and a blocking temperature of around 100 K. On the other hand, Co-V2O3 thin films with an implantation fluence of 3.5  ×  1016 ions cm-2 exhibit a clear antiferromagnetic (AFM) coupling at low temperatures without the EB effect. The different magnetic behavior of the Co-implanted films with different Co content leads us to conclude that the observed EB effect in the Co-ZnO films results from the FM/AFM coupling between sizable Co nanoparticles and their CoO/Co3O4 surroundings in the (Zn,Co)O matrix. On the other hand, the absence of EB effect in Co-V2O3 appears to be due to the small size of the FM Co nanoparticles in spite of an AFM magnetic order. Detailed studies of magnetic orders and EB effect in magnetic nanocomposite semiconductors can pave the way for their application in spintronics.status: publishe