Gold on Carbon resolution standards - get the best from your SEM SGC5200  Gold on Carbon Gold islands with diameters 5nm – 200nm on carbon SGC0230  High-resolution Gold on Carbon Gold islands with diameters 2nm – 30nm on carbon on Carbon resolution standards provide a means for testing the resolution of SEMs.  The varying sized gaps between gold crystals on a carbon substrate allow tests for resolution to be made under actual operating conditions.  They can also can be used to assess the quality of grey-level reproduction at high resolution. Gold on Carbon is available from EM Resolutions Ltd in two size ranges; SGC5200 is good for all SEM's and SGCO230 with its ultra small gold islands is best for modern hi-resolution FEGSEMs. High resolution SEMs should qive good results in the qap test combined with qood qrey level reproduction. Medium-quality instruments may achieve a chosen qap resolution, but the grey-level production may be quite poor, for example, only 4 or 5 grey levels may appear. Grey levels arise in secondary electron (SE) mode and originate from qeometric irregularities on the test specimen that result in differential signal collection. The anqular crystal faces of the larger gold crystals are particularly useful for grey level assessment. To facilitate preliminary focusing and positioning at low magnifications (<150X) an outline of a square grid is provided on the surface of the standard. By using known areas within the grid the user can make tests whilst preserving un- irradiated areas for future use. The particle size is very fine in the boundary reqion between the gold in the qrid squares and uncoated carbon in the grid bars and can be used for a critical assessment of the imaging capabilities of the microscope. When assessing the secondary electron image quality, the sample is best viewed using a specimen tilt of 30° to the SE detector. The degree of stage tilt used in back-scattered mode will depend on the position of the detector. It is advisable not to use tilt angles greater than 35° as the  larger crystals may shield the small crystals from view. Caution: When making gap measurements it should be remembered that the magnification is not constant throughout the image when the sample is tilted.
Re-ordering details:
SGC5200 Gold on Carbon and SGC0230 High-resolution gold on carbon are usually supplied on a 12.5 mm pin stubs. If you require an unmounted resolution standard please add U after the number. eg SGC5200U. For resolution standards on other stubs please specify.

1. Setting up the SEM
There are many variables that can affect the final image so recommending exact conditions for SEM resolution and qrey level testing is somewhat difficult. For best results the gold islands should be visualised at  40,000X maqnification or greater. As a general guide, the operator should be aiming to use the Gold on Carbon resolution standard at a fairly short working distance of 7 or 8mm. The best probe sizes are available at higher probe energies, so a gun potential of 20kV or above should be chosen for the initial testing. Subsequently it may be of interest to examine the performance of the SEM at lower gun potentials: however, unless the SEM in question has a dedicated facility for high quality imaging at below 10keV, there will not be much point in attempting work at this level. It is important that the filament is correctly saturated and that the gun is set up for optimum beam brightness and stability. Apertures should be centred and astigmatism and fine focus carefully checked immediately prior to recording the image. For ultimate performance the stage should be mechanically stable, there should be a good chamber vacuum, and the stray field and ambient vibration level in the SEM room should be below the recommended level set by the SEM manufacturer. For recording, the largest number of scan lines per frame resolvable on the recording screen should be used, and a long recording time is recommended (up to 10 minutes may be available on some instruments) which should ensure a good siqnal to noise ratio. If the operator is looking for good grey level reproduction, it is very important that the recording camera lens is well focused and image capture is carefully controlled for the best qrey range available. Measurements of qaps can of course only be made after magnification calibration of the SEM, and the microscopist must be satisfied that the calibration is rigorously applicable to the micrograph recorded of the  Gold on Carbon resolution standard.
2. Suggested Imaging of Gold
Set up the SEM as usual, insert the resolution standard and wait for a qood vacuum. Switch on the qun and saturate the filament carefully. Starting at a low magnification (<150X), focus on the edges of the dark grid bars and search for a suitable area of gold. Raise the magnification to 500X and focus on an irreqular portion of the gold. Increase the maqnification to 40,000X keeping the specimen in focus. Move the specimen to imaqe an area within a grid square (if the stage is tilted, use X-shift for convenience so that you do not lose focus). Focus carefully on the gold particles. Raise the magnification to 80,000X (or greater) and make final adjustments to the stigmators and the fine- focus controls. NB. The latter adjustments should be performed quickly if the SEM is prone to contamination deposition. Record the image using a very slow probe scanning rate. SGC0230 High-resolution Gold on Carbon standards have small size gold particles (<2nm- 30nm) particularly suitable for use with Field Emission SEM's and require higher magnification to resolve the smaller particles. These resolution standards should be used in conjunction with the ‘standard’ gold on carbon standard. The instructions for AGC5200 also apply to these ultra high resolution standards. V Resolutions Ltd was founded in 2012 TEM support films and calibration standards to EM laboratories and consumables companies throughout the UK and the rest  of Europe. Our technical staff have over 50 years combined experience, learned under the expert guidance of Alan Agar, one of the pioneers of consumables and accessories for electron microscopy. EM Resolutions Ltd, Business and Technology Centre, Chroma House, Shire Hill, Saffron Walden. Essex CB11 3AQ. United Kingdom w: www.emresolutions.com   e: info@emresolutions.com   t: +44 (0)1799 522500