Omicron Tip Etching Kit User manual

Tip Etching Kit User Manual
Version 1.2 • 16 December 2014
Help Line:
German Headquarters and Service Centre:
Scienta Omicron GmbH
Limburger Str. 75
65232 Taunusstein, Germany
Tel.: [phone] / 987-230
Fax: [phone]
E-Mail: [e-mail]
M6171

Preface 2 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
Preface
This document has been compiled with great care and is believed to be correct at the date of print. The
information in this document is subject to change without notice and does not represent a commitment on the
part of Omicron NanoTechnology GmbH.
Notice
Some components described in this manual may be optional. The delivery volume depends
on the ordered configuration.
Notice
This documentation is available in English only.
Notice
Please read the safety information on pages 8 to 9 before using the instrument.
Copyright
No part of this manual may be reproduced or transmitted in any form or by any means, electronic or
mechanical, including photocopying and recording, for any purpose without the express written permission of
Omicron NanoTechnology GmbH.
Warranty
Omicron acknowledges a warranty period of 12 months from the date of delivery (if not otherwise stated) on
parts and labour, excluding consumables such as filaments, sensors, etc.
No liability or warranty claims shall be accepted for any damages resulting from non-observance of
operational and safety instructions, natural wear of the components or unauthorised repair attempts.

Preface 3 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
Waste Electric and Electronic Equipment
In compliance with the WEEE directive (2002/96/EC) OMICRON ensures that all products supplied by
OMICRON which are de-commissioned and which are labelled with a WEEE Registration Number will be
taken back by OMICRON free of charge.
All costs of packing, transport, duty, etc. to the destination of the nearest OMICRON Returned-WEEE-Centre
shall be borne by the customer. The customer is required to:
Declare the returned material is free from contamination or hazardous materials
from usage (include Decontamination Declaration sheet),
Request a valid Return Material Authorisation (RMA) available from the OMICRON
service department,
Ship all returned goods to the advised destination "OMICRON Returned-WEEE-
Centre, DDP (INCOTERMS)".
Otherwise OMICRON will not accept any shipment.
Normal Use
The Tip Etching Kit shall always be used
with all cabling connected and secured, if applicable
with all electronics equipment switched on
in an indoor research laboratory environment
by personnel qualified for operation of delicate scientific equipment
in accordance with all related manuals.
Warning
Lethal Voltages!!
Adjustments and fault finding measurements as well as SPM experiments in
environments other than UHV may only be carried out by authorised
personnel qualified to handle lethal voltages.
Attention
Please read the safety information in the relevant manuals before using the instrument.

Preface 4 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
Conditions of CE Compliance
OMICRON instruments are designed for use in an indoor laboratory environment. For further specification of
environmental requirements and proper use please refer to your quotation and the product related
documentation (i.e. all manuals, see individual packing list).
The OMICRON UHV System complies with CE directives as stated in your individual delivery documentation
if used unaltered and according to the guidelines in the relevant manuals.
Limits of CE Compliance
This compliance stays valid if repair work is performed according to the guidelines in the relevant manual and
using original OMICRON spare parts and replacements.
This compliance also stays valid if original OMICRON upgrades or extensions are installed to original
OMICRON systems following the attached installation guidelines.
Exceptions
OMICRON cannot guarantee compliance with CE directives for components in case of
Changes to the instrument not explicitly agreed by OMICRON, e.g. modifications,
add-on's, or the addition of circuit boards or interfaces to computers supplied by
OMICRON.
The customer is responsible for CE compliance of entire experimental setups according to the relevant CE
directives in case of
Installation of OMICRON components to an on-site system or device (e.g. vacuum
vessel),
Installation of OMICRON supplied circuit boards to an on-site computer,
Alterations and additions to the experimental setup not explicitly approved by
OMICRON
even if performed by an OMICRON service representative.
Spare Parts
OMICRON spare parts, accessories and replacements are not CE labelled individually since they can only be
used in conjunction with other pieces of equipment.
Notice
CE compliance for a combination of certified products can only be guaranteed with respect
to the lowest level of certification. Example: when combining a CE-compliant instrument
with a CE 96-compliant set of electronics, the combination can only be guaranteed CE 96
compliance.

Preface 5 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
Contents
Preface...............................................................................................................................................................2
Copyright .................................................................................................................................................2
Warranty..................................................................................................................................................2
Waste Electric and Electronic Equipment................................................................................................3
Normal Use..............................................................................................................................................3
Conditions of CE Compliance..................................................................................................................4
Contents ..................................................................................................................................................5
List of Figures ..........................................................................................................................................5
List of Tables ...........................................................................................................................................6
1. Introduction..................................................................................................................................................7
2. Safety Information .......................................................................................................................................8
3. General .......................................................................................................................................................10
4. The Etching Control Unit...........................................................................................................................12
Front Panel............................................................................................................................................12
Rear Panel.............................................................................................................................................14
5. Cut-Off Procedures....................................................................................................................................15
Threshold Cut-Off ..................................................................................................................................15
Differential Cut-Off.................................................................................................................................15
6. DC Etching in Solution (Threshold Cut-off).............................................................................................16
7. DC Etching in Solution (Differential Cut-off) ...........................................................................................18
8. DC Etching "Lamella"................................................................................................................................20
9. Trouble Shooting .......................................................................................................................................22
10. Literature ..................................................................................................................................................23
Service at Omicron.........................................................................................................................................24
Index ................................................................................................................................................................25
List of Figures
Figure 1: Control unit front panel, schematic diagram. .....................................................................................12
Figure 2: Control unit rear panel, schematic diagram. ......................................................................................14
Figure 3: DC etching in solution, schematic diagram........................................................................................16
Figure 4: DC etching in solution, schematic diagram........................................................................................18
Figure 5: DC etching in lamella, schematic diagram.........................................................................................20
Figure 6: Meniscus slides down........................................................................................................................22

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List of Tables
Table 1: Tip etching materials classified........................................................................................................... 10
Table 2: Advantages and disadvantages of the etching methods. ................................................................... 11
Table 3: Tip etching parameters for polycrystalline tungsten tips in solution.................................................... 17
Table 4: Tip etching parameters for polycrystalline tungsten tips in solution.................................................... 19
Table 5: Tip etching parameters for polycrystalline tungsten tips in lamella..................................................... 21

1. Introduction 7 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
1. Introduction
The Tip Etching Kit is a device for producing sharp tungsten tips with smallest local radii of the tip apex. The
so-etched tips are well suited for use in STM, FIM, FEM and SEM.
The tip etching kit is a hardware and electronics package consisting of the following components
a control unit with adjustable etching voltage
a set of cables
an etching mount (tripod) with height adjustable rod
three insets for tip reception
a glass beaker
a stainless steel electrode (= cathode) for DC etching in solution
an Allen key 1.5 mm
a pair of tweezers
a pair of cutting pliers with hard metal inset
tungsten wire (0.38 mm )
The tip etching device shall always be used
with all cabling connected and secured, if applicable
with all electronics equipment switched on
in an indoor research laboratory environment
in accordance with all related manuals.

Attention
Please read the safety information in the relevant manuals before using the instrument.

2. Safety Information 8 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
2. Safety Information
Caution
Important:
Please read this manual and the safety information in all related manuals before
installing or using the instrument or electronics equipment.
The safety notes and regulations given in this and related documentation have to
be observed at all times.
Check for correct mains voltage and grounding/earth before connecting any
equipment.
Do not cover any ventilation slits/holes so as to avoid overheating.
The Tip Etching Kit may only be handled by authorised personnel.
Warning
Warning: Lethal Voltages!!
Adjustments and fault finding measurements may only be carried out by authorised
personnel qualified to handle lethal voltages.
Lethal voltages are present inside the control unit.
Caution
Always
All connectors which were originally supplied with fixing screws must always be
used with their fixing screws attached and tightly secured.
Always disconnect the mains supplies of all electrically connected units before
opening a control unit case,
touching any cable cores or open connectors,
Leave for a few minutes after switching off for any stored energy to discharge.

2. Safety Information 9 Tip Etching Kit User Guide
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Caution
NaOH Causes Severe Burns!
In case of contact with eyes, rinse immediately with plenty of water and seek
medical advice.
Always wear suitable gloves and eye/face protection when handling NaOH
solution.
In case of accident or if feeling unwell remove victim to fresh air and seek medical
advice immediately (show label when possible).
Store and use in areas with adequate ventilation and away from acids.
Caution
This product is only to be used:
indoors, in laboratories meeting the following requirements:
altitude up to 2000 m,
temperatures between 5°C / 41°F and 40°C / 104°F (specifications
guaranteed between 20°C / 68°F and 25°C / 77°F)
relative humidity less than 80% for temperatures up to 31°C / 88°F
(decreasing linearly to 50% relative humidity at 40°C / 104°F)
pollution degree 1 or better (according to IEC 664),
overvoltage category II or better (according to IEC 664)
mains supply voltage fluctuations not to exceed 10% of the nominal voltage
Condensation of humidity, particularly on water-cooled equipment, must be
avoided.

3. General 10 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
3. General
STM tips are normally made from cut-to-size pieces of high purity metal wire. There are many different ways
to make tips for atomic resolution, the very first STM tips simply were mechanically ground. A standard
method for STM tip fabrication is electro-chemical etching.
Different tip materials and diameters require different etching methods while the tip shape can be influenced
by varying the etching parameters. The metal wire for tip fabrication may be vacuum-annealed prior to
etching, but polycrystalline tungsten wire as received from the manufacturer also yields atomic resolution tips.
Tungsten tips may be etched in KOH or NaOH.
Notice
Tungsten wire pieces may be produced by cutting or breaking: Cut wire pieces
perpendicular to the wire axis prior to etching. Attention: Tungsten wire is very hard and
may damage your cutting device. Annealed tungsten wire can be fractured. Do not cut the
wire after etching!
The supplied tungsten wire is as received from the manufacturer. You may want to anneal the tungsten wire
prior to etching; to do so glow under vacuum (110-4 is sufficient) at a temperature of 2700 K for about 1 min.
After etching rinse the tips in distilled water and check for irregularities using an optical microscope.
Additionally in-vacuum tip treatments, e.g. field emission, may be used if required.
The prepared STM tips are inserted into the tip carrier tube. Use the supplied pair of tweezers to fix the tip in
the tube.
The following tip materials can be treated.
Tip Material
DC Solution
DC Lamella
polycryst. W
yes
yes
W(100)
yes
yes
W(111)
yes
yes
PtIr
no
no
Pt
no
no
Ir
no
no
Au
no
no
Table 1. Tip etching materials classified.

3. General 11 Tip Etching Kit User Guide
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Advantages and Disadvantages of Etching Methods
The Tip Etching Kit is supplied with insets for holding the tip during etching. These are a bare wire inset for
holding pieces of wire directly and two tip holders with adapters for different AFM and STM instruments.
In the tip holders a tungsten wire piece can be mounted prior to etching so that the complete tip holder may
afterwards be introduced into the SPM without any further handling of the fragile tip. However, care must be
taken not to wet the tip holder with the etching liquid or washing water, since considerable amounts of liquid
may otherwise collect in the capillaries of the tip / tip holder assembly and spoil your vacuum afterwards.
This manual introduces two different etching methods for tungsten tips. The following table lists the
advantages and disadvantages of these methods.
DC Solution
DC Lamella
Advantage
no supervision required
80% of the tips achieve ideal shape
ideal tip shape
smallest curvature
bottom end of tip may also be used
Disadvantage
dissolving takes about 1 day at room
temperature
meniscus may shift
needs constant supervision
Table 2. Advantages and disadvantages of the etching methods.
The tip etching control unit in addition also offers two different current cut-off methods. These may be
combined with the etching methods to give a total of three etching procedures described further on in the
manual.

4. The Etching Control Unit 12 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
4. The Etching Control Unit
Front Panel
Figure 1. Control unit front panel, schematic diagram.
Push-button switch with optical status indicator.
Green LED is lit during etching
(DIFF. mode or THRESHOLD mode).
Yellow LED is lit when wire touches the surface in TIP ADJ. mode.

4. The Etching Control Unit 13 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
Selectable digital display for threshold current, etching voltage and etching current.
3-position rotary knob for selecting display signal to be
threshold current in milliamps,
etching voltage in volts, or
etching current in milliamps.
Push-button switch for starting the etching process.
Push-button switch for stopping the etching process.
3-position rotary knob for selecting
etching with threshold function (responds to threshold current)
tip adjustment for moving the tip into the liquid
etching with differential limit stop (responds to current change)
Ten-turn potentiometer for pre-selecting the automatic switch-off sensitivity. This
input is only active if the mode selector OPERATION is set to "Diff.". Range: 0 to
10 units.
Ten-turn potentiometer for setting the (nominal) voltage between tungsten wire (tip)
and ring electrode continuously between zero and +10 V.
Ten-turn potentiometer for setting cut-off threshold between zero and 25 mA. This
input is only active if the mode selector OPERATION is set to "Threshold".

4. The Etching Control Unit 14 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
Rear Panel
Figure 2. Control unit rear panel, schematic diagram.
Banana monitor sockets for etching current:
red = +
black = -
small = earth/ground
0-10 V output for 0-100 mA etching current
maximum current output 20 mA
3-pin Renk socket for connecting the control unit to the etching mount. 0-10 V
output for 0-100 mA etching current.
Resistive output impedance of the tip etching device is 110 .
This unit is supplied with a 3-pin standard European mains socket for AC
input of 85-265 V ±10% and 50 or 60 Hz. Maximum power input 10 VA. The wire
insulations of the standard 3-lead mains cable are coloured in accordance with the
following code:
Brown: Live
Green/Yellow: Earth
Blue: Neutral
Mains fuse(s): 5 mm , 20 mm long
use 500 mA T for 85-265 VAC
To change the fuse
disconnect mains
lift the flap using a screw driver for leverage
replace the fuse as indicated above
re-fit the fuse holder.

5. Cut-Off Procedures 15 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
5. Cut-Off Procedures
In order to achieve high quality tips it is absolutely vital to cut the etching voltage in the instant the etched tip
or excess end of wire drops down. The tip etching control unit offers two different methods for detecting the
end of the etching process. Both methods employ the fact, that the etching current decreases when one end
of the wire drops down.
Threshold Cut-Off
The threshold method sets a minimum current (threshold) and compares the etching current to this value.
When the etching current is equal or below the threshold the etching voltage is switched off. This method is
not very accurate as it cannot detect very small current changes. It is, however, rather simple to use and
independent of small changes in NaOH concentration, wire length etc.
This method is well suited for DC etching in solution, it cannot be used for lamella etching (due to the small
current changes involved)
Differential Cut-Off
The differential method sets a current variation I (Diff.) and matches all current changes against this value.
When the current changes by more than I, the etching voltage is cut. This method can detect very small
current changes. This fact may, however, also lead to premature cut-offs.
This method can be used for both etching recipes but is the only choice for the lamella etching procedure.

6. DC Etching in Solution (Threshold Cut-off) 16 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
6. DC Etching in Solution (Threshold Cut-off)
Remarks concerning DC-etching of tunnel tips
Prepare a NaOH-solution from 100 ml distilled or de-ionised water and 20 g NaOH
pellets (see table 3). Attention: add pellets slowly! The pellets must be completely
dissolved - at room temperature this takes about 24 hours.
Fill the beaker of the tip etching device with part of the solution and insert the
cathode into the etching liquid.
Use 0.38 mm W-wire and cut (or break if annealed) off pieces for tunnel tips:
final length + insertion depth (2 mm).
Connect the electronics to the etching device using the provided cable set.
Fix a piece of tungsten to a holder and insert this into the reception of the etching
mount. Tighten the nuts firmly.
Switch the control unit on and set the desired etching voltage.
Switch the mode selector to "Tip Adjust" to move down the piece of tungsten into
the centre of the ring electrode by turning the hand wheel.
When the piece of wire touches the liquid surface (signal noise and "TIP IN FLUID"
lights up) lower the tip by another 2 mm (about 2 turns on the hand wheel). Make
sure the tip is adequately wet.
NaOH
W
cathode
anode
tip holder
Figure 3. DC etching in solution, schematic diagram.

6. DC Etching in Solution (Threshold Cut-off) 17 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
Set the front panel display to show the threshold current and adjust the Threshold
potentiometer for the desired stop current value, see table 3. If this current is
reached the etching voltage is cut and the etching process stops. Upon automatic
switch-off the electronics gives an optical and acoustic signal.
Set the OPERATION selector to "Threshold" and press START to start the etching
process.
The etching process produces H2at the cathode and the tungsten wire is etched
primarily at the liquid surface.
Leave the tip in the solution until the end drops and the current ceases to flow. The
power supply must be cut in the instant when the tip drops to ensure a sharp point.
Remove the tip and dip it into distilled water at least 10 times.
Check the shape of the tip with a microscope: for optimum quality, the tip should be
a symmetric V-shape and the apex should not be resolved in an optical microscope
at "500" magnification.
Store tips in a dry environment (desiccator) or in vacuum.
Thoroughly clean the tips with distilled water again directly before use, otherwise
NaOH crystallites may remain on the point. Additionally in-vacuum tip treatments,
e.g. field emission or vacuum annealing (several minutes at 1000°C and
p<10-4 mbar), may be used if required.
Table 3 gives an etching recipe.
Solution
20 g NaOH per 100 ml H2O distilled
Ring electrode
stainless steel, diameter app. 36 mm, thickness 0.5 mm to 1.0 mm
U
3 V…10 V DC
Iini
50 mA to 70 mA depending on insertion depth
Ifin
20 mA
Threshold
3 mA to 5 mA
Duration
5 min to 10 min depending on NaOH concentration, etching voltage and wire
diameter
Table 3. Tip etching parameters for polycrystalline tungsten tips in solution.
Notice
For this etching procedure the differential cut-off method may also be employed

7. DC Etching in Solution (Differential Cut-off) 18 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
7. DC Etching in Solution (Differential Cut-off)
Remarks concerning DC-etching of tunnel tips
Prepare a NaOH-solution from 100 ml distilled or de-ionised water and 20 g NaOH
pellets (see table 3). Attention: add pellets slowly! The pellets must be completely
dissolved - at room temperature this takes about 24 hours.
Fill the beaker of the tip etching device with part of the solution and insert the
cathode into the etching liquid.
Use 0.38 mm W-wire and cut (or break if annealed) off pieces for tunnel tips:
final length + insertion depth (2 mm).
Connect the electronics to the etching device using the provided cable set.
Fix a piece of tungsten to a holder and insert this into the reception of the etching
mount. Tighten the nuts firmly.
Switch the control unit on and set the desired etching voltage.
Switch the mode selector to "Tip Adjust" to move down the piece of tungsten into
the centre of the ring electrode by turning the hand wheel.
When the piece of wire touches the liquid surface (signal noise and "TIP IN FLUID"
lights up) lower the tip by another 2 mm (about 2 turns on the hand wheel). Make
sure the tip is adequately wet.
NaOH
W
cathode
anode
tip holder
Figure 4. DC etching in solution, schematic diagram.

7. DC Etching in Solution (Differential Cut-off) 19 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
Switch the mode selector to "Diff." and adjust the Sensitivity: potentiometer for the
desired stop current difference I, see table 4. If this value is reached the etching
voltage is cut and the etching process stops. If the sensitivity is set too low the
etching voltage may not be cut even when the tip drops. If the sensitivity value is
set too high the etching process may be stopped even if the tip is not etched off
completely. Upon automatic switch-off the electronics gives an optical and
acoustical signal.
Press START.
The etching process produces H2at the cathode and the tungsten wire is etched
primarily at the liquid surface.
Leave the tip in the solution until the end drops and the current ceases to flow. The
power supply must be cut in the instant when the tip drops to ensure a sharp point.
Remove the tip and dip it into distilled water at least 10 times.
Check the shape of the tip with a microscope: for optimum quality, the tip should be
a symmetric V-shape and the apex should not be resolved in an optical microscope
at "500" magnification.
Store tips in a dry environment (desiccator) or in vacuum.
Thoroughly clean the tips with distilled water again directly before use, otherwise
NaOH crystallites may remain on the point. Additionally in-vacuum tip treatments,
e.g. field emission or vacuum annealing (several minutes at 1000°C and
p<10-4 mbar), may be used if required.
Table 3 gives an etching recipe.
Solution
20 g NaOH per 100 ml H2O distilled
Ring electrode
stainless steel, diameter app. 36 mm, thickness 0.5 mm to 1.0 mm
U
3 V…10 V DC
Iini
50 mA to 70 mA depending on insertion depth
Ifin
20 mA
Sensitivity
6.0
Duration
5 min to 10 min depending on NaOH concentration, etching voltage and wire
diameter
Table 4. Tip etching parameters for polycrystalline tungsten tips in solution.
Notice
For this etching procedure the threshold cut-off method may also be employed.

8. DC Etching "Lamella" 20 Tip Etching Kit User Guide
December 2014 Omicron NanoTechnology Version 1.2
8. DC Etching "Lamella"
Notice
The ring electrode required for lamella etching, see figure 5, is not supplied with the
instrument.
Prepare a NaOH-solution from 100 ml distilled or de-ionised water and 8 g NaOH
pellets (see table 5). Attention: add pellets slowly! The pellets must be completely
dissolved - at room temperature this takes about 24 hours.
Fill the beaker of the tip etching device with part of the solution and insert the
cathode into the etching liquid.
Use 0.38 mm W-wire and cut (or break if using annealed wire) off pieces for
tunnel tips: final length + insertion depth (5 mm).
Or use pieces with 2 final length for etching two tips in one go. In this case catch
the bottom tip in a thick foam, e.g. shaving lather.
Connect the electronics to the etching device using the provided cable set.
Switch the control unit on and set the desired etching voltage.
Dip the electrode into the solution by lifting the filled glass beaker.
Move down the piece of tungsten into the centre of the ring electrode. The tip
should extent about 5 mm through the ring.
NaOH
cathode
Wanode
~ 15 mm
tip holder
Figure 5. DC etching in lamella, schematic diagram.