The fabrication of controlled nanostructures such as quantum dots, nanotubes, nanowires, and nanopillars has progressed rapidly over the past 10 years. However, both bottom-up and top-down methods to integrate the nanostructures are met with several challenges. For practical applications with the high level of the integration, an approach that can fabricate the required structures locally is desirable. In addition, the electrical signal to construct and control the nanostructures can provide significant advantages toward the stability and ordering. Through experiments on the negative resistance switching phenomenon in Pt-NiO-Pt structures, we have fabricated nanofilament channels that can be electrically connected or disconnected. Various analyses indicate that the nanofilaments are made of nickel and are formed at the grain boundaries. The scaling behaviors of the nickel nanofilaments were closely examined, with respect to the switching time, power, and resistance. In particular, the 100 nm x 100 nm cell was switchable on the nanosecond scale, making them ideal for the basis for high-speed, high-density, nonvolatile memory applications.

We report the presence of defects in CH3NH3PbI3, which is one of the main factors that deteriorates the performance of perovskite solar cells.

No abstract

No abstract

Universal memory, which combines the high-speed performance of present-day static random access memory (SRAM) [1] with the non-volatility of Flash [1] must realize several goals such as low operating current, size scalability, and compatibility with mass production to become a feasible memory alternative. The best approach towards the goal of high density is to utilize stackable structures with a crossbar geometry, [2] and to achieve low-temperature fabrication [3] while still retaining a selective switch (transistor or diode) as the data storage element. Thus for high-density applications, crossbar structures are ideal, whereas for non-volatility, resistance-change materials show the best promise. In order to realize the fabrication of universal memory elements, it is imperative to develop a class of materials and structures that combine robust processibility, strong scalability, and rapid programming speed with non-volatility and low power consumption. In our work, we have focused on defining just the storage node portion of the devices, which utilize the resistance change within the film to store information via two different stable resistance states. Here, we have attempted to determine the properties of such structures and to study the mechanisms behind resistance RAM (RRAM) storage. Our Ti-doped (0.1 wt %) NiO samples deposited at room temperature show favorable node characteristics such as the lowest write current reported thus far for a unipolar switching resistance-change-based device (ca. 10 lA). In addition, the programming speed is comparable to the write time of SRAM (10 ns). By combining this node element with an appropriate select switch, such as a high-performance diode, a threshold device, or a two-terminal non-ohmic device, it becomes possible to fabricate high-density universal memory. Indeed, the fabrication of universal memory as the next generation of non-volatile memory is the logical goal for research in this field. In comparison to Flash and dynamic RAM (DRAM), which are the current industry standards, next generation memories must combine the non-volatility of Flash with the high-speed performance of SRAM.[1] Several emerging non-volatile memory architectures have been investigated in order to fabricate materials that fit these specifications. [1,[4][5][6] For example, phase-change RAM (PRAM) [7] utilizes resistance switching accompanied by full or partial phase changes in chalcogenide materials induced by electrical pulses as a method for storing information. Recently, much effort has been devoted to investigations of magnetic race-track memory, a new concept in magnetic non-volatile memory involving the storage of information in the domain walls of materials. [8,9] Also, RRAM [3,[10][11][12][13][14][15][16][17][18] has been studied as a possible candidate for new memory storage devices. RRAM is based on either transition metal oxides that exhibit unipolar switching properties [10][11][12] or perovskite materials displaying bipolar switching properties; [13][14][15] essentially, this is...

Quercetin, a plant-derived flavonoid found in fruits, vegetables and tea, has been known to possess bioactive properties such as anti-oxidant, anti-inflammatory and anti-cancer. In this study, anti-cancer effect of quercetin and its underlying mechanisms in triple-negative breast cancer cells was investigated. MTT assay showed that quercetin reduced breast cancer cell viability in a time and dose dependent manner. For this, quercetin not only increased cell apoptosis but also inhibited cell cycle progression. Moreover, quercetin increased FasL mRNA expression and p51, p21 and GADD45 signaling activities. We also observed that quercetin induced protein level, transcriptional activity and nuclear translocation of Foxo3a. Knockdown of Foxo3a caused significant reduction in the effect of quercetin on cell apoptosis and cell cycle arrest. In addition, treatment of JNK inhibitor (SP 600125) abolished quercetin-stimulated Foxo3a activity, suggesting JNK as a possible upstream signaling in regulation of Foxo3a activity. Knockdown of Foxo3a and inhibition of JNK activity reduced the signaling activities of p53, p21 and GADD45, triggered by quercetin. Taken together, our study suggests that quercetin induces apoptosis and cell cycle arrest via modification of Foxo3a signaling in triple-negative breast cancer cells.

A chemical route to single-walled carbon nanotubes (SWCNTs) under ambient conditions has been developed. Silica powder was immersed in a mixture solution of ferrocene and p-xylene. After sonication at atmospheric pressure and room temperature, we obtained high-purity SWCNTs. Sonochemical effects may lead to producing high-purity SWCNTs. The process could be readily generalized to synthesize other forms of carbon-based materials, such as fullerenes, multiwalled nanotubes, carbon onions, and diamond, in liquid solution under ambient conditions.

We observed the atomic structures for each reset and set state in a phase-change random access memory fabricated using stoichiometric crystalline Ge 2 Sb 2 Te 5 . The reset state clearly showed a mixture of dome-shaped amorphous and crystal structure surrounding amorphous, but the set state showed abnormally grown large grains due to recrystallization of the amorphous structure. The crystal structure of the recrystallized grain was face-centered cubic. The element analysis indicated that the atomic composition changes to nonstoichiometric phase in the active regions of the reset and the set state, which is Sb-rich and Te-deficient compared to the pristine stoichiometric composition. Analysis showed that thermal interdiffusion of Sb and Te caused nonstoichiometric nature of the material to reach the energetically stable state in the active region.Great efforts to develop next generation memories with fewer technical barriers, longer lifetime, and better performance in comparison with existing memories, such as flash, and dynamic-static random access memories, have been attempted. Recently, there has been a great deal of interest in phase-change random access memory ͑PRAM͒ based on stoichiometric crystalline Ge 2 Sb 2 Te 5 ͓referred to as GST ͑2/2/5͔͒ films. PRAM takes advantage of electrically bistable status of resistance difference between its amorphous ͑reset state with high resistance͒ and crystalline phase ͑set state with low resistance͒. 1,2 Amorphous resistance is at least 10 2 times higher than crystalline resistance. Hence, PRAM is considered to be one of the promising memories owing to its nonvolatility, good scalability, large sensing signal, fast reading and moderately fast writing time, and long data endurance.In the operation, PRAM uses a high current pulse to make the amorphous state, and a low current pulse to get the crystalline state. The current is applied to heat up a contact region between GST and a bottom electrode ͑role of resistive heater͒ using Joule heating. During the high current pulse, the GST loses the polycrystalline ordering as temperature exceeds its melting point. After that, the GST is quenched and stays in a structurally disordered state. The low current pulse and its sufficient duration is used to maintain temperature in the crystallization range for both nucleation and crystallization of the GST. The amorphous and the recrystallized GST right near the contact region is the active region. The typical setreset characteristics of the device in this study are shown in Fig. 1, which is fully integrated in complementary metal-oxidesemiconductor ͑CMOS͒ technology.Because of high current driving operation mechanism, PRAM has suffered from device failure such as delamination. Recently, Ryu et al. reported another important issue regarding compositional alteration of GST͑2/2/5͒ during operation. 3 In their report GST͑2/2/5͒ phase is not stable and has changed to GST͑15/47/38͒. However, they have has not mentioned the detailed phenomena of the GST/TiN contact region, especially element t...