阳极氧化铝表面中光学常数检测方案(椭偏仪)

Application NoteMetallurgyMM-16SE09Spectroscopic Ellipsometry Spectroscopic Ellipsometry Characterisation of Aluminium Anodised Surfacesusingthe MM-16 Spectroscopic Ellipsometer Celine Eypert - Application Scientist - Thin Film Division The capacity of aluminium to respond to anodising， the most familiar of finishes， makes aluminium a mostimportant metal in a quite tundamental way. The fact that aluminium can take on this attractive， durable andhard-wearing ffinish makes it possible to exploit its strength and lightness in a large number of applications，particularly in building construction and in the automotive industry. Anodising is an induced thickening of the natural protectiveoxide film on the metal's surface. It is a conversion of the par-ent metal and thus is not a 'coating' in the usual sense. Vari-ation otthe conventional electrolyte composition andprocess variables produce anodic coatings with distinctivefunctional properties. Thus， very hard anodic films are devel-oped to provide abrasion resistant surfaces on gears， pistons，bearings， and similar components. Anodic films may also be coloured by a variety of methods.Conventional sulphuric acid films are microscopically po-rous， and organic or inorganic dyes and pigments may be in-corporated and sealed into the film. The functional and decorative potential on the metal cantherefore be widely exploited in applications ranging frombuilding components to domestic cookware. Being able tocharacterise the aluminium oxide non-destructively is very im-portant， and the use ot spectroscopic ellipsometry allows on-ine monitoring ot the anodised surtace on a production line. Results： Ellipsometric measurementwereperformedusingtheHORIBA Jobin Yvon MM-16 Spectroscopic Ellipsometer (SE)across the spectral range 450-850nm (1163 wavelengths). The measurement was performed at an angle of incidence of70°. The acquisition data was collected in 30s and the MM-16 provides the full polarisation state of the sample with onemeasurement cycle， without the need for several hardwareconfigurations. As a result the ellipsometric angles W and ▲are determined with very high accuracy and precision. The MM-16 also provides the full 16-element Mueller Matrixand this feature has major advantages for characterising de-oolarizing and otten anisotropic samples with complex struc-ture or geometry， where conventional ellipsometryisinapplicable. This feature can be also applied with successand accuracy to all cases currently covered by conventionalellipsometry. Aluminium oxide， Al2O3， is a medium refractive index andlow absorption material that often exhibits anisotropic behav- iour. A feature of the Mueller Matrix is that the off-diagonalelements are not equal to 0 when the sample exhibits aniso-tropic behaviour and especially when the measurement isdone in a random position， that is away from the direction ofthe optical axis and at rotation of 90° from this optical axis，and when the optical axis is not orthogonal to the sampleplane. In this example we can see the off-diagonal elementsare not equal to 0 as it is shownon fig. 1. This standard fea-ture of the MM-16 simplifies characterisation of such materi-als. The anisotropic model is illustrated below： Figure 1： The Mueller Matrix for an anisotropic alumina film measured inone direction with the MM-16 ellipsometer in reflection mode. The optical properties of the aluminium oxide have been de-termined using the Lorentz Oscillator： One can observe that the birefringence is An=0.01， whereAn is the difference between the ordinary and extraordinaryrefractive indices. Note that the Al2O3 layer is porous explaining the low indexfound. Conclusion： The aluminium anodised layer has been successfully charac-terised by the MM-16 Spectroscopic Ellipsometer with veryhigh speed and accuracy. USA：+1-732 494 8660France：+33 (0)1 64 54 1300Japan： +81 (0)3 3861 8231 Germany： +49 (0)89462317-0 UK： +44 (0)20 82048142 Italy： +390257603050 China： +86(0)10 6849 2216 Other Countries： +33 (0)1 64 54 13 00 HORIBAExplore the future Find us at www.jobinyvon.com or telephone：(All HORIBA Jobin Yvon companies were formerly known as Jobin Yvon)HORIBAExplore the future The aluminium anodised layer has been successfully characterised by the MM-16 Spectroscopic Ellipsometer with very high speed and accuracy.