N. Bohr

W. Röntgen

M. Faraday
754 Leona Lane
Mountain View
CA, 94040, USA
FAX: -1-650-961-8591
Tel: -1-650-961-6620



"Self-Consistent" Data-Base of Monochromatic XPS Spectra

The "XI  Library XPS Spectra" (US registered copyright © # TX4-560-881) is a unique "Self-Consistent" collection of more than 40,000 monochromatic XPS spectra that were measured over a 10 year time period by a single scientist who used two well-characterized SSI XPS systems equipped with Al Kα monochromatic X-ray sources. The "XI Library of Digital XPS Spectra" is stored in over 3,800 data-files;  systematically organized as a modular system of 80 directories with names easily understood by analysts, engineers, scientists and teachers. View Why We Made SpecMaster.

The unique, self-consistent nature of the XI Library is a big advantage for users because it is a collection of correlated spectra that maximize the reliability of interpretations and chemical species assignments based on the spectral data contained in the XI Library. 

The self-consistent nature of the Library minimizes or avoids the many systematic and random errors found in various BE data tables in handbooks, databases of BE numbers and spectral databases that were assembled by collecting spectra from hundreds of different researchers, who used hundreds of different XPS systems, many different methods of charge referencing, charge compensation, energy scale calibration and sample preparation.  The uncertainty of the BEs in the "self-consistent" XI Library is less than +/-0.15 eV, which is significantly better than the uncertainties in other sources that range from +/- 0.4 eV to +/- 1.5 eV, but that is not the best part of the data-base.  The best and most valuable part of the data-base is the spectra, correlated sets of spectra.  These spectra do much more than simply provide BEs and FWHMs.  They provide peak-shapes, energy loss bands, C 1s spectra, O 1s spectra and survey scans.  All of which can be used to identify an unknown or, in some cases, a mixture of unknowns.  BEs are simply single data points.  Spectra represent hundreds and thousands of data-points.

With 70,000+ spectra, the XI Library remains 20 years ahead of all competitors.  If we consider the self-consistent nature, then the XI Library is probably 30-40 years ahead of all other resources or competitors.

XI directories can be arranged into different configurations that suit the various needs of XPS users. We are ready to customize any of our systems.  Requests for customized systems are welcome.  The spectral data-base systems we currently offer are called "SpecMaster",   "SpecMaster Max" and "SpecMaster Pro" .

The spectral data contained within these data-base systems and libraries are designed to assist engineers, scientists, analysts, theoreticians, and teachers who use XPS on an everyday basis under practical working conditions. We believe that these spectra will help XPS users to analyze industrial problems, gather reference data, perform basic research, test theories, and teach others.

A list of valuable trends is shown below, most of which could never be realized from small sets of spectra and definitely not simple lists of BEs.

The spectra in the XI Library are 100% designed to be practical tools for everyday use and were obtained under practical working conditions that most anyone can reproduce in their lab.  Our main goal was to produce a spectral data-base system that can be used in a practical manner on a daily basis by many different XPS users with different needs and responsibilities.

Although we have not actually attempted to produce research grade spectra we have, in fact, produced thousands of research grade spectra because of the internal standardization of our methods.

By design, our directories, filenames and samples have names and descriptions that directly identify the contents or the purpose of the directory or data-file. Most of these names are very familiar to XPS users, analysts, engineers, scientists and teachers. We deliberately avoided numerical file-names which add an unnecessary level of complication. Our systems are designed to be practical, systematical, organized and easy to understand.

The complete collection of spectra occupies about 200 MB of memory in binary form or about 400 MB in ASCII form are normally supplied on CD-ROM, but can be supplied on various magnetic media.

To minimize manual search times and to satisfy the interests of various users, all individual directories are filled with only a modest number (10-100) of data-files that can be easily re-grouped if desired.  Each data-file usually contains from 3-6 individual spectra, but may contain as many as 20 spectra.

The entire collection is currently organized into two major groups of data directories, which are classified as a "Common Materials" Spectral Library and a "Practical Studies" Spectral Library.

The Common Materials (CM) library includes >8,500 spectra contained in >50 modular data directories. It has 10 major directories with spectral data obtained from the XPS analyses of elements, naturally formed native oxides of the elements, commercially pure binary metal oxides, alloys, semi-conductor materials, glasses, reference spectra for pure elements, minerals, and polymers. The CM spectral library also includes more than 40 other minor data directories which contain >500 multi-spectra data files from a variety of important industrial materials.

The Practical Studies (PS) on common materials spectral library includes >30 different practical experimental studies some of which are listed in section 1.03 of this document. These practical studies demonstrate or reveal a number of trends, methods, and interesting phenomena that can help the user to choose useful experimental conditions and to avoid various experimental difficulties.

To keep up with the needs of our users we are always busy updating, expanding, and improving the contents and features of the XPS Spectral Data-Base System, its Libraries, and its data processing capabilities.   We have developed and/or are currently developing other data-base systems to be used with the data processing software's produced by other companies and special research groups.  We have also just completed a Windows version of our Spectral Data Processor (SDP v4.3), which is a advanced, standalone spectral data processing software that can also import and export a very wide variety of ASCII file formats, including the ISO (14976) standard VAMAS DTF format.

Unless otherwise indicated most spectra are provided in raw form.   Many data-files (about 25-30%) contain partially or fully reduced spectral data.

Experimental Trends and Phenomena Found from the Practical Studies Spectra
        The series of data in the Practical Studies spectral library reveal or demonstrate the a variety of trends, methods, effects, results, applications, and phenomena, such as:
1 the tendency of many elements to naturally form native oxides that are 10-70 angstroms in thickness and behave as though the native oxide/metal system was electrically conductive,
2 the phenomenon that the C 1s)BEs of the hydrocarbons on the surface of these native oxides have been found to vary from 284.5 eV to 286.5 eV whereby these variations can be partially attributed to surface dipoles and/or other electric field effects at the oxide/vacuum interface.
3 the ability to use the aforementioned, experimentally measured C 1s)BEs of the adventitious hydrocarbons to provide more reliable reference energies for energy referencing the other XPS signals produced from non-conductive metal oxides. The results of using these experimentally determined C 1s BEs indicate that this method is more reliable than the traditional method that uses ill-defined, fixed values such as 284.6, 284.7, 284.8, 285.0 or 285.2 eV.
4 the tendency of non-aromatic hydrocarbon polymers to lose hydrogen due to long term exposure to monochromatic X-rays,
5 the tendency of polymers with aromatic groups and triple bond structures to minimize damage caused by long term or high dosage exposures to monochromatic X-rays,
6 the differential charging effects of flood gun electrons on naturally formed native oxides,
7 the tendency of the C 1s, O 1s, and the main element signals from simple metal oxides to have FWHM values between 1.0-1.3 eV, much smaller than previously believed,
8 the tendency of elements on the left side of the periodic table to form oxides and carbides after ion etching in cryopumped UHV,
9  Scofield photo-ionization cross-sections, which we have tested, are basically reliable for the main XPS signals, but may have errors for the weaker XPS signals,
10  a tendency for the BEs of pure elements to display a 0.03-0.06 eV increase in BE due to repeated and extensive ion etching of the pure elements,
11  the tendency for the BEs of freshly ion etched pure elements to show a time dependent de-crease in BE (0.03-0.06 eV) even at room temperature (i.e. surface reconstruction),
12  charge compensation results obtained by using grazing X-rays which indicates a potential new method to simplify charge compensation of insulators,
13  a method to directly study excited states by collecting XPS data while exposing materials to CW lasers tuned to various wavelengths,
14  a CW laser beam cleaning method which partially or completely removes hydrocarbons and/or water adsorbed on colored binary oxides, and
15  a significant BE shift due to ion etching of clean crystalline surfaces of silicon, germanium, and selenium.