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针对TEM样品制备过程中离子束对样品的损伤所产生的"非晶化"影响进行分析和研究.在总结已有成果的基础上,得到一些新的突破:通过可信、简便的制样方法,可以直接观察到"非晶层";可以量测聚焦离子束制备的可供TEM分析的lC硅衬底样品的极限厚度.通过一系列自主设计的实验,得到如下结果:离子束的能量对"非晶层"厚度的影像非常大;"非晶层"的厚度与切割时离子束的加速电压有关,与离子束电流及入射角度等基本无关. 相似文献
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采用磁控溅射法制备了SmTbFeCo/Cr/TbFeCo系列非晶垂直磁化膜,研究了不同的Cr中介层厚度tCr对薄膜的磁性能和层间交换耦合的影响.VSM检测结果显示:薄膜的垂直磁性能随着tCr的变化而变化,其中饱和磁化强度Ms的变化曲线呈明显的周期振荡特性.饱和场Hs、(1-M/Ms)随tCr的变化曲线表明,两个磁性层的层间交换耦合随着tCr的增加,在反铁磁耦合与铁磁耦合之间振荡变化,周期为16(A),耦合强度逐渐衰减.分析表明,矫顽力Hc的变化主要源于Cr中介层对SmTbFeCo层微结构的影响,而Ms的变化则与层间交换耦合作用有关.文中还分析了稀土非晶膜的氧化问题. 相似文献
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纳米材料具有独特的物理化学性质,在纳米电子器件和生物传感等方面显示了巨大的应用潜力.基于二维纳米材料的器件,需要利用金属电极来构建传感器或者场效应晶体管结构.目前,已有一些方法来制备金属电极,如光刻、聚焦离子束及纳米压印等方法,但是这些方法通常需要昂贵的设备,并且操作非常复杂.提出采用基于光诱导的金属纳米电极沉积方法,通过对多个实验参数(包括输入交流电信号的频率、幅值、溶液浓度以及氢化非晶硅层厚度)的分析,得到了优化的金属电极沉积条件.在此基础上,利用光学显微镜、原子力显微镜和扫描电子显微镜对制备的金属电极进行了表征. 相似文献
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针对样品堆积造成的近红外光谱散射、吸光度与噪声干扰差异,使得光谱的信噪比发生改变而产生分析误差的问题,研究了样品状态和测试条件对近红外分析结果的影响。采集了样品在不同装样厚度、装样次数和不同装样松紧程度条件下的近红外光谱,采用主成分分析压缩数据,建立遗传算法BP神经网络模型。通过比较不同样品状态模型的预测性能,确立了最佳的样品测试条件。实验表明重复装样和样品松紧程度不会明显改善模型预测性;在装样厚度为0.5mm时,水分、灰分、挥发分和发热量预测模型的决定系数分别为0.936 6,0.791 6,0.894 9,0.857 5,模型预测性能较好。 相似文献
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采用介质键合技术制备的Si基GaAs材料衬底,缺陷密度小。对待键合的器件结构电学性能影响小。对采用目前常见的介质材料制备的Si基GaAs材料的力学性能进行了仿真分析,得到用于制备MEMS衬底的最佳介质键合层是SiO2,其衬底材料应力转换率高、量程大、位移小、制备工艺简单且为亲水性,制备的Si基GaAs衬底键合强度大,机械特性好。同时,对不同厚度的介质层材料对Si基GaAs材料的力学性能影响进行了研究分析,得到介质厚度越厚,其应力转换率越高,衬底材料的力敏效应就会越好。 相似文献
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针对建立近红外光谱煤质定量分析模型时训练集中的异常样品严重影响模型预测精度的问题,提出一种二次诊断法剔除异常样品:利用模糊C均值聚类法对样品进行聚类,得到可疑样品;将可疑样品作为验证集,通过PCA-GA-BP模型进行二次诊断,剔除异常样品。实验对比了训练集中异常样品剔除前后,模型对15组待测样品的预测能力,结果表明该方法能够准确剔除异常样品,并有效提高模型的预测精度。 相似文献
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通过大量的实验研究,建立了一套纳米量级牺牲层腐蚀行为的实验研究方法.对牺牲层厚度对腐蚀速率的影响进行了详细地研究,并得到了如下结论:当牺牲层厚度达到微米量级时,其腐蚀速率随着牺牲层厚度的增大而加快,但当其达到纳米量级时,由于固体表面存在的静电荷而产生双电层效应,这种效应对腐蚀速率的影响超过了牺牲层厚度的影响,最终使得腐蚀速率和牺牲层厚度无关. 相似文献
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对旋转粘弹性夹层梁的非线性自由振动特性进行了分析.基于Kelvin-Voigt粘弹性本构关系和大挠度理论,建立了旋转粘弹性夹层梁的非线性自由振动方程,并使用Galerkin法将偏微分形式振动方程化为常微分振动方程.采用多重尺度法对非线性常微分振动方程进行求解,通过小参数同次幂系数相等获得微分方程组,并通过求解方程组及消除久期项来获得旋转粘弹性夹层梁非线性自由振动的一次近似解.用数值方法讨论了粘弹性夹层厚度、转速和轮毂半径对梁固有频率的影响.结果表明:固有频率随转速增大而增大,随夹层厚度增大而减小,随轮毂半径的增大而增大. 相似文献
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基于压阻检测的双端固支硅纳米梁谐振特性研究 总被引:1,自引:0,他引:1
我们利用压阻检测法对双端固支硅纳米梁的谐振特性进行了研究.在(111)硅衬底上,用KOH选择性腐蚀制作出了厚度约为242 nm的双端固支硅纳米梁;对梁上表面采用Ar离子进行局部轰击,受轰击侧的原子结构遭到破坏,电导率显著下降,未受轰击侧原子结构则保持原掺杂结构,在梁厚度方向形成非对称掺杂,表现出压阻特性.利用该局部压阻,我们首次完成了对双端固支硅纳米梁的谐振特性的测量,其共振频率为400 kHz;同时,我们对获得的低Q值进行了初步讨论. 相似文献
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Jie Zhou Gang Liu Xiaobo Zhang Xueliang Kang Ying Xiong Yangchao Tian 《Microsystem Technologies》2013,19(3):477-482
Photonic crystals have attracted much attention from researchers because of the control over the propagation and emission of light and particular optical properties. In this paper, we reported on the design, fabrication and test of a two-dimensional polymer photonic crystal laser. First of all, a two-dimensional polymer photonic crystal laser with a triangle-lattice structure was described. Rhodamine 6G doped in PMMA was chosen as the gain material. Then, plane wave method based on the Maxwell equations was utilized to calculate the distribution of the photonic band gap. We calculated the band structure of a triangle lattice photonic crystal with a low refractive index. High resolution electron beam lithography combined with electroplating was used to fabricate the silicon nitride mask. A high aspect ratio two-dimensional photonic crystal laser was fabricated by X-ray lithography in one-step process to overcome the limitation of the thickness by the conventional methods to realize a real two-dimensional laser. Meanwhile, processes of sample preparations and fabrication were optimized in order to avoid the oxidation of the gain material and reduce the diffraction effect on the structures. 相似文献
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Theoretical and experimental studies were made in obtaining the natural frequencies of cantilever sandwich beams subjected to only gravity forces. The method of minimizing the total energy of the system was used for determining the frequencies. A vibration system made by Unholtz-Dickie was utilized to set the beam in vibration. Resonance occurred when the frequency of the shaker coincided with the natural frequency of the beam. The resonance frequencies were measured by transducers mounted at various locations on the beam. A total of sixteen beams of various lengths, thickness and core density were tested.
It was found that the natural frequency of a cantilever sandwich beam depends largely upon the thickness, length, core density and stiffness of the beam. In addition, the natural frequency has a nonlinear variation with the mode and for any particular mode, the value of the frequency increases as the length of the beam decreases.
Design factors were developed based upon the ratios of the theoretical frequencies of homogeneous beams having the same thicknesses and stiffnesses of that of sandwich beams and of the frequencies experimentally determined for similar sandwich beams. 相似文献
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Thin films of hafnium oxide were deposited by electron beam evaporation. The effects of the film thickness and preparation conditions (films prepared on the heated substrate with or without the presence of oxygen environment during deposition) on the optical and carbon monoxide sensing properties of the films were studied. The films were characterized using X-ray diffraction and X-ray photoelectron spectroscopy and optical spectroscopy techniques. Films deposited on unheated substrates were amorphous, whereas those deposited on heated substrates showed a mixture of amorphous and polycrystalline structure. It was found that the sensitivity of the films to CO increased with the thickness and the porosity (as reflected by the refractive indices) of the films. 相似文献
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《Computers & Structures》2002,80(14-15):1329-1335
Buckling of elastic sandwich beams is analyzed accounting for the compliance of the interfaces between the skin and core. A relation between tractions and displacement jumps across the interfaces characterizes the interfacial compliance. Timoshenko co-rotational beam elements are used to discretize each layer of the sandwich. The dependence of the bifurcation load on the stiffness of the core and on the interfacial compliance are illustrated by considering examples of a sandwich beam with two sets of boundary conditions. It is shown that the load at bifurcation buckling is sensitive to the compliance of the interfaces and that a sufficiently large interfacial compliance can significantly decrease the bifurcation load. 相似文献
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Xiaofeng Zhou Lufeng Che Youling Lin Xiaolin Li Jian Wu Yuelin Wang 《Microsystem Technologies》2014,20(7):1365-1372
This paper presents a symmetrical double-sided serpentine beam-mass structure design with a convenient and precise process of manufacturing MEMS accelerometers. The symmetrical double-sided serpentine beam-mass structure is fabricated from a single double-device-layer SOI wafer, which has identical buried oxides and device layers on both sides of a thick handle layer. The fabrication process produced proof mass with though wafer thickness (860 μm) to enable formation of a larger proof mass. Two layers of single crystal silicon serpentine beams with highly controllable dimension suspend the proof mass from both sides. A sandwich differential capacitive accelerometer based on symmetrical double-sided serpentine beams-mass structure is fabricated by three layer silicon/silicon wafer direct bonding. The resonance frequency of the accelerometer is measured in open loop system by a network analyzer. The quality factor and the resonant frequency are 14 and 724 Hz, respectively. The differential capacitance sensitivity of the fabricated accelerometer is 15 pF/g. The sensitivity of the device with close loop interface circuit is 2 V/g, and the nonlinearity is 0.6 % over the range of 0–1 g. The measured input referred noise floor of accelerometer with interface circuit is 2 μg/√Hz (0–250 Hz). 相似文献
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研究了小扰度下轴向匀速运动粘弹性夹层梁的振动模态和固有频率.基于Kelvin粘弹性本构方程,建立了轴向运动粘弹性夹层梁横向振动控制方程.分别采用Galerkin截断和复模态分析方法,研究两端简支的粘弹性夹层梁的固有频率和模态函数,讨论了轴向运动速度、夹心层与约束层厚度比、初始轴力等参数对夹层梁固有频率、临界速度及稳定性的影响. 相似文献