镶嵌结构锗纳米晶电输运的研究

利用离子注入然后退火的方法制备了镶嵌有锗纳米晶的二氧化硅复合薄膜,从拉曼散射和透射电镜测量了解到薄膜中镶嵌有5~7nm大小的锗纳米晶层.研究了锗纳米晶层在常温和低温下的电输运性质.结果表明:锗纳米晶在100K~300K温度范围内符合莫特变程跳跃电导(VRH)导电,100K以下的低温电导基本上是一常数,导电主要是电子在相邻纳米晶之间的直接跃迁;经退火可消除离子注入引入的缺陷,能增加薄膜的电导;对由3×1017cm-2注量锗离子注入制备的薄膜观察到半导体向金属导电的转变.     

天然锗纳米晶的制备与中子嬗变掺杂研究

采用离子注入法及退火工艺,在硅基二氧化硅薄膜中制备了镶嵌结构的天然Ge纳米晶样品. 通过退火实验研究,发现随着退火温度的升高,纳米晶的晶态峰峰位红移,这意味着Ge纳米晶受到的应力减小. 当退火温度达到 700 ℃时,纳米晶的晶态峰强度显著增强,而且薄膜中与Ge有关的缺陷发光减弱. 采用中子嬗变掺杂法对天然Ge纳米晶进行了掺杂,X射线荧光光谱数据表明,样品中成功的引入了Ga杂质和As杂质. 薄膜中形成的与Ge有关的缺陷具有稳定的结构,中子辐照之后其发光仍然存在,而且,掺杂后的样品中没有发现与Ga或As有关的     

Ga掺杂70Ge纳米晶的制备与研究

通过离子注入及中子嬗变掺杂制备了Ga(镓)掺杂70Ge(锗)纳米晶,并对样品进行了质子激发X射线荧光分析谱(PIXE)、光致发光谱(PL)、激光拉曼散射谱(LRS)的测量与研究.结果表明：随着Ga杂质浓度的增加,580 nm附近的荧光峰的发光强度不断地下降,这可能是非辐射的俄歇复合过程与纳米晶数量的减少共同作用的结果.此外,从PL上面看到580 nm附近的荧光峰蓝移则可能是由纳米晶尺寸的减小和非辐射的俄歇复合过程引起的.     

Ge量子点材料的制备工艺研究

采用射频磁控技术,用Ge、SiO_2的复合靶制备锗纳米晶镶嵌在二氧化硅中的复合薄膜.作为量子点的Ge纳米晶粒的尺寸是决定这类材料物性的关键,因而研究对镶嵌在SiO_2中的Ge晶粒尺寸调制的工艺十分重要.本文研究了制备过程中各种工艺参数与薄膜中Ge晶粒尺寸的关系.结果表明通过溅射时控制基片温度能有效地对锗晶粒尺寸进行调制.     

Al金属多晶硅纳米膜欧姆接触的制作

利用低压化学气相淀积法(LPCVD)在表面有热氧化二氧化硅的(100)硅衬底上生长80nm厚多晶硅纳米膜,并对其界面进行表征.制作出单层Al金属的欧姆接触样品,在不同退火温度条件下对样片的电阻进行测量.结果表明,退火使欧姆接触的电阻率降低,接触电阻率可达到2.41×10-3Ω.cm2.     

Eu^3＋掺杂二氧化钛纳米粉末的制备及发光性质研究

以钛酸四丁酯为前驱物,利用溶胶一凝胶法制备了Eu3+掺杂TiO2纳米粉末.首先对纳米粉末的发光性质进行了一定的研究,找出了纳米晶发光效率最佳激发波长,然后用最佳激发波长对不同退火温度下摩尔分数为0.5%Eu3+离子掺杂TiO2纳米晶和同一退火温度下不同摩尔分数Eu3+离子掺杂的纳米晶进行激发,对发射光谱进行分析,从而得到制备纳米晶的最佳退火温度和最佳Eu3+离子掺杂的摩尔分数.     

纳米Ge-SiO2薄膜对1342nm激光的被动调Q

采用射频磁控溅射技术和热退火处理方法制备纳米锗镶嵌二氧化硅( Ge-SiO2)薄膜.利用光吸收谱和X射线衍射谱对薄膜材料进行表征,得到薄膜的光学带隙为1.12 eV,纳米Ge晶粒的平均尺寸约为16.4 nm.将纳米Ge-SiO2薄膜作为可饱和吸收体插入激光二极管泵浦的平-凹腔Nd∶YVO4激光器内,实现1 342 nm...     

回火对应力退火Fe基薄带磁各向异性的影响

对应力退火的Fe基纳米晶薄带进行540℃回火处理,采用HP4294A型阻抗分析仪测量回火不同次数样品的纵向驱动巨磁阻抗(LDGMI)曲线.对系列LDGMI曲线特征与回火次数的关系进行分析,结果表明:回火释放了Fe基纳米晶薄带应力退火导致非晶基体滞弹性形变而引入的拉应力,使得样品的磁各向异性场减小.经过7次回火处理,应力退火感生的磁各向异性场从2 632.29 A/m减小到1 139.39 A/m.     

射频磁控溅射技术制备Ge-SiO2薄膜的结构和光学特性研究

用射频共溅射技术和后退火的方法，制备出埋入SiO2基质中的Ge纳米晶复合膜(nc-Ge／SiO2)。用XRD对薄膜的晶体结构进行了测试，未经退火的样品呈现非晶状态，600℃退火后的薄膜中开始有Ge纳米晶粒出现。研究了薄膜的Raman散射光谱，发现了其红移和宽化现象。测量了薄膜的光致发光谱，所有样品都在394nm处发出很强的光，随着Ge纳米晶粒的出现，样品有310nm和625nm处的光发出，其强度随晶粒平均尺寸的增大而增强。     

退火对表面纳米化纯钛热稳定性的影响

采用表面机械研磨技术实现纯钛材料表面纳米化,并研究了纳米化处理后的材料表层组织结构,详细分析了样品表层纳米晶组织在不同温度、不同时间退火后的热稳定性.结果表明:纯钛TA2经过表面机械研磨处理后可以在表面形成等轴且取向随机的纳米晶层,晶粒尺寸约为12nm.对表面纳米化样品退火后发现,表层纳米晶组织在773 K以下温度退火后具有良好的热稳定性,晶粒尺寸没有明显增大;在773 K温度退火150min后晶粒尺寸稍有增大,而在773 K温度退火240min后晶粒尺寸明显增大,且横截面显微硬度也比表面纳米化后未退火样品显著下降,良好的热稳定性消失.     

Uniform fabrication of Ge nanocrystals embedded into SiO2 film via neutro transmutation doping

Nanocrystalline74Ge embedded SiO2 films were prepared by employing ion implantation and neutron transmutation doping methods.Transmission electron microscopy, energy dispersive x-ray spectroscopy, and photoluminescence of the obtained samples were measured. The existence of As dopants transmuted from74 Ge is significant to guarantee the uniformity and higher volume density of Ge nanocrystals by tuning the system’s crystallinity and activating mass transfer process. It was observed that the photoluminescence intensity of Ge nanocrystals increased first then decreased with the increase of arsenic concentration. The optimized fluence of neutron transmutation doping was found to be5.5 1017 cm 2to achieve maximum photoluminescence emission in Ge embedded SiO2 film. This work opens a route in the three-dimensional nanofabrication of uniform Ge nanocrystals.     

Effect of high pressure sintering and annealing on microstructure and thermoelectric properties of nanocrystalline Bi2Te2.7Se0.3 doped with Gd

Bi2Te2.7Se0.3of high performance doped with Gd bulk materials was prepared by a high pressure(6.0 GPa) sintering(HPS) method at 593 K,633 K, 673 K and 693 K. The sample was then annealed for 36 h in a vacuum at 633 K. The phase composition, crystal structure and morphology of the sample were analyzed by X-ray diffraction and scanning electron microscopy. The electric conductivity, Seebeck coefficient, and thermal conductivity aspects of the sample were measured from 298 K to 473 K. The results show that high pressure sintering and the doping with Gd has a great effect on the crystal structure and the thermoelectric properties of the samples. The samples are consisted of nanoparticles before and after annealing, and these nanostructures have good stability at high temperature. HPS together with annealing can improve the TE properties of the sample by decreasing the thermal conductivity of the sample with nanostructures. The maximum ZT value of 0.74 was obtained at 423 K for the sample, which was sintered at 673 K and then annealed at 633 K for 36 h. Compared with the zone melting sample, it was increased by 85% at423 K. Hence the temperature of the maximum of figure of merit was increased. The results can be applied to the field of thermoelectric power generation materials.     

变温霍尔效应测量n型锗半导体薄膜禁带宽度

文章介绍了变温霍尔效应测量半导体电学特性实验,通过77—400K的浅掺杂n型锗标准样品变温霍尔效应测量,根据对各种变温数据曲线中高温本征导电区斜率的计算,得到半导体样品的禁带宽度Eg,并对计算结果进行比较讨论。认为1g（｜RH｜T^3/2）-1／T曲线方法更合适用来计算禁带宽度。     

Bi系高温超导氧化物中掺杂(Pb、Sb、Eu)的研究

采用空气中固态反应的方法制备了一系列掺 Pb、Sb、Eu的 Bi系高温超导氧化物 .对这些样品进行了超导性能的测量 ,X射线衍射 ( XRD)分析以及扫描电镜 ( SEM)的形貌观察 ,发现 Pb、Sb的掺杂对 Bi系材料超导相 2 2 1 2相、2 2 2 3相的形成有明显的促进作用 ,而 Eu的掺杂只有利于 2 2 1 2相的形成却不利于 2 2 1 2相向 2 2 2 3相的转变 .在掺 Eu的样品中发现有Ca2 Cu O3 存在 .对 Bi系材料中调制结构的形成机制给予了定性解释     

Microstructure and mechanical properties of Cr doped WCoB based cermets by spark plasma sintering and first principle calculation

WCoB based cermet is a potential hard alloy to replace WC-Co cermets with high hardness and corrosion resistance. WCoB based cermets with different Cr doping contents were fabricated by spark plasma sintering in liquid phase sintering stage. The densification behavior, phase composition, microstructure and mechanical properties of Cr doped WCoB cermets were investigated by XRD, EDS and SEM. Due to the lower density of Cr,the density of WCoB cermets decreased with the increasing of Cr doping content. The phase composition consisted of Cr doped WCoB, unreacted W, Co–Cr binary binder phase. When the doping content exceeded11.736 wt%, the Cr enrichment zones appeared, which was harmful to the TRS. The increasing of Cr doping content contributed to the increase of unreacted W phases content and the formation of pores. The maximum value of Vickers hardness was 1751 Hv0.5 at 9.356 wt% Cr doping content. The variation trend was explained by first principle calculation, which is consistent with Hv-Zhou hardness model.     

Sm3+掺杂LnNbO4(Ln=La,Y)红色荧光粉的性能分析

通过高温固相法合成系列Sm3+掺杂LnNbO4(Ln=La,Y)红色荧光粉,并对样品的物相结构、荧光特性、衰减寿命和荧光热猝灭等性能进行实验分析。分析结果表明:合成的样品不含杂质相,可以被近紫外光LED和蓝光LED芯片有效激发,发出色坐标为(0615 5,0380 2)的红光对于LnNbO4(Ln=La,Y)基质来说,Sm3+掺杂LaNbO4基质的荧光强度比较强,最佳的Sm3+掺杂浓度为2%;随着Sm3+掺杂浓度的提高衰减寿命曲线由单指数线形变双指数线形,且衰减寿命不断变短;Sm3+之间的电偶极 电偶极作用是导致荧光浓度猝灭发生的原因;样品在293~450 K这一温度范围内具有良好的热稳定性。说明Sm3+掺杂的LaNbO4红色荧光粉具备成为白光LED用红色荧光粉的潜力。     

Al3+掺杂NaGdF4:Er3+/Yb3+纳米晶上转换发光性能的研究

稀土离子掺杂的上转换纳米材料具有优异的光学性能,在光电等领域具有广阔的应用前景。本文采用溶剂热法,以乙二胺四乙酸(EDTA)为络合剂合成了的粗细均匀的六棱柱形的六方相Al3+掺杂NaGdF4:Er3+/Yb3+纳米棒。X射线研究表明适量的Al3+掺杂对NaGdF4的晶相没有产生影响,但使主衍射峰的位置发生偏移。在980nm激光激发下,与未掺杂的纳米晶相比,在Al3+的掺杂浓度为15%时,红绿光发光最大强度分别增强了5.7倍和5倍,且4F9 /2能级的荧光寿命被延长。Al3+掺杂对上转换发光的改善是因Er3+附近局部对称性的降低和粒子表面吸附基团的减少所致。     

Doping semiconductor nanocrystals

Doping--the intentional introduction of impurities into a material--is fundamental to controlling the properties of bulk semiconductors. This has stimulated similar efforts to dope semiconductor nanocrystals. Despite some successes, many of these efforts have failed, for reasons that remain unclear. For example, Mn can be incorporated into nanocrystals of CdS and ZnSe (refs 7-9), but not into CdSe (ref. 12)--despite comparable bulk solubilities of near 50 per cent. These difficulties, which have hindered development of new nanocrystalline materials, are often attributed to 'self-purification', an allegedly intrinsic mechanism whereby impurities are expelled. Here we show instead that the underlying mechanism that controls doping is the initial adsorption of impurities on the nanocrystal surface during growth. We find that adsorption--and therefore doping efficiency--is determined by three main factors: surface morphology, nanocrystal shape, and surfactants in the growth solution. Calculated Mn adsorption energies and equilibrium shapes for several nanocrystals lead to specific doping predictions. These are confirmed by measuring how the Mn concentration in ZnSe varies with nanocrystal size and shape. Finally, we use our predictions to incorporate Mn into previously undopable CdSe nanocrystals. This success establishes that earlier difficulties with doping are not intrinsic, and suggests that a variety of doped nanocrystals--for applications from solar cells to spintronics--can be anticipated.     

嵌入SiO2薄膜中的GeO和Ge纳米晶光致发光的研究

作者通过离子注入法得到了镶嵌于SiO2薄膜中的Ge纳米晶，并通过系统的氧化性或还原性退火处理，以改变样品中Ge的氧化物成分组成．分析了不同样品在室温下的光致发光(PL)特性，并结合XRD分析表明：300与400nm附近的荧光峰的发光机制是GeO(nc-GeO)纳米晶发光，而不是GeO的缺陷发光；570nm附近的荧光峰的发光机制为Ge纳米晶(nc-Ge)发光，而不是Ge及Si界面的缺陷发光．     

CuO掺杂对10NiO-NiFe2O4陶瓷致密化烧结及其力学性能的影响

采用冷压成型和常压烧结工艺制备CuO掺杂10NiO-NiFe2O4陶瓷,研究CuO掺杂量对10NiO-NiFe2O4陶瓷的致密度、抗折强度及热震稳定性的影响。结果表明,在1 300℃烧结温度下,掺杂CuO能够有效提高10NiO-NiFe2O4陶瓷的致密度,其中添加6%CuO试样的相对密度（95.55%）最大;掺杂CuO可大幅提高10NiO-NiFe2O4陶瓷的抗折强度,其中添加8%CuO试样的抗折强度（139MPa）最高,且在800℃下经过1次和3次热循环后,该试样的抗折强度损失率仅分别为5.7%和8.6%,表现出良好的抗热震性能。