Influences of different oxidants on characteristics of La_2O_3/Al_2O_3 nanolaminates deposited by atomic layer deposition

A comparative study of two kinds of oxidants(H_2O and O_3) with the combination of two metal precursors(TMA and La(~iPrCp)_3) for atomic layer deposition(ALD) La_2O_3/Al_2O_3 nanolaminates is carried out. The effects of different oxidants on the physical properties and electrical characteristics of La_2O_3/Al_2O_3 nanolaminates are studied. Initial testing results indicate that La_2O_3/Al_2O_3 nanolaminates could avoid moisture absorption in the air after thermal annealing. However, moisture absorption occurs in H_2O-based La_2O_3/Al_2O_3 nanolaminates due to the residue hydroxyl/hydrogen groups during annealing. As a result, roughness enhancement, band offset variation, low dielectric constant and poor electrical characteristics are measured because the properties of H_2O-based La_2O_3/Al_2O_3 nanolaminates are deteriorated. Addition thermal annealing effects on the properties of O_3-based La_2O_3/Al_2O_3 nanolaminates indicate that O_3 is a more appropriate oxidant to deposit La_2O_3/Al_2O_3 nanolaminates for electron devices application.     

Fluorescence spectra of colloidal self-assembled CdSe nano-wire on substrate of porous Al_2O_3/Au nanoparticles

We present a self-assembly method to prepare array nano-wires of colloidal CdSe quantum dots on a substrate of porous Al_2 O_3 film modified by gold nanoparticles. The photoluminescence(PL) spectra of nanowires are in situ measured by using a scanning near-field optical microscopy(SNOM) probe tip with 100-nm aperture on the scanning near-field optical microscope. The results show that the binding sites from the edge of porous Al_2 O_3 nanopores are combined with the carboxyl of CdSe quantum dots' surface to form an array of CdSe nanowires in the process of losing background solvent because of the gold nanoparticles filling the nano-holes of porous Al_2 O_3 film. Compared with the area of nonself-assembled nano-wire, the fluorescence on the Al_2 O_3/Au/CdSe interface is significantly enhanced in the self-assembly nano-wire regions due to the electron transfer conductor effect of the gold nanoparticles' surface. In addition, its full width at half maximum(FWHM) is also obviously widened. The method of enhancing fluorescence and energy transfer can widely be applied to photodetector, photocatalysis, optical display, optical sensing, and biomedical imaging, and so on.     

B_2O_3—Al_2O_3—PbO玻璃组成和物化性质的研究

本文研究了在B_2O_3—Al_2O_3—PbO玻璃中引入SiO_2、Sb_2O_3、Ga_2O_3后,TF光学玻璃化学稳定性及相对部分色散P_(g·F)。论证了B_2O_3—Al_2O_3—PbO光学玻璃光学性质、化学组成和结构关系。TF光学玻璃在3.51铂坩埚熔制。     

利用倾斜角度蒸发法制备Al/Al_2O_3/Al超导隧道结

利用电子束曝光法对双层光刻胶进行曝光来制备悬空掩模结构,在此基础上利用电子束蒸发系统采用倾斜角度蒸发法制备铝超导薄膜,采用热氧化法在底层铝膜表面形成氧化铝作为势垒层,制备出铝SIS超导隧道结,并在360mK的情况下对铝结进行了Ⅰ～Ⅴ特性的初步测量.铝隧道结的成功制备为下一步构建超导量子比特器件,研究其量子特性奠定了良好的基础.     

Comparison between AlN and Al_2O_3 ceramics applied to barrier dielectric of plasma actuator

This paper reports the material characterization and performance evaluation of an AlN ceramic based dielectric barrier discharge(DBD) plasma actuator. A conventional Al_2O_3 ceramic is also investigated as a control. The plasma images,thermal characteristics and electrical properties of the two actuators are compared and studied. Then, with the same electrical operating parameters(12-kV applied voltage and 11-kHz power frequency), variations of the surface morphologies,consumed power and induced velocities are recorded and analyzed. The experimental results show that the AlN actuator can produce a more uniform discharge while the discharge of the Al_2O_3 actuator is easier to become filamentary. The later condition leads to higher power consumption and earlier failure due to electrode oxidation. In the plasma process,the power increment of the AlN actuator is higher than that of the Al_2O_3 actuator. The induced velocity is also influenced by this process. Prior to aging, the maximum induced velocity of the AlN actuator is 4.2 m/s, which is about 40% higher than that of the Al_2O_3 actuator. After 120-min plasma aging, the maximum velocity of the aged AlN actuator decreases by 27.8% while the Al_2O_3 actuator registers a decrease of 25%.     

Excellent-Performance AlGaN/GaN Fin-MOSHEMTs with Self-Aligned Al_2O_3Gate Dielectric

AlGaN/GaN fin-shaped metal-oxide-semiconductor high-electron-mobility transistors(fin-MOSHEMTs) with different fin widths(300nm and lOOnm) on sapphire substrates are fabricated and characterized.High-quality self-aligned Al_2O_3 gate dielectric underneath an 80-nm T-shaped gate is employed by aluminum self-oxidation,which induces 4 orders of magnitude reduction in the gate leakage current.Compared with conventional planar MOSHEMTs,short channel effects of the fabricated fin-MOSHEMTs are significantly suppressed due to the trigate structure,and excellent dc characteristics are obtained,such as extremely Bat output curves,smaller drain induced barrier lower,smaller subthreshold swing,more positive threshold voltage,higher transconductance and higher breakdown voltage.     

Performance enhancement of ZnO nanowires/PbS quantum dot depleted bulk heterojunction solar cells with an ultrathin Al_2O_3 interlayer

Depleted bulk heterojunction(DBH)PbS quantum dot solar cells(QDSCs),appearing with boosted short-circuit current density(J_(sc)),represent the great potential of solar radiation utilization,but suffer from the problem of increased interfacial charge recombination and reduced open-circuit voltage(V_(oc)).Herein,we report that an insertion of ultrathin Al_2O_3 layer(ca.1.2 A thickness)at the interface of ZnO nanowires(NWs)and Pb S quantum dots(QDs)could remarkably improve the performance of DBH-QDSCs fabricated from them,i.e.,an increase of V_(oc) from 449 mV to 572 mV,Jsc from21.90 mA/cm~2 to 23.98 mA/cm~2,and power conversion efficiency(PCE)from 4.29% to 6.11%.Such an improvement of device performance is ascribed to the significant reduction of the interfacial charge recombination rate,as evidenced by the light intensity dependence on Jsc and Voc,the prolonged electron lifetime,the lowered trap density,and the enlarged recombination activation energy.The present research therefore provides an effective interfacial engineering means to improving the overall performance of DBH-QDSCs,which might also be effective to other types of optoelectronic devices with large interface area.     

Synthesis of free-standing Ga_2O_3 films for flexible devices by water etching of Sr_3Al_2O_6 sacrificial layers

Flexible electronic devices have attracted much attention due to their practical and commercial value. Integration of thin films with soft substrate is an effective way to fabricate flexible electronic devices. Ga_2O_3 thin films deposited directly on soft substrates would be amorphous mostly. However, the thickness of the thin film obtained by mechanical exfoliation method is difficult to control and the edge of the film is fragile and easy to be damaged. In this work, we fabricated free-standing Ga_2O_3 thin films using the water-soluble perovskite Sr_3Al_2O_6 as a sacrificial buffer layer. The obtained Ga_2O_3 thin films were polycrystalline. The thickness and dimension of the films were controllable. A flexible Ga_2O_3solar-blind UV photodetector was fabricated by transferring the free-standing Ga_2O_3 film on a flexible polyethylene terephthalate substrate. The results displayed that the photoelectric performances of the flexible Ga_2O_3 photodetector were not sensitive to bending of the device. The free-standing Ga_2O_3 thin films synthesized through the method described here can be transferred to any substrates or integrated with other thin films to fabricate electronic devices.     

Substitution priority of Eu~(2+) in multi-cation compound Sr_(0.8)Ca_(0.2)Al_2Si_2O_8 and energy transfer

A blue phosphor was obtained by doping Eu~(2+)into a multi-cation host Sr_(0.8)Ca_(0.2)Al_2Si_2O_8 through high temperature solid state reaction.The emission spectra show a continuous red-shift behavior from 413 nm to 435 nm with Eu~(2+)concentration increasing.The substitution priority of Eu~(2+)in Sr_(0.8)Ca_(0.2)Al_2Si_2O_8 was investigated via x-ray diffraction(XRD)and temperature properties in detail:the Ca~(2+)ions are preferentially substituted by Eu~(2+)at lower doping,and with the Eu~(2+)concentration increasing,the probability of substitution for Sr~(2+)is greater than that of replacing Ca~(2+).Accordingly,we propose the underlying method of thermal property to determine the substitution of Eu~(2+)in the multi-cation hosts.Moreover,the abnormal increase of emission intensity with increasing temperature was studied by the thermoluminescence spectra.The energy transfer mechanism between the Eu~(2+)ions occupying different cation sites was studied by the lifetime decay curves.A series of warm white light emitting diodes were successfully fabricated using the blue phosphors Sr~+_(0.8)Ca_(0.2)Al_2Si_2O_8:Eu~2 with commercial red phosphor (CaSr)SiAlN_3:Eu~(2+)and green phosphor(Y Lu)_3Al_5O_(12):Ce~(3+),and the luminescent efficiency can reach 45 lm/W.     

A simulation study of field plate termination in Ga_2O_3 Schottky barrier diodes

In this work, the field plate termination is studied for Ga_2O_3 Schottky barrier diodes(SBDs) by simulation. The influence of field plate overlap, dielectric material and thickness on the termination electric field distribution are demonstrated.It is found that the optimal thickness increases with reverse bias increasing for all the three dielectrics of SiO_2, Al_2 O_3, and HfO_2. As the thickness increases, the maximum electric field intensity decreases in SiO_2 and Al_2O_3, but increases in HfO_2.Furthermore, it is found that SiO_2 and HfO_2 are suitable for the 600 V rate Ga_2O_3 SBD, and Al_2O_3 is suitable for both600 V and 1200 V rate Ga_2O_3 SBD. In addition, the comparison of Ga_2O_3 SBDs between the SiC and GaN counterpart reveals that for Ga_2O_3, the breakdown voltage bottleneck is the dielectric. While, for SiC and GaN, the bottleneck is mainly the semiconductor itself.     

基于Al2O3/Pt纳米晶/HfO2叠层的MOS电容存储效应研究

采用电子束蒸发Pt和后快速热退火的方法,研究了退火条件对Pt纳米晶的生长特性的影响,结果显示Pt纳米晶的密度随退火温度的升高和退火时间的延长均表现出先增大后减小的趋势.在800℃下退火20 s能得到分布均匀的、密度为30×10¹¹ cm^-2的Pt纳米晶.进一步研究了基于Al₂O₃/Pt纳米晶/HfO₂叠层的MOS电容结构的存储效应,表明其在-3—+8 V扫描电压范围下C-V< 关键词： Pt纳米晶 快速热退火 原子层淀积 存储效应     

低重复率的Ti:Al2O3飞秒激光放大器研究

本文报道了重复频率为10Hz的Ti:Al₂O₃飞秒激光放大器的研究.基于脉冲啁啾放大技术和采用再生/多通放大装置,得到了能量为8mJ的放大光脉冲,在该放大系统中,激光脉冲获M净增益约8×10⁷.     

Ca~(2+)离子替代对Sr_4Al_(14)O_(25):Eu~(2+),Dy~(3+)结构和发光性能的影响

采用高温固相反应按化学式Sr4-xCaxAl14O25:Eu2+,Dy3+(x=0,0.8,1.6,2.4,3.2,4)配比原料,合成长余辉发光材料.X射线衍射分析表明当x2.4时,产物物相均为Sr4Al14O25正交结构;当x2.4时,产物物相转变为CaAl4O7单斜结构.对掺Ca量不同,但结构仍保持Sr4Al14O25的样品采用360nm激光照射,发射光谱表明样品发光均由以Eu2+为发光中心的电子4f65d→4f7跃迁所致,并且随着Ca掺入量的增加,样品发射光谱峰位逐渐蓝移.这是由于Ca2+取代Sr2+位置后,导致晶格收缩,影响Eu2+的5d能级劈裂情况,从而影响电子4f65d→4f7跃迁.余辉衰减检测和热释光谱分析发现,不同Ca掺入量的样品余辉衰减快慢不同,是由于其中存在的陷阱能级深度不同,且陷阱能级越深,其余辉时间越长.     

Surface Leakage Currents in SiN and Al_2O_3 Passivated AlGaN/GaN High Electron Mobility Transistors

Surface leakage currents of AlGaN/GaN high electron mobility transistors are investigated by utihzing a circular double-gate structure to eliminate the influence of mesa leakage current.Different mechanisms are found under various passivation conditions.The mechanism of the surface leakage current with Al_2O_3 passivation follows the two-dimensional variable range hopping model,while the mechanism of the surface leakage current with SiN passivation follows the Frenkel-Poole trap assisted emission.Two trap levels are found in the trap-assisted emission.One trap level has a barrier height of 0.22 eV for the high electric Geld,and the other trap level has a barrier height of 0.12 eV for the low electric field.     

Electron transport properties of TiO_2 shell on Al_2O_3 core in dye-sensitized solar cells

The performance of dye-sensitized solar cells(DSSCs)is strongly affected by the properties of semiconductor nanoparticles.In this work,we used TiO_2 particles prepared by TiCl_4 hydrolysis n times on Al_2O_3 films(A/T(n)),and investigated morphology,photoelectric,and electron transport properties of A/T(n).The TiO_2 shell was composed of 10-20 nm nanoparticles and the number of nanoparticles increased with increasing TiCl_4 treatment times.The highest photoelectric conversion efficiency of 3.23% was obtained as A/T(4).IMPS results indicated that electron transport rate was high enough to conduct current,and was not the dominating effect to limit the Jsc.Jsc was mainly determined by dye loading on TiO_2 and the interconnection of TiO_2.These may provide a new strategy for preparing semiconductor working electrodes for DSSC.     

纳米氧化铝微柱富集ICP-AES测定大白口蘑中的痕量稀土元素

以负载了1-苯基-3-甲基-4-苯甲酰基-吡唑酮[5](PMBP)的纳米氧化铝为微柱吸附材料,采用电感耦合等离子体原子发射光谱法(ICP-AES),系统地研究了其在动态条件下对稀土离子Sc~(3+),Y~(3+)和La~(3+)的吸附性能,并确定了最佳吸附及解脱条件。实验结果表明:在pH为4.5时,分析物均可被上述吸附材料定量吸附;用0.5 mol·L~(-1)盐酸溶液可将吸附在微柱上的稀土离子完全解脱。该方法对Sc~(3+),Y~(3+)和La~(3+)的检出限分别为0.15,0.18和0.34μg·L~(-1);相对标准偏差(RSD)分别为2.5%,3.0%和1.7%(n=12,c=0.5μg·L~(-1))。方法应用于大白口蘑(Tricholoma giganteum)中痕量Sc,Y和La的测定,结果满意。     

Experimental evidence of photonic crystal waveguides with wide bandwidth in two-dimensional Al_2O_3 rods array

A cross-shaped photonic crystal waveguide formed by a square lattice Al_2O_3 rods array is numerically and experimentally investigated. The band gap of the TE mode for the photonic crystals and transmission characteristics of waveguides are calculated by the plane wave expansion method and the finite element method.We perform the experiments in the microwave regime to validate the numerical results. The measured reflection and transmission characteristics of the photonic crystals show a large band gap between 8.62 and 11.554 GHz(relative bandwidth is 29.34%). The electromagnetic waves are transmitted stably in the waveguides, and the transmission characteristics maintain a high level in the band gap.     

Y3Al5O12:Ce3+,Cr3+和Y3Al5O12:Ce3+,pr3+,Cr3+荧光粉体系中的能量传递

通过在YAG:Ce3+和YAG:Ce3+,pr3+荧光粉体系中分别掺入Cr3+离子来提高蓝光管芯白光LED的显色指数.Cr3+离子的加入,增加了红光发射,这归因于Cr3+的2E-4 A2跃迁的零声子线和声子边带发光.Ce3+→Cr3+的能量传递是增强红光发射的重要方式,在YAG:Ce3+,Cr3+体系中,由发射光谱得到...     

Low thermal expansion and broad band photoluminescence of Zr0.1Al1.9Mo2.9V0.1O12

A new material of Zr0.1Al1.9Mo2.9V0.1O12 is synthesized by the traditional solid state synthesis method.The phase transition,coefficient of thermal expansion,and luminescence properties of Zr0.1Al1.9Mo2.9V0.1O12 are explored with Raman spectrometer,dilatometer,and x-ray diffraction(XRD)diffractometer.The results show that the Zr0.1Al1.9Mo2.9V0.1O12 possesses the strong broad-band luminescence characteristics almost in the whole visible region.The sample is crystallized in a monoclinic structure group of P21/a(No.14)crystallized at room temperature(RT).The crystal is changed from monoclinic to orthorhombic structure when the temperature increases to 463 K.The material has very low thermal expansion performance in a wide temperature range.Its excellent low thermal expansion and strong pale green light properties in a wide temperature range suggest its potential applications in light-emitting diode(LED)and other optoelectronic devices.     

RF溅射的SiO_2和SiO_2/Al/SiO_2薄膜的喇曼散射光谱研究

用射频溅射(RF Sputtering)法制成了SiO_2和SiO_2/Al/SiO_2薄膜。应用喇曼光谱研究了薄膜结构。结果表明:RF溅射制成的SiO_2薄膜是含有大量环结构缺陷的玻璃态;SiO_2/Al/SiO_2层状薄膜的喇曼光谱中观察到Al_2O_3的特征峰,证实了Al/SiO_2薄膜界面确有氧化还原反应发生;从喇曼光谱中Al_2O_3的特性峰的位置和相对强度可推断出,SiO_2/Al/SiO_2薄膜界面处的Al_2O_3是非晶γ-Al_2O_3。