Thickness effect on solar-blind photoelectric properties of ultrathinβ-Ga_(2)O_(3)films prepared by atomic layer deposition

Theβ-Ga_(2)O_(3)films with different thicknesses are prepared by an atomic layer deposition system.The influence of film thickness on the crystal quality is obvious,indicating that the thicker films perform better crystal quality,which is verified from x-ray diffraction(XRD)and scanning electron microscope(SEM)results.The Ga_(2)O_(3)-based solar blind photodetectors with different thicknesses are fabricated and studied.The experimental results show that the responsivity of the photodetectors increases exponentially with the increase of the film thickness.The photodetectors with inter-fingered structure based on 900 growth cyclesβ-Ga_(2)O_(3)active layers(corresponding film thickness of 58 nm)exhibit the best performances including a low dark current of 134 fA,photo-to-dark current ratio of 1.5×10^(7),photoresponsivity of 1.56 A/W,detectivity of 2.77×10^(14)Jones,and external quantum efficiency of 764.49%at a bias voltage of 10 V under 254-nm DUV illumination.The photoresponse rejection ratio(R_(254)/R_(365))is up to 1.86×10^(5).In addition,we find that the photoelectric characteristics also depend on the finger spacing of the MSM structure.As the finger spacing decreases from 50μm to10μW,the photoresponsivity,detectivity,and external quantum efficiency increase significantly.

嵌入式共固化阻尼复合材料十字型加筋板的自由振动（英文）

为大幅度地提高嵌入式共固化复合材料阻尼结构固有频率,优化其刚度,以嵌入式共固化阻尼复合材料薄板为研究对象,利用有限元的方法对比分析了该结构薄板及十字加筋薄板固有振动特性,并得到了筋材薄壁宽度和高度对结构固有频率的影响规律。结果表明:加强筋大大提高了薄板结构的固有频率和刚度,加筋薄板结构的各阶固有频率随着加强筋高度增大而增加,其中一阶固有频率增加幅度最大。增加加强筋宽度可以提高薄板结构的各阶固有频率,随着加强筋宽度的增加,固有频率的增加幅度减小。

四边简支共固化复合材料阻尼结构的动力学性能研究（英文）

嵌入式共固化复合材料阻尼结构具有阻尼性能优良、抗老化、不脱落、耐疲劳等优点,在设施农业、机床制造业、航空航天、建筑等技术领域具有广阔的应用前景。应用模态应变能法研究了共固化复合材料阻尼结构各层的应变能,并计算了结构的一阶模态国有频率和损耗因子,得到了一阶固有频率和损耗因子随阻尼层厚度变化的规律。结果表明:当薄板总厚度不变时,增加阻尼层的厚度可以使一阶固有频率减小,模态损耗因子随着阻尼层厚度的增大而增大,阻尼层较厚时,一阶固有频率和模态损耗因子对阻尼层厚度的变化不再敏感;当复合材料层厚度不变时,一阶固有频率随着阻尼层厚度的增大而减小,增加阻尼层的厚度可以使损耗因子增大,阻尼层厚度较厚时,阻尼层厚度的变化对一阶固有频率和损耗因子的影响较小;当薄板总厚度不变,较复合材料层厚度不变,阻尼层较厚时对损耗因子的影响更小。

双曲壳结构复合材料的热临界屈曲温度研究

以双曲壳结构复合材料为研究对象,利用Block-Lanczos研究分析法对复合材料层合双曲壳结构在温度场下热屈曲行为进行研究,并研究了复合材料层合双曲壳铺层厚度、边界条件、纤维方向等对临界屈曲温度的影响。结果表明:在均匀温度场下复合材料层合双曲壳临界屈曲温度与边界条件、铺层厚度、纤维方向有密切关系并成一定规律分布。通过对复合材料双曲壳结构的热屈曲性能分析,为复合材料结构设计和实际工程应用提供了一种有效的分析及建模方法。

摩擦因数对轴对称零件冷挤压过程的影响（英文）

冷挤压件强度高、刚性好、生产率高,在装备制造业和液压系统中得到了广泛的应用。利用ANSYS软件对轴对称零件冷挤压过程进行了分析,得到了不同摩擦因数下的轴向、径向和周向应力图,对挤压应力的模拟数值进行了分析和拟合,利用最小二乘法对函数进行了逼近。结果表明:轴向拉伸应力,径向拉伸应力和圆周拉伸应力值分布在一条直线上,值随摩擦因数的增加而增加,轴向压应力、径向压应力和圆周压应力近似分布在二次曲线上,对生产具有重要的理论指导意义。

Direct growth of graphene films without catalyst on flexible glass substrates by PECVD

A hydrogen-plasma-etching-based plasma-enhanced chemical vapor deposition(PECVD)synthesis route without metal catalyst for preparing the graphene films on flexible glass is developed.The quality of the prepared graphene films is evaluated by scanning electron microscopy,x-ray photoelectron spectroscopy,high-resolution transmission electron microscopy,ultraviolet-visible spectroscopy,and electrochemical measurements.In a radio frequency(RF)power range of 50 W-300 W,the graphene growth rate increases with RF power increasing,while the intensity ratio of D-to G-Raman peak(I_(D)/I_(G))decreases.When the RF power is higher than 300 W,the I_(D)/I_(G)rises again.By optimizing experimental parameters of hydrogen plasma etching and RF power,the properties of as-prepared flexible graphene on glass are modulated to be able to achieve the graphene's transparency,good electrical conductivity,and better macroscopic uniformity.Direct growth of graphene film without any metal catalyst on flexible glass can be a promising candidate for applications in flexible transparent optoelectronics.

Electronic structure and optical properties of Ge-and F-doped α-Ga2O3:First-principles investigations

The prospect ofα-Ga2O3 in optical and electrical devices application is fascinating.In order to obtain better performance,Ge and F elements with similar electronegativity and atomic size are selected as dopants.Based on density functional theory(DFT),we systematically research the electronic structure and optical properties of dopedα-Ga2O3 by GGA+U calculation method.The results show that Ge atoms and F atoms are effective n-type dopants.For Ge-dopedα-Ga2O3,it is probably obtained under O-poor conditions.However,for F-dopedα-Ga2O3,it is probably obtained under O-rich conditions.The doping system of F element is more stable due to the lower formation energy.In this investigation,it is found that two kinds of doping can reduce theα-Ga2O3 band gap and improve the conductivity.What is more,it is observed that the absorption edge after doping has a blue shift and causes certain absorption effect on the visible region.Through the whole scale of comparison,Ge doping is more suitable for the application of transmittance materials,yet F doping is more appropriate for the application of deep ultraviolet devices.We expect that our research can provide guidance and reference for preparation ofα-Ga2O3 thin films and photoelectric devices.

The assisting and stabilizing role played by ω phase during the {112}〈111〉_β twinning in Ti-Mo alloys:A first-principles insight

The ω phase is commonly observed in β-Ti alloys and plays a significant role on various properties ofβ-Ti alloys.Although many results about the role of ω phase on mechanical properties of β-Ti alloys have been derived from theoretical and experimental studies,the role of ω phase on deformation mechanism hitherto remains elusive and deserves to be further studied.In this work,the role played by ω phase during the {112} <111>_(β) twining in Ti-Mo alloys were investigated by first-principles calculations at atomic scale.In the energy favorable interface of(112)_(β)(110)_(ω),we found that partial dislocations slipping on the successive(1010)_(ω)planes of ω phase can lead to the formation of {112} <111>_(β) twin nucleus.And the twin nucleus grows inwards ω grain interior through atomic shuffle.Thus,a new twinning mechanism of {112} <111>_(β) assisted by ω phase was proposed.Furthermore,our calculations indicated that the appearance of ITB(interfacial twin boundary) ω phase can improve the stability of the symmetrical{112} <111>_(β) twin boundary(TB),which can well explain the experimental phenomenon that the ITBω phase always accompanies the formation of {112} <111>_(β) twin.Finally,a probable microstructure evolution sequence was suggested,namely β matrix→β matrix+athermal ω phase→(112)[111]_(β) twin+ITB ω phase.Our calculations provide new insights on the role played byω phase during the twinning process of {112} <111>_(β),which can deepen the understanding on the deformation behaviors of β-Ti alloys.