新型MSM结构砷化镓半导体探测器的性能

研究一种新型双金属接触GaAs半导体探测器的性能,测量了²⁴¹Am 5.48MeVα粒子、⁵⁷Co 122keV的光子和⁹⁰Sr 2.27MeVβ粒子的最小电离粒子谱,比较了一个3×3mm²的GaAs芯片在经过¹³⁷Cs 662keV光子约1300rad辐照前后的电荷收集效率和能量分辨率.测量结果显示这种新型金属─半导体─金属(MSM)结构的半导体探测器不仅在室温下对各种粒子具有良好的探测能力,而且具有很好的抗辐照性能.     

电极间距对ZnO基MSM紫外光电探测器性能的影响

利用金属有机物化学气相沉积法在蓝宝石衬底上制备了ZnO薄膜。利用Au电极,在ZnO薄膜上制备电极间距不同的金属-半导体-金属结构紫外光电探测器。发现随着电极间距从150μm降至5μm,探测器响应度呈现出从15 mA/W到75 mA/W的明显提高。同时,随着电极间距的减小,器件的I-V曲线线形发生了显著改变。这被归结为电极间距变化改变了器件耗尽区宽度和电极间电阻造成的结果。     

基于垂直晶体管结构的低电压并五苯光电探测器

并五苯(Pentacene)具有优良的场效应晶体管特性及在可见光区的高吸收系数, 被广泛应用于光敏(电)晶体管中. 垂直晶体管的沟道长度可做到纳米量级, 能有效提高器件的性能和工作频率, 同时降低能耗. 本文制备了一种基于垂直晶体管结构的低电压并五苯光电探测器ITO(S)/Pentacene/Al(G)/Pentacene/Au(D). 实验发现, 在工作电压低至-3 V时, 并五苯光电探测器ITO/Pentacene (80 nm)/Al(15 nm)/ Pentacene(80 nm)/Au 的阈值电压为-0.9 V, “开/关”电流比为10⁴, 表现出了良好的P型晶体管特性以及低电压调控性能. 在350-750 nm的不同波长单色光照射下, 器件的“明/暗”电流比和响应度随入射波长而变化; 在350 nm单色光照射下, 该光电探测器的“明/暗”电流比的最大值达到308, 其对应的响应度为219 mA·W^-1, 大于标准硅基探测器在350 nm 单色光照射下的探测率. 这为制备低电压下工作的高灵敏度全有机光电探测器提供了一种可行的方法.     

基于二维材料的快速响应金属-半导体-金属结构光电探测器研究进展

快速响应光电探测器在光通信、高速摄影、生物医学成像等领域有广泛的需求。目前,市场上应用的快速响应光电探测器大多基于硅、砷化镓等传统的无机半导体材料,但是其制作工艺复杂、成本较高,并且机械灵活性差。以石墨烯、二硫化钼为代表的二维材料具有独特的层状结构以及良好的光学、电学、热学和机械特性,是制备光电探测器的理想材料。尤其是部分二维材料所拥有的超高载流子迁移率特性,十分适用于研制快速响应光电探测器。近年来,一系列基于二维材料的金属-半导体-金属结构光电探测器(Metal-semiconductor-metal photodetectors, MSM-PDs)被陆续报道,很多具有1μs以下的快速响应特性。本文以基于二维材料的快速响应MSM-PDs为主题进行综述。首先介绍了MSM-PDs中的基本结构及工作原理,深入剖析了决定其响应速度的主要因素。随后介绍了石墨烯、过渡金属硫化物、黑磷、二维钙钛矿、三元硒氧铋等二维材料的分子结构、光学、电学等特性,并对各类二维材料在MSM-PDs的应用进行对比。然后分类介绍了响应速度在1μs以下的欧姆接触型、肖特基接触型以及基于表面等离激元效应二维材料MSM-PD...     

基于HfO2插层的Ga2O3基金属-绝缘体-半导体结构日盲紫外光电探测器

作为一种新兴的超宽带隙半导体, Ga₂O₃在开发高性能的日盲紫外光电探测器方面具有独特的优势.金属-半导体-金属结构因其制备方法简单、集光面积大等优点在Ga₂O₃日盲紫外光电探测器中得到了广泛的应用.本文在传统的金属-半导体-金属结构Ga₂O₃日盲紫外光电探测器的基础上,利用原子层沉积技术引入高介电性和绝缘性的氧化铪(HfO₂)作为绝缘层和钝化层,制备出带有HfO₂插层的金属-绝缘体-半导体结构的Ga₂O₃日盲紫外光电探测器,显著降低了暗电流,提升了光暗电流比,同时提高了器件的比探测率和响应速度,为未来Ga₂O₃在高性能弱光探测器件制备提供了一种新通用策略.     

金属有机物化学气相沉积法生长Ga2(1-χ)In2χO3薄膜的结构及光电性能研究

采用金属有机物化学气相沉积(MOCVD)法在蓝宝石(0001)衬底上制备出了Ga2(1-χ)In2χO3(χ=0.1-0.9)薄膜,研究了薄膜的结构、电学和光学特性以及退火处理对薄膜性质的影响.测量结果表明:当In组分χ=0.2时,样品为单斜β-Ga2O3,结构;χ=0.5的样品,薄膜呈现非晶结构,退火处理后薄膜结构得到明显的改善,由非晶结构转变为具有(222)单一取向的立方In2O3结构;对于χ=0.8,薄膜为立方In2O3,结构,退火后薄膜的晶体质量得到提高.在可见光区薄膜本身的透过率均达到了85%以上,带隙宽度随样品中Ga含量的改变在3.76-4.43 eV之间变化,且经退火处理后带隙宽度明显增大.     

非晶态Mg_(70)Zn_(30)合金结构因子的预峰

利用X射线衍射仪对非晶态Mg70 Zn30 合金的结构进行了研究 ,获得了强度曲线、结构因子、双体分布函数和原子间最近邻距离 .结果表明 ,Mg70 Zn30 合金在小Q区间存在强烈的预峰现象 .根据预峰的特性 ,提出了Mg70 Zn30 熔体的结构模型 ,即Mg原子位于中心 ,8个Zn原子位于顶角所形成的简单立方结构模型 .该模型以共享顶点的方式相连接 ,能够满足预峰对Mg—Mg原子间距离的要求 .Mg70 Zn30 非晶合金中预峰的产生是相邻原子团中心Mg原子之间相互关联的表现     

Si(100)衬底上Mg_(0.33)Zn_(0.67)O薄膜的结构及光学性能

采用射频磁控溅射法在Si(100)衬底上制备了Mg_(0.33)Zn_(0.67)O薄膜,研究了Mg_(0.33)Zn_(0.67)O薄膜的结构和光学性能。结果表明,Si(100)衬底上Mg_(0.33)Zn_(0.67)O薄膜呈六方纤锌矿结构,薄膜沿c方向取向生长,且c轴方向晶格增大0.03 nm。薄膜呈现优异的半导体特性,激子吸收峰位于297 nm,禁带宽度约为4.3 eV。薄膜平均粒径约为20 nm。薄膜在深紫外激发下的荧光发射位于368 nm。     

La0.8Sr0.2Co1-xFexO3材料局域结构的研究

采用溶胶-凝胶法制备了La0.8Sr0.2Co1-xFexO3样品,并测量了各样品的X射线衍射谱（XRD）和X射线吸收精细结构（XAFS）谱。XRD分析研究发现Fe的掺杂引起了La0.8Sr0.2CoO3材料相分离;在前期对X射线吸收精细结构谱近边分析的基础上,进一步分析扩展边X射线吸收精细结构谱,表明在La0.8Sr...     

Raman studies and optical properties of some (PbO)x(Bi2O3)0.2(B2O3)0.8−x glasses

Five (PbO)_x(Bi₂O₃)_0.2(B₂O₃)_0.8−x glasses, where x = 0, 0.2, 0.3, 0.4 and 0.6, were prepared. The dilatometric glass transition temperature (T_g) was found in the region 470 (x = 0)≥ T_g ( °C) ≥ 347 (x = 0.6), and the density (ρ) varied within 4.57 (x = 0) ≤ ρ (g/cm³) ≤ 8.31 (x = 0.6). Raman spectra indicated the conversion of BO₃ to BO₄ entities for low x values but for x > 0.3, namely, for x → 0.6, back‐conversion occurred, most probably. From the measurements of the optical transmission on very thin bulk samples, the room temperature optical gap values (E_g) were determined to be in the range 4.03 (x = 0)≥ E_g (eV) ≥ 3.08 (x = 0.6). The temperature (T) dependence of the optical gap (E_g(T)) in the region 300 ≤ T(K) ≤ 600 was examined and approximated by a linear relationship of the form of E_g(T) = E_g(0)− γT, where γ × 10⁻⁴(eV/K) varied from 5.1 to 6.8. The non‐linear refractive index (n₂) was estimated from the optical gap values and it was found to correspond to the n₂ values calculated from the experimental third‐order non‐linear optical susceptibility taken from the literature. Copyright © 2008 John Wiley & Sons, Ltd.     

Enhanced ferroelectric,piezoelectric and dielectric properties of (1-x)CaBi2Nb2O9-xBaZr0.2Ti0.8O3 high-temperature piezoelectric composite ceramics

Among Aurivillius layer-structured materials, CaBi₂Nb₂O₉ is a best potential candidate for ultrahigh-temperature applications because of its highest Curie temperature of about 940 °C. In this paper, (1-x)CaBi₂Nb₂O₉-xBaZr_0.2Ti_0.8O₃ composite ceramics were prepared by conventional solid-state sintering method. The dielectric results show that the introduction of BaZr_0.2Ti_0.8O₃ not only increases the permittivity of the material, but also reduces its dielectric loss. The optimum electrical properties were obtained in the x = 0.01 sample with piezoelectric coefficient (d₃₃) of 15.1 pC/N and high ferroelectric remnant polarization (P_r) of 9.9 μC/cm². Furthermore, the composite samples show good thermal depoling performance, the d₃₃ of the x = 0.01 sample is 13.8 pC/N, which is about 91% of the initial value after depoling at 800 °C. Therefore, (1-x)CaBi₂Nb₂O₉-xBaZr_0.2Ti_0.8O₃ is one of the candidates for high temperature piezoelectric materials.     

Nonmonotonic variation of magnetization in Bi0.8La0.2−xPbxFeO3 (0≤x≤0.2) multiferroics

Systematic studies of crystalline structure, magnetic and ferroelectric properties have been performed on polycrystalline Bi_0.8La_0.2−xPb_xFeO₃ ceramic samples, in which x changes continuously from 0 to 0.2. Rietveld refinement of the x-ray diffraction (XRD) patterns shows that the compound crystal structure changes gradually from pseudotetragonal to pseudocubic with increasing Pb concentration. Coupled with the structural and compositional changes, magnetic ordering of the samples exhibits significantly non-monotonical variation corresponding to x. The compound remnant magnetization (M_r) and coercivity (H_c) both reach minimum values close to zero at x=0.07. This variation of magnetic property in co-doped samples can be attributed to the extent of suppression of cycloid spin structure in original BiFeO₃ with changing x. Unlike magnetic responses, the ferroelectric measurements show that the compounds have monotonical change in the remnant electric dipole polarization (P_r).     

基于LiCo0.8M0.2O2 (M=Ni,Zr)薄膜的全固态薄膜锂电池

用射频磁控溅射结合传统退火的方法制备LiCo0.8M0.2O2 (M=Ni,Zr)阴极薄膜．X射线衍射、拉曼光谱、扫描电子显微镜等手段表征了不同掺杂的LiCo0.8M0.2O2薄膜．结果显示,700℃退火的LiCo0.8M0．2O2薄膜具有类似α-NaFeO2的层状结构．通过对不同掺杂锂钴氧阴极的全固态薄膜锂电池Li／LiPON／LiCo0.8M0.2O2的电化学性能研究表明,电化学活性元素Ni的掺杂使全固态电池具有更大的放电容量(56μAh／cm2μm),而非电化学活性元素Zr的掺杂使全固态电池具有更好的循环稳定性．     

The variation of Mn-dopant distribution state with x and its effect on the magnetic coupling mechanism in Zn_(1-x) Mn_x O nanocrystals

Zn1-x Mn x O(x = 0.0005,0.001,0.005,0.01,0.02) nanocrystals are synthesized by using a wet chemical process.The coordination environment of Mn is characterized by X-ray photoelectron spectroscopy,Raman spectroscopy,and its X-ray absorption fine structure.It is found that the solubility of substitutional Mn in a ZnO lattice is very low,which is less than 0.4%.Mn ions first dissolve into the substitutional sites in the ZnO lattice,thereby forming Mn2+O4tetrahedral coordination when x ≤ 0.001,then entering into the interstitial sites and forming Mn3+O6octahedral coordination when x ≥ 0.005.All the samples exhibit paramagnetic behaviors at room temperature,and antiferromagnetic coupling can be observed below 100 K.     

In-situ X-ray microdiffraction analysis of local strain-field across the interface in a Pb(Zr0.52Ti0.48)O3/Ni0.8Zn0.2Fe2O4/Pb(Zr0.52Ti0.48)O3 tri-layered structure

We have performed a synchrotron X-ray microdiffraction to investigate the variation of the local strain-field across the interface in Pb(Zr_0.52Ti_0.48)O₃/Ni_0.8Zn_0.2Fe₂O₄/Pb(Zr_0.52Ti_0.48)O₃ (PZT–NZFO–PZT) tri-layered structure. In this study, we show that the in-plane lattice parameters of the NZFO lattice depend strongly on the piezoelectric strain of the PZT layer. This result explains that an electric-field-induced piezoelectric strain from the PZT layer is effectively transferred to the NZFO layer. Furthermore, the local strain persists within 20 μm away from the interface, inducing changes of magnetic responses via the inverse magnetostrictive effect.     

KxCoO2·yH2O(x<0.2,y≤0.8)的晶体结构、输运及磁学性质

利用熔融KOH和Co₃O₄在较低温度(480℃)下反应制备出K_0.36CoO₂，然后用高锰酸钾溶液和饱和的过硫酸钾溶液进行氧化处理.氧化的同时伴随有水分子嵌入.K_0.36CoO₂用高锰酸钾和过硫酸钾溶液处理后分别得到K_0.12CoO₂·0.8H₂O和K_0.16CoO₂·0.6H₂O.这两种化合物都属于六角晶系，表现出金属行为，脱水后主相变为正交结构并且呈现出半导体特性.K_0.16CoO₂·0.6H₂O在56K附近可能存在自旋玻璃转变行为或其他涨落.随着钾含量的减少和水含量的增多，样品的自旋玻璃行为受到抑制或发生磁性相分离.样品K_0.12CoO₂·0.8H₂O在零场冷却和有场冷却曲线上的分叉现象基本上消失.还讨论了产生K_xCoO₂与Na_xCoO₂体系结构和物性差别的原因. 关键词： xCoO₂')" href="#">K_xCoO₂ 晶体结构 自旋玻璃态 磁性