Nano-scale gap filling and mechanism of deposit-etch-deposit process for phase-change material

Ge2Sb2Te5 gap filling is one of the key processes for phase-change random access memory manufacture. Physical vapor deposition is the mainstream method of Ge2Sb2Te5 film deposition due to its advantages of film quality, purity, and accurate composition control. However,the conventional physical vapor deposition process cannot meet the gap- filling requirement with the critical device dimension scaling down to 90 nm or below. In this study, we find that the deposit-etch-deposit process shows better gap-filling capability and scalability than the single-step deposition process, especially at the nano-scale critical dimension. The gap-filling mechanism of the deposit-etch-deposit process was briefly discussed. We also find that re-deposition of phase-change material from via the sidewall to via the bottom by argon ion bombardment during the etch step was a key ingredient for the final good gap filling. We achieve void-free gap filling of phase-change material on the 45-nm via the two-cycle deposit-etch-deposit process. We gain a rather comprehensive insight into the mechanism of deposit-etch-deposit process and propose a potential gap-filling solution for over 45-nm technology nodes for phase-change random access memory.

Quantification constraints on time gap for comagmatic gold deposits:Evidence from chronological statistics

The time gap between diagenesis and mineralization (TGDM) for comagmatic gold deposits (CGD) plays an important role in confirming the genetic relationship between gold deposits and their related intrusions. With the help of preciously published isotopic ages of some typical gold deposits and their related rocks in China,the authors have discussed and quantified the distribution characteristics and scope of the TGDM. Statistical analyses and Kolmogorov tests showed that mineralizing events are either contemporaneous with or slightly postdate their cognate magma. The TGDM conforms with normal distributions at a 0.05 confidence level and clusters between 0 and 16.0 Ma with a mean of 7.0 Ma. Thus,if the TGDM of CGD is less than 16.0 Ma,it is reasonable to consider,with the aid of other evidence,the possibility of its comagmatic genetic affiliation. The authors also emphasized that to get a precise time gap it is necessary to strengthen the diagenesis-mineralization geological background of the deposits studied,and to pay attention to the study of time gap in combination with trace elements and isotope tracing.

非层状二维γ-In_(2)Se_(3)的各向异性生长及其光学特性

非层状二维(2D)γ-In_(2)Se_(3)具有优异的光学和电学性能,在超薄柔性器件和光电探测领域具有广泛的应用前景.然而,相较于层状的类石墨烯材料,非层状材料固有的各向同性化学键,使得其二维各向异性生长面临较大的挑战.本研究构建了一种新的化学气相沉积(CVD)生长策略,成功制备了高质量的2Dγ-In_(2)Se_(3).首次选用低熔点的铟粉为前驱体,有效降低了生长温度.此外,生长过程去除了CVD法合成二维硒化物时不可避免的危险气体H_(2),这不仅能有效抑制InSe副产物的形成,还降低了实验危险性.通过探究原料用量、生长温度及时间等参数对样品形貌和厚度的影响,获得了最佳生长窗口.详细表征了2Dγ-In_(2)Se_(3)的微观形貌、化学组分、晶体结构和光学特性等.结果表明,样品具有强烈的光致发光(PL)效应,与γ-In_(2)Se_(3)的直接带隙属性相吻合.随着厚度的减小,PL峰会发生蓝移,说明光学带隙随之增大.Raman光谱显示,不同厚度的样品其特征峰也会发生移动,说明厚度会影响2Dγ-In_(2)Se_(3)的分子振动行为.由此可见,通过生长参数调控2Dγ-In_(2)Se_(3)的厚度,可实现对其光学带隙和分子振动行为的调控,这将为相关的理论研究和光电器件应用提供基本的材料平台.

Narrow gap space contributes to chemical metallurgy of self-shielded arc welding

The slag-free self-shielded flux-cored wire was fabricated to apply for the narrow gap welding.The results showed that narrow gap welding shows lower welding spatter compared with hardfacing except under voltage of 30 V and current of 260 A.The deposition efficiency keeps over 90%for both 12 mm and 8 mm narrow gap welding.For 12 mm narrow gap welding,when the voltage is 28 V and the current is 264 A(or 286 A),no pores are found in the narrow gap weld.In the continuous welding process,manganese vapor,aluminum vapor and CO continuously generate to form gasbag and occupy the narrow gap space,thus protecting the droplet and molten pool from the invasion of air.

Enhanced Property of Thin Cuprous Oxide Film Prepared through Green Synthetic Route

Thin cuprous oxide films have been prepared by chemical vapor deposition(pulsed spray evaporation-chemical vapor deposition)method without post-treatment.The synthesis of cuprous oxide was produced by applying a water strategy effect.Then,the effect of water on the morphology,topology,structure,optical properties and surface composition of the obtained films has been comprehensively investigated.The results reveal that a pure phase of Cu2O was obtained.The introduction of a small quantity of water in the liquid feedstock lowers the band gap energy from 2.16 eV to 2.04 eV.This finding was mainly related to the decrease of crystallite size due to the effect of water.The topology analyses,by using atomic force microscope,also revealed that surface roughness decreases with water addition,namely more uniform covered surface.Moreover,theoretical calculations based on density functional theory method were performed to understand the adsorption and reaction behaviors of water and ethanol on the Cu2O thin film surface.Formation mechanism of the Cu2O thin film was also suggested and discussed.

Microstructure,optical,and photoluminescence properties ofβ-Ga_(2)O_(3)films prepared by pulsed laser deposition under different oxygen partial pressures

Theβ-Ga_(2)O_(3)films are prepared on polished Al_(2)O_(3)(0001)substrates by pulsed laser deposition at different oxygen partial pressures.The influence of oxygen partial pressure on crystal structure,surface morphology,thickness,optical properties,and photoluminescence properties are studied by x-ray diffraction(XRD),atomic force microscope(AFM),scanning electron microscope(SEM),spectrophotometer,and spectrofluorometer.The results of x-ray diffraction and atomic force microscope indicate that with the decrease of oxygen pressure,the full width at half maximum(FWHM)and grain size increase.With the increase of oxygen pressure,the thickness of the films first increases and then decreases.The room-temperature UV-visible(UV-Vis)absorption spectra show that the bandgap of theβ-Ga_(2)O_(3)film increases from4.76 e V to 4.91 e V as oxygen pressure decreasing.Room temperature photoluminescence spectra reveal that the emission band can be divided into four Gaussian bands centered at about 310 nm(~4.0 e V),360 nm(~3.44 e V),445 nm(~2.79 e V),and 467 nm(~2.66 e V),respectively.In addition,the total photoluminescence intensity decreases with oxygen pressure increasing,and it is found that the two UV bands are related to self-trapped holes(STHs)at O1 sites and between two O2-s sites,respectively,and the two blue bands originate from V_(Ga)^(2-)at Ga1 tetrahedral sites.The photoluminescence mechanism of the films is also discussed.These results will lay a foundation for investigating the Ga_(2)O_(3)film-based electronic devices.

PIC-EDDY Simulation of Different Impurities Deposition in Gaps of Carbon Tiles

A 3D Monte Carlo （MC） code PIC- EDDY, based on EDDY （erosion and deposition dynamic simulation） code, was used to investigate the redeposition of different impurities in the gaps of C tiles. By incorporating the rate coefficients of beryllium （Be） and tungsten （W） into the code, we obtain deposition profiles of hydrocarbon, beryllium and tungsten particles in the toroidal and poloidal gaps, respectively. The redeposition rate of tungsten was found to be higher than those of other impurities in the gaps, except at the bottom, due to its easier local deposition within one gyroradius. Due to the effect of reflection coefficients of hydrocarbon fragments on graphite, fewer hydrocarbons were resided at the entrance while more were deposited on the sides of the gap. At elevated plasma temperatures （such as 30 eV）, asymmetric deposition distributions were observed between the toroidal and poloidal gaps due to the dominant ionized particles. Ions were mainly deposited within 1 mm depth inside gaps, and the bottom deposition particles were almost all neutrals.

Effects of Deposition Temperature on the Properties of Fluorinated Amorphous Carbon Films

Fluorinated amorphous carbon films (a-C:F) were prepared at different temperatures using a microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) reactor with CHF3 and C2H2 as source gases. Films were annealed at 500℃ in vacuum ambience in order to investigate the relationship of their thermal stability, optical and electrical properties with deposition temperature. Results indicate that the films deposited at high temperature have a less CFX bonding and a more cross-linking structure thus a better thermal stability. They also have a lower bandgap, higher dielectric constant and higher leakage current.

Effect of Chamber Conditions and Substrate Type on PECVD of SiGeSn Films

In the past studies have shown that the addition of Ge and Sn into Si lattice to form SiGeSn enhances its carrier mobility and band-gap properties. Conventionally SiGeSn epitaxial films are grown using Ultra-High Vacuum (UHV) conditions with pressures ranging from 10-8 torr to 10-10 torr which makes high volume manufacturing very expensive. On the contrary, the use of low-pressure CVD processes (vacuum levels of 10-2 torr to 10-4 torr) is economically more viable and yields faster deposition of SiGeSn films. This study outlines the use of a cost-effective Plasma Enhanced Chemical Vapor Deposition (PECVD) reactor to study the impact of substrate temperature and substrate type on the growth and properties of polycrystalline SiGeSn films. The onset of polycrystallinity in the films is attributed to the oxygen-rich PECVD chamber conditions explained using the Volmer-Weber (3D island) mechanism. The properties of the films were characterized using varied techniques to understand the impact of the substrate on film composition, thickness, crystallinity, and strain.

基于信息差距决策理论的虚拟电厂报价策略

为进一步提升分布式能源的调节潜力,基于信息差距决策理论,将探讨虚拟电厂(virtual power plant,VPP)在参与需求响应(demand response,DR)策略时的竞价方式分为平衡型、保守型和进取型3种策略模型,并为每种策略设计鲁棒函数和机会函数,分别实现对不同类型决策的优化。同时,设置ε约束模型,考虑了碳排放和利润的权衡关系。采用IEEE 18节点系统作为仿真环境,验证了所提方法的优点和必要性。仿真结果表明,保守型VPP能够保证在未来价格落入最大鲁棒性区间时获得最小关键利润;进取型VPP能够从意外的价格波动中获益,并实现期望的利润。

涉农贷款与城乡收入差距——基于布吉尼翁指数的研究

布吉尼翁指数是测度城乡居民收入差距的一种指标。本文利用布吉尼翁指数,对我国31个省份2014—2020年城乡居民收入差距进行测度,并与涉农贷款情况进行比较分析,发现涉农贷款有助于增加农村居民收入,但涉农贷款占各项贷款的比例趋于下降,带来城乡收入差距扩大。在此基础上,利用31个省份2014—2020年数据对布吉尼翁指数和涉农贷款指标进行了面板数据向量自回归分析,并印证了上述观点,表明涉农资金有利于农村经济发展和农村居民收入水平提高,但农村金融约束、涉农资金不足的状况没有得到根本改变,国家在引导金融资源流入实体经济时,要采取切实措施促进农村金融发展,提高农村居民收入水平,缩小城乡居民收入差距。

农户信用贷款推广与县域内城乡收入差距——基于典型试验区的准自然实验研究

整村评级授信是中国农户信用贷款推广的主要模式,考察其对县域内城乡收入差距的影响,可以为共同富裕目标下的农村金融改革路径探索提供科学依据。基于信贷配给理论,本文论述了农户信用贷款推广对信贷供需双方的影响,从而揭示了其对县域内城乡收入差距的作用机理,并利用典型试验区102个县域的准自然实验进行实证检验。研究结果表明,农户信用贷款推广有助于缩小县域内城乡收入差距,且在一系列稳健性检验之后,该结论依然成立;通过增加农村信贷市场的供给和需求,农户信用贷款推广能够抑制村庄资金外流,从而缩小县域内城乡收入差距;在银行金融科技应用水平和第一产业占比较高的县域,农户信用贷款推广的效果较强。本研究为银行以整村评级授信的方式推广农户信用贷款、实现共同富裕提供了经验证据。

CdSe薄膜的制备及性能表征

室温下,以CdSO4、H2SeO3和Na2SO4为原料,采用二电极体系,利用电化学法在ITO玻璃基底上沉积了CdSe薄膜。采用高分辨X射线衍射仪(HRXRD)、场发射扫描电镜(FESEM)、原子力显微镜(AFM)、紫外-可见-近红外(UV-VIS-NIR)分光光度计、荧光分光光度计(PL)对不同沉积电压下所制备的薄膜的晶体结构、形貌及光学性能进行分析表征。结果表明:所制备的薄膜为立方相CdSe,呈纳米颗粒状,部分粒子表现出不均匀团聚。紫外吸收光谱的吸收峰较体相CdSe有较大的蓝移,且导致禁带宽度发生改变,表现出量子尺寸效应。样品发射光谱表现出荧光现象,且单色性好。适当的沉积电压对CdSe薄膜的形貌和质量起关键作用,同时讨论了其反应机理。

基于毛细管放电的大气压等离子体射流喷射装置放电特性

为满足更长间隙距离、更高电压等级气体开关在较低工作系数下的可靠触发,设计了一种基于毛细管放电的大气压等离子体射流喷射装置,即两间隙毛细管等离子体喷射装置(two gap capillary,TGC)。通过引入中间电极将毛细管通道分为触发通道和主通道,借助触发通道在放电初始时的弱毛细管放电引燃主通道的放电,实现了重复放电。等离子体射流在触发后的169μs时达到了11 cm左右。主通道电弧电阻呈现"U型"分布,电阻值开始时随主通道电弧电流的增长快速减小,最低时不到200 m?,而后随着电流的跌落快速增加。同时,主通道电弧电阻值在电流增长时要高于电流跌落时,这一差异在流过主通道电弧电流较小时十分明显,而后随着电流幅值的增加逐渐减小。由于没有传统放电结构金属丝电爆的过程,电容器所储能量主要释放于喷射装置主通道,主通道电弧能量沉积效率几乎是传统放电结构的2倍,达到了62.7%。喷射装置寿命大概在300次左右,使用扫描电子显微镜(SEM)拍摄触发通道表面,发现喷射装置TGC中间电极的烧蚀和触发通道的碳化是影响TGC寿命的关键因素,对TGC的寿命优化设计还需做进一步的努力。

宏观审慎视角下存贷期限错配流动性风险的识别与控制

存贷期限错配的流动性风险存在顺周期性与传染性,有必要从宏观审慎视角分析存贷期限错配流动性风险与系统性风险的关系。通过测算期限错配流动性缺口,对我国商业银行业资产占比很大的15家商业银行的存贷期限错配流动性风险进行识别,得出存贷期限错配流动性风险是2013年"钱荒"事件发生的重要导因的结论。采用适当的变量并通过面板回归模型分析,能够识别存贷款期限错配流动性风险的主要宏观影响因素和微观影响因素。因此,应从国家金融管理部门的外部控制和商业银行的内部控制两个方面控制存贷期限错配的流动性风险。

同源岩浆成因金矿成岩成矿时差的统计研究

同源岩浆成因金矿的成岩成矿时差是确定矿床与岩浆岩成因关系的重要基础。而中国同源岩浆成因金矿分布十分广泛，前人在成矿学和岩石学方面做了大量的研究，为此本文收集了国内一些典型金矿的成矿和相关同源岩浆岩的同位素测年数据，讨论并定量厘定了该类金矿床成岩成矿时差的分布特征及分布范围。数据统计分析及柯尔莫哥洛夫准则检验结果显示，成矿事件一般同步或略滞后于同源岩浆活动，成岩成矿时差在95％信度下服从正态分布，介于0～16．0Ma，均值约为7．0Ma。因此，若金矿成岩成矿存在着≤16．0Ma的时差，就应该重视二者之间的同源成因联系。同时，笔者也强调：准确的成岩成矿时差应加强对金矿成岩成矿地质背景的研究；重视时差研究与微量元素和同位素示踪相结合，从年代学和地球化学方面对矿床成因作出合理的解释。

中国流动性过剩原因辨析

存贷差和外汇占款以及M2与M1差额的不断拉大等都不是流动性过剩的直接成因,而是由于货币政策没有及时对经济发展出现的变化作出反应造成的。解决流动性过剩问题有三条思路:一是要加大货币政策的紧缩力度以收紧流动性,从而预防可能发生的通货膨胀;二是使用扩张性的财政政策,在货币政策紧缩的同时,通过财政政策的扩张保证经济的稳定发展;三是加快利率市场化进程,为汇率自由浮动提供前提和基础。

商业银行流动性影响因素研究

近期,我国银行业的流动性风险得到了理论界和实务界的普遍关注。本文基于上市银行2006至2012年的样本,以贷存比和流动性比率作为银行流动性的度量指标,从银行特征、宏观经济和货币政策等不同层面,考察了商业银行流动性的影响因素。较为稳健的结果显示,总资产中贷款占比越低、负债中存款占比越高,银行的流动性越好。这说明资产或负债结构是影响银行流动性的重要因素。与之相比,宏观经济和货币政策因素对银行流动性的影响在不同样本中结果不完全一致。本文的研究对于理解我国银行业的流动性风险具有一定的参考价值。

中国东部中生代钼矿成岩-成矿时差

与岩浆成因相关的钼矿床成岩-成矿时差是确定矿床与岩浆岩成因关系的重要基础。本文根据收集的中国东部中生代典型钼矿床的成矿及相关岩体的同位素测年数据,详细讨论并定量厘定了钼矿的成岩-成矿时差分布特征。结果表明,钼矿成矿同步或略滞后于同源岩浆活动,中国东部整个钼矿成矿高峰的两个阶段时差介于0～10.0Ma和0～15.0Ma;对于单个钼矿床,其成岩-成矿时差集中在0～14.0Ma,均值为3.9Ma;从斑岩型钼矿床→斑岩-矽卡岩型钼矿床→矽卡岩型钼矿床→石英脉型钼矿床,成岩-成矿时差呈逐渐增加趋势,这与岩浆热液成矿过程的地质事实吻合。

农村金融支持与城乡收入差距的经济效应研究

农村金融支持是我国促进农村经济发展和缩小城乡收入差距的战略性措施。文章基于我国1980—2005年统计数据资料,首先利用协整检验分析了城乡收入差距、农业贷款和乡镇企业贷款之间的长期均衡关系。并在VEC的基础上,运用脉冲响应函数和预测方差分解分析了我国自1980年以来城乡收入差距、农业贷款和乡镇企业贷款之间的交互影响情况。结果显示:乡镇企业贷款的提高有助于缩少城乡收入差距,而农业贷款的提高对城乡收入差距的缩小起到了抑制作用。这说明我国农业贷款相对于乡镇企业贷款来说,存在资金配置低效率的问题。