MBE-GaAs/Si的背散射沟道分析

对 MBE-GaAs/Si 进行离子注入和退火.GaAs 外延层的厚度为0.9-2.0μm.Si离子的注入能量及剂量分别为1.2-2.8MeV,l×10~(14)-7×10~(15).cm~(-2).退火采用红外瞬态退火(850℃,15s)及白光退火(1050℃,8s).背散射沟道分析采用4.2MeV~7Li.实验表明,注入结合退火是改善 GaAs 外延层晶体质量的一种有效方法.注入剂量过大,由于正化学配比遭到破坏,外延生长终止.     

MeV硅离子注入砷化镓的两步快退火

报道使用两步快退火(RTA)工艺对MeV Si~+注入的〈100〉取向SI-GaAs样品进行热处理。2 MeV,2×10~(14)cm~(-2)Si注入的GaAs样品,经低温(350～450℃),长时间(20～30 s)退火和高温(970～1050℃),短时间(1～2s)退火,使注入区晶格恢复好,二次缺陷密度大大降低,电特性得到明显改善。激活率达到了30％,迁移率为2400～2 515cm~2·V~(-1)·s~(-1),薄层电阻为42～46Ω。根据点缺陷和杂质原子的相互作用,结合载流子浓度分布的特点,对半绝缘砷化镓中MeV注入硅原子的激活机理进行了讨论。     

高剂量的~(40)Ar~+离子注入硅热退火行为的研究

用沟道—卢瑟福背散射技术(RBS)研宄了能量为50 KeV,剂量为3.8×10~(16)/cm~2和1.9×10~(16)/cm~2的~(40)Ar~+离子注入(111)硅衬底中的恒温等时热退火行为。结果表明,离子注入层中Ar 原子的扩散和释放以及非晶硅层的再结晶行为明显地依赖于~(40)Ar~+离子的注入剂量和退火温度。注入剂量为3.8×10~(16)/cm~2的样品,当退火温度为700℃时,表面层硅的密度明显减小,退火温度为750℃时,注入层中的大部分Ar 发生外扩散并从样品表面释放。注入剂量为1.9×10~(16)/cm~2的样品,退火过程中没有发现衬底硅表面密度的变化,而且当退火温度为900℃时,残留在注入层中的Ar 仍旧比较多。最后对这些现象进行了讨论和解释。     

MeV P^＋／Si^＋共注入SI—GaAs制备高品质n^＋埋层

采用不同注量和注入顺序的MeV能量的P~+(3MeV,1×10~(14)～3×10~(14)cm~(-2))与MeV能量的Si~+(3MeV,1×10~(14)cm~(-2))共注入于SI-LEC GaAs晶体中。对不同退火条件的共注入样品的有源层电特性、载流子浓度分布、晶格的损伤和恢复状况以及剩余缺陷等进行了分析。研究表明,较大注量的P~+与Si~+共注入,可以降低注区薄层电阻,有效地提高MeV Si~+的激活效率,改善有源层迁移率,得到高品质的n~+埋层。共注入样品的HALL迁移率大于2400cm~2/(V·s),激活率可达95％以上。     

Mev^28Si^＋注入GaAs的退火行为

报导 MeV 硅离子注入半绝缘 GaAs 的快退火行为,根据缺陷作用原理分析了硅的不均匀激活和载流子分布特征.指出应按载流子浓度、迁移率、埋层电阻和击穿等特性综合评价深埋层和近表面层的品质,优化注入和退火参数.     

用白光快速烧结制作离子注入层欧姆接触

研究了用白光快速烧结法制作的n型高浓度离子注入层欧姆接触的特性.选用硅和硫离子,获10~(18)cm~(-3)以上的高浓度.白光快速烧结温度为400～460℃.实测的比接触电阻的最好值达到10~(-6)·Ω·cm~2.该法已用于全离子注入平面型场效应晶体管和GaAs/GaAlAs异质结HOT晶体管,性能良好.     

硅中离子注入层的卤钨灯辐照快速退火研究

本文研究了硅中离子注入层的卤钨灯辐照快速退火,对注B 和注P 样品分别测量了经1100℃、15秒和1050℃、12秒退火后注入层的载流子浓度分布,并与950℃、30分钟常规热退火样品作了比较;结果表明,卤钨灯辐照快速退火具有电激活率高、注入杂质再分布小及易于推广使用等优点.对于100keV、1×10~(15)cm~(-2)P 注入样品,经1050、10秒卤钨灯辐照退火后,表面薄层电阻为74.8Ω/□;对通过920(?)SiO_2膜,25keV、1×10~(15)cm~(-2)B 注入样品,经1100℃、15秒卤钨灯辐照快速退火后表面薄层电阻为238.0Ω/□;而经过950℃、30分钟常规热退火后,以上两种样品的表面薄层电阻分别为72.0Ω/□和245.8Ω/□.采用这种退火方法制作出了结深为0.10μm 的近突变P~ N 结,并测量了结深与退火时间的关系.     

硫离子注入制备N.GaAs薄层

本文讨论了用S~ 注入掺铬的半绝缘GaAs衬底以制备N—GaAs薄层。目的是代替微波低噪声砷化镓肖特基势垒场效应管(SBFET)所需要的GaAs薄外延层。注入条件:能量100Kev,剂量1.5×10~(13)/cm~2,退火温度为825℃,退火时间15分钟。已经做出0.2～0.3μm厚的N型薄层,平均载流子浓度为5×10~(16)～1×10~(17)/cm~3。。载流子迁移率在2600～3400cm~2/V.S的范围。薄层厚度和载流子浓度的均匀性是好的。采用双注入即注入S~ 之后,再注入P~ 可以改善注入层的电特性。利用S~ 注入制备的N—GaAs薄层,已制出SBFET,其跨导和夹断电压可与气相外延薄层制备的SBFET相比拟。     

离子注入退火晶格恢复和电激活动力学研究

给出了As和P注入硅的电激活能与退火温度的关系.用这些结果和表示晶格去除率与退火温度的关系式,研究了损伤的晶格恢复和杂质电激活动力学,发现低剂量As注入硅,在退火过程中仅出现1～2个低的激活能.当注入剂量大于5×10~(15)cm~(-2)时,硅注入区转变成了无序层,退火过程中则出现无序层外延生长区、过渡区和电激活能区3个特征温区,并在激活能区可观察到2～3个激活能.当硅在300℃温度下注入As,注入剂量为1×10~(16)cm~(-2)时,注入层中未出现无序层,退火过程中仅有激活能区,在此区能测到3个激活能.     

瞬态退火中高密度缺陷对As增强扩散作用模型分析

分析了注入As在快速退火中的增强扩散效应,特别分析了注入层中缺陷生成过程所伴随的增强扩散效应。退火中引起高密度缺陷两种过程是:一反冲氧的作用;二高剂量注入As在品格中引入应力的作用。实验中发现,剂量高达2×10~(16)cm~(-2)和As通过SiO_2层注入硅时(As射程等于SiO层的厚度),注入的样品经高温退火后,As杂质剖面出现拐点。以拐点为分界划分出快扩散和慢扩散两个区域。用Boltzmann-Matano)方法计算了As在退火期间在硅中的扩散系数。用高压透射电镜观察表明,从硅表面到拐点处存在着高密度的缺陷,并且分析了缺陷在1～12s期间的发展过程。结果表明。在最初1～3s内已形成了高密度缺陷,且这种缺陷热稳定性很高,即使经1 150℃180s退火仍然存在。在此基础上分析高密度缺陷对增强扩散影响的模型。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the