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利用电镜中碳沉积现象,使碳沉积在约60(?)厚的非晶碳膜上,在同样实验条件下得到一系列不同厚度的非晶碳膜的电子能量损失谱。从这些谱中得到的信噪比与以等离子激发平均自由程λ_P表示的样品厚度的关系曲线表明:适合做电子能量损失谱的样品厚度在O.2～0.6λ_p之间。为了同时表征样品厚度对信噪比和多次散射的影响,引入参量I_n。此参量与样品厚度的关系曲线表明,最适合做电子能量损失谱工作的样品厚度在O.3λ_p左右的一个窄小范围内。
Electron microscopy of carbon deposition phenomenon, the carbon deposited on about 60 (?) Thick amorphous carbon film, under the same experimental conditions to get a series of different thickness of the amorphous carbon film electron energy loss spectrum. The curves of the signal-to-noise ratio obtained from these spectra and the sample thickness indicated by the mean free path λP of plasma excitation show that the thickness of the sample suitable for electron energy loss spectroscopy is between 0 and 0.6λ_p. In order to simultaneously characterize the effect of sample thickness on signal to noise ratio and multiple scattering, a parameter I_n is introduced. The curve of this parameter with the thickness of the sample shows that the thickness of the sample most suitable for the work of electron energy loss spectroscopy is within a narrow range of about O.3λ_p.