EMITECH K1250 Cryogenic Preparation System Instruction Manual

Transcription

1 EMITECH K1250 Cryogenic Preparation System Instruction Manual Emitech Ltd Units 1& 2 Eden Business Centre, South Stour Avenue, Ashford, Kent TN23 7RS Tel Fax emitech.co.uk 1

2 INDEX SECTION 1 DESCRIPTION SECTION 2 INSTALLATION SECTION 3 OPERATION SECTION 4 SPECIMEN PREPARATION SECTION 5 MAINTENANCE AND SERVICE SECTION 6 SPARES AND ACCESSORIES SECTION 7 APPENDIX SECTION 8 REFERENCES SECTION 9 DOCUMENT HISTORY NOTE: For Interfacing details - See specific Instructions for appropriate S.E.M. 2

3 K1250 CRYOGENIC PREPARATION SYSTEM INSTRUCTION MANUAL SECTION INDEX SECTION 1. DESCRIPTION SECTION 2. INSTALLATION 2.1 Preliminary Checks 2.2 Connections 2.2a Rear Panel Control Unit 2.2b Rear Panel Preparation Unit 2.2c Turbo Pump Unit 2.2d Connecting Up Procedure 2.3 Initial Operating Checks 2.3a Sputter System 2.3b Carbon - Radient 2.3c Freezing Chamber (Preparing Subcooled Liquid Nitrogen) 2.3d Sublimation Stage - Preparation Unit - SEM Stage 2.3e Cooling Down SECTION 3. OPERATION 3.1 Front Panel Diagram Preparation Unit 3.2 Front Panel Diagram Control Unit 3.2a Vacuum Section 3.2b Sputter Section 3.2c Carbon Radient Section 3.2d Sublimation Section 3.3 Transferring 3.3a Transfer Stage 1 (Freezing To Preparation Chamber) 3.3b Transfer Stage 2 (Preparation Chamber To SEM) 3.3c Transfer Stage 3 (SEM To Preparation Chamber) 3

4 INSTRUCTION MANUAL SECTION INDEX- Continued SECTION 3. OPERATION- Continued 3.3d Specimen Stub Location On Transferring 3.4 Fracturing 3.4a Macro Knife 3.4b Macro Manipulator 3.5 Coating Techniques 3.5a Sputter Coating 3.5b Carbon Coating 3.5c Metal Evaporation 3.6 Etching Techniques 3.6a Radient Heating 3.6b Sublimation 3.7 Sputter Target Exchange 3.8 Carbon Source Exchange (Metal Evaporation Exchange) 3.9 Protocol Summary 3.9a Start Up Procedure 3.9b Operational Procedure 3.9c Shutdown Procedure SECTION 4. SPECIMEN PREPARATION 4.1 Solid Samples 4.2 Liquid Samples SECTION 5. MAINTENANCE AND SERVICE 5.1 Maintenance 5.1a Specimen Stubs 5.1b Transfer Device 5.1c 'O' Rings 5.1d Transfer Rod Seal 4

5 INSTRUCTION MANUAL SECTION INDEX- Continued SECTION 5. MAINTENANCE AND SERVICE - Continued 5.1e Preparation Chamber 5.1f Preparation Chamber Cold Stage 5.1g Carbon Head 5.1h Sputter Head 5.1i General 5.2 Service SECTION 6. SPARES AND ACCESSORIES SECTION 7. APPENDIX 7.1 Figures 7.2 Fuse Listings 7.3 Electrical Supplies Worldwide 7.4 Pump Plug Wiring Pump Vacuum Connections 7.5 Deposition Charts SECTION 8. REFERENCES 5

6 CE Declaration: This Equipment of this Design and manufacture and marked CE, conforms with the requirements of the European Directives EMC 89/336/EEC & LVD 73/23/EEC. This Equipment will fail safe in the presence of excessive RF, Electrostatic Discharge or Mains Transients. While a loss of function could occur under extreme circumstances the Equipment s operation will be fully recoverable under normal operating conditions. Mains Lead. This Equipment must be Earthed and fitted with the correct lead for the country of operation. This will normally be achieved from the correct mains supply socket Earth Connector. This Equipment is normally supplied from 3 pin supply including Earth. If only 2 pin supply is available a separate Earth must be fitted. The supplementary Earth stud can be used to facilitate this requirement. Output: This is for the pump supply only and is the mains voltage at a maximum of 5 Amps. Output. This is for the preparation unit supply. It is at mains volts at max. of 5 Amps. 6

7 DESCRIPTION SECTION 1 The K1250 Cryogenic Preparation System is fully integrated, having all the facilities for L.T.S.E.M. this includes the preparation unit with its control instrumentation, together with the low temperature stage adaption to the existing sem stage, together with actively pumped vacuum transfer system. The preparation unit has a freezing chamber and a preparation chamber. The freezing chamber can be used to produce sub-cooled (slushy) liquid nitrogen. The frozen specimen can be transferred to the preparation chamber, and subsequently the SEM, using a transfer unit which maintains cryogenic protection. The preparation chamber has facilities for fracturing the specimen, which can be coated with Gold or Carbon, without the need to change heads. The dual Carbon head also has facilities for surface etching using a radient source or for metal evaporation. The system has two controlled heaters, both accurately temperature controlled, and with timing facilities. One heater is located in the preparation chamber, the other heater is located in the SEM coldstage. This allows the temperature to be raised to allow controlled 'bulk' etching of the specimen. The preparation chamber and SEM stage are maintained below -160 o C, which allows a good margin to -130 o C, the point for ice recrystallisation. It is important to avoid contamination of the frozen specimen, and the system has protective shielding. More significantly however, the system has a clean, contamination-free, vacuum by using a hydrocarbon-free turbo molecular pumping system, backed by a two-stage rotary vacuum pump. The System s unique cylindrical design of preparation chamber ensures high efficiency of the turbo unit, together with ease of use of all the chamber facilities. 7

8 INSTALLATION SECTION 2 It is important that this equipment is installed and operated by skilled personnel in accordance with these instructions. Failure to do so may result in damage and impair protection provided. 'If in doubt - ASK'. A suitable location should be provided for the unit - either operated on a bench, or the recommended trolley. The total weight of the System is 64 kg. The system operating environment ambient temperature range is 15 o C to 25 o C in a non condensing relative humidity of not more than 75%. Sufficient ventilation is required, and positioning should be out of direct sunlight. The System is rated for continuous operation other than those supplies specified. (See Section 2.3 a, b & c. 2.1 Preliminary Checks Remove Instrument from packing and place on appropriate operational position. Carry out visual inspection for any signs of transit damage. Remove Accessories Pack, and check contents against K1250 Accessories Pack shipping list. Ensure that all areas of the Instrument are free of loose packaging material. Check specifically the Instrument chamber, and 'L' gaskets. (Do not use vacuum grease on gaskets). Where a vacuum pump has been supplied, carry out preliminary checks in accordance with manufacturers recommendations. (Refer to: Appendix 7.4 for pump plug wiring & Appendix 7.4 for pump vacuum connections.) NOTE: If you are using existing or alternative vacuum pump, and have any difficulty with wiring, please advise. 2.2 CONNECTIONS. Connections should only be made in accordance with Instructions. UNDER NO CIRCUMSTANCES SHOULD ANY OTHER CONNECTIONS OR OUTLETS/INLETS BE USED FOR ANY OTHER EQUIPMENT OR SERVICES. 8

9 2.2a Rear Panel - Control Unit - Refer to: Appendix 7.1 Figure 1 Rear Panel Diagram. Title Rocker Switch Neon Power In Rotary Pump Out Turbo Pump Out Voltage Select A/B/C HT Output Carbon Radient Backing Vacuum (Red) Preparation Vacuum (Blue) Light Supply (Green) Multi-Way Connector SEM Heater (Orange) T1 Thermocouple(SEM) T2 Thermocouple (Prep) Function Main power on to Instrument. Main power on indication. Main power inlet socket Power out to rotary pump controlled by Instrument. Power out to Preparation Unit to supply turbo pump. Voltage select is pre-set for correct supply voltage all to same setting. See NOTE* Sputter output to Preparation Unit. Carbon Head Supply. (Black & Red connector.) Radient Head (Black & Blue connector.) Vacuum reading of backing line manifold to all parts of system, depending which is selected. Vacuum reading of Preparation Chamber. Low voltage supply to viewing light source. Low voltage control signals from control unit to Preparation Unit. Low voltage controlled by SEM temperature controller from control unit to SEM heater. Measures temperature of coldstage on sem from control unit to SEM. Measures temperature of sublimation position of coldstage of Preparation Unit. *NOTE*: A single phase AC supply with Earth is required - selected to the correct voltage for the country of operation. Either nominal 240V or nominal 120V. The voltage and frequency range is: Nominal 240 Max Current 10A 200V - 264V 47Hz To 63Hz Nominal 120 Max Current 20A 90V - 132V 47Hz To 63Hz 9

10 2.2a Rear Panel - Control Unit - Continued Fuse 1 Fuse 2 Fuse 3 Fuse 4 Fuse 5 Turbo Fuse (Internal) Electronics Power Supply Fuse. Vacuum Pump Out Supply. Supply To Preparation Unit (Turbo) Sputter Supply. Carbon/Radient Supply Internal Protection To Turbo Controller. For Fuse Ratings And Voltages Refer To: Appendix b Rear Panel - Preparation Unit - Refer to: Appendix 7.1 Figure 2 Rear Panel Diagram. Title Multi-Way Connector T2 (Thermocouple) Back Vacuum (Red) Preparation Vacuum (Blue) Mains Supply I/P (Turbo) Turbo Supply Output Nitrogen Argon Turbo Backing Transfer Device Dead Space Vacuum (Blue) Transfer Device Chamber Vacuum (Red) Vacuum Pump Function Input from control unit. Input from control unit (as control unit) To control unit To control unit To control unit To rear of turbo pump From nominal 5 psi. Regulated supply for purging From nominal 5 psi regulated supply for sputtering. Goes via needle valve on front of preparation unit. NOTE: if only one gas available - argon can be 'T' off and used for both functions. Connects backing line system to turbo unit. Connects with 3 / 8 vacuum tubing from preparation to transfer device to allow dead space evacuation. Connects with 3 / 8 vacuum tubing from preparation to transfer device to allow chamber pumping and vacuum transfer. Connects backing system to free standing rotary pump. NOTE: - Any other items on rear panel not listed are for common manufacturing and are not available for this Instrument. 10

11 2.2c Turbo Unit The turbo unit is packed separately to the main system, and is readily installed. (a) Remove clamp ring from end of preparation chamber and remove blanking piece. The turbo pump can now be fitted in place, ensuring the 10KF flange outlet to backing system is vertically down. (b) The backing system to the turbo is via a flexible metallic hose with 10KF flange, and nozzle inlet. The nozzle end is connected to the backing line via a knurled 'O' ring & sleeve type connection. Care should be taken to seat 'O' ring correctly on nozzle before retightening knurled nut. 2.2d Connecting Up Procedure The system can now be connected up, assuming the initial sem interface installation has been carried out as separate Instructions. The connections should be self explanatory, and carried out referring to rear panel control unit, and rear panel preparation unit functions list. Carry out process gas connections to rear panel with tubing and connectors provided. (Refer to: Appendix 7.1 Figure 1.) The connector is push-fit and will 'snap' into a locked position. It can be released by depressing the metal tongue. Argon gas is recommended at a nominal pressure of 5 p.s.i. Nitrogen gas is recommended at a nominal pressure of 5 p.s.i. (if only argon used - 'T' off with 'T' pieces provided). The electrical input to the Instrument is made with the power lead provided. The Instrument connection is standard, and the lead is fitted with the appropriate plug for the country of operation. Ensure the plugs are firmly located. Check the three voltage selector switches A/B/C (Refer to: Appendix 7.1 Figure 1.) are to the correct voltage for the country of operation which should correspond to the voltage label on the Instrument. The appropriate electrical supplies for countries are given in Appendix 7.3. The vacuum connection is made by 1.5 metre length of vacuum hosing. This is a push-on fit to the Instrument. Ensure that this is firmly in place to the full length of the vacuum connector. If recommended pump is used, this also has a push-on fit connector (See 7b). Ensure this connector is screwed firmly in place before push fitting vacuum hosing. NOTE:- If you are using an existing or alternative vacuum pump, and have any difficulty with connectors, please advise. An Oil Mist Filter with metal adapter should be fitted to outlet of vacuum pump (See Section 6). Check that the vacuum pump is filled with correct oil (See Section 6). If the vacuum pump is fitted with an ON/OFF switch, ensure that it is left in the 'ON' position as the instrument will carry out recommended control. Ensure that the HT connector to the lid is screwed firmly in place, and also screwed in firmly to the rear panel connection. Connect preparation unit mains (turbo supply). Connect supply to rear of turbo pump from preparation unit, ensuring plug is in place with retaining screw. Connect up back vacuum and preparation unit, ensuring correct notation from preparation unit to control unit. Connect carbon head with 'plug in' connector leads, from control to preparation unit. 11

12 2.2d Connecting Up Procedure - Continued Connect multi-way connector from preparation unit to control unit. This is a locking type connector, ensure it is fully 'home', and in the 'locked in' position. Connect up viewing lamp supply. IMPORTANT: - As this is similar connector to SEM heater stage, check correct identification and location. Connect up SEM heater supply from control unit. IMPORTANT: - As this is similar connector to viewing lamp supply, check correct identification and location. Connect T1 SEM thermocouple lead. NOTE: - These are different thickness contact blades with + and - identification to ensure thermocouples read correctly. Connect T2 preparation thermocouple lead to control unit. NOTE: - These are different thickness contact blades with + and - identification to ensure thermocouples read correctly. Connect up multi-way plug with heater and thermocouple leads to multi-way connector on dewar interface from control unit. NOTE: - This is an accurately locatable keyway connector. Ensure red dot lines up with Red notch. To release - pull back on knurled case which releases the three small latching keys. The male plug can be used to check that the female socket is screwed firmly in place in interface by locating in place and turning firmly clockwise. Connect up 2 x 3 / 8 vacuum tubing from preparation unit to transfer device. The top connection (Blue) on preparation unit is the front dead space on the transfer device. The bottom connection (Red) on the preparation unit is the rear chamber on the transfer device. 2.3 Initial Operating Checks (These should be made having become familiar with the controls under Section 3). 1. Ensure knife and pricker assembly are free to move and clear of cold stage area in Preparation Chamber. (In normal use they will be rested on cooled stage for pre-cooling) 2. Fit stub to transfer rod and locate transfer device on Preparation Chamber, ensuring locating pins are correct. Open transfer device valve and chamber valve, and ensure specimen stub slides freely along the full length of cold stage. IMPORTANT: - The cold stage has two recessed ident ball bearings positioned along its length, it also has an end stop. The first ball bearing positions the stub centrally under the sputtering head. By observation, as the stub is pushed forward under the sputtering head, slight resistance will be experienced - this is the central position. If the stub is pushed further on the stage, the second ball bearing positions the stub centrally under the carbon head. If the stub is pushed further on the stage, the end stop locates the stub on the sublimation stage Inital Operating Checks - Continued 12

13 2. Continued. Re-position and close valves. Horizontal - closed. Vertical - open. NOTE: - The valves are maintained in a locked posiition by a lever, and will automatically 'click' into a locked position when closed. To open - press the knurled top of the lever away, and this will release the valve shaft to allow it to be opened by the rotation of valve rod lever. 3. Check process gases are set at nominal 5 psi regulated pressure. 4. Ensure all controls are set to minimum. 5. Switch on mains electrical supply at rear of control unit. IMPORTANT:- Ensure that sem stage heater and sublimation stage heaters are OFF. This can be seen from led indication, if NOT, press ON/OFF switch once, and LED should go OFF. The SEM and sublimation heaters should NOT be used at ambient temperatures, but only when system is cooled down. Check that controls indicate approx. room temperature. 6. Ensure ALL other functions are in STOP/OFF mode, if not, select STOP/OFF switch as appropriate on the control unit. 7. Ensure all other functions are in STOP/OFF mode on preparation unit. 8. Check that purge gas is present by initiating appropriate purge switches. 9. Select start switch. This will operate rotary vacuum backing pump. At just below ATM. The two safety interlock LED s will illuminate. 10. At 5x10-1 mbar on the backing system, after approx. 5 minutes initial pumping, the associated trip LED will illuminate, accompanied by a short audible 'bleep'. 11. When the backing system has reached 5x10-1 mbar, the turbo pump can be initiated. NOTE: - The turbo controller ON/OFF power switch should be depressed. This is a latching switch, and can be left 'on' as the system will carry out any control. (It can be used as an override). The turbo controller START/STOP functions do NOT need to be operated as the system will carry out any control. 12. To initiate turbo - select preparation chamber evacuate. The 'ACCEL' light will come on. After approx. 1 minute the preparation chamber vacuum will have exceeded 5x10-1 mbar, and the associated trip led will illuminate. This trip will allow sputtering to be selected. Below this vacuum, sputtering cannot be activated. After approx. 3 minutes the preparation chamber vacuum will have exceeded 1x10-2 mbar, and the turbo controller 'norm' light will come on. NOTE:- If, after several minutes the turbo cannot attain it's full operating speed (not vacuum, as it can operate at vacuums down to 5x10-1 mbar without failure), then the fail light will illuminate indicating a gross vacuum leak or turbo pump fault Inital Operating Checks - Continued 13

14 13. Check correct vacuum application to other areas of system by appropriate selection of evacuate switches. 2.3a Sputter System 1. Select on-gas bleed on control unit, and adjust needle valve on preparation unit until preparation chamber vacuum is mid-way between 5x10-1 and 2x10-1 mbar. Allow period to stabilize. 2. Select timer to 1 minute. Select deposition switch, and increase deposition control slowly until a plasma is formed and a reading obtained on the meter. Vary control over range, and set at 20mA. 3. Sputtering will time-out, and switch off. 4. Select 'OFF' switch to stop the gas bleed. NOTE:- The timer, deposition control, and gas bleed needle valve can be left pre-set. It is recommended that occasional checks are made to ensure the required operational parameters are maintained. NOTE:- The sputter coating is rated for a max. 50mA for 5 minutes, with a duty cycle of 50% (off time - 5 minutes). 2.3b Carbon - Radient Carbon - Select Carbon LED 1. Prior to this, check the carbon head has been fitted with a carbon source, as described in Section 3.8, carbon cord is recommended source. 2. Check carbon is selected. Select variable control switch. Increase variable control knob slowly until a small current (5Amp or less with cord) is observed, and the carbon cord glows "dull Red". NOTE:- It is not recommended that the cord is evaporated at this 'preliminary check' stage. 3. Manually select OFF. NOTE:- The carbon variable control is rated for a max of 10A for 2 minutes with a duty cycle of 25% (off time - 4 minutes). The carbon 'flash' (full power) is rated for full power for 5 seconds with a duty cycle of 2% (off time - 4 minutes). CAUTION:- The electrodes may cause burns. 2.3b Radient - Select Radient LED 1. The radient head is located in the same position as the carbon head. This type of head can also be used for metal evaporation. 2. Exchange carbon head for radient head. Check radient is selected. Select variable control switch. Increase variable control knob until current is observed, and the radient filament glows 'Red'. 2.3b Radient - Select Radient LED - Continued 14

15 3. Manually select 'OFF'. NOTE:- The radiant variable control is rated for a max. of 10A for 2 minutes, with a duty cycle of 25% (off time - 4 minutes). CAUTION:- THE ELECTRODES MAY CAUSE BURNS. 2.3c Freezing Chamber 1. Remove large 'perspex' lid by removing locating 'O' ring. 2. Place polystyrene cup. Fill with liquid nitrogen inside retaining holder and 'O' ring. 3. Refit large lid and 'O' ring, and cap. NOTE:- It is not necessary to remove large lid if a suitable filling funnel is available. 4. Evacuate freezing chamber. After approx. 3 minutes liquid Nitrogen will solidify. 5. Switch off 'evacuate', and purge until liquid slush starts to form, then switch off 'purge'. 6. The cap can be removed immediately, and the specimen stub on the transfer rod plunged into the liquid Nitrogen slush. It may ocassionally be necessary to release cap by short Nitrogen purge. NOTE:- Subcooled liquid Nitrogen will maintain its state for several minutes. If not being used immediately, the cap must be left in place. The freezing chamber will have a slight vacuum. When ready to use Nitrogen, purge should be applied to the freezing chamber to allow the release of the cap, and, until transfer device is in place, to stop possible ingress of air which could cause contamination. 2.3d Sublimation Stage - Preparation Unit And SEM Stage. (The same procedure is applicable to both controllers.) 1. To carry out these checks, both the preparation stage and the SEM stage need to be cooled down first. 2. Adjust set point by first pressing SV/PV. The preset temperature is then displayed. To # adjust the preset temperature, first press the arrow below the individual digit. The digit will now flash. To increase the value of the digit, the same arrow should be pressed. To reduce this figure, the " down" button should be depressed. 3. Ensure initial temperature is colder than -130 o C. set -100 o C. On controller set point. 4. Set timer to 10 minutes. 5. Select heater on the set point. Temperature should be achieved within 10 minutes. When the timer times-out, heater will automatically switch off, and temperature will indicate return to original colder conditions. 2.3e Cooling Down. The initial cooling down should be carried out with the turbo pump operational and and all other functions in the 'OFF' mode. The initial usage of liquid nitrogen will be high, but will eventually slow down as temperatures fall below -100 o C. OPERATION SECTION 3 15

16 3.1 Front Panel Diagram Preparation Unit - (Refer to: Appendix 7.1 Fig. 3.) Title Function (Vacuum Measured On Back System Gauge) Solidify liquid Nitrogen Freezing Chamber (Purge) Applies process gas - Nitrogen at nominal 5 psi to back leak to freezing chamber to allow production of sub-cooled liquid Nitrogen. Transfer Device Evacuate (Vacuum measured on back system gauge) Applies vacuum to the dead space of the transfer device, to effect transfer between this and other chambers under vacuum. Transfer Device (Dead space-purge Applies process gas - Nitrogen - at nominal 5 psi. Transfer Device Evacuate (Chamber)(Vacuum measured onto back system gauge.) Applies vacuum to transfer device chamber which can be sealed by the gate valve on the transfer device, and allows a vacuum to be created and maintained whilst transferring specimen to the transfer device chamber. Transfer Device Purge (Chamber) Applies process gas - Nitrogen - at nominal 5 psi. Preparation Chamber Evacuate (measured on preparation chamber gauge). This applies vacuum to the preparation chamber by switching on the turbo to evacuate the chamber and also applying the backing vacuum to back-up the turbo. NOTE:- Cannot be operated until backing vacuum is 5x10-1 mbar or better. Preparation Chamber Bleed Applies process gas -argon- at nominal 5psi for sputtering process. 12V AC Indicates 12V AC control voltages are present. 12V DC Indicates 12 V DC control voltages are present.. 16

17 3.1 Front Panel Diagram Preparation Unit -Continued Title Function Turbo Controller Power ON/OFF Self maintaining switch applies power to turbo controller. NOTE:- Can be left depressed as the system controls turbo controller power. Turbo Controller - Start Non-latching switch to start turbo. NOTE:- Does not need to be operated in normal operation as system controls turbo. Turbo Controller - Stop Non latching switch to stop turbo. NOTE:-Does not need to be operated in normal operation as system controls the turbo. Preparation Chamber Macro Knife (See Fig 5.) Operates by hand on rotating action. Can be adjusted up and down by knurled nut - clockwise to raise. Anti-clockwise to lower. Preparation Chamber With Macro Pricker (See Fig 6) Operates by hand on swivel bearing longitudinal travel along shaft length. Preparation Chamber Sputter Head (See Fig 5) Preparation Chamber Sputters an area approx 25mm Dia on Cold Stage. Evaporates carbon cord or string onto area. Carbon Head 25mm. Dia. on Cold Stage. Preparation Chamber Radient Head Wire basket fitted to two terminals radiates heat on specimen or used for metal evaporation Preparation Chamber 30mm Sublimation Stage Stage heater which warms up the rear of cold stage. 17

18 3.2 Front Panel Diagram Control Unit - (Refer to: Appendix 7.1 Fig. 4) 3.2a Vacuum Section Title Function Vacuum- Backing System Measures the backing vacuum at whichever point in the system has been selected to evacuate. Vacuum - Trip LED illuminates when backing system reaches 2x10-1 mbar, plus audible sound. Vacuum - Preparation Chamber Measures the vacuum in the preparation chamber continuously. Vacuum - Trip LED illuminates when preparation chamber vacuum reaches 5x10-1 mbar. 3.2b Sputter Section Title Function Ma Meter Timer Measures sputtering current range to 50mA- normal operating position - 20mA. Sets sputtering time, can be left pre-set. Normal sputtering time - 1 min. Deposition Control Used to vary sputtering current On-Gas Bleed Operates the electromagnetic valve which backs up the needle valve on preparation unit. This needle valve controls gas flow to preparation chamber, and for sputtering, should be adjusted to give a vacuum mid way between 5x10-1 mbar and 2x10-1 mbar. Deposition Initiates sputtering cycle for the pre-set parameters of current and time. At the end of a cycle the deposition will switch off Off Can be used to interrupt sputtering cycle, and must be used to cancel gas bleed at conclusion of sputtering. 18

19 3.2 Front Panel Diagram Control Unit - Continued - (Refer to: Appendix 7.1 Fig. 4) 3.2c Carbon-Radient Section Title Function Ammeter Measures current depending on which option is selected. Select Switch Indicates which option selected by the Carbon/radient LED's. Variable Control Switch Enables the variable control. Variable Control Knob Allows variable current. When In Carbon Mode For outgassing the carbon cord or string. When In Radient Mode Varies the current through radient heater for surface etching and metal evaporation effected by variable control. Evaporate This applies full volts 25V AC to give full power to 'flash' the carbon source. 3.2d Sublimation Section Title Function SEM Stage This is a smaller heater which raises the Temperature of the complete cold stage of the S.E.M. Temperature Controller Continuously displays stage temperature. Type MDC4E. See Figure

20 3.2 Front Panel Diagram Control Unit - Continued - (Refer to: Appendix 7.1 Fig. 4). (A) Changing Set Values - S.V. 1. Press PV/SV so current setting is displayed (The SV LED will light). 2. Press the 'UP' arrow under the digit you wish to change (this will now start flashing). 3. Press the same 'UP' arrow to step the digit in value or the 'down' arrow to step down in value. (Only the flashing digit can be changed). NOTE: - (a) You will not be able to set a value outside the scale limits (+400 o C To -200 o C). (b) for minus values - use the 'down' arrow after selecting third digit from the right. See separate section on minus values (B). 4. Select a new digit to change and repeat. 5. Press 'E' to enter and store all new settings. (b) If controller is set for minus values - change settings as described in (A). If unit is set for plus values then to change to minus values adopt the following procedure (assume required setting is -55 o C). 1. Press PV/SV so current setting is diplayed (the SV LED will light). 2. Select third digit button from the right (the digit will flash). Select fourth digit button from the right (down button), press several times to achieve a minus value (-100 o C) and enter by pressing 'E' button. 3. Select second button fro the right, and adjust as previously described. Similarly for the first button from the right. assuming 5 & 5 have been selected for second & first button, the display will now show '-155'. 4. To achieve the desired -55 o C (values lower than -100 o C) select third digit button from the right, and reduce to 'O' 5. The reading can be stored by pressing the 'E' button. NOTE: - To get back to plus values from minus - select third digit button from right, then select fourth digit button from right and press several times to achieve 'O' - the minus sign will disappear. Carry out procedure as described in (A). 20

21 3.2 Front Panel Diagram Control Unit - Continued - (Refer to: Appendix 7.1 Fig. 4) Timer 0-20 Mins. This sets the time of sublimation. NOTE: -This time does NOT commence until the preset sublimation temperature has been achieved. On/Off Heater This initiates the stage heater and the timer. At the end of the time period it will switch off automatically. If depressed, it will interrupt timer & heater. NOTE:- The LED will 'FLASH' until the preset sublimation temperature has been achieved and will then stay on through time period. Sublimation Stage Heater This is a small heater which raises the Temperature of the rear section of the cold stage in the preparation chamber. Temperature Controller As SEM stage above Timer As SEM above On/Off Heater This initiates the stage heater and the timer. At the end of the time period it will switch off automatically. If depressed, it will interrupt timer & heater. NOTE:- The LED will 'FLASH' until the preset sublimation temperature has been achieved and will then stay on through time period. CAUTION: SUBLIMATION HEATERS MUST NOT BE OPERATED UNLESS SYSTEM IS COOLED DOWN. 21

22 3.3 Transferring The full transferring protocol will be considered, having first assumed that the sub-cooled liquid Nitrogen has been produced as described in Section 2.3, and that the specimen stub has been prepared under one of the techniques in Section a Transfer Stage 1. Transfer Device-Freezing Chamber-Transfer Device-Preparation Chamber 1. The specimen is withdrawn into the transfer device, and Nitrogen purge is applied to transfer chamber. 2. The cap is removed with 'PURGE' applied to the Freezing Chamber. 3. Locate transfer device on freezing chamber. Switch off purge to freezing chamber. 4. Switch off purge to transfer chamber. Plunge specimen stub into sub-cooled Nitrogen. NOTE:- The Nitrogen will initially 'boil', then subside as temperature equilibrium is reached after approx. 60 seconds. 5. Withdraw specimen stub into transfer device. Close gate valve and select evacuate. NOTE:- To select evacuate requires de-selection of any other evacuate. In the normal mode this would be evacuate on preparation chamber. When this is de-selected, the turbo is also de-selected, but vacuum will be maintained. 6. Remove transfer device from freezing chamber, and locate on preparation chamber (remembering to replace cap on freezing chamber). The vacuum in the transfer chamber should have reached, and exceeded, 5x10-1 mbar within the 30 seconds taken to transfer. 7. Evacuate 'dead space' between transfer device gate valve and preparation chamber gate valve, vacuum should exceed 5x10-1 mbar within 30 seconds. 8. Revert to evacuating transfer device chamber. 9. Open preparation chamber gate valve. 10. De-select evacuate on transfer device chamber, and open transfer device gate valve. 11. Select evacuate on preparation chamber and turbo will again become operational. 12. Locate specimen stub onto cold stage of preparation chamber. NOTE:- When vacuum is not required on any other part of the system, then preparation chamber evacuate should always be in the normal position with the turbo pump operational. 22

23 3.3b Transfer Stage 2. Preparation Chamber - Transfer Device - SEM Chamber NOTE: - Ensure Loading Co-Ordinates Are Pre-Set On SEM. 1. Withdraw specimen stub into transfer device chamber, closing both preparation chamber, and transfer device gate valve. 2. Select evacuate on transfer device chamber. 3. Locate transfer device on gate valve of SEM chamber. 4. Select evacuate on dead space of transfer device. Vacuum should exceed 5x10-1 mbar within 30 seconds. 5. Revert to evacuating transfer device chamber. 6. Open gate valve on SEM. 7. De-select evacuate on transfer device chamber, and open transfer device gate valve. 8. Select evacuate on preparation chamber, and turbo will again become operational. 9. Locate specimen stub on cold stage of sem, having first ensured that the loading coordinates have been pre-set. 10. Withdraw transfer rod, and close gate valve on SEM, subsequently removing the transfer device. 3.3c Transfer Stage 3. Sem Chamber - Transfer Device - Preparation Chamber (or ambient for another specimen). NOTE: - Ensure loading co-ordinates are pre-set on SEM. 1. Locate transfer device on SEM with both gate valves closed. 2. Evacuate transfer device chamber. 3. Evacuate dead space between transfer device gate valve, and SEM gate valve. 4. Revert to pumping the transfer device chamber. 5. Open gate valve on SEM. 6. De-select evacuate on transfer device chamber and open gate valve on transfer device. 23

24 3.3c Transfer Stage 3. - Continued. 7. Withdraw specimen stub into transfer device chamber. 8. Close gate valve on sem, and gate valve on transfer device. 9. Evacuate transfer device chamber, and repeat procedure for transferring to preparation chamber, as described previously. If specimen is to be discarded, de-select evacuate on transfer device, and revert to evacuating the preparation chamber. It would be beneficial to leave transfer device under vacuum by discarding stub, closing off gate valve, and evacuating for a short time. NOTE:- If dry Nitrogen is available as a process gas, then the purge can then be used to ensure a more suitable pumping environment. IMPORTANT: - Do not leave specimens in the SEM if the system is being allowed to warm up to ambient, as the specimen and any mounting medium will sublime, and may contaminate column. Specimens can be left in the K1250 preparation chamber, and infact some workers have used for freeze drying. 3.3d Specimen Stub - Location. Preparation Chamber Cold Stage. The specimen stub has 'V' guides which locate into 'V' guides on the cold stage. It is located on to the transfer rod with a screw thread. The rod should be screwed firmly into the specimen stub. When on the preparation stage it should be unscrewed slightly to prove it can be disconnected freely when required, or this could be more difficult when transferring and disconnecting in the SEM. SEM Coldstage The co-ordinates of the sem must be carefully set before loading the stub onto the SEM cold stage. Allow the rod and stub to find a 'Natural' central position. Try to avoid any excess side play when transferring. With experience this will become relatively easy. When disconnecting the rod and withdrawing, be careful not to catch any threads at the end, thereby dragging the stub off the stage. IMPORTANT:- The stub has spring loaded tension. This should be checked to ensure it holds the stub firmly in place, but not too tight as to make loading and unloading difficult. Also this avoids putting any stress on the sem stage which is usually spring loaded, as any stress would affect the loading co-ordinates. When reconnecting the rod to withdraw the specimen stub from the SEM, ensure co-ordinates are correct. On some stages where there may be a little extra play, certain co-ordinates may have to be 'centralised' by adjusting slightly either side of the loading co-ordinates while moving the rod forward. At the same time, turn the rod slowly in a clockwise direction so that when it locates the thread on the stub, it will screw in more readily. 24

25 3.4 Fracturing 3.4a Macro Knife (See Section 7.1 Fig..5) 1. The knife should be maintained cooled by lightly resting on the cold stage of the preparation chamber. This can be positioned by use of the knurled adjustment. 2. Clockwise raises the height of the knife. Anti-clockwise lowers the height of the knife. 3. Position specimen stub adjacent to the travel of the knife. 4. Adjust the height of the knife to where a suitable fracture point is required. NOTE:- At these low temperatures, a fracture action (rather than a cutting action) will occur following lines of least resistance. However, with care and correct orientation, it is normally possible to achieve the desired fracture. 5. The knife handle should be moved with a positive clockwise action to achieve fracture. NOTE:- Do not return knife handle position as this may 'smear' the specimen on the return path. 6. Raise knife height by approx. One turn on the knurled nut clockwise. The knife can now be returned to normal position. NOTE:- The knife can be used to fracture rivet assemblies for specific preparation techniques. 3.4b Macro Manipulator (See Section 7.1 Fig.6) 1. The manipulator should be maintained cooled by lightly resting on the cold stage of the preparation chamber. 2. The manipulator can be used in longitudinal and transverse movements to achieve fractures and operations not readily achievable with the knife. NOTE:- The manipulator can be used to fracture rivet assemblies for specific preparation techniques. GENERAL NOTE: Fracture debris can be left on the specimen surface. To remove, withdraw the stub until it is just clear of the cold stage. Rotate through 180 o and tap the end of the transfer rod. Re-Align, and re-position stub on cold stage. 3.5 Coating Techniques There are three coating techniques available with the K1250 system: 1. Sputter Coating (Sputter Head) - Sputtering of metal, commonly Gold, Gold/Palladium. 2. Carbon Coating (Carbon Head) - Carbon evaporation by 'flash', using Carbon cord or Carbon String. 3. Metal Evaporation (Evaporation Head) - Metal Evaporation from Evaporation Basket. The two most common requirements (1) and (2) are standard and can be used sequentially or independently, without the need to change heads. The technique (3) uses the same power supply source as the carbon coating, the carbon head being replaced by the evaporation head (which is also the radient head). 3.5a Sputter Coating 25

26 (Assuming initial set up has been carried out as section 1.) This procedure would normally be carried out after initial uncoated evaluation and appropriate fracturing and etching (sublimation) had been performed and assuming we now require to view the specimen at higher magnification. 1. Position specimen stub under the centre of the sputtering head (Fig.5). 2. Select on-gas bleed and allow approx. 60 seconds for vacuum to stabilise at between 5x10-1 and 2x10-1 mbar, assuming the needle valve has been pre-set. 3. Select deposition, assuming timer and deposition control have been preset. Typically 1 minute at 20mA is coating of 20nm. 4. At the end of time period, sputtering will stop automatically. It can be interrupted at any time by off switch. 5. Switch off argon at end of sputtering period. NOTE:- For changing target See Section 5.1h. 3.5b Carbon Coating Assuming initial set up has been carried out, and that a carbon source has been fitted as described in Section Position specimen under carbon head (See Fig.5) operate select switch to select carbon LED. 2. Select variable switch and increase variable control until a small current, approx. 3 Amps, is present, and the carbon source glows red. Allow outgassing process to take place for approx. 30 seconds then de-select variable control switch. NOTE:- The conditions for outgas current will vary depending on whether Carbon Cord or String is used. Cord is the recommended, and if used exclusively, the outgas parameters can be left pre-set. 3. Operate evaporate button, this will put full power on the Carbon source which will break as part of the process, this is normal. However, with familiarity, breaking of the carbon source can be avoided, and therefore getting 2 or even 3 operations from one loading of carbon source if carbon cord is used. To achieve this, apply power using variable control, NOT evaporate switch, in short bursts of 1 second, visually inspecting the specimen for sufficient Carbon Coating. NOTE:- For changing of carbon source - See Section

27 3.5c Metal Evaporation The decision to change the head would normally have been made prior to coating, and the appropriate metal for evaporation would be made in the basket. However, heads can be interchanged during operation by using the same procedure as in note above. See Section Operate select switch to select Carbon LED. 2. Select variable switch, and increase variable control until the basket glows 'white hot', and evaporation takes place. 3. Repeat (2) above in short bursts, inspecting specimen until sufficient material has been deposited. 3.6 Etching Techniques It is often necessary to etch the surface of the specimen. Reasons for etching are as follows: 1. It will remove superficial water droplets and films derived from environmental sources either naturally, or as contaminants. Thus, features of the specimen surface can be exposed that would otherwise be obscured. 2. It provides information on the nature, location, and source of extra-cellular secretion. 3. It accentuates the differences between fluid filled and gas filled compartments. 4. It enhances mass density differences between aqueous and organic regions of fracture faces, which enables greater distinctions to be made between cell types or layers within a tissue. 5. It can give us qualititive information on the amount and distribution of water, concentration of ice nucleation sites, and possibly the rate of freezing within cells and tissues. This information is based on the spacing of segregation zones caused by ice crystal damage. The K1250 has two techniques which achieve similar effects, but are termed differently to enable a distinction to be made. 3.6a Radient Heating (Surface Etching) A heat source is radiated onto the surface of the specimen to achieve etching - this technique is available only in the preparation chamber. This is used for coarse surface etching of a specimen, particularly when a lot of 'surface' water has to be removed. 1. Exchange carbon head for radient head. Position specimen under radient head. 2. Operate select switch to select radient LED. 3. Select variable switch and increase variable control until a small current flows. Increase until the radient heat glows Red, at approx. 5 Amps. 4. Leave set for approx. 60 Seconds. NOTE:- This is a course technique, and will need familiarity with operation and examination of specimen in the SEM to determine actual parameters for optimum radient etching. 27

28 3.6b Sublimation (Conductive Etching) The complete specimen temperature is raised by conductive means to achieve etching. The technique is available in both the preparation chamber and in the sem, the procedure for both being the same. However, in the SEMm, the process can be observed. Again, having established the parameters, it may be preferential in the preparation chamber to avoid contamination. The amount of etching required will vary, and is very sensitive to temperature. The following gives a guide as to the general order of sublimation rate: -130 o C 1x10-4 /Second (Ice recrystallisation point rate considered negligible for L.T.S.E.M.) -120 o C 1x10-2 /Second -100 o C 1nm /Second -70 o C 100nm /Second -50 o C 1000nm/Second A typical etching would be 3 mins. at -70 o C. However, as there are warm up and cool down times, together with any thermal delays, any precise calculation is not possible. Generally such parameters will be arrived at empirically. Typical warm up/cool down rate : 15 o C./minute. Provision of a timer allows good repeatability of the conditions. Remembering that etching will be occurring as we approach our set point, we can either position the specimen on the sublimation stage during the process, or alternatively position it when the set point has been reached. The latter is preffered, as it would more accurately compare the sublimation conditions as carried out under observation in the SEM, to those of the preparation chamber where we cannot observe. NOTE:- the timer only starts when the set point is reached. The following procedure is applicable to both the preparation chamber - sublimation stage, and to the electron microscope - SEM Stage. 1. Ensure dewars are topped up with liquid Nitrogen. 2. Position specimen stub on sublimation stage. 3. Select desired set point sublimation temperature on the temperature controller (typically -70 o C.) 4. Set timer as required (typically 3 Minutes):timer only starts when set point is reached. If specimen is on the stage, some sublimation will take place during 'warm up' and 'cool down'. 5. Select on/off heater. Heater will operate and switch off at end of time period. If interrupt is required re-select on/off heater. 6. At end of time period, allow specimen to stabilise to at least -120 o C although sublimation is minimal below -100 o C. NOTE:- After initial conditions have been established, these may be left pre-set for subsequent sublimation of specimens. 28

29 3.7 Sputter Target Exchange (See Section 7.1 Fig.7). The target should be checked for wear occasionally as it should not be necessary to exchange 'insitu' under cool down conditions. Ensure mains supply is off, and disconnect ht connector from sputter head. 1. Remove sputter head. 2. Unscrew target anticlockwise. 3. Fit new target which will already be bonded to backing plate. NOTE:- It may be easier to remove ring magnet to screw target in position. Then replace ring magnet which is held in place by its own magnetic attraction. 4. Replace head and reconnect HT connections. 3.8 Carbon Source Exchange (See Section 7.1 Fig.8) Ensure supply is off, and disconnect supply leads to head. 1. Select the appropriate carbon evaporation source. NOTE:- For two or three carbon string, twist together to form one source. For carbon cord, ONLY use as a single length. 2. Fit carbon source in 'straight' length between electrodes. The electrodes have spring loaded contact studs, under which the end of the carbon source can be loaded by positioning in the location slots in the electrodes. Trim any surplus carbon source either side of the electrodes. 3. It would be normal to fit carbon source before cooling down, and getting 1 or 2 coatings as previously described. It is possible to change 'in-situ' under cool down conditions as follows: a. Attach transfer device to preparation chamber with its gate valve closed, and pump out dead space. b. Open gate valve of preparation chamber, and allow it to pump out dead space. c. De-select evacuate on preparation chamber. d. Select purge on dead space, and the preparation chamber can be filled with dry Nitrogen gas until a positive pressure is achieved. e. Remove carbon head, and replace with blanking plate. f. Replace carbon source as in (1) and (2) above, and re-fit carbon head. g. Switch off purge, close gate valve, and select chamber evacuate. NOTE:- A similar procedure would be used when exchanging or replenishing the metal evaporation source if this head was being used instead of carbon head. (see Fig.9.) 29

30 3.9 Protocol Summary 3.9a Start Up Procedure (Assuming all connections made as in Installation) 1. Select start to switch on rotary pump at 5x10-1 mbar on backing system, select evacuate to switch on turbo. 2. At 1x10-2 mbar on preparation chamber, and with turbo in normal mode, commence cool down of preparation chamber cold stage. Typically 15 Minutes to -120 o C. Total liquid Nitrogen usage for days operation - 10 Litres. 3. Pump down SEM, and at normal operating vacuum commence cool down of cold stage. typically 15 Minutes to -120 o C. Total liquid Nitrogen usage for days operation - 5 Litres. 3.9b Operational Procedure 1. Plunge-freeze specimen using sub cooled liquid nitrogen at -210 o C. 2. Transfer to cold stage of preparation unit for initial viewing. 3. Carry out fracture procedure as required, depending on nature of specimen. 4. Transfer to SEM cold stage and view uncoated, fully hydrated, at low magnification x500 to x Etch the specimen if required. Typical time : 9 Minutes at -70 o C. a b Under observation in SEM. Or In preparation Chamber. NOTE:- The majority of specimens will require some etching, usually whilst being observed until familiarity is established, at which time the preset parameters may be used. This assumes surface topography is the prime interest. For X-ray, this may not be necessary. 6. Coat the specimen - most commonly this is sputter coating. a b c Sputter coat at vacuum between 5x10-1 mbar and 1x10-1 mbar in Argon for 1 minute at 20mA. Or Carbon Coat using Cord for X-Ray Microanalysis. Or Metal Evaporation using Tungsten Basket. 7. Transfer to cold stage of sem, and view coated at higher magnifications x5000 to x Note:- ltsem cannot be considered a high resolution technique as longer working distances have to be used, and there is an increase in interference signals from fully hydrated frozen specimens. 8. Remove specimens at end of the examination period. 30