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XPS Info - Technotes

This page provides some reference data and describes how some (less) frequently used actions can be performed.

Some actions should not be done by any user but can only be performed by the technician ( T ) or even only by the service engineer ( E ).

An argon purity check should be done after the argon line has been disconnected or when one suspects the argon contains either water or oxygen or both.

The argon purity check basically is creating a depth profile of oxygen and aluminium (and perhaps nitrogen) in aluminium foil. Initially there would be some oxygen because of aluminium oxide but deeper into the foil the oxygen should disappear.

Don't just look at the depth profile but also at the oxygen scans, because in constructing the depth profile the software might still assign some peak area to oxygen while there is no peak left.

A controlled shutdown may have to be applied for example when it is known in advance that the electrical power will be shut off or when the argon line needs the be flushed. The following steps describe how to perform a controlled shutdown:

  • In Avantage shut down all guns: Ion, Flood and X-Ray.
  • Shut down Avantage.
  • Turn off the PC.
  • On the K-Alpha remove the small panel with the LEDs in order to get access to the inside of machine.
  • Close the red valve at the left on the panel at the rear of the K-Alpha. This is the air supply for switching the pneumatic valves. With the air supply closed the valves can't switch and no inadvertent vent can take place. The vacuum remains and a bake out won't be necessary.
  • Turn off the K-Alpha with the yellow/red button at the backside.
  • Now, if so required, the gaslines can be disconnected for flushing.

After a (controlled) shutdown follow the following procedure:

  • Reconnect the gaslines if they had been disconnected.
  • Open the red valve of the air supply.
  • Turn the K-Alpha back on with the yellow/red button.
  • Turn on the PC.

The K-Alpha automatically executes its start procedure. Amongst others the high vacuum pumps will start automatically.

If the gaslines were disconnected the (internal) argon line needs to be flushed using Avantage.

PS. If the power supply of the backing pump isn't connected to the K-Alpha be sure it is turned on before starting the K-Alpha.

There are essentially 2 ways to export data:

1. Export data to an Excel spreadsheet.

2. Export data with the Dataspace Batchdump utility.

This utility lets you select the folder of which you want to export the data. It also lets you select an alternative folder to which to save the data. But in doesn't let you create a folder, so do so in advance.

If the Vacuum Transfer Unit (VTU) is used as sample holder, then further avoiding contact with oxygen can be accomplished by flushing the loadlock. This action cannot be done as 'Expert' but must be done as 'Engineer' and should only be performed by the technician. It is assumed that after loading the VTU the following is true:

  • V5 is closed (between backing pump and loadlock turbo pump)
  • V3 is closed (in the loadlock to analysis chamber line)
  • V2 is closed (N2 inlet)
  • T2 is off (the loadlock turbo pump)
  • the loadlock door is closed
From here the following procedure shows which steps to take:
  • if logged in as 'Expert':
    • close Avantage and run ServerStopper
    • log off and log in as 'Engineer'
    • start Avantage
  • close V4 (between backing pump and analysis chamber turbo pump)

Now repeat the following 3 times:

  • open V5
  • wait until Ploadloack < 1.10-1 mbar
  • close V5
  • open V2, which will actually open and close the valve several times
  • wait until Ploadlock > 5.102 mbar and V2 is actually open
  • close V2

After this:

  • open V5
  • wait until Pbacking < 5.10-2 mbar
  • start T2
  • wait until Pbacking < 5.10-3 mbar and T2 is at speed
  • open V4
  • close Avantage
  • run ServerStopper
  • log off and log in as 'Expert'

The basic ThermoFisher K-Alpha XPS at ChemE doesn't have options to add custom equipment like other X-ray sources or other etching sources. Also there are no provisions to perform some kind of reactions and to do in situ XPS measurements, but there is a work around to do some reactions and then to do XPS measurements shortly after.

It is possible to let a sample react with a certain gas and then to analyze the sample. The trick is to let this gas in through the venting line of the loadlock. Of course there are limitations to what gasses can be used and there is no control of the temperature and barely no control of the pressure at which the reaction takes place.

The general procedure for (almost) in situ XPS would be as follows:

  • enter the sample into the analysis chamber
  • the first time
    • : maybe etch away a protective layer
    • : pre-flush the line to the loadlock with the selected gas
  • do a measurement
  • move the sample to the loadlock
  • fill the loadlock with the selected gas (to approx 5.102 mbar)
  • keep the sample in the gaseous environment for a desired time
  • pump down the load lock and repeat the procedure as often as required

This method requires assistance from the technician (and must be performed as 'Engineer'). The actual steps are similar to those described in the 'flushing the loadlock' topic.

The composition of carbon tape is similar to the following:

peakatomic %
C1s 73.53
O1s 21.97
Si2p 4.49

 

The composition of copper tape is similar to the following:

peakatomic %
C1s 84.42
O1s 14.15
N1s 1.09
S2p ??? 0.34

 

The composition of the sample holder (if not etched) is similar to the following:

peakatomic %
C1s 69.71
O1s 23.28
Fe2p 2.31
Si2p 1.76
Cr2p ??? 1.40
Ca2p ??? 0.96
Ar2p ??? 0.58

The composition after etching (and leaving out argon) is similar to the following:

peakatomic %
O1s 28.12
C1s 25.63
Fe2p 24.56
Cr2p 11.33
Ni2p3 6.88
Si2p 1.78
Ca2p 1.70

 

The composition of a sample plate (if not etched) is similar to the following:

peakatomic %
C1s 53.77
O1s 35.59
Si2p 2.70
Fe2p3 2.46
N1s 2.22
Mn2p ??? 1.15
S2p ??? 0.92
Na1s ??? 0.68
Te3d ??? 0.49

The composition after etching (and leaving out argon) is similar to the following:

peakatomic %
Fe2p 50.07
O1s 25.88
Cr2p 15.42
Ni2p3 5.87
N1s 2.76

 

The composition of a sample clip (if not etched) is similar to the following:

peakatomic %
C1s 63.93
O1s 20.32
Al2p 11.27
Cu2p3 2.18
Cl2p3 1.37
S2p 0.71
Mn2p3 0.17
Cd3d 0.05

The composition after etching (and leaving out argon) is similar to the following:

peakatomic %
O1s 37.51
C1s 32.48
Cu2p3 14.23
Ca2p 6.07
N1s 2.78
S2p 2.63
Si2p 2.50
Cl2p 1.10
Na1s ??? 0.71

The reference gold sample in the ThermoFisher K-Alpha XPS is typically used for calibrating the XPS. The following scans show what kind of signal can be expected (without etching the sample). It has to be stated explicitly that the actual measurement on another machine can and probably will be quite different, with for example different count rates and resolution.

Au4f

Au4f is the default choice for a detailed gold scan.

Au4d

Au4d is also a good choice because the sensitivity factor is higher than that of Au4f. But the peaks are much wider and lower and the two peaks are quite far apart. The peaks are that much apart that while setting up an experiment they are only offered as such: Au4d5 (BE 332-340 eV) and Au4d3 (BE 350-358 eV). The scan above depicts a manually adapted scan for both peaks (BE 332-358 eV) for which apparently the range also had to be enlarged (BE 325-360 eV).

Au4p

Au4p is third in row as far as sensitivity factor is concerned.The peaks are really far apart and the scan range for Au4p1 (BE 639-647 eV) apparently had to be enlarged (BE 634-652 eV).

Au5p

Au5p has the lowest sensitivity factor at which still two peaks can be clearly identified. The peaks are again that much apart that while setting up an experiment they are only offered as such: Au5p3 (BE 53-61 eV) and Au5p1 (BE 71-79 eV). The scan above depicts a manually adapted scan for both peaks (BE 53-79 eV) for which apparently the range also had to be enlarged (BE 50-80 eV).

Au4s and Au5s

Au4s and Au5s do not show very clear peaks -using the default scan ranges- although Au4s does have a fair sensitivity factor (1.92, which is more than 1.1 for the Au5p3 peak).

The reference silver sample in the ThermoFisher K-Alpha XPS is typically used for calibrating the XPS. The following scans show what kind of signal can be expected (without etching the sample). It has to be stated explicitly that the actual measurement on another machine can and probably will be quite different, with for example different count rates and resolution.

Ag3d

Ag3d is the default choice for a detailed silver scan.

Ag3p

Ag3p is the next best as far as sensitivity factor is concerned.The peaks are also well split and can be used as alternative if Ag3d shows overlap with some other element.

Ag4p

The signal is quite complex not only because the Ag4p peaks overlap, but also because these peaks represent various silver species (elemental silver and silveroxide).
Note: The sample hasn't been etched.

Ag3s and Ag4s

Ag3s and Ag4s do show clear peaks, but in both cases the overall shape has a very high FWHM.
Note:The sample hasn't been etched.

The reference copper sample in the ThermoFisher K-Alpha XPS is typically used for calibrating the XPS. The following scans show what kind of signal can be expected (without etching the sample). It has to be stated explicitly that the actual measurement on another machine can and probably will be quite different, with for example different count rates and resolution.

Cu2p

Cu2p is the default choice for a detailed copper scan.

Cu3p

Cu3p is the next best as far as sensitivity factor is concerned but the peaks are not well split.

Cu2s and Cu3s

Cu2s and Cu3s do show clear peaks, but the Cu2s has a fairly high FWHM.

The composition of the reference phosphor sample is similar to the following:

peakatomic %
 Gd3d3  51
 O1s  39
 S2p  11

So the phosphor contains no phosphorus but rather a gadolinium compound, most likely Gd2O2S, that lights up when irradiated with an X-ray. The real purpose of the phosphor is to calibrate the Z position as shown in the next three pictures:

Z in focus of X-ray

Z too high

Z too low

There are essentially 2 methods to automatically start an experiment at some later point in time. Both these methods will keep the sampleholder in the loadlock until a given time after which the sampleholder will be moved into the analysis chamber after a given time.

These methods allow you to do an initial experiment overnight and to do more refined experiments the following day. Or using one of these methods you can do a really long experiment, for example for 16 hours.

The first method uses the 'Automatically Transfer Sample And Run Experiment After Waiting For nnn minutes' option. This option can be found on the sample page of the experiment panel. When you press the 'Transfer to Analysis Room' button, this will be postponed for a given time.

You can't enter a value for the time in minutes to postpone the actual start of the experiment. All you can do is increase or decrease the current value. In practice this doesn't have to take very long; it takes 7 seconds to go from the minimum value (1) to the maximum value (999).

You don't need additional 'objects' in your experiment to make this work.

The second method uses some additional objects in the experiment.

Add a 'Wait Object' as the first object of your experiment. In the 'Wait Object' properties window you should choose the 'Wait until date and time' option for entering the time when to start the actual experiment. Then add a 'Gun Shutdown' object as the second object of your experiment. In the 'Gun Shutdown Object' properties window select 'Transfer To Analysis' as the sample action. After that the experiment can be set up as normal.

Use these methods with caution:

  • be sure the z value of the selected points are within the correct range; the base plate is appr. at 34 mm, a 1 mm thick sample is at appr. 33 mm
  • use a wider than normal range for the autoheight function, e.g. ± 2.5 mm instead of 1 ± mm
  • be sure that the x,y position is well within the area of the sample; the loadlock camera can be 1 or 2 mm off in both directions
  • restrict this to samples your are familiar with (either films or powders are fine)
  • leave at least 5 hours for the loadlock to be evacuated (earlier similar experiments, with the same number of samples or more samples, should prove that this is valid)
  • be sure you (or your representative) will be available to check the XPS the next morning

Calculate the time to wait or when to start:

now:
delay:
start at:
duration: :
stop at: :

XPS info / ChemE / Delft University of Technology
version 20190603
anything else...
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