Photonics Spectra - September 2009

coatings created by other means. Of prime importance is that deposition takes place at room temperature. 8

Using atomic force microscopy9 (AFM), Figure 4 shows the surface micromorphol-ogy of a 2-μm-thick silicon film deposited by conventional thermal evaporation at room temperature. The resultant film morphology exhibits a rough, poorly nucleated, nonadherent columnar porous film.

Figure 5 is an AFM evaluation of a 2- μm silicon film created at room temperature by the reactive ion plating. In this case, the film is fully adherent, smooth and featureless, indicative of a fully densified bulklike thin-film structure.

Protected gold alloy-replicated mirrors

Replicated mirrors produced with Darius’ alloy subsequently were coated with elemental silicon at room temperature using RLVIP. A film thickness of 70 nm was employed to tune the optimal spectral performance for the desired 1580- to

15,000-nm spectral region. A silicon film thickness of 160 nm was used for creating mirrors for the alternative 1300- to 1700- nm band. The resultant measured reflectances demonstrate that these surface-

Figure 4. This AFM image shows the surface micro-morphology of a 2-µm-thick silicon film deposited by conventional thermal evaporation at room temperature.

Figure 5. An AFM evaluation of a 2-µm silicon film was created at room temperature by Newport’s patented Reactive Low Voltage Ion Plating process.

modified replicated mirrors are indeed well suited to critical infrared instrumentation applications (Figures 6 and 7).

For a comparative measurement of surface hardness and abrasion resistance, the moderate abrasion methods as described in MIL-M-13508C were re-employed. In both of the above cases, RLVIP-protected