Man Ding

Total dose response of hafnium oxide based metal-oxide- semiconductor structure under gamma-ray irradiation

The research of the total dose response of high dielectric-constant hafnium oxide under gamma-ray irradiation is important for the anti-irradiation study of the ultra-deep submicron electronic devices in space application. The response of the HfO2-based Metal Oxide Semiconductor (MOS) structure under various total doses of gamma-ray irradiation is investigated in this article. MOS capacitors which are composed of aluminum electrode, HfO2 gate dielectric on p-type silicon (Al/HfO2/pSi) are prepared and tested before and after 60Co gamma-ray irradiation to access the irradiation induced damage in HfO2/Si system. The surface morphology is obtained by the use of atomic force microscope(AFM), the chemical and physical characteristics are obtained using X-ray diffractometer (XRD) and X-ray photoelectron spectrometer(XPS), and the charge trapping characteristic of HfO2 film is calculated from the current-voltage(CV) curve by the semiconductor parameter testing. Crystallized HfO2, SiO2 and HfSiO4 are detected from the XRD spectrum and the crystallinity and grain size are found to decrease with the increase of gamma-ray total dose. Oxygen vacancy is found to increase after irradiation and it dominates the oxide charge trapping in the HfO2/Si system. Schottky emission is found to be the charge transport mechanism from the current-voltage curve at room temperature, and the barrier height of HfO2/Si interface is found to decrease with the increase of irradiation. Irradiation induced defects would lower the HfO2/Si interface barrier height and then give rise to the leakage current, this will consequently lead to the failure of HfO2 film and corresponding MOS structures.

Investigation of factors inducing simultaneous discharges in voids

Simultaneous discharge, characterized by single current pulse corresponding with more than one discharge spots in one PD (partial discharge), was observed in the partial discharge sequences, especially for the first discharge after voltage application. However, its mechanism has not been understood clearly. In this report, we investigated the effects of photoionization and overvoltage on the probability of simultaneous discharges. A combination measurement system was developed to simultaneously observe surface charge and partial discharge in the samples with double-spheres plate electrodes. Focusing on the first discharge, the single square voltage pulse was applied. When two spheres were separated by the glass slide, the simultaneous discharge probability was smaller than the case without glass slide, indicating that photoionization contributed to the simultaneous discharge. Moreover, as the gap distance between two spheres increased, the simultaneous discharge probability diminished, even in the case that the light effect was inhibited by using glass slide. Furthermore, the simultaneous discharge probability became larger as the overvoltage increased, in the both cases with and without glass slide.

Study on the vacuum surface flashover characteristics of epoxy composites with microTiO 2 fillers under steep high-voltage impulse

With the tendency towards higher power, higher capacity and less scale of the pulsed-power devices, the vacuum surface flashover strength turns to be a primary limitation of the development of the pulsed-power equipments, as it is much lower than the vacuum breakdown strength. To improve the different capabilities of the epoxy composite material, different kinds of micron inorganics are filled to the epoxy resin. TiO2 (TO) is a typical kind of oxide ceramic, as well as an important sort of broad band-gap oxide semiconductor material. With its unique optical and electrical properties, excellent chemical stability, high dielectric constant and semi-conductive properties, it is widely applied to enhance the performance of the organic composite material. In this article, the experimental results of vaccum surface flashover characteristics of epoxy resin and epoxy resin cast with 1μm powdered TO samples are presented. In addition, their dielectric spectrum and thermally stimulated depolarization current (TSDC) are measured. Considering the influence of the dielectric constant, the conductivity, the trap energy and the trap density, associated with the interface theory, the article analyzes the influence mechanism of micro-scale TO fillers on the vacuum flashover voltage of epoxy composite material.

Irradiation effect of HfO 2 MOS structure under gamma-ray

The effect of gamma irradiation upon Al/HfO2/SiO2/Si MOS structure under different doses of 60Co is studied in this article as a function of total dosage. MOS capacitors with a stacked gate dielectric of 2.8nm thick SiO2 and 15nm thick HfO2 having electrode areas of 1mm*1mm are prepared on the p-Si substrate using thermal oxidation and atomic layer deposition respectively. The MOS capacitors are under zero bias during irradiation under 60Co gamma ray with total dose of 100Krad (Si)/500Krad (Si)/1Mrad (Si) and dose rate of 50rad (Si)/s. The high frequency Capacitor-Voltage (C-V) and Current-Voltage (I-V) characteristic of each structure are measured at room temperature before and after irradiation. As well as the C-V and I-V property, Atomic Force Microscopy (AFM), Grazing Incidence X-ray Diffraction (GIXRD), and X-ray Photoelectron Spectroscopy (XPS) are also applied to determine the surface morphology, physical, and mechanical properties before and after different doses of radiation. The oxide trapped charge calculated from the high frequency C-V measurement is in the order of 1012 cm-2 and increases linearly with the increase of applied total dose. The XRD spectrum exhibits several phases of SiO2 and HfO2 variation under each total dose. The XPS result shows that each different total dosage leads to the binding energy peak drifting to a different degree demonstrating the influence of irradiation on the valence state of the elements, which can be attributed to the gamma-ray induced interface states.

Surface flashover of micro TiO 2 epoxy composite dielectric under nanosecond pulse in transformer oil

Micro TiO2/epoxy composite samples with different filler weight percentage were prepared. Their flashover voltages under the 50ns (rise time)/2.5μm (half-height width time) pulse in transformer oil were measured. The results of surface flashover voltages as the number of flashovers, weight percentage of the filler, fluid pressure and the steepness of the pulse were presented. It is demonstrated that the flashover strength of epoxy composite can be enhanced by filling with a huge mount of micro TiO2. Moreover, the results also show that the flashover characteristic of epoxy is significantly affected by the number of flashovers, fluid pressure and the steepness of the pulse.

Total dose response of Al 2 O 3 -based MOS structure under gamma-ray irradiation

The effect of gamma irradiation upon Al/Al2O3/Si MOS structure under different doses of 60Co is studied in this article as a function of total dosage. Al2O3 MOS capacitors with a gate dielectric thickness of 4nm and electrode diameter of Φ 1mm are prepared on the p-Si substrate using atomic layer deposition. The MOS capacitors are under zero bias during irradiation under 60Co gamma ray with total dose of 300Krad(Si)/500Krad (Si)/1Mrad (Si) and dose rate of 50rad (Si)/s. The high frequency Capacitor-Voltage (C-V) and Current-Voltage (I-V) characteristic are measured at room temperature before and after irradiation for each sample. In addition, Atomic Force Microscopy (AFM), Grazing Incidence X-ray Diffraction (GIXRD), and X-ray Photoelectron Spectroscopy (XPS) are also applied to determine the surface morphology, physical and mechanical properties under different doses of radiation. The oxide trapped charge calculated from the high frequency C-V characteristics is in the order of 1011 cm-2 and increases with the applied total dose. The XRD spectrum shows several phases of Al2O3 variation under each total dose. The XPS result shows that different total dosage leads to the drift of binding energy peak to a different degree, which indicates the influence of irradiation on the valence state of the elements attributed to the gamma-ray induced interface states.

A way to prepare nano-Ag/epoxy resin composite and study of LSPR in composite

Comparing to the base epoxy resin, nano-composites usually have enhanced mechanical, thermal and electrical properties, and a lot of technology was introduced to get high quality nano-composites. In this work, Ag nanoparticles have been synthesized by using ethanol (and DMF) as reducing agent and solvent in the presence of ultraviolet radiation and polyvinyl pyrrolidone. The particle size can be controlled by changing the time of radiation and the concentration of silver nitrate. Localized surface plasmon resonacnces (LSPR) of colloidal Ag nanoparticles were observed by UV-visible absorption spectra, and the absorption peak position is determined by the size and shape of Ag nanoparticles. After mixing the ethanol containing Ag NPS into epoxy resin, and then removing the solvent by the method of reduced pressure distillation, cured Ag/epoxy resin nanocomposites were well prepared. It is confirmed that the LSPR of Ag NPS still exist in the composites and its UV-visible absorption spectra is tunable by choosing Ag NPS with different size and shape.

Gamma-irradiation effect on electrical properties of SiO 2 gate dielectric of MOS structure

The total dose effect of 60Co gamma-irradiation on MOS (metal-oxide-semiconductor) structure of Al/SiO2/p-Si with different insulation layer thickness has been investigated in this article. MOS capacitors with oxide layer thickness of 5nm/19nm/29nm and electrode area of 1mm2 were prepared using thermal oxidation method. Each structure was stressed with no bias during 60Co gamma-source irradiation with the total dose of 100k/500k/1Mrad. The low and high frequency C-V characteristic of each structure was measured at room temperature before and after gamma-irradiation. Besides of the electric properties, Atomic Force Microscopy (AFM), Grazing Incidence X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) with Ar+ etching were also measured before and after different total dose gamma-irradiation. AFM results showed that the surface of the oxide was relatively smooth with the roughness under 5%. Low and high frequency C-V results indicated that the interfacial states between Si and SiO2 and oxide traps varied with insulation layer thickness and different total dose. On the other hand, the XRD property change under gamma irradiation differs with oxide layer thickness. And the Si 2p peak and O 1s peak result derived from the XPS drifted with different total dose and oxide layer thickness. These results offered necessary theory assistance for the nuclear hardening of the microelectronic devices with ultrathin insulation layer, which can advance the safety of weapons in the high-tech warfare.

Damage effect of typical electronic device under EMP

In the high technology condition, the weapon safety and survive capability is severely threatened by the complicated and changeable electromagnetic environment, especially for the electromagnetic field produced by HPM and ESD high rise current pulse. Electronic devices are gradually sensitive to the high electromagnetic pulse as the reducing characteristic size, increasing integrated degree, reducing power consumption, increasing working band and so on. Its significant to study the damage and failure mechanism of electronic devices under high power electromagnetic field (HPEM) either for the civilian use or for the military application. The damage effect of typical electronic devices including diode, transistor, and digital integrated circuits under lightning surge pulse and nano-second square pulse is studied in this article. The damage law of various electronic devices under different pulse width is obtained, and the damage and failure mechanism of each device under different pulse power is analyzed, and some defending suggestion is proposed in the end of the article.

The study on ablation resistance of epoxy resin based composite in vacuum

This paper mainly studies the influence of nano/micro Al2O3 and Al(OH)3 in epoxy composites on the ablation resistance, by quantifying the mass loss and observing the surface topography of sample after several times surface flashover in vacuum (the peak value is approximately 10kA, and the wave front is 8us, wave tail is 20us(8/20us)). The experimental results show that the addition of inorganic filler to epoxy resin is useful for improving the ablation resistance. The performance of Al(OH)3 filler is much better than Al2O3. Nano-particles are much smaller and dispersed more uniformly than micro-particles. Thus the composite with nano aluminium hydroxide is of better heat dissipation. But the blocking effect of adding micro-particles is better than adding nano-particles.