SEMI-QUANTITATIVE ANALYSIS of π~*/ σ~* RATIO MAP with WAVELET TRANSFORMED ESI METHOD

摘要

Diamond-like carbon (DLC) film having optimum ratio of σ~* /π~* could act as a key protection layer for the recording head and media because it's suitable hardness. Homogeneous distribution ofσ~*/π~* in nano-scale in diamond-like film is also required and very crucial for application in the recording media industry. In the recent years, many techniques for electron energy loss spectrometry (EELS) are proposed and make EELS not only determine the composition of specimen but also measure the chemical bonding and local structure at near atomic scale. To quantitatively analyze distribution of σ~* /π~* , two dimensional EELS spectra of C K-edge have to be recorded. There are two kinds of methods have been established to acquire the spatial (two-dimensions, 2-D) and spectra information which can be quantification. The first technique is spectrum-image which was proposed by Jeanguillaume & Colliex at 1989~2. The other method is called electron spectroscopic imaging (ESI) or image spectroscopy which was proposed by Jeanguillaume at 1978 and comprehensive summarized by Reimer at 1995. Comparing these two techniques, the spectrum-image has higher energy resolution but cost much recording time. The advantages of image-spectrum are total acquired time is shorter and larger acquired area but sacrifices energy resolution. In this study, the Fourier interpolation, Maximum entropy deconvolution and Wavelet transform are used to improve the image-spectrum as good quality as EEL-spectrum. The wavelet transform is one kind of methods to decompose the signal into difference frequency domain. The advantage of wavelet transform is that has better localization in time and frequency domain than Fourier transform. There are many wavelet functions, ψ(E), like Daubechies' (dbN), Haar (db1), Meyer, Coiflet and Symlet wavelets functions and all of them were satisfied three criteria : 1) ∫ψE)=0, 2) ∫ψ(E)= 1, 3) orthogonal basis set. The dbN wavelet is used in this article.