126Ce的EC/β+衰变

利用187 MeV的40Ca离子轰击同位素靶92Mo, 由熔合蒸发反应生成目标核126Ce。 藉助氦喷嘴快速带传输系统和X-X-t与X-γ-t符合测量, 首次建立了126Ce的EC/β+衰变纲图。 建议了可能属于126Ce一个高自旋同核异能态的衰变, 其β衰变后布居在与126La的高自旋同核异能态相关的低位能级区, 测定的半衰期是57(9) s。 也建议了可能属于126Ce基态的衰变, 其β衰变后布居在与126La的低自旋同核异能态相关的低位能级区,它的半衰期被测定为12(4) s。 但偶偶核126Ce存在高自旋同核异能态的物理原因还有待进一步探究。 Ce was produced by bombarding an enriched target of 92Mo with 187 MeV 40Ca beam and studiedby using a helium jet fast tape transport system in combination with X-γ and γ-γ coincidencemeasurements. An EC/β+ decay scheme of 126Ce was proposed for the first time. A group of low lying states associated with the low spin isomer in 126La feeding by β decay was possibly from the ground state EC/β+ decay of 126Ce with the measured half-life 12(4) s. Another group of low lying states associated with the high spin isomer in 126La feeding by β decay was possibly from a high spin isomer EC/β+ decay of 126Ce with the measured half-life 57(9) s. However, the physical reason for the existence of a high spin isomer in even-even nucleus 126Ce is still an open problem.     

A two-dimensional threshold voltage analytical model for metal-gate/high-k/SiO2/Si stacked MOSFETs

In this paper the influences of the metal-gate and high-k/SiO 2 /Si stacked structure on the metal-oxide-semiconductor field-effect transistor（MOSFET） are investigated.The flat-band voltage is revised by considering the influences of stacked structure and metal-semiconductor work function fluctuation.The two-dimensional Poisson＇s equation of potential distribution is presented.A threshold voltage analytical model for metal-gate/high-k/SiO 2 /Si stacked MOSFETs is developed by solving these Poisson＇s equations using the boundary conditions.The model is verified by a two-dimensional device simulator,which provides the basic design guidance for metal-gate/high-k/SiO 2 /Si stacked MOSFETs.     

基于工程能力和创新能力培养的实践教学改革

工程实践能力及创新能力是当今社会急需的实用型、创新型工程技术人才的基本素质。针对以往实践教学存在的问题和不足,提出了基于工程能力和创新能力培养的实践教学改革措施。     

Influences of different oxidants on the characteristics of HfAlOx films deposited by atomic layer deposition

A comparative study of two kinds of oxidants(H2O and O3) with the combinations of two metal precursors [trimethylaluminum(TMA) and tetrakis(ethylmethylamino) hafnium(TEMAH)] for atomic layer deposition(ALD) hafnium aluminum oxide(HfAlOx) films is carried out.The effects of different oxidants on the physical properties and electrical characteristics of HfAlOx films are studied.The preliminary testing results indicate that the impurity level of HfAlOx films grown with both H2O and O3 used as oxidants can be well controlled,which has significant effects on the dielectric constant,valence band,electrical properties,and stability of HfAlOx film.Additional thermal annealing effects on the properties of HfAlOx films grown with different oxidants are also investigated.     

激光测油液污染的原理及其测定装置

选取了光测法检测油液污染度，在适合的波段内，油样对光均具有一般吸收，透光率相对稳定且较大，油样粘度的变化对透光率影响较小，而油液颜色的深浅对透光率有影响，导出了定量分析油液污染程度，消除油液颜色影响和提高检测精确度的理论公式，讨论了影响检测结果的因素及相应的解决办法。     

改善硅基功率晶体管电流放大倍数高低温变化率的工艺研究

依据功率晶体管电流放大倍数高低温变化率的实际电参数指标要求,利用TCAD半导体器件仿真软件和晶体管原理对其进行深入的分析。结果表明,针对较大测试电流、较高电流放大倍数的功率晶体管,在一定程度上降低发射区掺杂浓度、提高基区掺杂浓度可有效改善电流放大倍数的高低温变化率。并在一定的发射区表面浓度和基区表面浓度下,通过优化发射区结深和基区宽度可满足常温电流放大倍数的指标要求。结合仿真研究结果,通过实际流片,对关键的工艺进行工艺攻关。流片结果表明,采用降低发射区掺杂浓度并提高基区掺杂浓度的工艺方法,电流放大倍数高低温变化率得到有效改善,并能控制其他参数实测值满足设计要求。     

怎样预防奶牛乳房炎

绝大多数奶牛患乳房炎是由于乳区被细菌感染而引起的，因此，预防奶牛患乳房炎的关键是要保持牛舍的环境卫生。牛床设计要合理，大小要合适，牛床过大会使奶牛把粪便排泄在牛床上，当其趴卧时乳房容易被粪便污染；牛床过小又容易使奶牛接近粪沟。牛床内要铺足够的垫草，并及时更换。要及时清理牛舍中的粪便，保持牛舍内干燥清洁，要经常刷试牛体，尤其要注意保持奶牛的后躯及尾部的清洁。奶牛群的饲养密度要合理，并注意经常通风换气。     

基于小波增强的多分辨率图像融合算法

在图像融合中,由于源图像的降质使得部分隐藏信息无法在融合过程中提取出来,影响了源图像的融合效果.针对这一问题,提出了一种基于小波增强的图像融合算法:在融合之前先对源图像进行适当的增强,突出图像中隐藏的信息,然后采用合适的规则对源图像和增强之后的图像进行融合.实验分析表明,在融合之前对源图像进行增强,能够改善图像融合的效果,获得直接融合难以获取的信息.     

Migration of weakly bonded oxygen atoms in a-IGZO thin films and the positive shift of threshold voltage in TFTs

Amorphous indium-gallium-zinc oxide (a-IGZO) thin films are prepared by pulsed laser deposition and fabricated into thin-film transistor (TFT) devices. In-situ x-ray photoelectron spectroscopy (XPS) illustrates that weakly bonded oxygen (O) atoms exist in a-IGZO thin films deposited at high O₂ pressures, but these can be eliminated by vacuum annealing. The threshold voltage (V_th) of the a-IGZO TFTs is shifted under positive gate bias, and the V_th shift is positively related to the deposition pressure. A temperature variation experiment in the range of 20 K-300 K demonstrates that an activation energy of 144 meV is required for the V_th shift, which is close to the activation energy required for the migration of weakly bonded O atoms in a-IGZO thin films. Accordingly, the V_th shift is attributed to the acceptor-like states induced by the accumulation of weakly bonded O atoms at the a-IGZO/SiO₂ interface under positive gate bias. These results provide an insight into the mechanism responsible for the V_th shift of the a-IGZO TFTs and help in the production of reliable designs.     

不同加料方式对共沉淀法制备YAG纳米粉体的影响

用共沉淀法制备了钇铝石榴石(Y3Al5O12)纳米粉体,研究了正滴定、反滴定和一步注入工艺对钇铝石榴石纳米粉体合成过程及最终产物的影响。利用X射线衍射仪、傅立叶红外光谱仪、同步热分析仪、场发射电子显微镜对YAG前驱体及不同温度煅烧后的粉体进行表征。结果表明:通过正滴定、反滴定和一步注入工艺,分别制备出化学组成为10[8.9Al(OH)3+1·1NH4Al·(OH)2CO3]·3[Y2(CO3)3·3H2O]、10[7.3Al(OH)3+2.7NH4Al·(OH)2CO3]·3[Y2(CO3)3.3H2O]、10[Al(OH)3]·3[Y2(CO3)3·3H2O]的前驱体。前驱体经900℃煅烧2 h后,正、反滴定工艺得到的粉体主相为YAG(Y3Al5O12),但有少量的YAP(YAlO3),一步注入工艺则得到纯的YAG相。晶粒尺寸分别为85 nm、70 nm和65 nm,且一步注入工艺获得的粉体粒径分布较窄,分散性良好。