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.     

阵列式薄膜锰铜计的动态压阻响应研究

 利用直流磁控溅射薄膜工艺制备阵列式薄膜锰铜压阻计,以氧化铝作为基片和绝缘封装材料。在结构上,4个具有相同阻值的薄膜锰铜计在同一氧化铝基片上呈对称分布。51.72 GPa压力下的动态加载实验表明,4个计的压阻一致性好,无高压旁路效应,验证了薄膜锰铜压阻计动态测试的准确性和可靠性。     

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.     

Prediction of 2D Li2X (X=Se,Te) monolayer semiconductors by first principles calculations

Two dimensional monolayer materials play important roles in new generation of electronic and optical devices in nano scale. In this paper, by using first principles calculations, the existence of 2D Li₂X (X=Se, Te) monolayer materials are theoretically predicted. Through cohesive energy calculation and phonon dispersion simulation, it is proved that the proposed 2D Li₂Se and Li₂Te monolayer materials are energetically and dynamically stable suggests their potential experimental realization. Our study shows that these newly predicted compounds are direct semiconductors and have strain tunable wide band gaps. As direct semiconductors, these new monolayers may have many applications in electronics and optoelectronics devices.     

Performance Improvement in Hydrogenated Few-Layer Black Phosphorus Field-Effect Transistors

A capping layer for black phosphorus(BP) field-effect transistors(FETs) can provide effective isolation from the ambient air; however, this also brings inconvenience to the post-treatment for optimizing devices. We perform low-temperature hydrogenation on Al_2 O_3 capped BP FETs. The hydrogenated BP devices exhibit a pronounced improvement of mobility from 69.6 to 107.7 cm~2 v~(-1) s~(-1), and a dramatic decrease of subthreshold swing from8.4 to 2.6 V/dec. Furthermore, high/low frequency capacitance-voltage measurements suggest reduced interface defects in hydrogenated BP FETs. This could be due to the passivation of interface traps at both Al_2 O_3/BP and BP/SiO_2 interfaces with hydrogen revealed by secondary ion mass spectroscopy.     

Coupling-induced spectral splitting for plasmonic sensing with ultra-high figure of merit

We investigate a kind of spectral splitting effect in a plasmonic multilayer system, which consists of stacked Al_2 O_3 and SiO_2 layers, a thin metal film, and a dielectric prism substrate. The results illustrate that an obvious peak appears in the center of the surface plasmon resonance(SPR)-induced reflection spectral dip in the structure with the SiO_2/Al_2 O_3/SiO_2 layers. This spectral splitting response can be regarded as an electromagnetically induced transparency(EIT) like effect,which is attributed to the coupling and interference between the SPR on the metal film and guided-mode resonance(GMR)in the Al_2 O_3 layer. The theoretical calculations agree well with the numerical simulations. It is also found that the reflection spectrum will be further split by the introduction of another Al_2 O_3 layer into the multilayer structure. The reintroduced GMR in the Al_2 O_3 layer changes the coupling and interference process between the SPR and GMR field, giving rise to the generation of ultra-narrow reflection dip. Especially, the spectral splitting can facilitate the realization of plasmonic sensors with ultra-high figure of merit(583), which is about 5 times larger than that of traditional SPR sensors. These results will provide a new avenue to the light field manipulation and optical functionalities, especially biochemical and environmental sensing.     

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.     

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.     

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。     

Optical and defect properties of S-doped and Al-doped GaSe crystals

S-doped and Al-doped GaSe crystals are promising materials for their applications in nonlinear frequency conversion devices. The optical and defect properties of pure, S-doped, and Al-doped GaSe crystals were studied by using photoluminescence(PL) and Fourier transform infrared spectroscopy(FT-IR). The micro-topography of(0001) face of these samples was observed by using scanning electron microscope(SEM) to investigate the influence of the doped defects on the intralayer and interlayer chemical bondings. The doped S or Al atoms form the S_(Se)~0 or Al_(Ga)~(+1) substitutional defects in the layer GaSe structure, and the positive center of Al_(Ga)~(+1) could induce defect complexes. The incorporations of S and Al atoms can change the optical and mechanical properties of the GaSe crystal by influencing the chemical bonding of the layer structure. The study results may provide guidance for the crystal growth and further applications of S-doped and Al-doped GaSe crystals.     

Prediction of Interesting Ferromagnetism in Janus Semiconducting Cr2AsP Monolayer

2D half-metallic materials that have sparked intense interest in advanced spintronic applications are essential to the developing next-generation nanospintronic devices. This study has adopted a first-principles calculation method to predict the magnetic properties of intrinsic, Se-doped, and biaxial strain tuning Cr₂AsP monolayer. The Janus Cr₂AsP monolayer is proven to be an intrinsic ferromagnetic (FM) semiconductor with an exchange splitting bandgap of 0.15 eV at the PBE+U level. Concentration-dependent Se doping, such as Cr₂As${}_{1-x}$Se_xP (x = 0.25, 0.50, 0.75), can regulate Cr₂AsP from FM semiconductor to FM half-metallicity. Specifically, the spin-up channel crosses the Fermi level, while the spin-down channel has a bandgap. More interestingly, the wide half-metallic bandgaps and spin bandgaps make them have important implications for the preparation of spintronic devices. At last, it also explore the effect of biaxial strain from -14% to 10% on the magnetism of the Cr₂AsP monolayer. There appears a transition from FM to antiferromagnetic (AFM) at a compressive strain of -10.7%, originating from the competition between the indirect FM superexchange interaction and the direct AFM interaction between the nearest neighboring Cr atoms. Additionally, when the compressive strain is -2% or the tensile strain is 6%, the semiconducting Cr₂AsP becomes a half-metallic material. These charming properties render the Janus Cr₂AsP monolayer with great potential for applications in spintronic devices.     

Epitaxy of III-nitrides on two-dimensional materials and its applications

III-nitride semiconductor materials have excellent optoelectronic properties, mechanical properties, and chemical stability, which have important applications in the field of optoelectronics and microelectronics. Two-dimensional (2D) materials have been widely focused in recent years due to their peculiar properties. With the property of weak bonding between layers of 2D materials, the growth of III-nitrides on 2D materials has been proposed to solve the mismatch problem caused by heterogeneous epitaxy and to develop substrate stripping techniques to obtain high-quality, low-cost nitride materials for high-quality nitride devices and their extension in the field of flexible devices. In this progress report, the main methods for the preparation of 2D materials, and the recent progress and applications of different techniques for the growth of III-nitrides based on 2D materials are reviewed.     

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.     

Tm3+和 Yb3+共掺杂PGETYA玻璃的直接敏化上转换发光

制备了一种稀土离子掺杂的PGETYA氟氧玻璃材料,它不仅具有较高的上转换发光效率,而且还避免了氟化物基质的缺点。其组分为58.52PbF₂-34.43GeO₂-3Al₂O₃ -0.05Tm₂O₃-4Yb₂O₃,以共掺杂Tm³⁺和Yb³⁺离子为上转换研究的对象。测量了该玻璃系统在980 nm LD激发下的上转换发光光谱,观察到很强的476 nm的蓝色荧光,它来源于Tm³⁺离子的¹G₄→³H₆跃迁。同时,还有两个较弱的红色荧光来源于Tm³⁺离子的¹G₄→³H₄和³F₃→³H₆跃迁。对上转换发光强度与泵浦电流关系曲线的拟合结果表明:此材料的蓝色上转换为三光子过程,红色上转换为双光子过程。     

微通道板离子壁垒膜及其对入射离子的阻止作用

给出了三代微光像管中微通道板离子壁垒膜对入射正离子阻止作用的描述,引进了核阻止本领、电子阻止本领和平均射程的概念。结合Tomas-Fermi屏蔽势进行了分析讨论和Monte-Carlo模拟计算,给出Al₂O₃和SiO₂薄膜对不同能量垂直入射时的核、电子阻止的定量结果。得出了Al₂O₃薄膜阻止本领比SiO₂阻止本领高的结论。证实了选用Al₂O₃离子壁垒膜的科学性和可行性。     

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%.     

氧化处理的蓝宝石基片上沉积的ZnO/MgO多量子阱的结构及光学性质研究

采用射频反应磁控溅射的方法,在经过氧化处理的Al₂O₃（0001）基片上制备了具有良好调制结构的ZnO/MgO多层膜量子阱.利用X射线反射率测量、X射线衍射分析、电子探针显微分析、原子力显微镜、透射光谱以及光致发光光谱等表征技术,研究了ZnO/MgO多量子阱的结构、表面形貌和光致发光等特性.XRD以及扫描的结果表明多层膜样品具有高c轴择优取向并且与蓝宝石基片有良好的外延关系.通过X射线反射率测量的结果得到多量子阱的调制周期,结合电子 关键词： ZnO/MgO 多量子阱 反应磁控溅射 变温光谱     

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.     

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.     

Improvement of Performance of HfS_2 Transistors Using a Self-Assembled Monolayer as Gate Dielectric

This work details a study based on HfS_(2 )transistors utilizing an n-octadecylphosphonic acid-based self-assembled monolayer(SAM)as the gate dielectric.The fabrication of the SAM-based two-dimensional(2D)material transistor is simple and can be used to improve the quality of the interface of air-sensitive 2D materials.In comparison to HfS_(2) transistors utilizing a conventional Al_2O_(3) gate insulator by atomic layer deposition,HfS_(2) transistors utilizing an SAM as the gate dielectric can reduce the operation region from 4 V to 2 V,enhance the field-effect mobility from 0.03 cm~2/Vs to 0.75 cm~2/Vs,improve the sub-threshold swing from 404 m V/dec to 156 m V/dec,and optimize the hysteresis to 0.03 V,thus demonstrating improved quality of the semiconductor/insulator interface.