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命案现场分析是法医的一项重要工作

Partially-depleted silicon-on-insulator (PDSOI) MOSFETs with full dielectric isolation structure are widely used in the high temperature field of 225 °C, but affected by the threshold voltage and carrier mobility, the saturated output current has a rate of change as high as 24.9% at 25 °C–300 °C, which will reduce the working speed and accuracy of the analog circuit. This paper studies the high temperature output current characteristics of ultra-thin body and buried oxide (UTBB) fully-depleted silicon-on-insulator (FDSOI) MOSFETs with the 28 nm low voltage threshold structure. The experimental results show that when the gate voltage of the device is constant, the saturation current change of 28 nm short-channel FDSOI device is 1.93% in the temperature range from 25 °C to 300 °C, which is 12.9 times more stable than that of 0.13 μm PDSOI device, 4.5 times and 8.4 times higher than that of 0.3 μm and 2 μm long-channel FDSOI device. When the gate voltage of the device drifts from the zero-temperature coefficient (ZTC) point by ±10%–±20%, the output current change of the short-channel FDSOI device is still the lowest. It is proved by theory and simulation that the low temperature change rate of the carrier velocity of the short-channel FDSOI device is the main factor affecting the stability of the output current. From the analysis of the saturation current model and the ZTC operating point, reducing the gate operating voltage of the device or increasing the threshold voltage of the device can further improve the stability of the output current at high temperatures. The research in this paper proves that the 28 nm UTBB FDSOI device has good high temperature saturation current stability, which can well meet the output current stability requirements of high temperature analog circuits.

Partially depleted silicon-on-insulator (PDSOI) MOSFETs are widely used in 225 °C high-temperature electronic system applications with integrated circuits. But the process node stays at 0.5 µm for a long time and no further breakthrough can be achieved. This paper reports the high-temperature characteristics of 28 nm ultra-thin body and box fully depleted SOI (FDSOI) CMOS transistors with low threshold voltage (LVT) structure. Experimental results demonstrate that V t shift changes with temperature as low as 0.59 mV °C−1, the subthreshold slope (SS) is 145.35 mV dec−1 at 300 °C, and the related parameters are optimized by 3.7 times and 2.2 times respectively compared with 0.13 µm PDSOI. Combined with theoretical analysis, it is proved that the ultra-body FDSOI has an LVT drift rate and better SS than 0.13 µm PDSOI at high temperature. The advantage of this performance is mainly due to the difference between α VT α VT and β VT coefficients related to the back gate effect. Under negative back-gate bias, the I on/l off ratio can be increased by two orders of magnitude without affecting V t shift changes with temperature, this proves that the FDSOI is capable of high-temperature applications above 300 °C. This paper provides substantial support for future high-temperature system integrated circuits from the micro-scale to the nano-scale.

Changing cultivars in established litchi (Litchi chinensis Sonn.) orchards is commonly carried out by top-grafting. However, there is little information about performances of different scion-rootstock combinations in grafted litchi trees. In this study, scions of different cultivars ('Guiwei', 'Nuomici' and 'Feizixiao') were top-grafted onto branches about 1 cm in thickness in trees of different cultivars ('Baitangying', 'Baila', 'Feizixiao', 'Heiye' and 'Shuangjianyuhebao') in the summer of 2006, and the length of shoots developed from the scions were measured 8 month later on June 7, 2007. The results showed that scions of 'Guiwei' grew vigorously on 'Baitangying' and 'Baila', but less vigorously on 'Heiye', while the growth was stunted when grafted onto 'Shuangjianyuhebao' and 'Feizixiao'. 'Nuomici' scion grew most vigorously on 'Baitangying', less vigorously on 'Baila' and least vigorously on 'Shuangjianyuhebao'. 'Feizixiao' shoot grew very well on 'Heiye'. The results showed a poor compatibility between 'Guiwei' and 'Feizixiao' and that 'Shuangjianyuhebao' might serve a dwarfing rootstock for 'Guiwei' and 'Nuomici'.

A novel method with ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) as a stabilizing agent was developed to prepare highly dispersed Pt nanoparticles on carbon nanotubes (CNTs) to use as proton exchange membrane (PEM) fuel cell catalysts. These nanocatalysts were obtained by altering the molar ratio of ethylenediaminetetraacetic acid disodium salt to chloroplatinic acid (EDTA-2Na/Pt) from 1:2, 1:1, 2:1 to 3:1. The well-dispersed Pt nanoparticles of around 1.5 nm in size on CNTs were obtained when the EDTA-2Na/Pt ratio was maintained at 1:1. And the Pt/CNT catalyst exhibited large electrochemical active surface areas, very high electrocatalytic activity and excellent stability in the oxidation of methanol at room temperature. The Pt/XC-72R catalyst with narrow size distribution was also prepared by this method for comparison purposes. Comparison of the catalytic properties of these catalysts revealed that the activity of the Pt/CNT catalyst was a factor of ∼3 times higher than that of the Johnson Matthey catalyst and ∼2 times higher than that of our Pt/XC-72R catalyst, which can be assigned to the high level of dispersion of Pt nanoparticles and the particular properties of the CNT supports.