Fabrication of silicon nanowires

2 at 750 °C and 850 °C. The oxide and interface morphology are characterized by cross-sectional scanning electron microscope images. It is found that the oxidized nanowire following oxidation at 750 °C still keeps its pentagon shape even if it has been oxidized for 19 h. However, the oxidized samples at 850 °C become circular in shape. The oxidation-temperature dependence of the sample shapes is discussed. Our results should be useful in generating silicon nanowires coated with SiO₂ in microelectronic technology with careful selection of the SiO₂ growth temperatures. Received: 26 September 1997/Accepted: 8 December 1997     

正线性算子对无穷区间上有界变差函数的点态逼近度

用ＢＶ［０，∞）表示在［０，∞）的每一有限子区间上为有界变差函数的函数构成的空间。用表示ＢＶ［０，∞）上的正线性算子，其中ｄｔＫｎ（ｘ，ｔ）是非负测度且，则有定理如果Ｌｎ（｜ｔ－ｘ｜β，ｘ）≤Ｃ（ｘ）／ｎｖ，，这里β＞０，ｖ≥１，Ｃ（ｘ）是一个与ｘ有关的常数，对ｆ∈ＢＶ［０，∞）和ｘ∈（０，∞）有这里作为应用，给出算子的逼近估计．     

向心加速度公式的教具制作及其教学研究——基于Tracker和Phyphox软件的定量探究

从教具制作、定量实验探究和教学启示等三方面来探究匀速圆周运动的向心加速度公式,即利用自制教具探究向心加速度αc与圆周运动半径r和角速度ω之间的定量关系.实验发现,结果非常好地符合理论预期.最后讨论了该教具所蕴含的教学启示,可以将其设计成适合高中物理教学的验证性、探究性实验及课外科创活动,从而培养学生的科学探究能力、科学...     

Diversity-oriented synthesis and antifungal activities of novel pimprinine derivative bearing a 1,3,4-oxadiazole-5-thioether moiety

Molecular Diversity - Based on the strategy of diversity-oriented synthesis and the structures of natural product pimprinine and streptochlorin, two series of novel pimprinine derivatives...     

Influence of dislocations in the GaN layer on the electrical properties of an AlGaN/GaN heterostructure

This paper reports on a comparative study of the spatial distributions of the electrical, optical, and structural properties in an AlGaN/GaN heterostructure. Edge dislocation density in the GaN template layer is shown to decrease in the regions of the wafer where the heterostructure sheet resistance increases and the GaN photoluminescence band-edge energy peak shifts to a high wavelength. This phenomenon is found to be attributed to the local compressive strain surrounding edge dislocation, which will generate a local piezoelectric polarization field in the GaN layer in the opposite direction to the piezoelectric polarization field in the AlGaN layer and thus help to increase the two-dimensional electron gas concentration.     

BaCuO_2的添加对YBa_2Cu_3O_(7-δ)临界电流密度的影响

掺入BaCuO2杂相的YBa2Cu3O7-δ(YBCO)粉末样品采用固相反应方法制备获得。XRD的Rietveld精修显示BaCuO2杂相和YBCO并存。在YBCO+xBaCuO2(x=0,0.05,0.1,0.2,0.3)的一系列样品中,当x=0.05时,样品的临界电流密度最大。在磁场中,微量BaCuO2杂相的添加,使YBCO的临界电流(Jc)提高了,但超导转变温度(Tc)稍微有所下降。临界电流密度的这些特征行为来自于两方面的共同作用,一方面是超导性的变化,另一方面纳米尺寸范围内的空间分布的非均匀性。     

超宽带减反射膜的设计和制备

设计了400～900 nm波段上的超宽带减反射膜,在410～850 nm范围内的平均残余反射率设计值约为0.2%,在设计的全波段上约为0.24%.讨论了初始膜系结构的选择原则,分析了带宽、膜层折射率差、最外层折射率和膜层总厚度等因素对宽带减反射特性的影响.对特定的带宽.增加两种薄膜材料的折射率差和选择尽可能低的最外层折射率对获得优良的减反射特性是非常重要的.实验制备了K9玻璃上TiO2/MgF2两种材料组成的8层结构的超宽带减反射膜,实测结果表明,在带宽520 nm范围内的平均残余反射率约为0.44%,说明用二种材料设计超宽带减反射膜是成功的,对垂直入射的减反射膜.多种材料的膜系并不比两种材料更具优越性.     

Top-hat cw laser induced thermal mirror: a complete model for material characterization

A complete theoretical model is presented for the thermal mirror technique under top-hat laser excitation. Considering the attenuation of the top-hat excitation laser intensity along the thickness of a sample due to its optical absorption coefficient, we calculate the laser-induced temperature and surface deformation profiles. A simplified theoretical model for a high absorption sample is also developed. The center intensity of a probe beam reflected from the thermal mirror at a detector plane is derived. Numerical simulation shows that the thermal mirror under the top-hat laser excitation is as sensitive as that under Gaussian laser excitation. With top-hat laser excitation, the experimental results of thermo-physical properties of opaque samples are found to be well consistent with literature values, validating the theory.     

Microstructures and properties of high Cr content coatings on inner surfaces of carbon steel tubular components prepared by a novel mechanical alloying method

In the present work, a novel mechanical alloying method was developed to prepare high Cr content coatings on the inner surface of carbon steel tubular components using a planetary ball mill. The microstructure and elemental and phase composition of mechanically alloyed coatings at different processing conditions were studied using SEM, XRD, and EDX. It showed that a proper increase in the applied milling time and the disc rotation speed favored the improvement in the thickness, surface smoothness, densification level, and microstructural homogeneity of the deposited coatings. With processing conditions optimized (rotation speed of 500 rpm and milling time of 10 h), a fully dense, 120 μm thick, high Cr content coating, consisting of metal Cr and Fe-20Cr solid solution alloy, was metallurgically bonded to the inner substrate. Comparative studies on the microhardness, corrosion resistance, and anti-oxidation capability of carbon steel substrates with and without coatings were performed. It was found that the maximum microhardness of the coating reached HV_0.1667, showing a threefold improvement upon the substrate. The coated surfaces exhibited favorable resistance against corrosion and thermal oxidation as compared with the bare substrate. Based on two important action mechanisms (i.e., friction effect and impact effect) associated with a planetary ball mill, a reasonable mechanism was presented for the formation of mechanically alloyed coatings on inner surfaces of tubular components.     

沉积速率和氧分压对HfO2薄膜残余应力的影响

采用ZYGO MarkIII-GPI数字波面干涉仪对以K9玻璃为基底的电子束蒸发方法制备的HfO₂薄膜中的残余应力进行了研究,讨论了沉积速率、氧分压这两种工艺参量对HfO₂薄膜残余应力的影响.实验结果表明：在所有的工艺条件下,薄膜的残余应力均为张应力;随着沉积速率的升高,氧分压的减小,薄膜的堆积密度逐渐增大,而残余应力呈减小趋势.同时用X射线衍射技术测量分析了不同工艺条件下HfO₂薄膜的晶体结构,探讨了HfO₂薄膜晶体 关键词： 残余应力 2薄膜')" href="#">HfO₂薄膜 沉积速率 氧分压