INFICON Guardian EIES Controller - Manual (Page 125)

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Guardian Co-Deposition Controller Operating Manual
Chapter 6
Theory & Calibration
6.1 Introduction
This chapter contains information that is useful for determining calibration values
to achieve the best possible performance and accuracy from your EIES-IV
Guardian system.
6.2 Theory of EIES Measurements
Electron Impact Emission Spectroscopy (EIES) uses a thermionic emitter to excite
outer shell electrons to a higher valence band. When these excited electrons return
to their normal state, they emit photons of a characteristic wavelength(s). An optical
filter passes the characteristic wavelength to a photomultiplier tube (PMT) detector.
The intensity of the characteristic wavelength is proportional to the rate of
deposition of the selected material.
6.2.1 Sensor
The EIES emitter assembly (referred to as the "sensor" for historical reasons)
consists of a hot cathode filament used to emit high-energy electrons. The sensor
is installed so that a portion of the evaporant stream passes through the active
sensor region. See
Figure 6-1 .
Figure 6-1 Sensor
Electron Beam
from Hot Filament
Characteristic
Spectra to Detector
Evaporant
Stream
Sensor
Housing