好文章，the coating process: requirement to delivery

dreamingwill · 发表于 2004-10-16 18:52:00

我在CERAC上下载的文章，上面还好多关于镀膜方面的东东，大家可去看看！

好文章，the coating process: requirement to delivery

chiangshu · 发表于 2004-10-16 21:27:00

TANTALUM OXIDE, Ta₂O₅ FOR OPTICAL COATING

Introduction Tantalum pentoxide, Ta₂O₅, is a high-index, low-absorption material usable for coatings in the near-UV (350 nm) to IR (~8 µm) regions. Dense layers can be deposited by electron-beam evaporation or sputtering. Typical applications include near-UV to near-IR antireflection and multilayer filter designs. Tantala can be used in combination with silicon dioxide layers to form high index-contrast multilayer structures. A particular advantage over titanium dioxide layers for near-IR laser and bandpass coatings is the absence of absorption above 900 nm. This makes tantala well suited for Nd:YAG laser applications.

Film Properties Completely oxidized tantala films are absorption-free over the range below 400 nm to at least 8 µm. Evaporation causes some amount of dissociation and oxygen loss and requires a partial pressure of oxygen during deposition. Adhesion is excellent to glass and to most other oxides. The films generally grow with a crystalline microstructure. Under some evaporation conditions, such as low energy resistance-heated evaporation, low substrate temperature, or excessive background pressure, the films grow with low packing density and can exhibit index changes when vented to moist air. Deposition by sputtering, ion assist, or at very high substrate temperatures, improves the packing density and eliminates spectral shifting due to moist air-vacuum cycling, producing very stable layers.

The refractive index responds to high energy deposition techniques and to substrate temperature because both parameters decrease the void volume by increasing the packing density of the microstructure. Post-deposition baking in air can raise the refractive index of electron-beam and resistance-heated depositions.

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Refractive Index The refractive indices are dependent on the degree of oxidation and the film density achieved. Approximate values are plotted below.

REFRACTIVE INDEX FOR TANTALUM OXIDE (note scale discontinuity)

Wavelength (nm)

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Material Behavior The starting material form is either tablets or sintered pieces. Recommended preconditioning consists of slowly sweeping a low power electron beam to slowly and uniformly fuse the surfaces of the material and avoid hole drilling by the beam. Monitor the pressure and crucible to minimize outgassing and spitting while slowly increasing the power to just below evaporation temperature.

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Evaporation Parameters

Evaporation temperature	~2000° C
Source Container	Tantalum or graphite liner for E-beam
Rate	2-5 Å/sec.
Partial pressure of oxygen	2-5 x 10^-5 Torr
Substrate temperature	175° C to 300° C.

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Physical Properties of Solid Material

Molecular Weight	441.89
Melting Point	1872° C
Color	White
Crystal Density	8.2 g/cc

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Applications Because the index below wavelengths 300 nm is greater than 2, tantala can be combined in multilayers with silicon dioxide (n = 1.48) for UV laser applications. Hard, scratch-resistant and adherent coatings can be deposited. Films are also used for dielectrics in film capacitors and as gate insulators in large scale integrated circuits requiring low leakage voltage characteristics.

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Forms and Sizes Available

Item No.	Purity	Description
T-1186	99.95%	8-9 mm dia. x 4-5 mm thick sintered tablets
T-1202	99.95%	3-12 mm sintered pieces
SS-620	99.997%	Sputtering Target
SS-112	99.99%	Sputtering Target

dreamingwill · 发表于 2004-10-16 23:41:00

怎么上载文件，我上载的怎么没有链接？是否是操作系统的关系，小弟现在在日本，用的机器也是日文系统的，请高手指教。

TIANNAN · 发表于 2004-10-19 01:06:00

http://www.cerac.com/pubs/pubs.htm


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好文章，the coating process: requirement to delivery

TANTALUM OXIDE, Ta2O5 FOR OPTICAL COATING

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TANTALUM OXIDE, Ta₂O₅ FOR OPTICAL COATING