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Resistively switching devices are considered promising for next-generation nonvolatile random-access memories. Today, such memories are fabricated by means of "top-down approaches" applying thin films sandwiched between nanoscaled electrodes. In contrast, this work presents a "bottom-up approach" disclosing for the first time the resistive switching (RS) of individual TiO2 nanoparticles (NPs). The NPs, which have sizes of 80 and 350 nm, respectively, are obtained by wet chemical synthesis and thermally treated under oxidizing or vacuum conditions for crystallization, respectively. These NPs are deposited on a Pt/Ir bottom electrode and individual NPs are electrically characterized by means of a nanomanipulator system in situ, in a scanning electron microscope. While amorphous NPs and calcined NPs reveal no switching hysteresis, a very interesting behavior is found for the vacuum-annealed, crystalline TiO(2-x) NPs. These NPs reveal forming-free RS behavior, dominantly complementary switching (CS) and, to a small degree, bipolar switching (BS) characteristics. In contrast, similarly vacuum-annealed TiO2 thin films grown by atomic layer deposition show standard BS behavior under the same conditions. The interesting CS behavior of the TiO(2-x) NPs is attributed to the formation of a core-shell-like structure by re-oxidation of the reduced NPs as a unique feature.

The high voltage LiNi 0.5 Mn 1.5 O 4 spinel suffers from severe capacity fade when cycled against a graphitic anode as well as a relatively low theoretical capacity. Using metallic lithium as counter electrode, the stability is improved and the ability of the spinel structure to host 2 Li eq. can be used to improve the capacity. This leads to a theoretical specific energy of ∼1000 Wh kg −1 . Unfortunately, the cycling of 2 Li eq. involves a phase transition from cubic to tetragonal associated with material degradation. In this work doping is used to improve capacity retention when cycling between 2.0 and 5.0 V. Initial capacities and stabilities are directly dependent on synthesis conditions and doping elements. Therefore, Fe-and Ti-doped spinels are compared with Ru-and Ti-doped spinels and tested at different cycling conditions. The cycling stability can be improved significantly by using reannealed material and by changing the discharge cutoff criteria. Thus a capacity of 190 mAh g −1 is achieved at a rate of C/2 with a capacity retention of ∼92% after 100 cycles. Furthermore, differences in the discharge behavior between the differently treated Ru-and Ti-doped materials are discussed based on the electrochemical behavior, the particle morphology and in-situ XRD analysis. The LiNi 0.5 Mn 1.5 O 4 spinel (LNMO) is a potential candidate for a high-energy cathode material in Li ion batteries. This is due to the high operating voltage of ∼ 4.7 V vs. Li + /Li. 1,2 Regardless of the high voltage the spinel offers a lower specific energy compared with other cathode materials (e.g. Li-rich layered oxides with capacities of ca. 220 -250 mAh g −1 ). 3-5However, the ability to host an additional lithium on the 16c octahedral sites 6,7 when a lithium metal anode is used, leads to an increased specific energy. The theoretical capacity increases up to 294 mAh g −1 and a theoretical energy of around 1000 Wh kg 9,10 Furthermore the trivalent manganese is Jahn-Teller active and cycling is accompanied by a strong Jahn-Teller-distortion.7,9 The c-axis parameter is increased by ∼6% while the a-and b-axis parameters shrink by ca. 0.6% leading to a phase transition from cubic to tetragonal symmetry. 11,12 The loss of manganese and the mechanical strain due to the phase transition lead to a severe capacity fade. Therefore, stable cycling of 2 Li eq. in the LNMO\\Li metal system is not possible.In order to enhance the electrochemical stability of spinel cathode materials several studies use various elements as dopants (e.g. Cr, Fe, Ga;13 Fe, Cu, Al, Mg; 14C r, Fe, Co, Ga; 15 Ti 16 ). In many publications the positive influence of Fe-and/or Ti-doping on the electrochemical stability of LNMO has been shown. 13,14,[16][17][18][19][20] Another promising doping element is Ruthenium. It has also been investigated as dopant in previous studies for the manganese spinel 21 and the LNMO spinel. 22-25It leads to an increased rate capability due to a higher electronic conductivity as well as faster lithium diffusion. However, except from z E-mai...

Resistively switching devices are promising candidates for the next generation of non-volatile data memories. Such devices are up to now fabricated mainly by means of top-down approaches that apply thin films sandwiched between electrodes. Recent works have demonstrated that resistive switching (RS) is also feasible on chemically synthesized nanoparticles (NPs) in the 50 nm range. Following this concept, we developed this approach further to the sub-10 nm range. In this work, we report RS of sub-10 nm TiO2 NPs that were self-assembled into monolayers and transferred onto metallic substrates. We electrically characterized these monolayers in regard to their RS properties by means of a nanorobotics system in a scanning electron microscope, and found features typical of bipolar resistive switching.