[3dem] Carbon evaporation systems for TEM

Svetomir B Tzokov s.b.tzokov at sheffield.ac.uk
Thu Oct 7 03:46:28 PDT 2010

Dear Joaquin,

We have the Cressington carbon coater and recently I had to reply to a colleague who was asking similar questions. I am just quickly modifying the text for this Email. Please, let me know if you need more info.

The Cressington Carbon Coater is simple and reliable instrument that can give very reproducible results when used properly. We use it for preparation of mainly continuous films, but also for holey films, if need arises.

Some more information about its performance:

A. Carbon film thickness.

Thickness control can be achieved in three ways.

1. Thickness monitor. It has replaceable sensors that are also sensitive to the vacuum in the chamber and eventually get covered with carbon film, so they can't be used more then several times. If used with a new sensor and always at the same vacuum, the Thickness Monitor can be quite reliable. However, we use it very rarely, now, because the two other methods for controlling the carbon thickness give very good results, too - without the need to worry about sensors, vacuum etc.

2. Small object (piece of paper, the mica itself), creating a shadow on the supporting filter paper. The contrast of the shadow can give you very good idea about the actual film thickness. Obviously, you will need a clean glass for that observation.

3. The rod that is evaporated can be sharpened to give desired thickness of the carbon film. The longer the fine tip of the rod, the thicker the carbon film. With some practice, you can easily "calibrate" the length of the evaporating carbon section to the thickness of the film.

We quite reproducibly obtain films with thickness of 100 to 250 Angstroms, we aim at about +/-50 Angstroms accuracy or better. In practice, it is not very difficult to get about +/- 20 Angstroms accuracy.

B. Shadowing.

We (at least myself) never used our coater for shadowing, I am not sure if it has the right attachment for that and I cannot comment. What I know is that you can select different attachments for different purposes, this coater can be quite flexible.

Apparently, Jeol are making quite good Carbon Coaters, as well - but we don't have experience with their coater or the Quorum Tech coater.

This is only our experience, hope it is helpful.

Kind regards,

On 7 Oct 2010, at 02:15, Joaquin Ortega wrote:

> Dear Colleagues,
> I am looking into buying a compact bench-top carbon evaporation system to prepare continuos and holey carbon grids for cryo-TEM. 
> I was wondering which systems people are using out there and whether they produce good quality and resistant carbon films.
> Two systems that I found browsing in the web are:
> 1. 208C High Vacuum Turbo Carbon Coater from Cressington (http://www.tedpella.com/cressing_html/cres208C.html)
> 2. K975X Turbo-Pumped Thermal Evaporator (http://www.quorumtech.com/products/bench-top-vacuum-evaporators/k975x-bench-top-vacuum-evaporator-digital-control.html)
> Any experiences (good or bad) with these two particular systems. 
> Thank you for your input. 
> Best
> Joaquin
> Joaquin Ortega. Ph.D.
> Associate Professor
> Department of Biochemistry and Biomedical Sciences 
> Michael DeGroote Institute for Infectious Disease Research
> McMaster University, HSC 4H24
> Hamilton. ON Canada L8N 3Z5
> 905-525 9140 x22703.
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