Violet/blue photoluminescence from CeO2 thin film

CeO2 thin film was fabricated by dual ion beam epitaxial technique. The violet/blue PL at room temperature and lower temperature was observed from the CeO2 thin film. After the analysis of crystal structure and valence in the compound was carried out by the XRD and XPS technique, it was inferred that the origin of CeO2 PL was due to the electrons transition from Ce4f band to O2p band and the defect level to O2p band. And these defects levels were located in the range of 1 eV around Ce4f band.

Magnetic properties and rectifying behaviour of silicon doped with gadolinium

The magnetic/nonmagnetic p-n junction was prepared by implanting gadolinium into the n-type silicon with low-energy dual-ion-beam epitaxy technology. The magnetic layer GdxSi1-x shows excellent magnetic properties at room temperature. High magnetic moment 10mu(B) per Gd atom is observed, which is interpreted by RKKY mechanism. Magnetic/nonmagnetic p-n junctions show rectifying behaviour, but no magnetoresistance is observed.

Content analyses in GaMnAs by double-crystal X-ray diffraction

A model for analyzing point defects in compound crystals was improved. Based on this modified model, a method for measuring Mn content in GaMnAs was established. A technique for eliminating the zero-drift-error was also established in the experiments of X-ray diffraction. With these methods, the Mn content in GaMnAs single crystals fabricated by the ion-beam epitaxy system was analyzed.

The PL "violet shift" of cerium dioxide on silicon

CeO2 thin film was fabricated by dual ion beam epitaxial technique. The phenomenon of PL violet shift at room temperature was observed, and the distance of shift was about 65 nm. After the analysis of crystal structure and valence in the compound were carried out by XRD and XPS technique, it was concluded that the PL shift was related with valence of cerium ion in the oxides. When the valence of cerium ion varied front tetravalence to trivalence, the PL peak position would move from blue region to violet region and the phenomenon of "violet shift" was observed.

Growth and photoluminescence of epitaxial CeO2 film on Si (111) substrate

A CeO2 film with a thickness of about 80nm was deposited by a mass-analysed low-energy dual ion beam deposition technique on an Si(111) substrate. Reflection high-energy electron diffraction and x-ray diffraction measurements showed that the film is a single crystal. The tetravalent state of Ce in the film was confirmed by x-ray photoelectron spectroscopy measurements, indicating that stoichiometric CeO2 was formed. Violet/blue light emission (379.5 nm) was observed at room temperature, which may be tentatively explained by charge transitions from the 4f band to the valence band of CeO2.

Evolution from point defects to arsenic clusters in low-temperature grown GaAs/AlGaAs multiple quantum wells

Optical transient current spectroscopy (OTCS), photoluminescence (PL) spectroscopy and excitonic electroabsorption spectroscopy have been used to investigate the evolution of defects in the low-temperature grown GaAs/AlGaAs multiple quantum well structures during the postgrowth rapid thermal annealing. The sample was grown at 350 degrees C by molecular beam epitaxy on miscut (3.4 degrees off (001) towards (111)A) (001) GaAs substrate. After growth, the sample was subjected to 30s rapid thermal annealing in the range of 500-800 degrees C. It is found that the integrated PL intensity first decreases with the annealing temperature, then gets a minimum at 600 degrees C and finally recovers at higher temperatures. OTCS measurement shows that besides As,, antisites and arsenic clusters, there are several relatively shallower deep levels with excitation energies less than 0.3 eV in the as-grown and 500 degrees C-annealed samples. Above 600 degrees C, OTCS signals from As,, antisites and shallower deep levels become weaker, indicating the decrease of these defects. It is argued that the excess arsenic atoms group together to form arsenic clusters during annealing. (C) 2000 Elsevier Science B.V. All rights reserved.

Influence of (001) vicinal GaAs substrates on the optical properties of defects in low-temperature grown GaAs/AlGaAs multiple quantum wells

Photoluminescence (PL) spectroscopy and carrier lifetime measurement has been used to characterize optical properties of defects in the low-temperature (LT) grown GaAs/AlGaAs multiple quantum well structures. Two sets of samples were grown at 400 degrees C by molecular beam epitaxy on nominal (001) and miscut [4 degrees off (001) towards (111) A] GaAs substrates, respectively. After growth, samples were subjected to 30 s rapid thermal annealing at 600-800 degrees C. It is found that after annealing, two defect-related PL features appear in the samples grown on nominal (001) GaAs substrates, but not in those grown on miscut (001) GaAs substrates. The carrier lifetimes are about 31 and 5 ps in as-grown samples grown on nominal and miscut (001) GaAs substrates, respectively. The different PL spectra and carrier lifetimes in two sets of samples are attributed to different structures of the As-Ga-like defects formed during LT growth. (C) 1999 American Institute of Physics. [S0003-6951(99)00230-2].

Low Temperature Deposited Nano-structured Vanadium Oxide Thin Films for Uncooled Infrared Detectors

A novel process of room temperature ion beam sputtering deposition of vanadium oxide films and low temperature post annealing for uncooled infrared detectors was proposed in this work. VOx thin films with relatively low square resistance (70 K Omega / square) and large temperature coefficient of resistance (more than 3%/K) at room temperature were fabricated using this low temperature process which was very compatible with the process of uncooled infrared detectors based on micromachined technology. Furthermore, chemical composition and film surface have been characterized using X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) respectively. The results showed that the main composition of the processed thin films was V2O5 and the thin films were in the process of crystallization.

Selective and lithography-independent fabrication of 20 nm nano-gap electrodes and nano-channels for nanoelectrofluidics applications

A new method has been developed to selectively fabricate nano-gap electrodes and nano-channels by conventional lithography. Based on a sacrificial spacer process, we have successfully obtained sub-100-nm nano-gap electrodes and nano-channels and further reduced the dimensions to 20 nm by shrinking the sacrificial spacer size. Our method shows good selectivity between nano-gap electrodes and nano-channels due to different sacrificial spacer etch conditions. There is no length limit for the nano-gap electrode and the nano-channel. The method reported in this paper also allows for wafer scale fabrication, high throughput, low cost, and good compatibility with modern semiconductor technology.

茚基含氮、氧侧链分子内配位稀土有机化合的合成和性质

稀土有机碳σ-键配合物和氢化物不仅可以催化许多有机反应,而且还可以催化极性单体与非极性单体的聚合.作为稀土有机碳σ-键配合物与氢化物的前体,双配稀土氯化物(C<,9>H<,7>)<,2>LnCl一直是稀土有机化学中研究的热点.1.合成了一系列双配(四氢糠基茚基)稀土氯化物(C<,4>H<,7>OCH<,2>C<,9>H<,6>)<,2>LnCl(Ln=La,Pr,Nd,Sm,Gd,Dy,Y,Ho,Er,Yb,Lu).除了Pr以外,所有化合物的晶体结构都被X-射线衍射表征.2.合成并用X-衍射表征了3-(2-吡啶甲基)茚基锂(C<,5>H<,4>NCH<,2>C<,9>H<,6>)Li(THF)<,2>的晶体结构.3.合成了双配[3-(2-吡啶甲基)茚基]稀土氯化物(C<,5>H<,4>NCH<,2>C<,9>H<,6>)<,2>LnCl(Ln=Sm,Nd),并得到了配合物Nd的晶体结构.4.用二碘化钐(镱)与3-(2-吡啶甲基)茚基锂反应合成了二价双配[3-(2-吡啶甲基)茚基]稀土配合物(C<,5>H<,4>NCH<,2>C<,9>H<,6>)<,2>Ln(Ⅱ)(THF)(Ln=Sm,Yb).5.在用无水氯化稀土YbCl<,3>与3-(2-吡啶甲基)茚基锂反应合成双配[3-(2-吡啶甲基)茚基]稀土氯化物时,由于发生了还原反应,得到了二价双配[3-(2-吡啶甲基)茚基]镱化物(C<,5>H<,4>NCH<,2>C<,9>H<,6>)<,2>Yb(Ⅱ)(THF).6.二价双配[3-(2-吡啶甲基)茚基]稀土配合物(C<,5>H<,4>NCH<,2>C<,9>H<,6>)<,2>Ln(Ⅱ)(THF)(Ln=Sm,Yb)对已内酯具有很好的催化聚合活性.聚合反应可控,并具有活性聚合的特征.

Ce~(3+)在稀土取代的卤磷酸盐中的发光与能量传递的研究

本工作用固相反方法、以炭保护或在N_2-H_2还原气氛中，两次灼烧，合成了一系列烯土取代的卤磷酸盐发光体，其反应是M_2~ICO_3 + M_3~(II)(PO_4)_2 + M_2~(III)O_3 + (NH_4)_2HPO_4 + M~(II)F_2 → M_x~IM_(10-2x)~(II)M_x~(III)(PO_4)_6F_2 + NH_3 + H_2O式中：M~I = Li~+, Na~+, K~+; M~(II) = Ca~(2+), Sr~(2+); M~(III) = Y~(3+), La~(3+), Gd~(3+); X = 0.5, 1, 2, 3。通过X－射线分析法和以Eu~(3+)作为荧光离子探针方法确定了样品的物相和晶体结构，表明它与M_(10)~(II)(PO_4)_6F_2同属六方晶系(Pb_3/m)。并用图解外推法求得样品的晶胞参数a和c分别为9.41和6.89 A。在研究了M~I, M~(II)和M~(III)为不同阳离子，X为不同值时，取代物的物相和结构变化以及对Ce~(3+)发光和能量传递影响规律的基础上，以Na_2Ca_6La_2(PO_4)_6F_2为基本体系比较详细地研究了Ce~(3+)的发光，Ce~(3+)-Mn~(2+), Ce~(3+)-Re~(3+) (Re~(3+) = Pr~(3+)、Nd~(3+)、Sm~(3+)、Tb~(3+)、Dy~(3+)、Tm~(3+)、Ho~(3+)、Er~(3+))以及Ce~(3+)-Mn~(2+)-Re~(3+) (Re~(3+) = Dy~(3+), Nd~(3+))的能量传递。实验发现，Na_2Ca_6La_2(PO_4)_6F_2:Ce~(3+)是较强的紫外光发射体，发射谱带是由338和358nm两个宽带峰组成的，相应于~2D-~2F_(5/2)和~2D-~2F_(1/2)跃迁。发射强度和~2D-~2F_(6/2)，~2D-~2F_(7/2)两种辐射跃迁几率相对大小与温度，Ce~(3+)的浓度有关；F~-含量对发射强度也有强烈的影响。我们认为，浓度和温度的影响是由于Ce~(3+)-Ce~(3+)的能量迁移作用。实验发现，Ce~(3+)能有效地敏化Mn~(2+)的发光，得到高效的黄色荧光发射体。Ce~(3+)对Re~(3+)的作用可以分为三类：A）. Ce~(3+)-Sm~(3+)、Tb~(3+)、Dy~(3+)、Tm~(3+)；B）．Ce~(3+)-Nd~(3+)，Pr~(3+)；C）. Ce~(3+)-Ho~(3+), Er~(3+)。在A，B类型中，Ce~(3+)能有效地敏化这些稀土离子，但能量传递效率(η_T)_A > (η_T)_B。在Ce~(3+)-Ho~(3+)、Ce~(3+)-Er~(3+)类型中，Ho~(3+)、Er~(3+)不产生可见辐射，Ce~(3+)的发射强度也显著降低。在Ce~(3+)-Mn~(2+)-Re~(3+)三元中心体系中，Ce~(3+)的能量可直接传递给Mn~(2+)和Re~(3+)中心，还可通过Ce~(3+)-Mn~(2+)-Re~(3+)的途径传递。通过研究中心离子的浓度效应，温度效应、测定激发光谱、荧光光谱、荧光衰减曲线的荧光寿命，能够证实：在Ce~(3+)-Mn~(2+)、Ce~(3+)-Re~(3+)、Ce~(3+)-Mn~(2+)-Re~(3+)的能量传递属于无辐射共振传递相互作用类型。符合M. Yokata等人提出的偶极－偶极相互作用扩散限制传递历程。我们还利用Ce~(3+)、Ce~(3+)-Mn~(2+)、Ce~(3+)-Re、Ce~(3+)-Mn~(2+))-Re~(3+)激活体系中Ce~(3+)的发射强度和荧光寿命等数据计算了Ce~(3+)的能量传递效率。发现两种结果相差较大，为了准确地表达Ce~(3+)的敏化效果，在分析上了产生这种误差的原因后，提出了两种传递效率表示式(η_f, η_R)。

24-二甲基戊二稀土化合物的合成

本文叙述了2.4-二甲基戊二烯基稀土金属有机化合物的合成并通过元素分析，红外光谱、核磁共振谱及质谱的鉴定。测定了Gd(2.4-GH_(11))_3的单晶结构，此外还合成了（2.4-GH_(11)K.TMEDA及K_2C_8H_8·3THF并也测定了它们的晶体结构。在所合成化合物的红外光谱中，没有属于C=C双键的吸收峰，表明分子中配位体以η~5形式的大π键体系与稀土金属离子结合，在Ln(2.4-GH_(11))_2Cl·TMF和Ln(2.4-GH_(11))Cl_2·GH_THF的红外光谱中，于1060波数附近出现一强而宽的吸收峰，即化合物中有四氢呋喃分子络合。化合物的室温NMR谱有四个吸收峰，2.4-二甲基戊二烯配位体可能为η~5平面∪或W构型。化合物的水解'H-NMR谱与质谱都证实水解产物为2.4－二甲基－1.3－戊二烯。它是－2.4二甲基戊二烯阴离子水解所得的唯一产物，它表明化合物中的配位体确为2.4－二甲基戊二烯阴离子。(2.4-GH_(11))_2Cl·TMDA配合物晶体结构是应用低温X－射线衍射技术用Nicolet R_3 M/E型四园衍射仪LT－1低温装置并利用重原子法测定的最小二乘法精修至收敛时的一致性因子R=0.055. Rw=0.057。晶体属单斜晶系P21/n空间群。晶胞参数a=11.322(4)A, b=9.242(3)A, c=15.956(5)A. β=106.70(3)分子中2.4－二甲基戊二烯阴离子呈平面∪构型。钾离子与四甲基乙二胺二啮体结合形成的络合阳离子和2.4-二甲基戊二烯阴离子相间排列形成无限链状结构分子。2.4－二甲基戊二烯阴离子的C－C键长明显分为中间与外端C－C键两组。外端组C－C键双性质较强键长较短。表明C3具有负电荷的共振杂化体贡献较大。分子中K－C键最短的是K-C(1.5)。而不是具有较多负电荷的C3－K键。这可能是由于几何因素造成的。K_2C_8H_8·3THF的晶体结构是采用与前者相同的方法测定的。它属三斜晶系，PT空间群，晶胞参数a=10.263(3)A, b=13.157(4)A, c=9.443A, α=87.51(2)°, β=114.93(2)°, γ=76.81(2)°. V=1111.6A, R=0.051. 晶体中负二价的环辛四烯阴离呈平面构型，具有中心对称性，两侧与两中心对称相关的钾离子连接，相邻的非等效的钾离子间通过两四氢呋喃分子的氧原子相连接，从而形成了无限链状结构的分子。环辛四烯反映了Huckel的4n+2芳香性规则。该结构的特别之处在于四氢呋喃分子的氧原子以桥键形式与两个钾离子同时连接。而这种形式的桥键在其它化合物中似还未发现。Go(2.4-GH_(11))_3的晶体结构亦是采用与前述相同的方法测定的。其晶体为三斜晶系，PT空间群，晶胞参数a=12.541A, b=12.853A, c=8.432A, α=91.44°, β=108.61°, γ=117.97°, V=112.54A~3. 结构测定表明，Gd(2.4-GH_(11))_3分子具有C_3h对称性。三个配位体阴离了的九个带负电荷的碳原子近似以三帽三角棱柱形式与钆离子配位。分子中2.4－二甲基戊二烯阴离子的C－C键长－亦分为而组。外端C－C键较中间C－C键强，键长较短，亦表明C3具有较多的负电荷。2.4－二甲基戊二烯阴离子本身近似呈平面∪构型。C2,C4偏离由C1 C3 C5三碳原子构成的平面0.067A。方向上远离中心钆离子。可能在此以离子性为主的化合物中，钆离子与不带电荷的C2 C4间的相互作用有些排斥性质。与Nd(2.4-GH_(11))_3不同的是，在Gd(2.4-GH_(11))_3分子中，Gd-(C(1,5）键最短，而不是Gd-C(3)键。这可能是由于钆离子的半径较小，化合物的空间位阻效应较大所致。

铜的多元复合物组成、结构和电学性质的研究

本论文包括三个部分的内容，第一部分研究了Y-Ba-Cu-O材料中，钙、钾、氟离子的掺入对材料结构和电、磁学性质的影响。1、在Y_(1-x)Ca_xBa_2Cu_3O_(7-y)系列中，当x ≤ 0.15时，钙离子进入了YBa_2Cu_3O_(7-y)晶格中钇离子的位置，使晶胞参数略为增大，但没有引起正交 → 四方相变。钙离子渗入导致123相中Cu~(3+)含量上升，同时材料的监界超导转变温度下降。因此，Cu~(3+)含旱管高可能是对超导电性不利的。由于钇离子位置紧邻着Cu(2)-O平面而与Cu(1)-O链相隔较远。因此，钇离子被钙离子替代时主要影响了Cu(2)-O平面的性质。少量钙离子的渗入即明显影响材料的超导电性，这说明Cu(2)-O平面的性质与超导电性密切相关，并可能起着关键的作用。2、在Y(Ba_(1-x)Ca_x)_2Cu_3O_y系的研究中，当x = 1，YCa_2Cu_3O_y是一个单一的化合物，文献未见报道，本文研究了它的结构，电学性质与热学性质，确定它的结构属正交晶系，a = 5.286 A、b = 7.636 A、c = 9.286 A。热分析表明YCa_2Cu_3O_y在1080 ℃分解，分解前于380 ℃ 和608 ℃出殃失氧现象。这个化合物是黑色n型半导体。室温电阻率1.2 * 10~5Ω·cm。与热分析中的失氧温度相对应，lnρ-1/T曲线上在370 ℃、620 ℃ 出现两个转折点。3、在Y-Ba-Cu-O材料中渗入钾离子能细化材料晶粒，降低超导转变宽度，提高零电阻温度，但由于KOH、K_2CO_3等强吸湿性杂质的存在也降低了材料的稳定性。4、在Y-Ba-Cu-O材料中间时掺入钾和氟离子时，材料的超导电性的变化与仅掺钾时相似。这种变化可能主要是钾离子的影响造成的。第二部分中，我们研究了Ca-Sr-Ca-O系的相图和新化合物Sr_3Cu_5O_(8+x)、CaSrCu_3O_(5+x)的结构和电学性质。在第三部分中，广泛研究了组成为Bi_tSr_vCa_wCu_zO_y超导材料的制备，结构和超导电性。铋系超导材料的形成貌与YBa_2Cu_3O_y材料有较大差异，前者是片状层叠的晶粒堆积而成，后者是球状小颗粒堆积而成的。我们合成的材料最高起始转变温度124K，最高零电阻温度112K，与国际上已达到的最高Tc值一致。Jc值达到131A/cm~2。

稀土功能薄膜的离子束外延法制备生长研究

介绍了一种利用离子束外延（Ion-beam Epitaxy, IBE）技术制备生长高纯稀土功能薄膜的新方法. 以纯度要求不高的低成本稀土氯化物为原材料来产生大束流稀土元素离子, 通过准确控制双束合成或单束浅结注入掺杂的同位素纯低能离子的能量、束斑形状、沉积剂量与配比及生长温度, 在超高真空生长室内实现了稀土功能薄膜的高纯生长和低温优质外延. 文中除了对新方法的技术特点、实施方式和应注意的关键技术进行了阐述, 还结合CeO2, Gd2O3, GdxSi1-x等薄膜的制备研究, 讨论了离子的束流密度、剂量配比、能量和生长温度等生长参数对成膜质量的影响.

Fabrication of Windowed Very-Small-Aperture Laser Diodes

A windowed very-small-aperture laser 9VSAL0 source for use in high-resolution near field optical data storage is fabricated. The windowed regions are introduced to avoid shorting the pn junction with metal coating and suppress the COD effect. It facilitates producing VSAL by simplified technology and improves the laser performance. A VSAL with 400nm small sperture is demonstrated by focused ion beam (FIB0 and the output power is 0.3mW at 31mA.