Quadrupole Mass Filter

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OXFORD APPLIED RESEARCH

Quadrupole Mass Filter

Quadrupole Mass Filter QMF200

OXFORD APPLIED RESEARCH

QMF200 Operation and Maintenance

 Oxford Applied Research Nanotech House, Nursery Rd North Leigh Business Park Witney Oxfordshire OX29 6SN United Kingdom Telephone: (0)1993 880005 Fax: (0)1993 880060

http://www.oaresearch.co.uk Sales: [email protected]

Table of Contents Safety Principle of Operation

1 3

Quadrupole Mass Spectrometry Mass Resolution

3 4 4

The QMF200

4

Installation

6

Mounting and Pump Down

6

Source Bakeout

6

Electrical Connections

6

Operation

9

Front Panel Control of the Power Supply Filter Mode Scan Mode Cluster source Mode Other Information

9 10 14 15 16

Notes on Operating the QMF200 with the NC200U Nanocluster Source Acquiring a Mass Spectrum Mass-Selecting Clusters Frequency Effects Using the QMF200 to Focus Cluster Ions

17 17 18 18 19

QUVI-2 Software Control Overview Installation

20 21

Operation of the QMF200 using software control 22 Quadrupole Parameters 22 Cluster source Parameters 23 Scan Parameters 24 Acquiring a Scan 24 Scaling the data on the Screen 24 Storing and Viewing Multiple Spectra 25 Other Features 25 Maintenance

27

Quadrupole removal and cleaning

27

Quadrupole Exit Apertures

29

Specifications

31

i

Quadrupole Mass Filter

31

Power Supply

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Oxford Applied Research Quadrupole Mass Filter – QMF200

Section

Version: 2.0

1 Safety

U

sers of this equipment must be made aware of the hazards associated with its use. Throughout this manual attention is drawn to the safety hazards as follows;

!WARNING! Failure to observe a warning could lead to injury or death to personnel.

!CAUTION! Failure to observe a caution could lead to damage to the equipment. Failure to observe these cautions will invalidate the warranty

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 2.0

(i.)

Become familiar with the principle of operation of the equipment and be aware of the function and operating voltage of each part of it.

(ii.)

Disconnect the power supply from the mains before adjusting any of the cables.

(iii.)

Disconnect the electrical feedthrough leads before handling the source.

(iv.)

Do not probe the power supply or the connector leads. There are no user serviceable components within them.

(v.)

Ensure that all electrical, control, water, and gas connections are properly made.

(vi.)

Ensure that all of the equipment is properly earthed (grounded).

(vii.)

Ensure that there is sufficient ventilation for the electronics unit. The air intakes are in the base of the box with the outlet at the rear.

!WARNING! Failure to earth the equipment could lead to high voltages appearing on exposed surfaces.

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Section

Version: 2.0

2

Principle of Operation

T

he QMF200 quadrupole mass filter can be used to analyse and filter charged nanoparticles from the NC200U nanocluster deposition source. This section briefly explains the basic principles of quadrupole mass spectrometry and describes the QMF200 mass filter.

Quadrupole Mass Spectrometry Mechanically the core of the quadrupole assembly consists of four rods and a detector plate on which the cluster ion current can be measured. The opposite rods are electrically connected to each other. A voltage, which has a dc and ac component (of frequency f), U+Vcos 2πft is applied to one pair of poles; the negative (-U-Vcos 2πft) is applied to the other pair (see figure 1). The cluster ions enter along the axis of the quadrupole and oscillate due to the electric field. Clusters can be selected according to their mass to charge ratio by the quadrupole electric field so that only ions of a defined mass will be transmitted to the ion detector plate. The quadrupole acts as a band-pass filter. The parameters which can be varied to allow clusters of a particular mass to pass through the filter are U, V and f. Detector

- (U+Vcos2πft)

U+Vcos2πft

Cluster Ions

Figure 1: Quadrupole schematic

Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Mass The mass (M) is directly proportional to the amplitude of the ac voltage (V) and inversely proportional to the square of the frequency (f2) applied to the poles: M=7x107(kV/f2d2)……….1 Where d is the diameter of the poles and k is a correction factor. Scanning V, whilst monitoring the ion current from the quadrupole exit, allows a mass spectrum of the cluster beam to be acquired. The ratio of U/V (resolution) must be kept constant throughout. The frequency applied to the poles determines the mass range over which is scanned. Resolution The ratio of U/V defines the width of the cluster mass band transmitted through the filter. This relationship can be proven by solving the Mathieu equations for particle trajectories along a quadrupole† . The theoretical resolution can be expressed as: ∆M/M = 7.936(0.16784-(U/V))……..2 As the ratio of U/V is increased the narrower the mass band transmitted through the filter. Theoretically it should be possible to resolve one particular cluster mass; however in reality the optimum resolution is determined by a number of other parameters including the mechanical construction (diameter, tolerance and length of rods) and variations in the initial cluster ion energy. There is also a large compromise between the resolution and the cluster flux. The optimum resolution is given by the expression: ∆M = 4x109 Vz/f2L2…....3 Where Vz is the energy of the ions and L is the length of the quadrupole rods.

The QMF200 A schematic of the un-mounted QMF200 is shown in figure 2. Grounded entrance and exit apertures shield the cluster beam from the end of the quadrupole rods and also help to define the beam. An isolated aperture plate beyond the exit aperture is used to monitor the transmitted cluster ions. This plate can also be biased (+12V or – 12V) to extract more of the ions from the beam during measurement of the cluster size. Ion steering plates fitted at the end can be used to separate the ionised mass-selected cluster beam from the neutral cluster beam. Unlike other quadrupole devices the QMF200 does not require an ioniser before the entrance †

D. Bassi: in Atomic and Molecular Beam Methods, G.Scoles(ed.), Vol I, Chap 8, (Oxford University Press, Oxford 1988)

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

aperture since the NC200U source produces a high content of ionised clusters (typically >30%) and these can be utilised by the filter. The QMF200 has a variable voltage range of 1-250V and a frequency range of 3100kHz. The quadrupole rods are 2.54cm in diameter and have a length of 25cm. These parameters allow particles to be measured and filtered between ~30 and ~3x106 a.m.u. The typical usable cluster size resolution is ~ 2%. The mechanical resolution should, in theory, be better than 0.01%, however in order to achieve a useful flux, in conjunction with the source, it is not practical to obtain this value. The QMF200 has two operational modes. The “scan” mode allows the user to scan V (and hence the cluster mass) whilst monitoring the cluster ion current. During this operation the U/V ratio is kept constant and U cannot be controlled by the user. The “filter” mode allows the user to select a chosen V (mass) and adjust the resolution (U/V).

Cluster ion steering plates

Entrance aperture Mounting plate

Quadrupole rods

Exit aperture

Figure 2: Schematic of un-mounted QMF200

5

Ion collection aperture plate

Oxford Applied Research Quadrupole Mass Filter – QMF200

Section

Version: 3.0

3

Installation Mounting and Pump Down •

Standard UHV practice should be adopted in installing the QMF200 quadrupole mass filter.

•

The QMF200 comes ready mounted within a straight tubulation or differential pumping T-piece depending on customer requirements. The filter should be mounted with the deflection plates facing into the chamber and the opposite flange facing towards the NC200 nanocluster source.

Source Bakeout •

The QMF200 can be baked to 150oC but all external electrical cabling must be removed beforehand.

Electrical Connections !WARNING! Failure to earth the equipment could lead to high voltages appearing on exposed surfaces. Ensure that the GROUND connection (grounding stud, figure 3) of the power supply is connected to same ground as the system

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Grounding stud Air vent from cooling fan

Interlock connector (2 pin) Input connection from ion current Mains input collector plate (universal voltage) Connection to ReBus100 (3 pin) remote interface for PC remote Output to X and Y control option deflection plates (5 pin) (4 pin)

Output connection to quadrupole rods

Interlock connector shorting link

Quadrupole rod-pair 2 (Q2)

Y deflection plate (Y)

Quadrupole rod-pair 1 (Q1)

Collector plate (C)

X deflection plate (X)

Focussing lens (L) Not connected BNC shorting link

Figure 3: QMF200 electrical connections

The following electrical connections should be made from the power supply to the instrument. •

Quadrupole Output – Connect the blue BNC cable from the Quadrupole power supply (labeled “output” on the back of the power supply) to the 2 BNC flange connections. The BNC connections are labeled Q1 and Q2 on the flange,

•

Ion Current Input Connect the black wire with the 3 pin connector to the connection labeled “collector” on the power supply and to the BNC connection labeled “C” on the quadrupole

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•

Ion Steering Plates and focus facility –. Connect the cables labeled X and Y up to the X and Y BNC feedthroughs and to the X,Y connector on the back of the power supply. Optionally one of the X or Y voltages may be connected to the focusing lens (labeled “L”) depending on user requirements. Whichever connection (X,Y or L) is not used should be shorted out to ground using the BNC shorting link supplied. This will prevent charging of the disconnected isolated plate which might cause unexpected distortion of the cluster beam. !WARNING! It is recommended that the BNC shorting link is used for the disconnected plate to prevent charging

•

Remote Connection – If software has been supplied connect the multipin cable from the “remote” connection on the power supply to the ReBus200 interface box. Do not plug in the USB cable from the ReBus200 to the PC until the software installation has been completed as described later in this manual.

•

Interlock connection – The QMF200 can optionally be used with an interlock switch which will disable the power supply outputs if the interlock connection is broken. This could be used with an appropriate pressure gauge over-pressure trip for example. If this facility is used, it should be noted that the maximum recommended operating pressure of the QMF200 is 1x10-3 mbar. If the user does not wish to make use of this facility, the interlock connection shorting link shown in figure 3 should be connected to the port labeled “interlock” on the back panel. This connector permanently connects the two pins of the interlock connection together. !WARNING! The interlock connection must be made to operate the power supply without any error messages

!WARNING! Ensure that the power supply is switched off when making these connections and never remove the OUTPUT connections when the power supply is turned on.

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Section

Version: 3.0

4

Operation

B

efore operating the equipment ensure that all personnel are familiar with the contents of this manual. Also ensure the following:


The instrument is installed in a vacuum system whose operational pressure is below 1x10-3mbar.
The electrical connections from the power to the quadrupole are made.

Front Panel Control of the Power Supply This section describes the control of the QMF200 using the front panel of the power supply. For operation using the software control please refer section 5 of this manual. All operating parameters of the QMF200 may be set via the single control knob on the front panel, and their status viewed in the digital multi function display screen. The control knob is used by rotating in either direction until the desired value is displayed on the digital display and then depressing the knob in order to make a selection or accept the displayed value. Power on/off switch

Control knob

Multi-function display screen

Figure 4 QMF200 power supply front panel

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Turn on the power supply using the orange on/off switch. An animated OAR logo will be displayed for a few seconds. Once the animation has finished, depress the control knob once to clear the logo. There are two main operation modes of the QMF200, scan mode and filter mode. Scan mode is used to establish the mass distribution of clusters emerging from the cluster source; filter mode is used to select the desired portion of this mass distribution for deposition onto the sample. Filter Mode The filter mode screen will be displayed as shown in figure 5 after the logo screen is cleared on first start-up. Remote / Local control mode status indicator

Figure 5. The power supply display panel when in filter mode

The filter mode screen also doubles as a set-up screen for setting up all the parameters prior to scanning. In order to change a parameter, depress the control knob so that the pop-up menu is shown on the screen (figure 6). Select the desired parameter from the menu by rotating the knob and depress the control knob again. The control knob may now be rotated in order to control that parameter. The parameter which is currently being controlled is denoted in the filter mode screen by an arrow “>” on the left hand side.

Pop-up menu box

Figure 6. The power supply display showing the menu

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Some items in the pop-up menu will launch a sub-menu, these items are shown between two arrows “<” and “>”. The menu items are described as follows: •

X deflection: Sets the voltage on the X axis deflection plates at the quadrupole exit between -100 and +100 V. This voltage is used to deflect the charged clusters (which have been mass filtered) away from the neutral clusters which are not affected by the mass filter. In order to ensure that only the mass filtered beam is deposited onto the sample, the sample should be placed off axis and the deflection voltage used to deflect the charged clusters onto the sample. The voltage required will be determined by the sample position and size.

•

Y deflection: As above but for the plates in the Y axis deflection plates

Note: If desired, one of the X or Y axis deflection voltages may be attached to the focus electrode instead and be used to focus the cluster beam. See “Electrical connections” in section 3. •

Frequency: Adjusts the frequency of the AC voltage (V) applied to the quadrupole rods between 3 and 100 kHz.

•

V: Adjusts the amplitude of the AC voltage applied to the quadrupole rods between 0 and 250V. As this value is adjusted, the displayed value of U (the DC voltage bias applied to the rods) will be observed to change according to the resolution which is set. The displayed mass will also change, so it can be seen that by adjusting V the selected mass for the filter mode is changed (equation 1).

•

Resolution: Adjusts the cluster mass band passing through the quadrupole for a given selected mass. The value is adjusted between 2% and 100% ∆M/M. This equates to a U/V value between 0.165 and 0.042 respectively according to equation 2 on page 4. Note that when a low percentage value is selected, the flux of nanoclusters passing through the filter is correspondingly reduced.

•

: Mass Calibration Factor – This is the correction factor used in equation 1 (on page 4). It can have a value between 0.5 and 2 and is used by the processor in the supply to calculate the cluster mass. It should be used when calibrating the cluster mass with other characterisation techniques such as TEM or AFM. The default value for this is 1.0.

•

: This menu displays the following options: -

Filter mode: Change the display mode to filter mode (this option should be used to enter the filter mode when the display is in scan mode or cluster source mode)

-

Scan mode: Change the display mode to scan mode

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

•

-

Cluster Source Change the display mode to show Cluster source parameters

-

:This menu displays the following options 

Invert display: If this option is selected everything on the screen is displayed as a negative image. Everything black becomes white and vice versa. This may make the display easier to see under certain light conditions.



: Adjust the contrast of the display to optimize it for the best viewing under the ambient light conditions.

: -

Remote ON: Switches the power supply to remote control mode so that all parameters are controlled from the QUVI2 software on the PC. See section 5 for further information. The software must be running and the power supply connected to the PC via the ReBus200 interface box before this option is selected. Any parameter settings for f, V, resolution, X and Y from the power supply front panel will be disregarded in this mode.

-

Remote OFF: Will enable control from the power supply front panel. Any parameter settings for f, V, resolution, X and Y from the PC software will be disregarded in this mode.

The current remote / local status is shown by the status indicator in the top right of the screen (figure 5). “No remote” is displayed if remote control is selected but the software is not running or the PC is not connected. •

: -

Ouputs ON: Switches on the output voltages to the quadrupole for V,U, f, X and Y.

-

Outputs OFF: Switches off the output voltages to the quadrupole.

The current status of the outputs is shown by the indicator in the top left of the screen as either “O/P’s: OFF” or “O/P’s: ON”. !WARNING! Do not forget to switch on the quadrupole outputs before attempting to make a scan!

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

•

: -

: 

Positive ions: Changes the polarity of the Y axis in scan mode to positive.



Negative ions: Changes the polarity of the ion current (Y axis) in scan mode to negative.

Note: the display in scan mode only shows one polarity of ions at a time. If nothing can be seen on the screen, it may be that the current is the opposite polarity from the one selected. -

-

: 

Full scale 2 nA: Changes the scale of the Y axis to a 2 nA or -2 nA maximum depending on the ion polarity selected. This option is useful when the ion current level is low and mass spectrum cannot easily be seen on the screen.



Full scale 20 nA: Changes the scale of the Y axis to a 20 nA or -20 nA maximum depending on the ion polarity selected.

: This feature is used to apply a bias voltage to the ion collector plate. This can be used to extract more ions from the beam for current measurement when the measured current is low. 

Zero bias: No bias voltage is applied to the collector if this option is selected.



Negative bias: A bias voltage of -12V is applied to the collector to extract more positively charged cluster ions from the beam.



Positive bias: A bias voltage of +12V is applied to the collector to extract more negatively charged cluster ions from the beam.

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Scan Mode The scan mode allows a mass spectrum of the clusters from the NC200 source to be acquired. To access the scan mode go to the menu as described above and select Scan mode. The scan mode screen layout is shown in figure 7. Resolution

Ion current meter input status indicator

Frequency of AC voltage on quadrupole rods Output status indicator (”ON” or “OFF”) Y axis: Ion current (nA)

Scan status indicator (”STOP” or “PLOT”) Current value of AC voltage on rods (V)

Plotting area X axis: AC voltage (V)

Figure 7: SCAN MODE page layout

In the scan mode all the quadrupole output parameters are also displayed, however to change their values, the user must revert to the filter mode screen. In scan mode some of the menu items for parameter control are replaced with new ones for controlling the scanning process (figure 8). The voltage is shown along the X-axis and the cluster ion current is shown along the Y axis. The plot parameters can be selected from the new items in the menu as described below.

Pop-up menu Figure 8: Menu in scan mode

•

Stop Scan: Will stop a scan currently in progress. The current scanning status is shown on the right hand side of the screen (figure 7). Stop scan will change the displayed status from “PLOT” to “STOP”. Any displayed spectra will be cleared from the screen when this option is selected.

•

Start Scan: Will start a scan. The AC voltage (V) will then be scanned and the ion current value plotted on the screen. To stop the plot at any time, select stop scan from the menu. The scanning process will continue until

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

stop scan is selected, with multiple spectra being superimposed onto each other. •

<Start Point>: Sets the start voltage for the scan.

•

<Stop point>: Sets the stop voltage for the scan.

•

: Sets the range of voltages on the X axis which are displayed. This does not have any effect on the voltage range actually being scanned. To change this the start point and stop point options should be used.

•

: Mass Calibration Factor –(see Filter mode fro description)

•

: (see Filter mode fro description)

•

: (see Filter mode fro description)

Cluster source Mode The cluster source mode allows access to the mass/flow controllers and the aggregation length, motor controls on the NCU200 cluster source.. To access the Cluster Source mode go to the menu as described above and select Cluster Source mode. The Cluster source mode screen layout is shown in figure 9. Resolution

Ion current meter input status indicator

Frequency of AC voltage on quadrupole rods Output status indicator (”ON” or “OFF”) Y axis: Ion current (nA)

Scan status indicator (”STOP” or “PLOT”) Current value of AC voltage on rods (V)

Plotting area X axis: AC voltage (V)

Figure 9: CLUSTER SOURCE MODE page layout

In cluster source mode the NCU 200 input gas mass/flow controllers & motorized aggregation length parameters are displayed. To change their values, the user must enter the appropriate menu. change the setpoint, then turn the control on or off.. The cluster source mode display shows the setpoints and actual readings for both process gasses and the motorized “Z-shift” aggregation length (figure 10). The menu options are as described below.

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Figure 10: Menus in Cluster mode

•

: This is the NCU200 cluster source main process gas control. Use the knob to select the required the mass/flow setting on the slider scale.( figure 10) Pressing the knob for the first will select the desired value. The arrow should now disappear and the knob can be turned to select the valve ON or OFF actions, pressing the knob for the second time will activate your selection and return to the cluster source mode display.

•

: This is the NCU200 cluster source secondary process gas control. Use the knob to select the required the mass/flow setting on the slider scale. Pressing the knob for the first will select the desired value. The arrow should now disappear and the knob can be turned to select the valve ON or OFF actions, pressing the knob for the second time will activate your selection and return to the cluster source mode display.

•

: Aggregation length Adjust. Use the knob to select the required the aggregation length on the slider scale. Pressing the knob for the first will select the desired value. The arrow should now disappear and the knob can be turned to select the motor ON or OFF actions, pressing the knob for the second time will activate your selection and return to the cluster source mode display.

•

>Back< returns to cluster source mode display

•

: ( see filter mode fro description)

•

: ( see filter mode fro description)

Other Information • Turning the power supply off – First deactivate remote mode if engaged and close down the PC software (QUVI2). Turn off the outputs using the menus and turn the power supply off using the orange switch on the front panel.

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Notes on Operating the QMF200 with the NC200U Nanocluster Source Acquiring a Mass Spectrum 1. Turn on the NC200U source as described in the separate NC200 manual. 2. Turn on the QMF200 power supply unit. 3. Monitor the ion current of the cluster beam with the outputs turned off. The current will vary as the source warms up and it will take a few minutes to equilibrate. 4. Vary the cluster source parameters to achieve an ion current of the order of >0.1nA. (positive or negative). NOTE: A bias can also be applied to the quadrupole ion collection aperture plate. This will draw some of the ions out of the beam that passes through the aperture and lead to an increase in the detectable ion current. The collector plate bias value is set in the ion meter menu as described above. 5. With an ion current of >0.1nA (positive or negative) switch on the outputs. Allow the power supply a few minutes to warm up. 6. Set V to around 150V and optimise the ion current by varying the frequency. The frequency is used to set the mass range covered by a scan from 1-250V (equation 1). The lower the frequency, the larger the mass range. If the ion current exceeds the maximum value increase the resolution (U/V), or increase the ion current range from 2nA to 20nA. Note the maximum value of the ion current. 7. Once a suitable frequency has been determined reduce V to zero and enter the scan mode. 8. In scan mode select the polarity of the clusters according to the previously observed ion current. 9. Take a scan of the clusters. If the full spectrum does not fall within the screen then decrease the frequency. This will increase the mass range over which the spectrum is taken (see equation 1). 10. Adjust the source parameters and observe the shifts in the spectra for various source conditions (refer to the test data for examples).

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Mass-Selecting Clusters 1. Once a mass spectrum of the desired cluster size has been achieved switch to filter mode. 2. Go to the desired cluster mass by varying V. 3. Adjust the resolution (U/V) as required, whilst monitoring the ion current. Note: The nominal current should be higher than 1nA in order to deposit a fraction of a monolayer (ML) in a reasonable amount of time (as a rough guide 1nA corresponds to ~10% of a ML in an hour). 4. If using the collector bias, switch this off to allow all ionised clusters to pass through the aperture. 5. Apply the required voltage to the beam steering plates and expose the substrate (off-axis) to the beam. Note: The required voltage used in steering the clusters will depend on the cluster size and the polarity. The deposited beam will not result in two separate spots (i.e the neutrals and the ionised clusters) but a broadening of the beam. As an example for ~6nm diameter clusters at distance of 100mm the neutral beam diameter is ~18mm. With a +10V steering voltage applied the beam broadens on both sides (due to positive and negative clusters) to a diameter of 32mm. therefore putting the sample off-axis by 10mm will result in the deposition of the mass-selected ionised clusters. Frequency Effects At lower frequencies there is a drop in the overall transmission of the quadrupole due to fringe field effects. Using higher frequencies will give a larger ion current also give the highest degree of accuracy for mass peak measurement. In addition at low values of the resolution (U/V) there may be shifts in the spectra peak positions for different frequencies. This can be overcome by winding the resolution up to the maximum achievable.

!WARNING! When high frequency is used (higher than 90 kHz), do not operate the power supply more than one hour continuously.

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Using the QMF200 to Focus Cluster Ions The QMF200 can be used to focus the ionised clusters along its axis and can improve the deposition rate at the sample. In this case the resolution must be set at 100% to give the best deposition rate.

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Oxford Applied Research Quadrupole Mass Filter – QMF200

Section

Version: 3.0

5

QUVI-2 Software Control Overview The QUVI-2 control software package is designed to be used solely with the Oxford Applied Research QMF200 Quadrupole Mass Filter. The software allows complete remote control and monitoring of the instrument.

Figure 11: QUVI control window

The software is designed to run on IBM compatible computers with the following minimum specification:
750 MHz processor speed
64 MB RAM
Windows 98SE or later (ME / 2000 / XP)
Free USB port
Display resolution 1024x768 pixels or more All software was written in Visual Basic 6.0 and, as such, a number of VB run-time libraries are required, these will be installed on running the setup program. 20

Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Installation IMPORTANT: Before connecting the anything to the computer, the software should be installed first. 1) First make sure that all other programs are closed down before installing the software. Insert the OAR QUVI2 CD into your CD-ROM drive. 2) If the contents of the CD are not automatically displayed, you should double click on “My computer” on the Windows Desktop and then double click on your CD-ROM drive. 3) First of all the driver for the ReBus200 USB remote interface should be installed. Run the executable file called “SUB-20”. Follow the instructions on the screen and accept all the default options. 4) Second the QUVI-2 software itself should be installed. This can be found in the “OAR” folder on the CD and can be installed by running the “setup.exe” installation program. 5) Connect the cable with the 5 pin “DIN” connectors at both ends to the ReBus200 control box (connection labeled “I2C Bus”) and to the QMF200 power supply (connection labeled “remote”). Ensure that the screw fitting is tightened at both ends. 6) Now connect the USB cable from the connector labeled USB on the ReBus200 controller to a spare USB port on your PC. This can be done while the PC is switched on. 7) As soon as the ReBus200 is connected to the USB port, the found new hardware wizard should appear with a message saying the new hardware (“I2C bridge U2C-12” or “U2C-12 USB-I2C/SPI/GPIO Interface Adapter”) has been found. You should select not to use Windows Update to search for software updates and select to install the software automatically. You may get a message saying that the software has not passed the Windows Logo testing to verify its compatibility with your version of Windows. You should select to “continue anyway” at this point. The software is now installed and ready to use.

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Operation of the QMF200 using software control To enter software control mode, follow these steps: 1) Run the QUVI-2 program. A shortcut to this will be found in the start menu under “OAR QMF200” and “QUVI-2” assuming that the steps in the installation section have been followed. 2) Turn on the power supply. 3) Using the menu system as described in section 4, switch the power supply into remote control mode. 4) The remote local status indicator in the bottom left of the software screen should now indicate "Control: QUVI Software". And the status indicator in the top right of the QMF200 power supply display should indicate “REMOTE”. 5) Switch on the quadrupole outputs using the button labeled in figure 9. The writing on the button change from red to green to indicate outputs have been switched on, and the status indicator at the bottom of the software screen should indicate "Outputs: ON" if this message has been received by the power supply. Additionally the indicator on the power supply screen will also show this. Quadrupole Parameters As for front panel control, the following parameters can be set up or monitored. Parameters are displayed twice, once in green for the set value and once in red for the actual value. If the set and actual values differ, check that remote mode is engaged and that the outputs are switched on. To enter a new set-point, use the up and down arrows next to each parameter, alternatively simply edit the setpoint by typing it in and press return to set the new value. •

Frequency – This can be set from 3-100kHz. The actual frequency value is displayed in red and the mass range (in a.m.u.) over which the scan will take place is shown below the frequency display.

•

Resolution – This can be set from 100% to 2%. The equivalent U/V value is also displayed below. If the “show resolution” button is depressed the mass range for the currently selected voltage is shown in the grey area of the scan window. This is useful when using the QMF200 as a filter, so that the mass range

•

Voltage – This can be set from 0-250V for the purposes of mass filtering. The cluster parameters for the voltage and frequency selected are shown in

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

the top half of the cluster information panel. Note that the correct material must be selected in order to display the correct values for diameter and number of atoms (n). Cluster source Parameters As for front panel control, the following parameters can be set up or monitored. Parameters are displayed twice, once in green for the set value and once in red for the actual value. If the set and actual values differ, check that remote mode is engaged and that the outputs are switched on. (the maganetron voltage & current parameters may differ as the power supply switches between constant voltage & constant current mode ) To enter a new set-point, use the up and down arrows next to each parameter, alternatively simply edit the setpoint by typing it in and press return to set the new value. •

Argon Flow – This can be set from 0-100 sccm. The actual mass flow value is displayed in red and the Valve on/off condition is shown on a green/red indicator next to the flow on/off button.

•

Helium Flow – This can be set from 0-100 sccm. The actual mass flow value is displayed in red and the Valve on/off condition is shown on a green/red indicator next to the flow on/off button.

•

Agg. Position – (Z shift) This can be set from 0 to 100mm. The equivalent U/V value is also displayed below. If the “show resolution” button is depressed the mass range for the currently selected voltage is shown in the grey area of the scan window. This is useful when using the QMF200 as a filter, so that the mass range

•

Mag. Voltage – This can be set from 0-500V for the purposes of generating a plasma in the magnetron. The voltage setpoint (limit) is shown in green and the actual monitored value is shown in red. Note when a plasma is obtained, the monitored voltage may fall below the setpoint if the magnetron current is equal the setpoint limit. The voltage output can be turned on or off using the button below the monitored value.

•

Mag. Current – The setpoint current limit can be adjusted from 0 – 1.2A. Set values are shown in green and actual values in red.

•

Mag. Power – this monitor of power input to the magnetron is calculated from the voltage & current monitors. Note: The Magnetron power supply parameters are remotely sent via an RS232 link, directly from the PC com port (or USB com port) .The magnetron power supply is not controlled via the QMF200 PSU. If the Magnetron power supply does not respond to remote commands, please check ‘Com port settings’ under the tools menu. The correct settings will not take effect until the software program is closed and restarted.. 23

Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Scan Parameters The following scan parameters can be set up: •

Scan from: The starting value of V for the scan

•

Scan to: The ending value of V for the scan

The mass value equivalent to each of these voltages is shown below. Acquiring a Scan Once the parameters above have been set a scan can be taken: •

Scan - This will start a mass spectrum over the range set. The data from the scan will be kept in one of the 5 memory slots selected in the “use” section on the right hand side of the window. This data can be saved to a file for later use.

•

Scan cont –This will continue scanning and show each scan on the screen. A limited number of scans will be saved in the memory slot selected in the “use” section on the right hand side of the window. Once the memory slot is full the data is erased and scanning process starts again. This cycle will be repeated indefinitely until the user presses the stop button.

• •

Stop – Stops the scan at any time. Clear - This button will erase all data from the 5 memory slots and clear the screen.

Scaling the data on the Screen To fit the scan to the screen: •

Scale Screen to Range – by pressing the “Scale Screen to Range” button under the frequency slider the spectrum is fitted to the mass range of the frequency selected.

•

Offset Slider – This positions the zero offset of the cluster ion current on the screen.

•

Scale – This expands the vertical scale of the cluster ion current.

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

•

This button will expand the screen so that it fits the spectrum with the maximum and minimum observed values.

•

This button will expand the display to show the full range of the quadrupole.

•

Mass/Diameter selection – The spectrum can be either displayed as a function of the mass or the diameter. Note that the diameter information is only correct if the correct material has been selected.

Storing and Viewing Multiple Spectra A total of 5 spectra can be stored and viewed. To use a spectrum select one of the “use” option buttons. If a spectrum is now taken (or loaded from a file) the data is temporarily stored to this number and will overwrite any previous spectrum. To view the spectrum on the display screen select the show check box of the desired spectrum. Up to 5 spectra can be viewed on the screen at once. •

Info – The Info button will show the information about the spectrum selected. Additional information about the cluster source parameters can also be added by editing the boxes with red text. These cluster source parameters may then be set as the default for future spectra so that they need not be re-entered for every spectrum.

•

Save– To save a spectrum ensure that the “use” option button of the spectrum is selected. Enter the file name and save. Note : the data is stored as a type .qu2. This is a comma delimited ASCII data file which can be imported into Notepad, Excel or data analysis programs.

•

Load - To load a spectrum first ensure that the data stored under the “use” number is saved. Only .qu2 type files can be loaded up.

Other Features • Material Selection – To load a new material select the “Load New” button. Select an element from the periodic table provided by clicking on that element. Data on the density and atomic mass will be loaded from memory. Alternatively for non-elemental or compound targets, the material name, density and unit mass may be entered manually. Selecting the correct material is essential for the diameter calculation in the software. The material information is saved when the software is closed down and restarted.

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

•

Calibration factor – The calibration factor (k in equation 1) can be set using the box below the material data.

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Oxford Applied Research Quadrupole Mass Filter – QMF200

Section

Version: 2.0

6

Maintenance The performance of the QMF200 may deteriorate over time due to a build up of clusters on the apertures and quadrupole rods.

Quadrupole removal and cleaning 1. Remove the 2 NW35CF BNC feedthrough flanges and disconnect the connections from the vacuum side. Note or mark the connectors X,Y etc. 2. Carefully undo the 8 M3 countersunk screws which hold the assembly within the tubulation. Support the quadrupole and remove it from the Tpiece assembly. 3. Remove the outer quadrupole shield. 1 x M3 radial screw and 1 x M3 nut at the collector plate end and put the quadrupole on its side. The quadrupole base can now be removed and replaced if necessary.

Figure 10: Un-mounted quadrupole

4. . Take care when feeding the quadrupole connections through the hole in the can.

Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

5. Remove the quadrupole connecting cable from the pole by removing the M3 cap head screw with an Allen key. Remove , clean and replace each rod individually. Note that the opposing poles of the quadrupole are electrically connected.

Figure 11: Pole connections

6. To remove the poles take out the screws which hold the poles against the Macor blocks and slide the poles out. Note: The Macor blocks can be easily chipped. Take care not to knock them hard with the poles. 7. The poles are best cleaned with, for example, isolproyl alcohol or acetone. Try to avoid abrasive cleaners. 8. On re-assembly ensure that the poles are aligned and the correct electrical connections are made.

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Quadrupole Exit Apertures The exit apertures may, after time, become blocked with clusters. The apertures can easily be removed and cleaned by removing the 4 M3 nuts which secure them. The inner plate is grounded. The second plate is isolated and used for the collection of the cluster ions. The outer plate is also isolated and may be externally grounded, or connected to a voltage supply for use as a focus electrode. Note the position of these plates and the ceramics when disassembling.

Figure 12: Order of aperture plates (note old design and connectivity shown)

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Oxford Applied Research Quadrupole Mass Filter – QMF200 Version: 3.0

Figure 13: Electrical connectivity of apertures (current design)

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Oxford Applied Research Quadrupole Mass Filter – QMF200

Section

Version: 3.0

7

Specifications Quadrupole Mass Filter Mounting: Poles diameter: Poles length: Total length: Quadrupole first aperture: Grounded outer inner aperture: 5mm Ion collection plate aperture: Grounded outer aperture:

in tubulation or T-piece. 25.4mm 25mm 285mm 13mm 4mm 5mm

Power Supply General Frequency range: AC voltage range: DC voltage range: X and Y Steering voltage range: Internal ammeter range: External Input (if provided): Mains: Input mains voltage: Protection: Fuses: Fused Externally:

3-100kHz 0-250V 0-50V -100V to +100V +/- 0.04 nA to +/- 20nA Set up for Keithley 6485 picoammeter. 0 to +/- 1V (+1V= -10nA, -1V= +10nA) Universal - 85-264 VAC 47-63Hz VDE approved IEC320 input mains filter 6.3AT @ 230V 10AT @ 110V

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Oxford Applied Research Quadrupole Mass Filter – QMF200

Section

Version: 3.0

8

Please contact us directly at the address below: Oxford Applied Research Nursery Rd North Leigh Business Park Witney Oxfordshire OX29 6SN United Kingdom Telephone: (0)1993 880005 Fax: (0)1993 880060

http://www.oaresearch.co.uk

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