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采用直流电化学刻蚀方法制备扫描隧道显微镜钨针尖,研究了电化学刻蚀过程中NaOH溶液浓度、钨丝浸入长度和刻蚀电压对针尖形貌的影响。通过扫描电子显微镜(SEM)测量针尖曲率半径和针尖纵横比值,以表征针尖的尺寸和形状;通过能谱仪(EDS)分析针尖表面成分,以表征表面清洁度;通过场发射显微镜(FEM)得到Fowler-Nordheim (F-N)曲线来检测针尖发射性能。实验结果表明,当溶液浓度为2 mol/L、钨丝浸入长度为4 mm、刻蚀电压为3 V时,可以得到曲率半径约为100 nm、纵横比值为13的针尖,且表面无钨的氧化层。FEM结果显示当对针尖施加500 V的负偏压时,针尖可以稳定发射50 nA量级的电流,且针尖性能具有良好的一致性。 相似文献
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利用STM构建金属有机材料的纳米结构和改变电学性质 总被引:2,自引:0,他引:2
研究和开发利用扫描隧道显微镜(STM)对材料进行纳米尺度加工的功能,藉助于STM针尖和样品之间的强电场在金属有机络合物Ag-TCNQ薄膜表面构建了纳米点、纳米点阵和纳米线等纳米结构。伏安(I-U)特性曲线和扫描隧道的测试表明,在针尖强场作用后材料表面的局域电子态密度迅速增大,在电学上由高阻态转变为低阻态,这种效应可能归因于金属原子和有机分子之间的电荷转移。这些纳米结构展示了用作高密度存储器和纳米导线的可能性,有机导电材料将是未来纳米电子材料的理想候选者,而STM则将成为纳米电子学微细加工的有力工具。 相似文献
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结合扫描隧道显微镜(STM)成像实验和第一性原理原子级模拟计算的方法已经成为材料界面表征的重要手段。超高真空条件下的STM可用于直接观察单原子等微观结构,但其成像原理还未被理解清楚。STM扫描测得的试件表面原子级图像并不直接反映材料原子的形态,实际上是表面形貌和表面电子态局域密度的综合结果。为了解释STM成像,采用第一性原理Siesta方法,研究了Si(001)面STM成像过程的电子结构,对表面粒子的原子轨道和相应的电荷密度进行计算。讨论了等高模式下扫描高度对局域电子云密度分布的影响,并分析了STM针尖几何形状对模拟结果的影响。研究表明,材料表面原子的电子云密度分布可以用来解释STM成像精度和扫描高度对比的变化。 相似文献
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一种新型的STM探针 总被引:2,自引:0,他引:2
以普通的石英光纤为材料,用熔拉腐蚀复合的方法制备出nm量级的光纤探针,而后在针尖表面镀上数十nm厚的金属膜,达到导电性,使其能传导隧道电流,从而研制出一种新型的扫描隧道显微镜(STM)光纤隧道探针,在STM上取得了比较理想的实验结果。本文将光纤隧道探针与金属隧道探针作了比较,并对其性能作了分析。 相似文献
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T. K. Zvonareva V. I. Ivanov-Omskii S. G. Yastrebov A. O. Golubok O. M. Gorbenko V. V. Rozanov 《Semiconductors》2001,35(2):230-234
A study of the surface morphology of copper-modified amorphous hydrogenated carbon films a-C:H(Cu) by scanning tunnel microscopy (STM) is reported. An algorithm is presented for the digital analysis of STM images to obtain the size distribution function for the longitudinal component of the surface relief. a-C:H(Cu) films were deposited by magnetron co-sputtering of graphite and copper onto two types of substrates: (100) n-Si with a heavily doped surface layer, and Si covered with a chromium layer. A mesoscopic surface structure of crystalline silicon, a chromium layer, and a-C:H(Cu) film has been revealed. A correlation between the structural elements of the film and the substrate is considered and a conclusion is made that inherent grains with characteristic size of 6–8 nm are formed in the film. 相似文献
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K. Pond J. Ibbetson R. Maboudian V. Bressler-Hill W. H. Weinberg U. K. Mishra A. C. Gossard P. M. Petroff 《Journal of Electronic Materials》1993,22(12):1383-1386
Scanning tunneling microscopy (STM) has been used to investigate the effect of low-temperature (LT) growth of GaAs by molecular
beam epitaxy on the morphology of the resulting surface. We present STM images of a GaAs(001) surface that was grown at ∼300°C
and subsequently annealed at 600°C and show that there is a recovery of the (2×4) reconstruction. We also report images of
a surface grown on top of a buried LT GaAs layer and show that the LT layer has little effect on the resulting surface morphology.
In addition, scanning tunneling spectroscopy spectra are presented which demonstrate that the current-voltage characteristics
of annealed and unannealed LT grown GaAs are significantly different. 相似文献
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High-resolution electron microscopy (HREM) was used to detect the surface Fe3O4 iron-oxide layer formed on [011] Fe4N iron nitride due to electron irradiation in the transmission electron microscope. The existence of a surface oxide layer was confirmed by both image processing and through-focus observation. Images of the iron oxide were revealed using the process of fast Fourier transformation (FFT) of experimental HREM images, filtering of the FFT patterns and inverse FFT. By through-focus observation, HREM images of iron oxide were obtained based on the tuning of contrast transfer function. Fourier filtering is effective for examining the beginning of phase transformation, because at this stage the diffraction spots of iron oxide are too weak to be detected. At the time when the iron oxide layer has developed to some extent, through-focus observation is useful to obtain an image of oxide layers. 相似文献
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P. A. Dement’ev M. S. Dunaevskiĭ I. V. Makarenko V. N. Petrov A. N. Titkov A. N. Baranov D. A. Yarekha R. Laiho 《Semiconductors》2006,40(11):1247-1254
Formation of a natural oxide in ambient atmosphere of the mirrors of a GaSb/GaInAsSb/Ga0.1Al0.9As0.93Sb0.07 laser heterostructure at places of emergence Al-rich layers on the mirror surface is studied. The evolution of topography of the laser mirrors produced by cleavage under ambient and ultrahigh vacuum conditions was studied by AFM and STM for mirrors cleaved. The oxidation of Ga0.1Al0.9As0.93Sb0.07 layers on the mirror surface was monitored for more than a year. It is shown that the oxide layer develops over the course of several months and then attains a constant thickness of about 1 μm. In the course of natural oxidation, the volume of the oxide layer increases, which results in its protrusion above the laser mirror surface approximately by a third of the total thickness of the oxide formed. Ultrahigh vacuum studies ruled out the previously assumed occurrence of the effect of plastic extension of Al-rich layers at the instant of cleavage and the resulting protrusion over the cleavage plane. At the initial stage of oxidation, the oxide protruding above the surface demonstrates an unusual concave region in the upper part, which disappears as the oxide grows further. An explanation of the observed transformation of the shape of the oxide layer is offered. It is assumed that the chemical composition of the oxide varies as its thickness increases. 相似文献
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应用激子动力学方法 ,计算机模拟了 W、Mo、Pt、Pd探针恒流、恒高模式扫描隧道显微镜 (STM)图谱。结果显示出 ,不同探针恒流模式 STM图谱分辨率基本一致 ,而恒高模式的 STM图谱以 Pd探针分辨率较高 ,W、Mo探针次之 ,Pt探针较差 相似文献