感应加热的立式MOCVD反应室中一种∧形槽的基座

利用有限元法对感应加热的金属有机化学气相淀积（MOCVD）反应室的温度场进行了数值计算研究,研究发现,由于集肤效应,MOCVD反应室中传统的圆柱形基座中的温度分布不均匀,本文提出了一种∧形槽结构的基座,∧形槽改变了基座中的传热方式和速率,从而提高了被加热晶片温度分布的均匀性。通过对加热四英寸的基座优化发现,与传统的基座相比,优化后的基座,使晶片温度均匀性提高了85%,而且对这种优化的加热结构,在不同的温度下,晶片温度分布仍保持一定的均匀性,这有利于薄膜材料的生长。     

Reduction of Lasing Threshold by Deforming a Circular Resonator

We have reduced the lasing threshold of a circular resonator,formed by a dye-doped pendant drop,by changing its shape from a circle to an oval.This phenomenon can be explained by the decrease of the number (p) of modes that support lasing in the resonator.A theory that connects wave and ray pictures in dealing with the cavity resonance is used to estimate p and its dependence on the eccentricity of an oval-shaped resonator.The measured lasing threshold and the calculated p have a linear relationship in agreement with our prediction.     

A susceptor with a ∧-shaped slot in a vertical MOCVD reactor by induction heating

By using the numerical simulation for the temperature field in the metal organic vapor deposition （MOCVD） reactor by induction heating, it is found that the temperature distribution in the conventional cylinder-shaped susceptor is nonuniform due to the skin effect of the induced current, which makes the temperature distribution of the wafer nonuniform. Therefore, a novel susceptor with a A-shaped slot is proposed. This slot changes the mode and the rate of the heat transfer in the susceptor, which improves the uniformity of the temperature distribution in the wafer. By using the finite element method （FEM）, the susceptor with this structure for heating a wafer of four inches in diameter is optimized. It is observed that the optimized susceptor with the A-shaped slot makes the uniformity of the temperature distribution in the wafer improve by more than 85%, and a good uniformity of temperature distributions is kept under different wafer temperatures, which may be beneficial to the film growth.     

新型铝电解电容器阳极箔耐水合试剂研究

基于密度泛函的第一性原理计算,采用新型膦酸盐乙二胺四甲叉膦酸钠作为耐水合试剂对化成后的铝电极箔进行耐水合处理。研究了γ-Al2O3(110)面上水分子的吸附机理以及铝电极箔的耐水合性能。计算结果显示水分子在γ-Al2O3(110)面上的Al原子上方可发生吸附,且四面体位置上的Al原子吸附活性优于八面体位置上的Al原子。红外光谱及原子力显微镜检测表明铝电极箔耐水合性能优良。新方法处理后,升压时间从15.1s缩短到7.8s。     

太赫兹量子级联激光器注入区结构研究

主要研究了THz量子级联激光器注入区结构的隧穿特性。通过量子力学方程设计出透射率最大的注入区结构。模拟结果表明,周期间势垒宽度为4.7 nm时,注入区的透射率最大。对于含有此注入区的QCL结构,模拟了在不同偏压下,电子波函数的空间分布和能级位置,进而模拟出该模型的隧穿点。计算结果表明,当每个周期两端的外加偏压为45 mV时达到THz工作点,同时满足周期间的电子隧穿条件。之后通过器件工艺,把外延片制作成实验样品。电流电压(I-V)测试曲线表明,在周期间偏压为50 mV时发生隧穿,这和理论计算的周期偏压为45 mV十分接近。     

铝电解电容器用高比容阳极箔制备技术进展

综述了近10年来铝电解电容器用高比容阳极箔制备技术的研究现状与发展趋势。重点评述了sol-gel法、水解沉积法、电化学沉积法及热处理手段等提高阳极箔比容的技术,对上述方法所制备阳极箔的氧化膜生长机理进行了探讨,提出了发挥有效面积S、形成常数K与相对介电常数εr的共同作用是高比容铝阳极箔制备技术的发展方向。     

压缩条件下玄武岩柱尺寸效应及破裂机理数值模拟研究

为研究压缩条件下玄武岩柱强度和变形的尺寸效应,及其破裂机理和破坏模式,本研究构建不同尺寸的玄武岩柱图像,然后将细观损伤力学、统计强度理论、连续介质力学相结合,基于RFPA^3D-CT的数字图像处理,将玄武岩柱图像转化为有限元网格模型,并分别赋予节理、岩石的材料力学参数,其中,考虑节理及岩石的非均质。开展压缩条件下的玄武岩柱数值试验,分析侧压、垂直柱轴方向(Ⅰ/Ⅱ)对玄武岩柱的力学尺寸效应的影响,以及玄武岩柱破裂过程的应力场演化与损伤破裂特征。研究表明：对于垂直柱轴方向Ⅰ的情况,当侧压为0 MPa,试件抗压强度无明显的尺寸效应;当侧压为2 MPa,试件抗压强度的尺寸效应临界值为4 m;当侧压为4、6、8 MPa,试件抗压强度的尺寸效应临界值为6 m。对于垂直柱轴方向Ⅱ的情况,当侧压为0、2 MPa,试件抗压强度无明显的尺寸效应;当侧压为4 MPa,试件抗压强度的尺寸效应临界值为4 m;当侧压为6、8 MPa,试件抗压强度的尺寸效应临界值为6 m。当侧压为0～8 MPa,随着模型尺寸的增加,试件抗压强度的横观各向异性系数变化范围为0.75～1.15;试件等效变形模量的横...     

共振声子THz QCL有源区结构设计

利用Airy函数代换与传输矩阵方法精确计算了有外加偏压下电子在共振声子太赫兹量子级联激光器有源区单个周期内的透射系数与波函数,得到了不同偏压下的电子波函数分布以及准束缚态能级位置与外加偏压的关系曲线.在仿真计算的基础上设计了一种共振声子太赫兹量子级联激光器的有源区结构.计算结果表明,对于设计的结构,当单个周期两端的外加...     

Theoretical study on the lasing plasmon of a split ring for label-free detection of single molecules and single nanoparticles

This paper reports the plasmonic lasing of a split ring filled with gain material in water. The lasing mode(1500 nm)is far from the pump mode(980 nm), which can depress the detection noise from the pump light. The laser intensities of the two modes simultaneously increase by more than 10~3 in amplitude, which can intensify the absorption efficiency of the pumping light and enhance the plasmonic lasing. The plasmonic lasing is a sensitive sensor. When a single protein nanoparticle(n = 1.5, r = 1.25 nm) is trapped in the gap of the split ring, the lasing spectrum moves by 0.031 nm, which is much larger than the detection limit of 10~(-5) nm. Moreover, the lasing intensity is also very sensitive to the trapped nanoparticle. It reduces to less than 1/600 when a protein nanoparticle(n = 1.5, r = 1.25 nm) is trapped in the gap.