CHEM02200704003 Nilamadhab Pandhy - Homi Bhabha National ...

Chapter 3
is to separate out electrons in a desired band of energies from all other electrons entering the
spectrometer with wide range of energies. The most common type of spectrometers used is
concentric hemispherical analyzer (CHA). The current reaching the exist slit of the energy
analyzer from the energy analyzed electrons is very low, and usually requires electron multiplier
for detecting the photoelectrons of different energy. There are two types of electron multiplier
currently in use, those are (a) discrete dynode and (b) channel electron multiplier. The current
gains from such electron multipliers are within 10 4 -10 8 . In the detector, photoelectron spectra give
directly the detected electron density versus their binding energy. The identification of elements
on the surface is realised with their characteristics peaks appearing on wide range energy
spectrum.
In the present investigation, XPS was used to investigate the passive film composition of
304L SS in nitric acid medium developed in in-situ condition using electrochemical atomic force
microscope (EC-AFM), and the bonding state of nitrogen in nitrogen ion implanted 304L SS.
Measurements were carried out using XPS system (SPECS) that employed monochromatized Al
K radiation as probe and a hemispherical analyzer for energy analysis with pass energy of 20 eV
having an optimum energy resolution of 0.6 eV. The passive film as formed on 304L SS in 0.1 M,
0.6 M and 1 M nitric acid in in-situ EC-AFM study were analyzed to understand the overall
change in chemical composition of the passive film as a function of increasing nitric acid
concentration. Survey scans and high resolution spectra of major alloying elements in as polished
condition as well as nitric acid passivated condition were acquired to analyze the chemical state of
the alloying elements in aforementioned condition. Similarly, XPS analysis of nitrogen ion
implanted 304L SS was carried out to study the bonding of implanted nitrogen with certain
alloying elements in 304L SS leading to the formation of certain phases. XPS spectra for nitrogen
ion implanted specimens were carried out after different sputtering time interval at a sputtering