Characteristics and Cleaning of Apertures

Platinum Melting Point: 1768°C (3214.4°F)
Molybdenum Melting Point: 2610°C (4730°F)
Tungsten Boat Melting Point: 3422°C (6191.6°F)
(With coated ceramic Al2O3 tabs)

Aperture contamination occurs when it is exposed to the electron beam, in which case regular cleaning or replacement is required. The smaller the hole, the more quickly contamination builds up and astigmatism increases. Dirty aperture systems make alignment difficult due to beam deflection caused by dirt charging up.

Platinum/Iridium apertures may be cleaned by flaming them and applying temperature where the aperture does not exceed a color of cherry-red (not white-heat). Bunsen burner or small flame devices (alcohol, butane) have been used for this procedure. About 10-15 seconds should be sufficient for this procedure. "Flamers" for this purpose are described below. The entire surface will reach the same color when completely clean.

Molybdenum apertures must be heated in a vacuum below 10-4 mbar. After proper vacuum is reached and current applied, a color of cherry-red is achieved. Use a tungsten boat. This will require about 20-30 seconds. Molybdenum apertures can be successfully cleaned more frequently and used again, than Platinum/Iridium.

Platinum/Iridium disc apertures can be flamed in our platinum gauze "Aperture Flamer" (No. 60001) for cleaning purposes. Other Aperture Flamers (No. 60003, 60004) are shown for Platinum/Iridium discs, small and large, and for hanging strip Platinum/Iridium apertures.

The cleaned aperture(s) should be inspected on a clean glass slide at 30-40X. The hole should be clean and round. Misshapen apertures should be rejected.

Bils RF, 1992. Electron Microscopy Laboratory Manual and Handbook, 2nd ed, Alpha Editions, 329p.
Chapman SK, 1986. Maintaining and Monitoring the Transmission Electron Microscope, Royal Microscopy Society, Microscopy Handbooks 08, Oxford University Press.

Platinum Gauze Aperture Flamer

Prod #	Description	Unit	Price	Order / Quote
60001	PELCO Aperture Flamer	each	$326.00	Qty:

Platinum Cup Flamers

with small hole at bottom, removable cover and insulated handle

Standard Small Cup

For aperture discs (up to 6mm) or aperture strips while flaming. 4.7mm (3/16") diameter cup. 0.152mm (6 mil) platinum foil with 0.8mm (1/32") diameter hole to encourage a good air flow. A 0.76mm (30 mil) platinum wire attaches the cup to the heat resistant handle. A hook formed at the wire-cup attachment may be used for hanging an aperture strip and flaming

Prod #	Description	Unit	Price	Order / Quote
60003	Small Cup Aperture Flamer w. handle and cover	each	$457.00	Qty:

Large Cup

Prod #	Description	Unit	Price	Order / Quote
60004	Large Cup Aperture Flamer w. handle and cover	each	$520.00	Qty:

Molybdenum, Platinum and Tantalum Metal Boats

7.9mm W x 76.2 mm L (5/16" W x 3" L), trough: 4.8 x 12.7mm (3/16" W x 1/2" L) x .8mm (1/32") deep.
Thickness: 0.05mm (0.002").

Prod #	Description	Unit	Price	Order / Quote
81	Molybdenum Boat, 3/16" x 1/2" trough, pkg/5	each	$17.80	Qty:
82	Platinum Boat, 3/16" x 1/2" trough	each	149.00	Qty:
83	Tantalum Boat, 3/16" x 1/2" trough, pkg/5	each	43.60	Qty:

Molybdenum Metal Boat (long) for Strip Aperture Cleaning

go to Molybdenum Foil