Significant suppression of residual nitrogen incorporation in diamond film with a novel susceptor geometry employed in MPCVD

This work proposed to change the structure of the sample susceptor of the microwave plasma chemical vapor deposition (MPCVD) reaction chamber, that is, to introduce a small hole in the center of the susceptor to study its suppression effect on the incorporation of residual nitrogen in the MPCVD diamond film. By using COMSOL multiphysics software simulation, the plasma characteristics and the concentration of chemical reactants in the cylindrical cavity of MPCVD system were studied, including electric field intensity, electron number density, electron temperature, the concentrations of atomic hydrogen, methyl, and nitrogenous substances, etc. After introducing a small hole in the center of the molybdenum support susceptor, we found that no significant changes were found in the center area of the plasma, but the electron state in the plasma changed greatly on the surface above the susceptor. The electron number density was reduced by about 40%, while the electron temperature was reduced by about 0.02 eV, and the concentration of atomic nitrogen was decreased by about an order of magnitude. Moreover, we found that if a specific lower microwave input power is used, and a susceptor structure without the small hole is introduced, the change results similar to those in the surface area of the susceptor will be obtained, but the spatial distribution of electromagnetic field and reactant concentration will be changed.     

新型双子表面活性剂的制备及性能研究

制备了一系列羧基支化改性双子表面活性剂,其利用马来酸酐将2个疏水性基团和2个亲水性基团通过弱酯键连接基团连接在一起,以反丁烯二酸为羧化试剂在过氧化自由基的引发下进行羧化接枝反应接入了阴离子亲水基团。用红外光谱和核磁共振表征了合成物的分子结构。测定了合成产物的表面张力、胶团形貌、疏水性能、泡沫性能、润湿性能、乳化性能和分散性能。结果显示所合成的双子表面活性具有优异的表面性能。     

Ga掺杂ZnO薄膜的MOCVD生长及其特性

利用低压MOCVD技术在(0002)蓝宝石上外延获得高质量的ZnO:Ga单晶薄膜,并研究了Ga的不同掺杂浓度对材料电学和光学特性的影响.当Ga/Zn气相摩尔比为3.2 at%时,ZnO(0002)峰半高宽仅为0.26°,载流子浓度高达2.47×1019cm-3,透射率高于90%;当载流子浓度升高时,吸收边出现明显的Burstein-Moss蓝移效应.同时室温光致发光谱显示,紫外峰位随载流子浓度的增加而发生红移,峰形展宽,这和Ga高掺杂所引起的能带重整化效应有关.当Ga/Zn比达到6.3 at%时,由于高掺杂浓度下Ga的自补偿效应导致载流子浓度下降.     

采用介质PBG盖板Fabry-Perot谐振器的宽频带高增益印刷天线

研究了采用介质盖板组成的Fabry-Perot (F-P)谐振器结构的宽频带高增益平面印刷天线.比较了不同结构参数对天线性能的影响,并在此基础上通过引入二维光子带隙(PBG)结构,提出了两种既能提高增益、又能减小背向辐射的新型结构.通过软件仿真计算和实验,都验证了这两种结构的天线具有较好的实际应用性能.     

抛物线的伴随圆系及其性质

1伴随圆系的意义所谓抛物线的伴随圆,是指与抛物线有关的圆.如抛物线的内切圆就是最常见的一种伴随圆.此外还有以焦点弦为直径的圆,以及以焦点弦为弦且过顶点的圆等.同类的伴随圆构成一个圆系,圆系中有无数多个圆.本文将对这种圆系的方程与性质进行探讨.2伴随圆系及其方程2.1抛