X-ray detection based on complementary metal-oxide-semiconductor sensors

Complementary metal-oxide-semiconductor(CMOS) sensors can convert X-rays into detectable signals; therefore, they are powerful tools in X-ray detection applications. Herein, we explore the physics behind X-ray detection performed using CMOS sensors. X-ray measurements were obtained using a simulated positioner based on a CMOS sensor, while the X-ray energy was modified by changing the voltage, current, and radiation time. A monitoring control unit collected video data of the detected X-rays. The video images were framed and filtered to detect the effective pixel points(radiation spots).The histograms of the images prove there is a linear relationship between the pixel points and X-ray energy. The relationships between the image pixel points, voltage, and current were quantified, and the resultant correlations were observed to obey some physical laws.

Growth of pure zinc blende p-type GaAs nanowires by metal-organic chemical vapor deposition

Vertical p-type gallium arsenide （GaAs） nanowires with pure zinc blende structure were grown on GaAs （111） B substrate by metal-organic chemical vapor deposition via a Au-catalyst vapor-liquid-solid mechanism. The p-type doping was investigated by additional diethyl zinc （DEZn）. In the high Ⅱ/Ⅲ ratio range （Ⅱ/Ⅲ〉9.1%）, there exists a critical length beyond which kinking takes place. Two possible reasons are discussed. Zn occurrence in the nanowires was verified by energy dispersive X-ray （EDX） analysis. Corresponding to Ⅱ/Ⅲ = 0.2%, the doping concentration is about 8 × 10^18 cm^-3.

Chemical composition and source apportionment of PM2.5 and PM2.5-10 in Trombay （Mumbai, India）, a coastal industrial area

PM2.5 and PM2.5 lo concentrations, elemental constituents, and sources in a densely populated coastal industrial area （Trombay, Mumbai） were investigated in 2010 and 2011.The PM2.s and PM2.s lo concentra- tions were 13.50-71.60 and 22.40-127.78 p^g/m3, respectively. The daily PM25 concentrations exceeded the Indian Central Pollution Control Board limit （60 μg/m3） several days in winter. Of the elements analyzed, Si then Al had the highest concentrations in PM2.5- 10, but black carbon then Si had the highest concentrations in PM2.s. The element concentrations varied widely by season. Al, Ca, Fe, Si, and Ti con- centrations were highest in summer, Cl, Mg, and Na concentrations were highest in the monsoon season, and the other trace metal concentrations in both PM2.5 and PM2.5-10 were highest in winter. The PM2.5 and PM2.5-10 sources were apportioned by positive matrix factorization. PM2.5 and PM2.5-10 had six dominant sources, crustal material （8.7% and 25.3%, respectively）, sea salt spray （6.1% and 15.0%, respectively）, coal/biomass combustion （25.5% and 13.8%, respectively）, fuel oil combustion （19.0% and 11.2%, respectively）, road traffic （ 17.7% and 12.6%, respectively）, and the metal industry （ 10.6% and 7.0%, respectively）. Anthropogenic sources clearly contributed most to PM2.5 but natural sources contributed most to PM2.5-10.

Characterization of positive bias temperature instability of NMOSFET with high-k/metal gate last process

Positive bias temperature instability（PBTI） characteristics and degradation mechanisms of NMOSFET with high-k/metal gate last process have been systematically investigated. The time evolution of threshold voltage shift during PBTI stress still follows a power law. However, the exponent n decreases from 0.26 to 0.16 linearly as the gate stress voltage increases from 0.6 to 1.2 V. There is no interface state generation during stress because of the negligible sub-threshold swing change. Moreover, the activation energy is 0.1 e V, which implies that electrons directly tunnel into high-k bulk and are trapped by pre-existing traps resulting into PBTI degradation. During recovery the threshold voltage shift is linear in lgt, and a mathematical model is proposed to express threshold voltage shift.