Access Programme FAQ

How much does it cost to use the instrument?
It is free of charge for any UK university user. We can also pay for travel and subsistence from within the UK.

How do I apply for access?
Fill out an application form, add a single-page case for support and e-mail it to Paul Warburton (p.warburtonee.ucl.ac.uk) at LCN/UCL. Proposals will be considered by the Access Management Group (AMG) which currently consists of Dr Paul Warburton, Dr Rachel McKendry, Prof. Gabriel Aeppli and Prof. Ian Robinson. Proposals will be considered in line with EPSRC’s policy on confidentiality (see “Confidentiality of our Assessment Process”).

When is the deadline for applying for access?
There are no deadlines. Applications can be received at any time (after 1/11/07) and will be considered on a monthly basis (from early December 2007 onwards).

What criteria will be used to prioritise applications for access?
There are three criteria for access:

1. the scientific quality of the proposal;
2. the feasibility of the proposed experiments;
3. the degree to which the proposal makes use of the unique functional capabilities of the instrument (e.g. a proposal which only uses the SEM functionality is unlikely to gain access).

What is the difference between a class “B” user and a class “A” user?
Class “B” users are beginners. Maybe they have no prior experience of FIB work; maybe they have some experience but on a different machine. Class “B” users will be accompanied at all times by UCL technical support staff. This will enable a class “B” user to (a) do some “proof-of-principle” type experiments; and (b) to get trained in how to use the machine. Class “B” users may apply for access up to two months in advance.

Class “A” users are mode advanced users. They have been previously trained by UCL technical staff in how to operate the machine safely and effectively, and may use the machine unaccompanied. Class “A” users may apply for access up to six months in advance.

How do I graduate from being a class “B” user to being a class “A” user?
Fill out an application form for class “A” access and attach to it a single page of results from your previous (class “B”) work. If the Access Management Group is satisfied that (a) your previous work justifies further experiments with the machine, and (b) you have received sufficient training to use the machine unaccompanied, then you will be granted class “A” user status.


How long should I book the instrument for?
The day is divided into three sessions for booking purposes, each session being three hours long. If you have never used the instrument before you’ll need two sessions to be given the basic training on imaging and milling and (maybe) to make a start on a simple job of your own; but three sessions is more realistic if you want to make real progress on a first visit.

Once you have received the basic training you’ll be in a better position to estimate how much time you will need. But as a rule of thumb you could take about an hour loading the sample and doing basic focussing and alignment of the two beams. To estimate how long it takes to do milling, see below.


How long does the milling process take?
Here we are NOT talking about the time taken for alignment and focussing – just the actual time taken to remove material. This is very sample dependent, so we can only give a rough guide. For milling through silicon the rule of thumb is that you remove half a cubic micron per nanoAmp per second. The highest beam current is 50 nA – but the beam diameter for this current is of order 100 nm, so this cannot be used for milling fine features. The lowest beam current is nominally 1 pA. This has beam diameter of around 6 nm FWHM so can mill fine features, but clearly has a milling rate which is 50,000 times slower than the largest beam current.

What is the smallest feature I can mill?
The smallest beam diameter is about 6 nm FWHM – but in all applications the smallest millable feature size is never beam-size limited. Due to scattering of ions in the sample, the milled area is always larger than the beam diameter, though this is very sample dependent. In addition there is always a damaged surface layer which has not been removed by ion milling but which is implanted by gallium ions. This typically consists of an amorphised region extending 10 nm or so into the sample. As a rule of thumb one can mill features of (say) 100nm size without too much effort. Going below that is certainly possible but one might need to do some process development specific to your particular sample.


What is the highest aspect ratio which I can achieve?
If you want to create a narrow tall structure standing up proud of its surroundings then one is only limited by time – i.e. how long it takes to remove the surroundings by milling.

If you want to create a narrow deep structure (i.e. drilling a hole in your sample) then one is limited by redeposition of sputtered material on the sidewalls of the structure. As a rule of thumb an aspect ratio of 2:1 is easy; 3:1 is hard; and any more than that is likely to be impossible

How do I define in software the structures to be milled?
For simple rectangles, lines and circles it’s easiest to just define them as you go along using the standard software. For more complicated and/or repetitive jobs bitmaps can be imported.

What materials can be grown in the FIB?
You can do ion-beam induced chemical vapour deposition of the following materials:

1. “tungsten” – room temperature resistivity is about 300 μΩcm; superconducting transition temperature is about 5.5 K
2. “platinum” – less conductive than the “tungsten”
3. “silica” – nominally insulating

(In each case the deposited material is in inverted commas since it is highly defective and contains significant amounts of carbon and gallium.)

Can I use the instrument for TEM sample preparation?
TEM sample prep can be done using the XB1540 and its software. Note, however, that there is no in-situ nanomanipulator for transferring the lamella to the TEM grid. We do have an external manipulator for this purpose.