Metal-Ferroelectric-Oxide-Si (MFEOS) field effect transistor (FET) with ferroelectric polyvinylidene fluoride trifluoroethylene copolymer (PVDF-TrFE) gate for nonvolatile memory application is demonstrated. Memory window ascribed to ferroelectric polarization switching has been quantified by shift of threshold voltage are ~ 4-5V. Non saturating IDS is due to free ionic polarization field. IDS-VDS characteristics of functional FET are realized after AC poling.

CuTCNQ (TCNQ=7,7,8,8-tetracyanoquinodimethane) is a resistive switching charge-transfer complex which can be used for organic nonvolatile memories. In this contribution we report on a thorough investigation of the electrical switching of CuTCNQ memories. Our memories currently achieve an endurance of up to 10000 write/erase cycles with a clear distinction between ON and OFF reading currents. ON and OFF threshold voltages follow a Gaussian distribution. Temperature dependent measurements of CuTCNQ based organic memories show a semiconductor like behavior for the ON state. The retention time of the ON state exceeded 60 hours at room temperature. Electrical switching of CuTCNQ memories in air was virtually not affected by temperatures up to 80°C, but becomes erratic at 120°C. The CuTCNQ material itself already starts to decompose around 200°C in presence of oxygen as shown by thermogravimetric analysis.

The polarity of gates and the threshold voltages are primary parameters that determine the electric fields in the gate stack region of non-volatile memories. This field is central to programming, retention and the other characteristics of the devices. We have investigated the effect of the gate polysilicon polarity, experimentally, for silicon-oxide-nitride-oxide-silicon (SONOS) memory devices on silicon-on-insulator (SOI) wafers. An ultra-thin oxide-nitride-oxide (ONO) film with high trap density and strong localization of the trapping provides the scalability and retention in our structures. The effect of ONO film, grown and deposited and of doping was simulated and characterized. Retention is affected by the electric field between the control gate and the storage node. Our experiments and simulations verify the consequences of different polarity of control gates through the change in electric field that they cause in retention and erase times for n+ and p+ polysilicon gate SONOS memories is verified through the characteristic energies of the processes.

With photoelectron spectroscopy, we study the interface chemistry of the copolymer poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) and different electrode materials. We compare the interfaces aluminum/P(VDF-TrFE) and PEDOT:PSS/P(VDF-TrFE). PEDOT:PSS is a conductive polymer (Poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate)). The data sug-gest that we have an interface layer for electrodes, made of aluminum. An interface reaction occurs in both cases: for aluminum as top and as bottom electrode. In contrast, the organic PE-DOT:PSS electrode shows no chemical interaction with the P(VDF-TrFE) polymer. The much lower reactivity of organic electrodes, compared to aluminum, gives a direct hint to im-proved functional properties of thin organic ferroelectric films.

A parallel resistance model (PRM), in which the total resistance, Rtotal, is given by a parallel connection of resistance of a filament, Rfila, and that of a film excluding a filament, Rexcl, was proposed to understand DC electric properties of resistive RAM (ReRAM). Here, the relationship of 1/Rtotal = 1/Rfila + 1/Rexcl is satisfied. To prove the validity of this model, the dependence of the relationship between resistance and temperature, R(T), of Pt/NiO/Pt on an area of a top electrode, S, was investigated. It was clarified that R(T) depended on S, which is the result definitely expected by the PRM. It was also clarified that smaller S is crucial to observe intrinsic properties of a filament of ReRAM.

Nonlead perovskite type, Ba(Cu1/3Nb2/3−xWx)O3 (x = 0, 0.025), ferroelectric ceramic powders (BCN) were prepared by the microwave-assisted citrate-nitrate sol-gel technique. The gel was formed from a stable and homogeneous sol prepared by mixing stable solutions of barium- and copper-nitrate, tungsten citrate, and peroxo-citrato-niobium precursors. Microwave irradiation of the gel resulted in a dark, fluffy precursor material after auto-combustion. Calcination of the as-combusted samples produces a single phase with tetragonal splitting in X-Ray diffraction patterns. The crystallite size of the synthesized samples was found to be 41 nm. Particle morphology and the size of nanocrystalline powders were characterized by scanning electron microscopy and photon correlation spectroscopy, respectively. Electrical and dielectric properties of sintered samples were investigated by impedance spectroscopy. The isothermal ac measurements were performed from room temperature, up to 600 °C for W6+ doped and undoped BCN samples.

We have characterized the in-film stress and the mechanical constants of a growth-dominated phase-change SbTe-alloy, a material beneficially used in the line-cell phase change memory architecture. The influence of the thickness of the films (5-120 nm) and of the substrate used for its deposition (Si, SiO2 and SiC) was studied. The characterizations were carried out on both amorphous and crystalline films. The crystallization temperature was determined by the resistance changes as a function of the temperature. The mechanical characteristics of the films were measured by the wafer curvature method. We observed that the mechanical behavior of these films was strongly dependent on their thicknesses and on the substrate material. For the thinnest amorphous films, the in-film stress was highly compressive (with the largest compressive stress for films on SiC), while it tended to be very low (fully relaxed films) for films thicker than 20 nm. The amorphous films furthermore did not reveal any stress relaxation in time-dependent stress measurements. Therefore, it was not possible to quantify the viscosity of the SbTe-alloy. This result maybe related to a lower defect state in the very thin films used, or to a blocking of the defects by enhanced reactivity of these thin SbTe-alloy films with their surroundings, both resulting in the absence of relaxation in the amorphous state. Finally, the coefficients of thermal expansion (CTE) of the amorphous and crystalline SbTe-alloys were similar, 1–3×10−6 K−1. These values were comparable to the CTE's of the substrates, clearly indicating that for thin films the substrates dominate their thermal expansion behavior.

Current mainstream memory technologies are unlikely to completely fulfill the solid state data storage requirements that will be imposed beyond the 32 nm node of the International Technology Roadmap for Semiconductors. One potential replacement technology is resistance change memory based on solid electrolytes and a number of significant research and development efforts are already underway. The lowering of the resistance is attained by the reduction of ions in a relatively high resistivity electrolyte to form a conducting bridge between the electrodes. The resistance is returned to the high value via the application of a reverse bias that results in the breaking of the conducting pathway. Germanium chalcogenides and Ag-Ge-S ternaries in particular possess good thermal processing characteristics while maintaining the necessary high ion mobility for rapid switching. Thermally diffused copper in deposited SiO2 also is of interest, as thermal stability in excess of 600°C and commonly used constituents makes this material system compatible with the widest range of back-end-of-line processes. This paper details some of the developments in the understanding of the materials used in solid electrolyte resistance change devices and presents a short review of the electrical characteristics of devices based on Ag-Ge-S and Cu-Si-O electrolytes.

In the use of single/few electrons in distributed storage for non-volatile, low power, and fast memories, providing statistical reproducibility at the nanoscale is a key challenge since relative variance has dependence and the devices operate with limited number of storage sites. We have used defects at interfaces of dielectrics to evaluate this reproducibility and the performance of memories. These experiments show that nearly 100 electrons can be stored at 30 nm dimensions, sufficient for reproducibility, and that a minimum of tunneling oxide thickness is required to assure reliable retention characteristics. Different tunneling oxide thicknesses and the effect of LDD process are investigated to draw these conclusions.

Organic memory devices are considered as a viable approach for future information processing. We demonstrate this type of memory devices evolving from multiple layers structure to solution synthesis hybrid biomolecule structure. By forming a thin organic-nanoparticle layer or virus-nanoparticle layer in the crossbar junction, electronic memory effect based on electrical bistable states with a large on/off ratio, and long retention time is achieved. Temperature dependent data retention shows the nanoparticle formation determines the charge storage activation energy. Such organic, bio-inorganic nanostructures are promising for future memory technology.

Resistance random access memory (RRAM) has attracted intense attention in recent years for the potential application as nonvolatile memory. One of the tempting properties of RRAM is the multi-level memory, in which several resistance states can be obtained and each of them can be used to save information. In this paper, the electric-pulse-induced multi-level resistance switching of the Ag-La0.7Ca03MnO3-Pt heterostructures was studied. The multi-level resistance switching (MLRS) was observed in the switching from high to low resistance state (HRS→LRS) by applying electric pulse with various pulse voltages. The threshold pulse voltages of MLRS are related to the initial resistance values as well as the switching directions. On the other hand, the resistance switching behavior from low to high resistance states (LRS→HRS) shows unobvious MLRS. MLRS was explained by the parallel effect of multi-filament forming/rupture in the Ag/La0.7Ca0.3MnO3 interface layer. The present results suggest a possible application of Ag-La0.7Ca03MnO3-Pt heterostructures as multi-level memory devices.