Open Counter for Low Energy ElectronCounting Sensor : LE

Stationary sensor
Example: LE-6118

1. Brief description

Detectable objects

This is the world's only sensor designed for surface analyses that is capable ofcounting low-energy electrons released into the air. RIKEN invented an initial modeland Waseda University invented an improved version. Our company hascommercialized them.

2. Structure and principles[Substance surface analysis]
Work function, surface contamination,
film thickness, etc.

[Structure][Structure]A

The sensor consists of two metal nets (G1 and G2), called grids, andan anode (A) made of a very thin wire.

[Principles]

SG1

G2

[Conceptual rendering of voltage fluctuations]
VAVoltageLow-energy electrons released from a sample enter the sensor
through the grids. These electrons cause electric discharges near theanode, which are counted as discharge pulses. If a discharge
continues, the sensor cannot count the second electron captured as
the second pulse. As a solution to this, the sensor changes thevoltages (VG1 and VG2) of G1 and G2 immediately after it has
counted a pulse.
This stops the discharge to neutralize the cations generated in thedischarge process and prevents the next electron from entering. Aftera certain duration, the sensor restores the voltages of G1 and G2 tocount the next pulse. By repeating this process, the sensor counts
electrons one by one.

S : Sample
A : Anode
G1: Grid 1
G2: Grid 2(V)+400
VG2+100
+80
-30

VG1t
Time (ms)

3. Features

By combining a ultraviolet optical system, you can use this sensor to perform surface analyses in the atmosphere based on photoelectronyield spectroscopy. Typical photoelectron spectroscopy, a very effective method for obtaining information about the surface of a sample,
requires a vacuum to measure electrons, which involves difficult measurement, and also requires expensive equipment. In contrast, thissensor allows you to easily make work function measurements and angstrom film-thicknesses measurements in the atmosphere, which had
to be inevitably made in a vacuum before.

○ Film thickness and counting rate

○ Density of states

4.5

5.0
5.5
Energy(eV)

6.0

Measurement based on photoelectron
yield spectroscopy provides a chart asshown in the figure. The vertical axis
shows electron yield (Y) to the nth power;
n is often 1/2 or 1/3. The point ofintersection of the regression line of thelinear part and the background is thethreshold of photoemission.

ln(N)DOSY1/2○ Photoemission characteristics

4.5

5.0

5.5 6.0
Energy(eV)

6.50

7.0

The electron yield differentiated withrespect to the energy of the applied light is
to reflect the density of states (DOS). Thismeasurement provides the electronic statenear the top of the valence band, which isan important element that determines
various physical properties.

4. Applications (examples)
Atmospheric photoelectron yield spectroscopy-Analysis of the electronic states of materials-Measurement of the thickness and contamination of ultrathin
films on solid surfaces

4080120Film thickness (Å)

If the surface is covered with another layer,
the counting rate, N (In (N)), and the film
thickness, T, are linearly correlated witheach other. Based on this correlation, thesensor estimates the thickness of any verythin film (such as an oxide film or
lubricating oil film) formed on the surfaceof metal or a semiconductor.

5. Products of this type (examples)○Stationary products... AC-2S, AC-3, AC-5

AC-2S