Q150T Sample Preparation System
Q150T - Instruction Manual
37
10473 - Issue 5
5.7.3
Adjusting coating thickness
The default settings in the Ramped Profile will produce a 15 to 20nm coating suitable for
SEM use. The actual coating thickness will depend on the stage height and the diameter
of the spigot produced by your sharpener.
As an approximate guide, the coating thickness is proportional to the square of the
distance between the stage height and the rods (the same amount of material is
distributed over an increasing area as it travels away from the rods).
New Thickness = Distance from source
2
x Thickness at original distance
Required distance
2
Example.
Assume that a coating thickness of 18nm has been achieved with a separation
between the rods and source of 125mm (equivalent to a stage height of 75mm using the
extended height chamber). To achieve a coating thickness of 11nm you would need to
increase the separation to 160mm.
The thickness of the deposited carbon can also be controlled by changing the property
“Evaporation current”. This property is the final current achieved during the ramped
profile (see Figure 5-5). The default current is 46A and this is the maximum that should
be used for a 1.4mm spigot. However, reducing the Evaporation Current reduces the
thickness of the coating. For example, with the Evaporation Current set to 38A the
thickness of the coating (at a distance of 125mm) is reduced to approximately 5nm.
5.7.4
How to create a carbon support layer For TEM
1.
Install the carbon insert as described on page 35. Ensure that the carbon rods are
prepared correctly as described on page 57.
2.
Ensure the stage is fitted with the longer support shaft adjusted to a height of
75mm above the base plate.
3.
Ensure the extended height cylinder 10429 is fitted as described on page 69.
4.
Create a new profile based on
QT Ramped Carbon.
5.
Edit the newly created profile setting the parameters as shown in Table 8.
6.
Run the new profile.
Table 8
QT Ramped Carbon TEM parameters for 5nm coating
Parameter
Value
Material
Carbon
Evaporation Current
41A
Evaporation Time
1 minute
Current ramp rate
0.25A/S
Out Gas Time
10 seconds
Out Gas Current
20A
Pre Evap End Current
32
Pre Evap Rate
1.00 A/S
Summary of Contents for Q150T S
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