Q150T Sample Preparation System
10473 - Issue 5
40
Q150T - Instruction Manual
5.9
Glow Discharge
This process can be used to clean hydrocarbon contamination from components. It is
only available with Q150T S and ES models which are equipped with the Sputter power
supply
1.
Carefully fit the insert as described on page 62.
2.
Select
QT Glow discharge
from the process menu and run the process.
The default settings should be sufficient to create a hydrophilic surface on a
carbon film. The process can be varied by creating a new profile.
3.
Create a new profile from the default
Glow discharge -ve
process.
4.
Edit the glow discharge current from 20mA to a higher value, for example, 25mA.
The current may also be increased manually during the process but this setting would
not be retained for future runs.
5.9.1
Hydrophilisation
Freshly made carbon support films tend to have a hydrophobic surface which inhibits the
spreading of suspensions of particles in negative staining solutions. However, after Glow
Discharge treatment with air, the carbon film is made hydrophilic and negatively
charged, thus allowing easy spreading of aqueous suspensions. With subsequent
Magnesium Acetate treatment the surface is made hydrophilic and positively charged.
In addition to Glow Discharge treatment using air, other process gases may be used to
modify surface properties. For example, if alkylamine is used as a process gas, the
carbon film surface will become hydrophobic and positively charged. On the other hand,
using methanol as a process gas results in the surface becoming hydrophobic and
negatively charged.
Such treatments can facilitate the optional absorption of selected biomolecules.
5.9.2
Surface Cleaning
In many instances, surfaces need to be completely cleared of contamination films or
deposits. This applies particularly to EM components where such deposits impair the
maintenance of a clean vacuum system. A Glow Discharge treatment can be used to
clean such components of undesirable residues.
Table 11
Glow discharge treatments
GLOW DISCHARGE
Atmosphere
Surface
Charge
Air
Hydrophilic
Negative
Air
Hydrophilic
Positive (With subsequent magnesium
acetate treatment)
Alkylamine
Hydrophobic
Positive
Methanol
Hydrophobic
Negative
Summary of Contents for Q150T S
Page 92: ......
