M. B. Pyun

Reproducible hysteresis and resistive switching in metal-CuxO-metal heterostructures

Materials showing reversible resistance switching between high-resistance state and low-resistance state at room temperature are attractive for today’s semiconductor technology. In this letter, the reproducible hysteresis and resistive switching characteristics of metal-CuxO-metal (M-CuxO-M) heterostructures driven by low voltages are demonstrated. The fabrication of the M-CuxO-M heterostructures is fully compatible with the standard complementary metal-oxide semiconductor process. The hysteresis and resistive switching behavior are discussed. The good retention characteristics are exhibited in the M-CuxO-M heterostructures by the accurate controlling of the preparation parameters.

Uniform resistive switching with a thin reactive metal interface layer in metal-La0.7Ca0.3MnO3-metal heterostructures

A thin samarium (Sm) metal layer was introduced to improve the resistive hysteresis and switching uniformity. Sm reacts with the La0.7Ca0.3MnO3 and forms a thin interface oxide layer, which is responsible for the switching. The switching occurs without any forming process. Compared with conventional resistive memory device based on localized filament formation, Sm∕La0.7Ca0.3MnO3 devices show area-dependent resistance which indicates uniform resistive switching. Under a positive bias, electromigration of oxygen ions (O2−) forms thicker oxide (SmOx), which dissociates under a negative bias, causes high and low resistance states, respectively. Estimated data retention of more than 10yr was observed at 85°C.

Excellent uniformity and reproducible resistance switching characteristics of doped binary metal oxides for non-volatile resistance memory applications

We have investigated various doped metal oxides such as copper doped molybdenum oxide, copper doped Al₂O₃, copper doped ZrO₂, aluminium doped ZnO, and Cu_xO for novel resistance memory applications. Compared with non-stoichiometric oxides (Nb₂O_5-x, ZrO_x, SrTiO_x), doped metal oxides show higher device yield. Moreover, Cu:MoO_x have demonstrated excellent memory characteristics such as reliability under programming cycles, potential multi-bit operation, good data retention, highly scalable property, and fast switching speed. The switching mechanism of the copper doped molybdenum oxide can be explained by the generation and rupture of multi-filaments under the electrical stress

Electrical and reliability characteristics of copper-doped carbon (CuC) based resistive switching devices for nonvolatile memory applications

We have investigated copper-doped carbon (CuC) as a new solid-state electrolyte material for resistive switching devices. Compared with CuS electrolytes, CuC devices demonstrate good memory characteristics such as a high resistance ratio of over two orders, higher operation voltage, and high temperature retention characteristics. Using 1000 cell array devices, we have also confirmed uniform distributions of resistance and switching voltages. Both high and low resistance states showed negligible degradation of resistance for over 104 s at 85 °C, confirming good retention characteristics.

Nanoscale Resistive Switching of a Copper–Carbon-Mixed Layer for Nonvolatile Memory Applications

The nanoscale resistance switching property of copper-carbon-mixed (Cu-C) layer was investigated for nonvolatile memory applications. The Cu-C layer of the cross-point cell array showed typical filament switching with two orders of on/off ratio, exhibiting stable resistance switching and a narrow distribution of set and reset voltages in the nanoscale junction. In addition, we investigated the area dependence of operation current. Based on these results and current-voltage dependence on temperature, we discussed a potential switching mechanism of Cu-C layer.

Effect of ruthenium oxide electrode on the resistive switching of Nb-doped strontium titanate

We studied resistance switching characteristics of ruthenium oxide (RuOx)/niobium-doped strontium titanate (Nb:STO) contact. With increasing oxygen content of oxide electrode, the resistance window was improved. The switching speed of RuOx electrode also showed improvement compared to platinum (Pt) electrode. The RuOx film contains amorphous phase and also forms an interface oxide layer at the RuOx/Nb:STO contact, which suggests defect generation near the interface. Additionally, the interface reaction disturbs the crystalline orientation of Nb:STO. These defect sites facilitate switching properties by easy drift of current and oxygen ion and also by modulation of barrier height.

Resistive switching characteristics of metal oxide for nonvolatile memory applications

The resistance switching characteristics of several metal oxides has been reported recently for nonvolatile memory applications (NVM). However, various issues such as the switching mechanisms, switching uniformity, scalability and reproducibility have not yet been solved. In this paper, we discuss the recent progress of switching mechanisms and switching behaviors of various materials.