PECVD法低温沉积多晶硅薄膜的研究

在玻璃衬底上采用常规的PKCVD法在低温(≤400℃)条件下制得大颗较(直径＞100nm)、择优取向(220)明显的多晶硅薄膜。选用的反应气体为SiF4和H2混合气体。加入少量的SiH4后，沉积速率提高了近10倍。分析认为，在低温时促使多晶硅结构形成的反应基元应是SiFmHn(m n≤3)，而不可能是SiHn(n≤3)基团。     

铜蒸气激光器种子注入光腔的参数计算

用矩阵光学理论计算了由主振荡器和功率放大器组成的种子注入光腔。主振荡器光腔是由曲率半径R1=-250mm,R2=5000mm,相距L=2375mm的球面镜组成的正支非稳腔;功率非稳腔是由曲率半径R3=400mm,R4=5600mm,相距S=3000mm的球面镜构成的负支非稳腔。理论计算表明,该种子注入光腔可输出光束发散角约几十微弧的激光,可满足铜蒸气激光器主振荡器功率放大器(MOPA)的技术要求。     

Thermal gradient induced sidebranching in directional solidification

The polycrystalline perovskitelike manganese oxides La_1-xA_xMnO (A = Na, and K, ) have been fabricated by sol-gel technique. For all the compositions explored in this work, the average manganese oxidation state is practically constant, at for A = Na, and for A = K, respectively. A close relationship is confirmed to hold between the Curie temperature (T_c) and the bond distance of Mn-O. Results of magnetic measurements show that these materials can be utilized as suitable candidates for magnetic refrigerants with wide applied temperature span, for their significant entropy change and the easily tuned Curie temperature. Received: 12 September 1997 / Revised: 18 December 1997 / Accepted: 21 January 1998     

GaN and AlGaN high-voltage rectifiers grown by metal-organic chemical-vapor deposition

In this paper, we report the study of the electrical characteristics of GaN and AlGaN vertical p-i-n junctions and Schottky rectifiers grown on both sapphire and SiC substrates by metal-organic chemical-vapor deposition. For GaN p-i-n rectifiers grown on SiC with a relatively thin “i” region of 2 μm, a breakdown voltage over 400 V, and forward voltage as low as 4.5 V at 100 A/cm² are exhibited for a 60-μm-diameter device. A GaN Schottky diode with a 2-μm-thick undoped layer exhibits a blocking voltage in excess of ∼230 V at a reverse-leakage current density below 1 mA/cm², and a forward-voltage drop of 3.5 V at a current density of 100 A/cm². It has been found that with the same device structure and process approach, the leakage current of a device grown on a SiC substrate is much lower than a device grown on a sapphire substrate. The use of Mg ion implantation for p-guard rings as planar-edge terminations in mesageometry GaN Schottky rectifiers has also been studied.     

碳纳米管(CNT)场发射显示器的关键技术的研究

对碳纳米管阴极的制备以及场发射显示器的真空封装技术进行了研究.利用一种新的碳纳米管生长工艺制备出了具有优良场发射性能的碳纳米管阴极.并将这种直接生长的碳纳米管薄膜作为阴极,结合一种弹性封装工艺,开发了一种具有简单字符显示功能的场发射显示器.该显示器在较低的工作电压下就可获得高亮度的显示效果,并且器件的亮度与驱动电压成较好的线性关系,这将有利于未来的碳纳米管场发射显示器实现高亮度和多级灰度显示.器件的持续工作寿命测试已经超过5500小时,充分验证了碳纳米管作为场发射阴极的应用潜力.     

WEAK CONVERGENCE FOR NON-UNIFORM φ-MIXING RANDOM FIELDS

Let $\{\xi_{\bold t}, {\bold t} \in {\bold Z}^d\}$ be a nonuniform $\varphi$-mixing strictly stationary real random field with $E\xi_{\bold 0}=0, E|\xi_{\bold 0}|^{2+\delta}<\infty$ for some $0<\delta<1$. A sufficient condition is given for the sequence of partial sum set-indexed process $\{Z_n(A),\ A\in \Cal A\}$ to converge to Brownian motion. By a direct calculation, the author shows that the result holds for a more general class of set index ${\Cal A}$, where ${\Cal A}$ is assumed only to have the metric entropy exponent $r, 0相似文献   

设计性、研究性实验对学生创新能力的培养

根据设计性、研究性实验的特点,从几个方面、不同的角度,阐述了设计性、研究性实验对学生创新能力培养的作用与意义。     

GaN氢化物气相外延生长系统的设计与制作

根据GaN氢化物气相外延生长(HVPE)的原理,设计制作了双温区卧式HVPE系统．根据实际生长中出现的问题和CaN样品的测试情况,对系统进行了逐步的调试和改进．     

Roles of SiH4 and SiF4 in growth and structural changes of poly-Si films

The structural properties of polycrystalline silicon films, prepared by plasma enhanced chemical vapor deposition system, with different flow rates of SiH₄/SiF₄ mixtures at 300 °C were investigated. This study indicates that the low hydrogen coverage on the growing surface, under optimum fluorine radicals, will be leaded to an improvement of crystallized area as compared with case of high hydrogen coverage surface. Moreover, the studies of the role of SiH₄ and SiF₄ radicals show that the SiH₄ radicals are important in the nucleation and growth of grains. However, SiF₄ radicals are effective in the structural change of grain boundaries regions and by this way, in the present system, establish the growth of grains under the dominant 〈1 1 0〉 direction. The stress investigation indicates that addition of high flow rate of SiF₄ in amorphous film, results in the nearly stress free films. Finally, we found that the changes in g-value reflect the changes in the intrinsic compressive and tensile stress in the both polycrystalline and amorphous silicon films.     

Analysis of G/D/1 Queueing Systems with Inputs Satisfying Large Deviation Principle under Weak* Topology

The large deviation principle (LDP) which has been effectively used in queueing analysis is the sample path LDP, the LDP in a function space endowed with the uniform topology. Chang [5] has shown that in the discrete-time G/D/1 queueing system under the FIFO discipline, the departure process satisfies the sample path LDP if so does the arrival process. In this paper, we consider arrival processes satisfying the LDP in a space of measures endowed with the weak^* topology (Lynch and Sethuraman [12]) which holds under a weaker condition. It is shown that in the queueing system mentioned above, the departure processes still satisfies the sample path LDP. Our result thus covers arrival processes which can be ruled out in the work of Chang [5]. The result is then applied to obtain the exponential decay rate of the queue length probability in an intree network as was obtained by Chang [5], who considered the arrival process satisfying the sample path LDP.