Feng Shun-shan

Formation of high density TiN nanocrystals and its application in non-volatile memories

Non-volatile memory based on TiN nanocrystal (TiN-NC) charge storage nodes embedded in SiO2 has been fabricated and its electrical properties have been measured. It was found that the density and size distribution of TiN-NCs can be controlled by annealing temperature. The formation of well separated crystalline TiN nano-dots with an average size of 5nm is confirmed by transmission electron microscopy and x-ray diffraction. x-ray photoelectron spectroscopy confirms the existence of a transition layer of TiNxOy/SiON oxide between TiN-NC and SiO2, which reduces the barrier height of tunnel oxide and thereby enhances programming/erasing speed. The memory device shows a memory window of 2.5V and an endurance cycle throughout 105. Its charging mechanism, which is interpreted from the analysis of programming speed (dVth/dt) and the gate leakage versus voltage characteristics (Ig vs Vg), has been explained by direct tunnelling for tunnel oxide and Fowler–Nordheim tunnelling for control oxide at programming voltages lower than 9V, and by Fowler–Nordheim tunnelling for both the oxides at programming voltages higher than 9 V.

Analysis of action mechanism of graphite bombs and reaction method of power system

The short circuit collapse problem of electric power system attacked by graphite bombs was investigated. The harm of graphite bombs and the vulnerability of electrical network were analyzed. Two kinds of failure modes called direct short circuit failure and indirect short circuit failure were presented accordingly. The arc generation mechanism of conductive filaments dispensed from graphite bombs was analyzed and the concept of compulsively consecutive arc was presented. Then the verifying experiments under the condition of high voltage and small current were done. The short circuit blockade principle of electric power system by graphite bombs was also analyzed. In order to react to the attack of graphite bombs effectively, the clearing methods of conductive filaments such as mechanical removal, combustion and lightning impulse were presented which are helpful to recover the current supply capability of electric power system rapidly.

Study on Hydrodynamic Outline of an Unmanned Underwater Vehicle

Unmanned Underwater Vehicle (UUV) is being widely developed and used in many areas. In order to meet the low resistance and low noise requirements of a kind of UUV for long voyage, the outline curve and parameters of different sections of the UUV are figured out by using method of superposition of point-source and uniform-flow, superposition of constant-strength-line-congruence and uniform-flow, and empirical formula, and thus total hydrodynamic outline of the UUV is obtained. In addition, pressure distribution of the head of the UUV is analyzed, and the maximum motion velocity that cannot induce cavitation is obtained. These results provide a strong basis for the analysis and design of the power propulsion system of the UUV. The water tunnel and sea trial demonstrate that the figuration of hydrodynamic outline can meet the need of low resistance and low noise requirements of the UUV.