Outgassing of CCD Components in the Vacuum

Annex

Annex A

Manual for the residual gas analyzer
("Pfeiffer QMS 200 F2")

  1. The software ("Quadstar 422 V 6.0")
  2. Getting started
  3. Measuring a probe
  4. Known problems
Annex B

Key fragment ions

 

 

Annex A:

Manual for the residual gas analyzer
("Pfeiffer QMS 200 F2")

1.   The software ("Quadstar 422 V 6.0")

Quadstar 422 consists of seven independent subprograms. These programs were actually developed to operate the Pfeiffer QMS 422, but most functions work for the QMS 200 in the same way. The subprograms of interest in our case are the following four:

  • Measure   is the actual measurement program. With this, various scans of a probe can be started and controlled.

     

  • Dispsav   is a short form for "Display Saved Values" and represents the analyzing program. Stored data can be displayed and processed here.

     

  • Service   is a service program. From here, leak tests and measurements of the total pressure can be made.

     

  • Utility   contains a spectra library.

 

2.   Getting started

  1. Assemble the vacuum chamber with the turbo-molecular pump, the residual gas analyzer and a vacuum sensor. With a cable, connect the latter two.

    Never run the system without this connection!

    As the gas analyzer could be damaged at pressures higher than 10-4 mbar, it will be switched off automatically using this control device if critical pressures are reached.

     

  2. Connect the residual gas analyzer via a serial interface with a PC or laptop. The software needs WINDOWS 3.1 or higher.

     

  3. Switch on the turbo-molecular pump, the system has to be closed before.

     

  4. Make a leak-test to check that all parts of the experimental chamber are hermetically sealed. Helium can be used as a test gas. Start the   Service   subprogram and click on   Measure: Leak Test . A smaller window appears, in which the measured pressure in the chamber is plotted versus time.

     

  5. Start the   Parset   subprogram and click on   Config: QMS . Check that ``SEM + FIL'' is set to ``INTERN'', so the emission can be started and switched off manually. In the same subprogram now click on   Setup: General   and check that the ``Simulation Mode'' is ``Off''.

 

3.   Measuring a probe

Preparing the measurement

 

  • Switch off the vacuum pump and wait until its rotation frequency is nearly 0.

     

  • Allow nitrogen gas into the probe chamber, until its pressure is similar to that outside the chamber. Open the chamber and put your probe onto the probe holder in a way which ensures optimal heat conduction. Close the chamber immediately and restart the turbo-molecular pump.

     

  • In the   Service   subprogram click on   Measure: Total Pressure. A display will show the pressure inside versus time. If the pressure is below 10-4 mbar the residual gas analyzer can be started. To do this, start the   Measurement   subprogram and click on   Setup: SEM/Emission Control. In the small window which appears switch the emission on. The heating symbol will change to yellow.
Making a spectrum of a probe

Start the program   Measurement. Spectral scans can be plotted as a histogram ("bargraph") or as a continuous curve ("analog").

  • For a bargrapg spectrum select   Scan: Bargraph. You will be prompted for a parameter file which describes the time and range of the scan. To make a scan for the atomic masses 0 to 200 amu, lasting 1 second per amu, select the file "scbf.sbp". We used this as default. Additional parameter files can be created.

     

  • In order to make an analog scan of the probe click on   Scan: Analog. As a default parameter file we used "scaf.sap".
For both cases you can select in   Scan: Setup   whether you would prefer a single or a continuously repeated scan of the probe. To finish a spectral scan click   File: Close.
Saving a spectrum

Start a bargraph or analog scan as explained above.

  • To save the next cycles select   File: Save cycle data   and give a name to the file with not more than eight letters (DOS standard), click "Ok". In the small window which will appear enter the number of cycles to be saved (usually one cycle). After that, in another window you may enter additional informations (time, temperature, pressure, probe data) to be saved together with the spectrum.

     

  • If you need to subtract one spectrum from another (see below), you can save it right at the beginning as a reference spectrum. To do this select   File: Save reference   and proceed as explained above. Analog data can be converted between cycled data and references. This is not possible for bargraph scans, where you need to know in advance what you are going to subtract from what.
Data processing

Saved spectra can be viewed in the subprogram   Dispsav. Select   Scan: Analog Data   or   Scan: Bargraph Cycles   respectively.

  • Analog spectra can be converted to ASCII data or processed with a graphic editor. Annotations as well as a three dimensional view of several cycles are possible.

     

  • These features are not available for bargraph cycles. However this data format is more important in our case.
Printing

By selecting   File: Print   in the subprogram   Dispsav   the current spectrum will be printed as an ASCII table only.

  • Press simultaneously "Ctrl" + "Shift" + "F12" and a prompting window will occur: You can print the currently active window or the whole screen to the standard printer or to a bmp-file. Shrinking or magnification of the output is also possible.

     

  • A screen capture can be copied via the WINDOWS clipboard into other applications. Press the button "Print Screen" for a copy of the entire screen or "Alt" + "Print Screen" to copy only the active window. You can paste this with "Shift" + "Insert" into another program.
Subtracting two spectra

 

  • The software contains a spectra library for 63 chemical substances. Various spectra of the probes could be appended and therein overlayed to other spectra or subtracted. However, these spectra must not possess more than 32 lines, otherwise some peaks will be cancelled.

     

  • In order to subtract a spectrum stored as a reference (see above) from a spectrum which is currently saved, select the reference with   File: Load reference. Click on   Scan: Setup   and choose in the window which will appear "Save data as difference". You can also select which spectra (current, reference, difference) will be displayed, but only the difference will be saved. Don't forget to reset to "Save data as current" if you want to store a spectrum as it is.

     

  • Analog data can be converted to ASCII and processed with other programs. When importing these into EXCEL, the exponents' values will be falsified. To solve this problem go to the WINDOWS "Control Panel" - "Regional Settings" - "Number Format" and enter as "Digit Grouping Symbol" (the 1000-separator) a quotation mark (').

 

4.   Known problems

  1. Some subprograms of "Quadstar 422 V 6.0" cannot be run simultaneously.

     

  2. Don't forget to switch off the emission explicitly. Closing the program or a reboot of the PC leaves the emission unchanged.

     

  3. There are only inconvenient possibilities of subtracting spectra.

Annex B:

Key fragment ions

Mass number [m/e] Key fragments Probable parent molecule Additional mass number [m/e]
1 H+ H2 2
H2O 16, 17, 18
CxHy 12, 13, 14, 26, 27
2 H2+ H2 1
He2+ He 4
4 He+ He 2
6 C2+ CO 12, 28, 29
CO2 12, 28, 44
CxHy 12, 13, 14, 26, 27
7 N2+ N2 14, 28, 29
8 O2+ O2 16, 32, 34
H2O 16, 17, 18
12 C+ CO 28, 29
CO2 28, 29, 44
CxHy 13, 14, 26, 27
13 CH+ CxHy 12, 14, 26, 27
14 N+ N2 28, 29
NH3 15, 16, 17
CH2+ CxHy 12, 13, 26, 27
CO2+ CO 28, 29
15 CH3+ CxHy 12, 13, 14, 26, 27
NH+ NH3 14, 16, 17
16 O+ O2 32, 34
H2O 17, 18
CH4+ CH4 12, 13, 14, 15
NH2+ NH3 14, 15, 17
17 OH+ H2O 16, 18
NH3+ NH3 14, 15, 16
18 H2O+ H2O 16, 17
19 F+ F2 38
HF 20
20Ne+ Ne 22
Ar2+ Ar 40
20 HF+ HF 19
22 CO22+ CO2 6, 12, 28, 29, 44
22Ne+ Ne 20
24 C2+ CxHy 12, 13, 14, 26, 27
26 C2H2+ CxHy 12, 13, 14, 24, 27
27 C2H3+ CxHy 12, 13, 14, 24, 26
28 N2+ N2 7, 14, 29
C2H4+ CxHy 12, 13, 14, 24, 26
CO+ CO 6, 12, 29
CO2 6, 12, 29, 44
29 C2H5+ CxHy 12, 13, 14, 24, 26, 27, 28
14N15N+ N2 7, 14, 28
30 C2H6+ C2H6 12, 13, 14, 24, 26, 27, 28, 29
NO+ NO 14, 16
31 C2H2OH+ C2H3OH 26, 28, 29
CF+ CF  
32 O2+ O2 8, 16, 34
S+ H2S 33, 34
SO2 34, 64
34 H232S+ H2S 32, 33
34S+ 32, 33
16O18O+ O2 8, 16, 32
35 35Cl+ Cl2 37, 70, 72, 74
HCl 36, 37, 38
36 H35Cl+ HCl 35, 37, 38
36Ar+ Ar 20, 38, 40
37 37Cl+ Cl2 35, 70, 72, 74
HCl 35, 36, 38
38 H37Cl+ HCl 35, 36, 37
C3H2+ CxHy 12, 13, 14, 24, 26, 27, 28
38Ar+ Ar 20, 36, 40
39 C3H3+ CxHy 12, 13, 14, 24, 26, 27, 28, 38
39K+ K 41
40 Ar+ Ar 36, 38
C3H4+ CxHy 12, 13, 14, 24, 26, 27, 28, 38, 39
41 C3H5+ CxHy 12, 13, 14, 24, 26, 27, 28, 38, 39
41K+ K 39
42 C3H6+ CxHy 12, 13, 14, 24, 26, 27, 28, 38, 39
43 C3H7+ CxHy 12, 13, 14, 24, 26, 27, 28, 38, 39
C2H3O+ C2H5OH
(alcohol)
31, 44, 45, 46
44 C3H8+ C3H8 41, 42, 43
CO2+ CO2 6, 12, 28, 29
C2H4OH+ C2H5OH
(alcohol)
31, 43, 45, 46
N2O+ N2O 14, 16, 28
45 C2H5O+ C2H5OH
(alcohol)
31, 43, 44, 46
13CO2+ CO2 6, 12, 28, 29, 44
46 NO2+ NO2 14, 16
C2H5OH+ C2H5OH
(alcohol)
31, 43, 44, 45
48 SO+ SO2 32, 64
50 CF2+ CF2  
55 C4H7+ CxHy 12, 13, 14, 24, 26, 27, 28, 38, 39
57 C4H9+ CxHy 12, 13, 14, 24, 26, 27, 28, 38, 39
58 (CH3)2CO+ C3H6O
(acetone)
43
64 SO2+ SO2 32, 48
69 CF3+ CF3  
77 C6H5+ Phenyl 50, 51, 52
78 C6H6+ C6H6
(benzene)
50, 51, 52
"92.5" 185Re2+ Rhenium "93.5", 185, 187
"93.5" 187Re2+ Rhenium
(filament)
"92.5", 185, 187
149   Phthalic ester
(softening agent)
 
182 182W+ Tungsten
(filament)
183, 184, 186
183 183W+ Tungsten
(filament)
182, 184, 186
184 184W+ Tungsten
(filament)
182, 183, 186
185 185Re+ Rhenium
(filament)
187
187 187Re+ Rhenium
(filament)
185