Effect of Mo doping on phase change performance of Sb_(2)Te_(3)

Mo,as a dopant,is doped into SbTe to improve its thermal stability.It is shown in this paper that the Mo-doped Sb_(2)Te_(3)(Mo_(0.26)Sb_(2)Te_(3),MST)material possesses phase change memory(PCM)applications.MST has better thermal stability than Sb_(2)Te_(3)(ST)and will crystallize only when the annealing temperature is higher than 250℃.With the good thermal stability,MST-based PCM cells have a fast crystallization time of 6 ns.Furthermore,endurance up to 4×10^(5) cycles with a resistance ratio of more than one order of magnitude makes MST a promising candidate for PCM applications.

Local structural characteristics of Sb_2Te_3 films studied by reverse Monte Carlo modeling

Atomic configuration and connectivity of Sb_2Te_3 thin film are investigated using high-energy X-ray diffraction and reverse Monte Carlo simulation. Atomic model details of Sb_2Te_3 thin film are compared with liquid and amorphous Sb_2Te_3 reported in other article. Simulations show that both Sb–Sb and Te–Te homopolar bonds are present in the models. In phase transition process,atomic configuration of the sample rearranges gradually through the forming of Sb–Te bonds and the breaking of Sb–Sb and Te–Te bonds.

Mechanism of titanium-nitride chemical mechanical polishing

During the preparation of the phase change memory,the deposition and chemical mechanical polishing(CMP)of titanium nitride(TiN)are indispensable.A new acidic slurry added with sodium hypochlorite(NaClO)as an oxidizer is developed for the CMP of TiN film.It has achieved a material removal rate of 76 nm/min,a high selectivity between TiN film and silica(SiO_(2))films of 128:1,a selectivity between TiN film and tungsten film of 84:1 and a high surface quality.To understand the mechanism of TiN CMP process,x-ray photoelectron(XPS)spectroscope and potentiodynamic polarization measurement are performed.It is found that the mechanism of TiN CMP process is cyclic reaction polishing mechanism.In addition,both static corrosion rate and the inductively coupled plasma results indicate TiN would not be dissolved,which means that the mechanical removal process of oxide layer plays a decisive role in the material removal rate.Finally,the mechanism of TiN polishing process is given based on the analysis of surface potential and the description of blocking function.

Crystallization Process of Superlattice-Like Sb/SiO_2 Thin Films for Phase Change Memory Application

After compositing with SiO_2 layers, it is shown that superlattice-like Sb/SiO_2 thin films have higher crystallization temperature（~240°C）, larger crystallization activation energy（6.22 e V）, and better data retention ability（189°C for 10 y）. The crystallization of Sb in superlattice-like Sb/SiO_2 thin films is restrained by the multilayer interfaces. The reversible resistance transition can be achieved by an electric pulse as short as 8 ns for the Sb（3 nm）/SiO_2（7 nm）-based phase change memory cell. A lower operation power consumption of 0.09 m W and a good endurance of 3.0 × 10~6 cycles are achieved. In addition, the superlattice-like Sb（3 nm）/SiO_2（7 nm） thin film shows a low thermal conductivity of 0.13 W/（m·K）.

A novel non-volatile memory storage system for I/O-intensive applications

The emerging memory technologies, such as phase change memory （PCM）, provide chances for high- performance storage of I/O-intensive applications. However, traditional software stack and hardware architecture need to be optimized to enhance I/O efficiency. In addition, narrowing the distance between computation and storage reduces the number of I/O requests and has become a popular research direction. This paper presents a novel PCM- based storage system. It consists of the in-storage processing enabled file system （ISPFS） and the configurable parallel computation fabric in storage, which is called an in-storage processing （ISP） engine. On one hand, ISPFS takes full advantage of non-volatile memory （NVM）＇s characteristics, and reduces software overhead and data copies to provide low-latency high-performance random access. On the other hand, ISPFS passes ISP instructions through a command file and invokes the ISP engine to deal with I/O-intensive tasks. Extensive experiments are performed on the prototype system. The results indicate that ISPFS achieves 2 to 10 times throughput compared to EXT4. Our ISP solution also reduces the number of I/O requests by 97% and is 19 times more efficient than software implementation for I/O-intensive applications.

Synthesis of colloid silica coated with ceria nano-particles with the assistance of PVP

In this paper, a facile synthesis of 100 nm commercial colloid silica coated with nano-ceria core-shell composite particles by the precipitation method using ammonium cerium nitrate and urea as a precipitator with polyvinylpyrrolidone （PVP） as an assistant was briefly introduced. The results showed that the colloid silica was surrounded by nano-ceria uniformly forming the core-shell composite particles. The synthesis process was further discussed and optimized. It was found that the type and quantity of surfactant played a key role in the process. PVP connected the surface of colloid silica and that of the ceria precursor.