M. R. Latif 1 , I. Csarnovics 1,2 , T. Nichol 1 , S. Kökényesi 2 , A. Csik, 3 M. Mitkova 1

1. Photolithography Free Ge-Se Based Memristive Arrays Material Characterization and Devices Testing • M. R. Latif1, I. Csarnovics1,2, T. Nichol1, S. Kökényesi2, A. Csik,3 M. Mitkova1 • 1. Department of Electrical and Computer Engineering Boise State University, Boise, ID - USA • Department of Experimental Physics, University of Debrecen, Debrecen - Hungary • Institute of Nuclear Research (ATOMKI), Debrecen - Hungary VI. Electrical Testing I. Motivation IV. FilmCharacterization - AFM • The IV curves for cells # 20 in the arrays are presented in the following figures. It is obvious that ChG surface with higher roughness results in a poorer device performance. • Devices threshold voltages (Vth) and the resistance plots are shown below: • The array allows individual device addressing. • Devices show six orders of magnitude difference between the low resistive state (LRS) and high resistive state (HRS). • Vth of Ge30Se70 and Ge40Se60 shows excellent repeatability. • Increase in Ge concentration results in improvement of the devices’ performance which is attributed to the formation of Ge-Ge bonds. • Devices performance depends on the film roughness which results in voids occurrence that obstructs bridge formation. • The devices showed good endurance at over 103 cycles. • Success already achieved at the single cell level suggests that conductive bridge memristor is well positioned for ultra high performance memory, neuromorphic computing and logic applications. • A high density conductive bridge memristor arrays on thin films metal/insulator/metal (MIM) stack is demonstrated in this work. RMS value of surface roughness in 25µm2 area of cells # 1, 10 and 20 in the array. The result shows that the SNMP method is suitable for via formation. Quality of the surface depends upon the films’ structure. II. Experimental Details • GexSe1-x films (where x = 0.2, 0.3 & 0.4) were thermally evaporated on top of 100nm sputtered W layer over a SiO2 film on a <100> Si substrate. • The thickness of the deposited chalcogenide (ChG) films was 1µm. • The samples were bombarded by Ar+ ions using Secondary Neutral Mass Spectrometry (SNMS) through a 50μm by 50μm Cu mesh for via formation. V. Raman Spectroscopy Analysis Areas (Arb.) Ge20Se80 Counts (Arb.) SNMS Setup Profilometer Image Profilometer Scan SNMS Measurement III. EDS Mapping Areas (Arb.) • EDS mapping of the data provides evidence of compositional distribution of different elements in the array stack. VII. Conclusion Ge30Se70 Counts (Arb.) Areas (Arb.) • A memristive array with devices build by Ge-Se thin films and Ag bridging the two device electrodes is demonstrated. • SNMP method for array formation shows excellent yield with stable ON/OFF ratio. • The individual devices demonstrate reliable performance. • Additional improvement in the cells can be achieved by formation of smoother layers within the vias and filling them homogeneously with thick Ag films. Virgin Via Ge40Se60 Counts (Arb.) Counts (Arb.) Counts (Arb.) Acknowledgment: This work was supported by the IMI-NFG under NSF Grant # DMR 0844014, TAMOP 4.2.2./B-10/1-2010-0024 and TAMOP 4.2.2.A-11/2/KONV-2012-0032 projects, which are co-financed by the European Union and European Social Fund. The financial support of the Czech Science Foundation (under the project No. P106/11/0506) is also acknowledged.