Low-energy electron-flood

Because polymers are typically non-conductive, sample charging can occur and has to be compensated carefully, e. g. by use of a low-energy electron-flood gun, to avoid line-shape distortion and misinterpretation of the measurements. 

The transmission electron microscopy was done with a 100-kV accelerating potential (Hitachi 600). Powder samples were dispersed onto a carbon film on a Cu grid for TEM examination. The surface analysis techniques used, XPS and SIMS, were described earlier (7). X-ray photoelectron spectroscopy was done with a Du Pont 650 instrument and Mg K radiation (10 kV and 30 mA). The samples were held in a cup for XPS analysis. Secondary ion mass spectrometry and depth profiling was done with a modified 3M instrument that was equipped with an Extranuclear quadrupole mass spectrometer and used 2-kV Ne ions at a current density of 0.5 /zA/cm2. A low-energy electron flood gun was employed for charge compensation on these insulating samples. The secondary ions were detected at 90° from the primary ion direction. The powder was pressed into In foil for the SIMS work. 

The XPS spectra were obtained on an escaiab Mk II (VG Scientific Ltd.) photoelectron spectr< eter with an Al X-ray source, charge conpensatiinstrumental resolution, measured as full width... 

The problem can be alleviated to some extent by use of low energy electron flood guns, but this introduces other complications. 

Charging can be a significant problem when the sample is an insulator. Bombarding the sample with positive ions can lead to implantation of positive ions as well as the emission of electrons. One way that this problem can be overcome is by flooding the sample surface with a beam of low-energy electrons [50]. 

One can compensate for charging by using a so-called flood gun, which sprays low-energy electrons onto the sample. Charging can also be minimized by using a beam of atoms instead of ions as primary particles. In this case, kinetic emission of electrons is the only source of charging, if we ignore the low yields of secondary ions. 

Some XPS valence band spectra of thick insulating samples have been obtained using a low energy electron emission source (flood gun) to neutralize the positive surface charge. This... 

Figure 7.18 Compensating the electron loss due to photoelectron escape using low-energy electron flux from a flood gun.

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