Total Dose Radiation Tolerance of Phase Change Memory Cell with GeSbTe Alloy

Phase change memory （PCM） cell array is fabricated by a standard complementary metal-oxide-semiconductor process and the subsequent special fabrication technique. A chalcogenide Ge2Sb2Te5 film in thickness 50hm deposited by rf magnetron sputtering is used as storage medium for the PCM cell. Large snap-back effect is observed in current-voltage characteristics, indicating the phase transition from an amorphous state （higher resistance state） to the crystalline state （lower resistance state）. The resistance of amorphous state is two orders of magnitude larger than that of the crystalline state from the resistance measurement, and the threshold current needed for phase transition of our fabricated PCM cell array is very low （only several μA）. An x-ray total dose radiation test is carried out on the PCM cell array and the results show that this kind of PCM cell has excellent total dose radiation tolerance with total dose up to 2 ×10^6 rad（Si）, which makes it attractive for space-based applications.     

Quantum—Confined Stark Effect of Vertically Stacked Self—Assembled Quantum Discs

We study the electronic energy levels and probability distribution of vertically stacked self-assembled InAs quantum discs system in the presence of a vertically applied electric field. This field is found to increase the splitting between the symmetric and antisymmetric levels for the same angular momentum. The field along the direction from one disc to another affects the electronic energy levels similarly as that in the opposite direction because the two discs are identical. It is obvious from our calculation that the probability of finding an electron in one disc becomes larger when the field points from this disc to the other one.     

Optical spectra and Exciton State in Vertically Stacked Self—Assembled Quantum Discs

We study the oscillator strengths of the optical transitions of the vertically stacked self-assembled InAs quantum discs.The oscillator strengths change evidently when the two quantum discs are far apart from each other.A vertically applied electric field affects the oscillator strengths severely.while the oscillator strengths change slowly as the radius of one disc increases.We also studied the excitonic energy of the system.including the Coulomb interaction.The excitonic energy increases with the increasing radius of one disc.but decreases as a vertically applied electric field increases.     

Single Crystal Si Layers on Glass Fabricated by Hydrophilic Fusion Bonding and Smart-Cut Technology

A single crystal Si thin film on a glass substrate has been obtained successfully by hydrophilic fusion bonding and the smart-cut technology. Tensile strength testing shows that the bonded interface has strong adhesion and the bonding strength is about 8.7MPa. Crystallinity and microstructure of the samples have been characterized by transmission electron microscopy (TEM). Electrical properties have also been investigated by Hall measurements and four-point probe. The mobility of the transferred Si layer on glass is about 122cm^2//V.s. The results show that the single-crystal silicon layer transferred onto glass by direct bonding keeps good quality for the applications of integrated circuits, transducers, and fiat panel display.     

Reactive Ion Etching as Cleaning Method Post Chemical Mechanical Polishing for Phase Change Memory Device

In order to improve nano-scale phase change memory performance, a super-clean interface should be obtained after chemical mechanical polishing （CMP） of Ge2Sb2Te5 phase change films. We use reactive ion etching （RIE） as the cleaning method. The cleaning effect is analysed by scanning electron microscopy and an energy dispersive spectrometer. The results show that particle residue on the surface has been removed. Meanwhile, Ge2Sb2Te5 material stoichiometric content ratios are unchanged. After the top electrode is deposited, currentvoltage characteristics test demonstrates that the set threshold voltage is reduced from 13 V to 2.7V and the threshold current from 0.1 mA to 0.025 mA. Furthermore, we analyse the RIE cleaning principle and compare it with the ultrasonic method.     

处方应用三种葛根水煎液的二维相关红外光谱分析

中药是复杂的化学体系,建立快速、有效的分析方法有助于中药水煎液的实时质量控制。葛根在处方中常用有三种,分别为粉葛、野葛和煨葛(葛根炮制品),且传统应用中多采用水煎煮的方式,因此,采用傅里叶变换红外光谱技术(FTIR),二阶导数光谱(SD-IR),结合二维相关红外光谱(2D-IR)对三种葛根水煎液进行快速分析。结果表明,通过FTIR和SD-IR光谱能够将粉葛水煎液明显区别于野葛和煨葛水煎液。经过2D-IR分析,发现野葛经过煨制后水煎液化学成分发生了变化,二者在主要的自动峰和交叉峰的位置和强度方面存在较大差异,在1 800~1 300 cm-1范围内,野葛水煎液中最强的自动峰为1 556 cm-1,次强峰为1 561 cm-1,而在煨葛水煎液中最强自动峰为1 563 cm-1,次强为1 572 cm-1,再次为1 556 cm-1。另外,在野葛水煎液中出现了明显的1 536和1 634 cm-1自动峰,二者的强度相当。野葛及煨葛水煎液的2D-IR光谱中,出现的自动峰1 448和1 518 cm-1的相对强度有较大的差异。在野葛水煎液的2D-IR光谱中,交叉峰(1 518,1 561)和(1 518,1 563) cm-1强于煨葛水煎液中相应峰。凭借2D-IR自动峰和交叉峰可以较直观地鉴别野葛和煨葛水煎液,并揭示二者相应各官能团的变化规律,能够为葛根在临床处方应用过程中,水煎液的快速质量控制提供依据。利用FTIR,SD-IR结合2D-IR的整体性和宏观指纹性,可以为中药等复杂体系的逐级鉴别提供快速、准确的方法和手段。     

喷雾热解法制备YBO3：Eu球形发光粉

用喷雾热解两段法制备了YBO3：Eu荧光粉．其粒径分布窄(1～2μm)，为规则的球形，且在高温下不会团聚．考察了PEG浓度(聚乙二醇，分子量为10 000)对发光粉形貌和发光强度的影响、温度对结晶性和发光强度的影响、前躯体溶液的浓度对粒径大小的影响以及掺杂浓度对发光强度的影响．当PEG的浓度为0．004mol/L时．得到实心球形的发光粉，PEG的浓度过高或过低都会使小球产生破裂和空心．从而降低发光粉的发光强度；样品在700℃时开始结晶，1100℃时结晶性最好，相应的发光强度也最强；通过改变前驱体溶液的浓度．可以很容易地调控发光粉小球的粒径，控制前驱体溶液的浓度在0．07mol／L，可以得到粒径为1～2μm的球形发光粉；Eu^3 在YBO3基质中的最佳掺杂摩尔分数为10％。     

双核钨簇合物W2Cl4（OR）4（ROH）2结构的EXAFS研究

我们曾用EXAFS和X射线单晶衍射研究了M_3W_2Cl_9类双钨簇合物的结构,发现簇胳[W_2Cl_9]~(3-)的结构很牢固,改变阳离子M~+的性质和大小,都不会改变其结构。W_2Cl_9(RO)_4(R′OH)_2类簇合物与M_3W_2Cl_9类似,具有一个双钨簇胳。Anderson等曾研究R为甲基或乙基的两个簇合物的单晶结构,正四价的两个钨原子间用双键及两个氧桥键相联接。与M_3W_2Cl_9另一不同处是取代基RO及R′OH与钨原子直接相联,其间还形成氢键,故RO或R′OH对簇胳的影响要大于M_3W_2Cl_9中阳离子M~+。本文合成6种具有不同取代基的W_2Cl_4·(RO)_4(ROH)_2化合物,用EXAFS研究其结构,以期了解不同取代基对簇胳结构的影响。     

Preparation and Characterization of Divanadium Pentoxide Nanowires inside SBA-15 Channels

One-dimensional V2O5 nanowires have been synthesized inside the channels of mesoporous silica SBA-15 through chemical approach, which involves aminosilylation of silanol groups on the silica surface, anchoring of isopoly acid, H6V10O28, by neutralization of basic amine groups, and thermal decomposition. The formation and physicochemical properties of the nanowires were monitored and studied by TG-DTA, variable temperature in situ XRD, TEM, N2 sorption measurements and UV-Vis DRS. The results indicate that V2O5 nanowires formed within SBA-15 channels belong to orthorhombic polycrystal domains. The oxygen-to-metal charge transfer band of V2O5 nanowires shows a blue shift in comparison with bulk V2O5, which clearly exhibits the quantum size effect of nanowires.     

Simulation of Confined and Interface Phonons Scattering in Terahertz Quantum Cascade Laser

We have performed the calculation of resonant-phonon transition in a terahertz quantum cascade laser. The electron wavefunctions and energy levels are obtained by solving the Schroedinger and Poisson equations selfconsistently. The scattering rates of the confined, interface, and bulk phonons are calculated by using the Fermi golden rule. It has been shown that the confined phonon scattering is comparable to the interface phonon scattering and should be taken into consideration in the calculation.