Weilong Li

Comparison of discrete-storage nonvolatile memories: advantage of hybrid method for fabrication of Au nanocrystal nonvolatile memory

In this paper, the memory characteristics of two kinds of metal-oxide-semiconductor (MOS) capacitors embedded with Au nanocrytals are investigated: hybrid MOS with nanocrystals (NCs) fabricated by chemical syntheses and rapid thermal annealing (RTA) MOS with NCs fabricated by RTA. For both kinds of devices, the capacitance versus voltage (C–V) curves clearly indicate the charge storage in the NCs. The hybrid MOS, however, shows a larger memory window, as compared with RTA MOS. The retention characteristics of the two MOS devices are also investigated. The capacitance versus time (C–t) measurement shows that the hybrid MOS capacitor embedded with Au nanocrystals has a longer retention time. The mechanism of longer retention time for hybrid MOS capacitor is qualitatively discussed.

The Synthesization of Si Nanocrystals Embedded in HfO2 Matrix by Electron Beam co-Evaporation Technique

Silicon nanocrystals synthesized by electron beam co-evaporation (EBCE) of Si and HfO2 mixture are studied. HfO2 and Si powder are uniformly mixed together in certain proportion. The mixed Si & HfO2 powder is evaporated by electron beam evaporation technique. Then the SRO thin films are annealed at different temperatures at 2 hours in N2 ambient to synthesize Silicon nanocrystals. For the sample annealed at 1050 ° at 2 hours, silicon nanocrystals with different size between 3 nm to 5 nm, the mean diameter of 4.0 nm, and the density of 3×1012 cm-2 are evidently observed by high resolution transmission electron microscopy (HRTEM). Then the Raman scattering and photoluminescence spectra arising from Silicon nanocrystals are further confirmed the above result. In addition, the samples annealed at 900 ° for 2 hours to 8 hours are carefully studied by Raman spectra. This way of preparing SRO thin films and Si NCs has unique advantage and is controllable and flexible

Formation of silicon nanocrystals embedded in high-κ dielectric HfO2 and their application for charge storage

Annealing thin films of silicon containing HfO2 films deposited by an electron-beam coevaporation produces silicon nanocrystals embedded in high-κ dielectric HfO2. Such films can be used to fabricate nonvolatile memory devices. By changing the Si content in the precursor HfSixO2 (x=1, 2, 3, or 4) film, the size and density of silicon nanocrystal could be controlled and high-density of silicon nanocrystals could be obtained. Transmission electron microscopy observations showed that the maximum density of silicon nanocrystals was as high as 1.3×1013 cm−2 for HfSi4O2 and the average nanocrystal diameter was 4.3 nm. The metal-oxide semiconductor capacitor memory structure with embedded silicon nanocrystals in HfSi4O2 exhibited the largest memory window, 3.94 V under ±5 V sweep voltage.

Enhanced charge storage characteristics of silicon nanocrystals fabricated by electron-beam coevaporation of Si and SiOx(x=1 or 2)

In this article, a simple and flexible electron-beam coevaporation (EBCE) technique has been reported of fabrication of the silicon nanocrystals (Si NCs) and their application to the nonvolatile memory. For EBCE, the Si and SiOx(x=1 or 2) were used as source materials. Transmission electron microscopy images and Raman spectra measurement verified the formation of the Si NCs. The average size and area density of the Si NCs can be adjusted by increasing the Si:O weight ratio in source material, which has a great impact on the crystalline volume fraction of the deposited film and on the charge storage characteristics of the Si NCs. A memory window as large as 6.6 V under +/- 8 V sweep voltage was observed for the metal-oxide-semiconductor capacitor structure with the embedded Si NCs.

A hybrid method for fabrication of Au nanocrystals nonvolatile memory

This paper demonstrates the integration of Au nanocrystals (NCs) into nonvolatile metal-oxide-semiconductor (MOS) with a hybrid method operated at room temperature. The comparison of structural and electrical characteristics between the hybrid Au NCs fabricated by chemical syntheses and film deposition Au NCs fabricated by rapid thermal annealing (RTA) was carried out. The size of the Au NCs formed by chemical method has been investigated more unique and small than the ones by the film deposition and RTA process. The electrical characteristics of MOS structure with two kinds of Au NCs has shown the larger memory window, lower P/E voltage and good retention time for the hybrid NCs due to its small diameter and low temperature process.