CIROM-IRX*
A Non-Radioactive Replacement for ThF4
Introduction
A non-radioactive replacement for thorium fluoride, ThF4,
is now available. CIROM-IRX* can be used for applications
ranging from low-loss laser mirrors to filter and AR coatings.
The material provides a refractive index of 1.4 near 10 µm
wavelength and is compatible with other layer components typically
used in IR multilayer coating designs. Coatings of CIROM-IRX*
show good adhesion and low stress for layer thicknesses at least
twice the thickness of pure CeF3 films.
Material
Description
CIROM-IRX* is a modified form of cerous fluoride. The material
can be handled using standard safety precautions.There
is no radioactivity associated with CIROM-IRX*.
CIROM-IRX* is manufactured as fully melted ingots at
a very high temperature in a controlled atmosphere. The ingot
is crushed and sized to lumps, granules or small grains, depending
on customer application. Any required particle size range can
be produced on short notice.
Crystal Structure and Purity
The X-ray pattern of CIROM-IRX* matches that of CeF3
but with an altered cell size. The material is over 99.9% pure.
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Recommended
Procedures for Coating Applications
Substrate Preparation
Clean the substrate surface thoroughly in an organic solvent
such as acetone or xylene using cotton to scrub the surfaces.
Rinse in alcohol before permitting the previous solvent to evaporate
to dryness on the surface. Scrub lightly using cotton in Micro.
Flush thoroughly in deionized water. Wipe with alcohol using
cotton. Freon drying can also be used.
Insert in vacuum tooling and begin pumpdown immediately. Under
vacuum, a short, approximately two-minute period of glow discharge
cleaning can be used just before deposition. For difficult adhesion
cases, such as to ZnS or ZnSe substrates, apply a thin nucleation
layer of Y2O3 or an equivalent binding
layer. Y2O3 can be deposited to a thickness
of ~100Å at a rate of 2Å/sec. in a vacuum of 1-2
x 10-5 Torr.
Material Preconditioning
A short period of low power sweeping of the E-beam is recommended
to dehydrate and fuse the surface of the material charge. While
sweeping, advance the power slowly to reach an evaporation rate
of 1Å/sec. in a period of 5 minutes. Hold for about 2 minutes
before opening the shutter. This is usually a sufficient time
to eliminate outgassing and spitting. It has been found that
this minimal preconditioning will completely eliminate spitting
and outgassing during the deposition run and ensure a constant
evaporation rate. The preconditioning step does not need to be
repeated for subsequent runs.
Evaporation
CIROM-IRX* is best evaporated from a graphite crucible liner
with a swept E-beam source operating at low power. A granule
size of 2-3 mm is preferred. A steady rate of 20Å/sec.
or greater can be achieved without the emanation of volatiles
or spatter particles. The substrate temperature should be 225-250°C
and the chamber pressure mid-10-6 to 1 x 10-5
Torr. The minimum substrate temperature is 150°C, and since
film hardness will be sacrificed, low temperatures should only
be used when CIROM-IRX* is combined with materials requiring
low temperatures, such as ZnS.
Resistance heating from tantalum baffled box sources can also
be used for evaporation. The charge should be discarded when
severe discoloration appears.
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Typical
Performance
Layer thicknesses greater than 1 µm on germanium and glass
substrates exhibit virtually no haziness. The refractive index
is above 1.6 in the visible region, and the films are transparent
from below 300 nm to greater than 11 µm. High rate E-beam
or high energy ion beam deposition can cause the depletion of
fluorine and result in some absorption in the UV region. Transparency
is maintained to nearly 16 µm, but absorption begins above
11 µm.
The mechanical durability and moisture resistance of CIROM-IRX*
films are excellent. Film thicknesses up to 2000 nm have been
grown on glass and germanium substrates without crazing or lifting.
Thicknesses up to 1500 nm can be applied to ZnS and ZnSe substrates.
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Properties
of Solid Material
|
Color |
Tan to brown |
|
Melting Temperature |
~1430°C |
|
Evaporation Temperature |
~1000°C |
|
Solubility |
Insoluble in water |
|
Density |
~6.2 g/cc |
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Deposited
Film Properties
(Film thickness ~1500 nm)
|
Clarity, IR-UV |
Exceptionally clear and scatter-free |
|
Refractive Index |
1.66 at 400 nm
1.64 at 600 nm
1.61 at 800 nm
1.62 at 1,000 nm
1.48 at 4,000 nm
1.44 at 8,000 nm
1.43 at 10,000 nm
1.42 at 12,000 nm |
|
Absorption |
~1% at 10,600 nm
~2% at 11,000 nm
~2% at 12,000 nm |
|
Water Absorption |
2-3% in 2800-3200 nm and 5600-7300
nm bands. |
|
Eraser Test Durability |
Ge and glass: Show very fine
scratches |
|
Humidity Testing |
Ge and glass: Pass |
|
Adhesion Test |
Ge, ZnS and glass: Pass |
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Forms
and Sizes Available from CERAC
|
Item No. |
Purity |
Description |
|
I-3000 |
99.9% |
1-3 mm melted pieces |
|
I-3001 |
99.9% |
3-6 mm melted pieces |
CERAC offers other materials for evaporation as well as sputtering
targets. To view pricing on the items listed above, please visit
our on-line catalog and look-up
by item number or chemical name. If you require a custom manufactured
item, please contact our sales department at 414-289-9800 or ceracsales@beminc.com
with your
specific requirements. You can also fill out our quotation
request form.
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CIROM-IRX* is not radioactive and can be handled
as any normal coating material. Proper safety precautions are
always recommended, and inhalation of dust or vapor should be
avoided. Disposal of coating wastes should follow established
local and governmental regulations.
NOTE:
Facts pertaining to properties and processing parameters of CIROM-IRX*
were derived from published literature sources and testing. Although
this information is believed to be correct, CERAC does not guarantee
its accuracy.
*CIROM-IRX
is a Trademark of CERAC, inc. |
