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ZnS is one of the excellent materials that are used as long wave window in infrared, but the reflection of the surface is high. In order to reduce the reflection of the ZnS surface, we designed the sub-wavelength antireflective structure on ZnS by coupled-wave theory. The parameters of the sub-wavelength antireflective structure were optimiged and the two-dimensional sub-wavelength antireflective structure on ZnS was fabricated by reactive ion etching technique. The results show that the transmittance of etched ZnS is significantly better than that of bare ZnS at wavelengths of 8—12 μm. This is a new antireflection method using ZnS.

GaP thick films were prepared on ZnS substrates by RF magnetron sputtering starting from a GaP target in an Ar atmosphere. Plasma emission diagnostics was employed to investigate the glow discharge during the deposition process. Only the emission lines of Ar atom appear and effects of the deposition parameters on the intensities of the emission lines were studied systematically. The deposition parameters were optimized through increasing the RF power and decreasing the working gas pressure of Ar simultaneously, with the intensity of the emission lines kept constant. And thus, stoichiometric GaP thick films with high IR transmission performance were deposited at an elevated deposition rate.

GeC thin films were deposited on ZnS substrates with reactive RF magnetron sputtering, and the influences of the processing parameters on sputtering of the Ge target and IR transmission properties of the GeC films were studied. At low substrate temperatures, the GeC film contained H atoms in forms of CH2，CH3 and Ge-CH3 groups, which caused IR absorption, whereas the absorption decreased obviously at elevated substrate temperatures. Target-substrate distance, RF power, Ar:CH4 gas flow ratio and total gas pressure had great impacts on the poisoning and sputtering of the Ge target, but their impacts on the IR absorption of the GeC film was small. When the Ge target was poisoned greatly, adhesion of the GeC film was inferior, with the weakening of the target poisoning, adhesion of the GeC film increased. Hydrogen-free GeC film with excellent adhesion was prepared on ZnS substrate under optimized parameters, and its refractive index was about 1.78. The C content in the GeC film was larger than the Ge content, and C and Ge formed mainly C—Ge bonds. GeC/GaP antireflective and protective film system was prepared on ZnS substrate, giving good antireflective effect.

GaP IR thin films were deposited through RF magnetron sputtering with a GaP disk as the target. The intensity of Ar I 750nm optical emission line was kept the same in different experiments, with which various deposition parameters were got, and the deposition processes were studied with computer simulation. The results showed that under low sputtering power and high working gas pressure, the sputtering yields and transporting efficiencies of Ga and P atoms as well as their energies at arriving the substrate's surface are small, the sputtering yield and transporting efficiency of Ga atom are both larger than those of P atom, hence the depositing rate of GaP film is low, the content of Ga in the film is larger than that of P, which makes the film have high absorbance in IR waveband. But under high sputtering power and low working gas pressure, the atoms' sputtering yields, transporting efficiencies and energies at arriving the substrate's surface all increase, the sputtering yield of Ga atom is larger than that of P atom, whereas its transporting efficiency is smaller than that of P atom, hence the depositing rate of GaP film is high and stoichiometric film with low absorbance is deposited, which is advantageous to depositing large-thickness GaP film.