XPS分峰软件

XPS Peak Fitting Program for WIN95 XPSPEAK95 Version 3.1 Introduction I had spent >1000 hours on XPS peak fitting when I was a graduate student. During that time, I have dreamed of many features in the XPS peak fitting software that could help to obtain more information from the XPS peaks and reduce my processing time. In 1994, I wrote a program that converts the Kratos XPS spectral files to ASCII data. Once this program was finished, I found that the program could be easily converted to a peak fitting program. Then I added the dreamed features into the program, e.g., a better way to locate a point at a noise baseline for the Shirley background calculations, combine the two peaks of 2p3/2 and 2p1/2, fitting different XPS regions at the same time. After the first version and Version 2.0, many people have emailed me and gave me a lot of suggestions. I also found additional features that I can put into the program. The major change in version 3.0 is the addition of Newton`s method for optimization. I found that Newton`s method can greatly reduce the optimization time for multiple region peak fitting. For version 3.1, I have removed all the run-time errors that reported to me. A "Shirley + Linear" background was added. The "copy to clipboard" function was added as requested by a user. Some other minor graphical features were added. I have promised to add asymmetrical peak functions to the program. However, I realized that it is very difficult to correlate the function parameters to peak area and FWHM and I got many bugs. I will need more time to solve this problem. I hope I can add this feature in the next version. This version of the program was written in Visual Basic 5.0 and uses 32 bit processes. This is a freeware. You may ask for the source program if you really want to. I hope this program will be useful for people without a modern XPS software. I also hope that the new features in this program can be adopted by the XPS manufacturers in the later versions of their software. If you have any questions/suggestions, please send an email to me. Raymund W.M. Kwok Department of Chemistry The Chinese University of Hong Kong Shatin, Hong Kong Tel: (852)-2609-6261 Fax:(852)-2603-5057 email: rmkwok@cuhk.edu.hk Finally, I would like to thank the comments and suggestions from many people. I hope I will add other features into the program in the near future. Program Installation Unzip the XPSPEA3.ZIP file and run Setup.exe program in Win 95. Features of the program (1) Peak parameters This program uses four parameters for each peak, i.e., peak position, area, FWHM, and the %Gaussian-Lorentzian. Since peak area depends on peak height, FWHM and %GL, use of peak height as a peak parameter cannot directly reflect concentration. Thus, peak area is used as a better way of correlating the concentration ratios. (2) Peak types: p, d and f. Each of these peaks combines the two splitting peaks. The FWHM is the same for both the splitting peaks, e.g. a p-type peak with FWHM=0.7eV is the combination of a p3/2 with FWHM at 0.7eV and a p1/2 with FWHM at 0.7eV, and with an area ratio of 2 to 1. If the theoretical area ratio is not true for the splitted peaks, the old way of setting two s-type peaks and adding the constraints should be used. The �s.o.s.� stands for spin orbital splitting. Note: the FWHM of the p, d or f peaks are the FWHM of the p3/2, d5/2 or f7/2, respectively. FWHM are not the combined peaks, e.g. not the combined peak of p3/2 and p1/2. (3) Peak constraints Each parameter can be referenced to the same type of parameters in other peaks. For example, for four peaks (Peak#0, 1, 2 and 3) with known relative peak positions (0.5eV between adjacent peaks) , the following can be used Position: Peak 1 = Peak 0 + 0.5eV Position: Peak 2 = Peak 1 + 0.5eV Position: Peak 3 = Peak 2 + 0.5eV You may reference to any peaks except with looped references. The optimisation of the %GL value is allowed in this program. A suggestion to use this feature is to find a nice peak for a certain setting of your instrument and optimise the %GL for this peak. Then fix the %GL in the later peak fitting process when the same instrument settings were used. This version also includes the setting of the upper and lower bounds for each parameter. (4) Background This program provides the choices of Shirley, Linear or Tougaard backgrounds. For Tougaard background, the program can optimize the B1 parameter by minimizing the "square of the difference" of the intensities of ten data points in the high binding energy side of the range with the intensities of the calculated background. Averaging at the end points of the background can reduce the time to find a point at the middle of a noisy baseline. The program includes the choices of None (1 point), 3, 5, 7, and 9 point average. This will average the intensities around the binding energy you selected. The "Shirley + Linear" background was added for sloped background. The "Shirley + Linear" background is the Shirley background plus a straight line with starting point at the low BE end-point and with a slope value. If the slope value is zero, the original Shirley calculation is used. If the slope value is positive, the straight line has higher values at the high BE side, which can be used for spectra with higher background intensities at the high BE side. Similarly, a negative slope value can be used for a spectrum with lower background intensities at the high BE side. The optimization button may be used when the Shirley background is higher than the signal intensities. The program will increase the slope value until the Shirley background is below the signal intensities. Please see the example: Cu2p_bg.xps. I believe that the background subtraction calculation cannot remove exactly the background signals. For quantitative studies, the best procedure is "consistency". (5) Optimization You can optimize a single peak parameter, the peak (the peak position, area, FWHM, and the %GL if the "fix" box is not ticked), a single region (all the parameters of all the peaks in that region if the "fix" box is not ticked), or all the regions. During optimization, you can press the "Cancel" button and the program will stop the process in the next cycle. (6) Options for Optimization The %tolerence allows the optimization routine to stop if the change in the "difference" after one loop is less that the %tolerence. The default setting of the optimization is Newton's method. This method requires a delta value for the optimization calculations. You may need to change the value in some cases, but I found that the existing setting is enough for all of my data. For the binary search method, it searches the best fit for each parameter in up to four levels of value ranges. For example, for a peak position, in first level, it calculates the chi^2 when the peak position is changed by +2eV, +1.5eV, +1eV, +0.5eV, -0.5eV, -1eV, -1.5eV, and -2eV (range 2eV, step 0.5eV). Then, it selects the position value that gives the lowest chi^2. In the second level, it search the best values in the range +0.4eV, +0.3eV, +0.2eV, +0.1eV, -0.1eV, -0.2eV, -0.3eV, and -0.4eV (range 0.4eV, step 0.1eV). In the third level, it selects the best value in +0.09eV, +0.08eV, ...+0.01eV, -0.01eV, ...-0.09eV. This will give the best value with two digits after decimal. Level 4 is not used in the default setting. The range setting and the number of levels in the option window can be changed if needed. The Newton's Method or Binary Search Method can be selected by clicking the "use" selection box of that method. (7) Region Shift A "Region Shift" parameter was added