Effects of bombardment on optical properties during the deposition of silicon nitride by reactive ion-beam sputtering

Modifications of ion beam sputtered tantala thin films by secondary argon and oxygen bombardment

Amorphous tantala (Ta₂O₅) thin films were deposited by reactive ion beam sputtering with simultaneous low energy assist Ar⁺ or Ar⁺/O2+ bombardment. Under the conditions of the experiment, the as-deposited thin films are amorphous and stoichiometric. The refractive index and optical band gap of thin films remain unchanged by ion bombardment. Around 20% improvement in room temperature mechanical loss and 60% decrease in absorption loss are found in samples bombarded with 100-eV Ar⁺. A detrimental influence from low energy O2+ bombardment on absorption loss and mechanical loss is observed. Low energy Ar⁺ bombardment removes excess oxygen point defects, while O2+ bombardment introduces defects into the tantala films.

Characterization of silicon oxynitride films deposited by a high-power impulse magnetron sputtering deposition technique

In this research, silicon oxynitride films were prepared by high-power impulse magnetron sputtering with 45/955 pulse on/off time. The extinction coefficient was smaller than 1×10^-3 from 250 to 700 nm after introducing 2.2 sccm O₂ gas at room temperature. A three-layer of AlF₃/SiO_xN_y AR coating was designed and fabricated on double-sided quartz, and a high transmittance of 99.2% was attained at 248 nm. The silicon oxynitride films deposited at 350°C had the better mechanical and optical properties in the visible range. The hardness of all deposited films was greater than 19 GPa, and the greatest hardness could reach to 29.8 GPa. A film structure of six-layer transparent hard coating/glass/four-layer AR coating was designed and deposited. Its average transmittance was 96.0% in the visible range, while its hardness was 21 GPa and its surface roughness was 0.23 nm.

Radio Frequency Plasma-Enhanced Reactive Magnetron Sputtering Deposition of α-SiN x on Photonic Crystal-Laser Diodes for Facet Passivation

Amorphous silicon nitride (α-SiN _x ) films were coated on a photonic crystal-laser diode by the radio frequency magnetron sputtering method. Sputtering deposition conditions were changed to obtain α-SiN _x films with different properties. The optical parameters and morphologies of the products were systemically characterized by spectroscopic ellipsometry fitting, energy-dispersive X-ray spectroscopy, atomic force microscopy, and performance of LDs coated with α-SiN _x films were tested at 25 °C. Physical mechanisms of sputtering were explained in detail. α-SiN _x with a band gap of 4.4 eV and a refractive index of 2.03 at 980 nm were grown. The extinction coefficient equal to 0 at 980 nm, and the surface morphology tended to be homogeneous and dense. The main influencing factors related to the catastrophic optical mirror damage (COMD) phenomenon were investigated. Then plasma pretreatment was implemented to eliminate defects and improve the cavity surface quality and further optimized by measuring the intensity of photoluminescence. Afterward, a rapid annealing method was also carried out to improve coating performance. Finally, α-SiN _x acted as a passivation layer in the antireflection film coated on the LD facet, and the COMD threshold increased from 5 to 15.2 W, which led to a higher reliability than nonoptimized LDs and elimination of the COMD phenomenon.

Improving optical properties of silicon nitride films to be applied in the middle infrared optics by a combined high-power impulse/unbalanced magnetron sputtering deposition technique

Silicon nitride films are prepared by a combined high-power impulse/unbalanced magnetron sputtering (HIPIMS/UBMS) deposition technique. Different unbalance coefficients and pulse on/off ratios are applied to improve the optical properties of the silicon nitride films. The refractive indices of the Si3N4 films vary from 2.17 to 2.02 in the wavelength ranges of 400-700 nm, and all the extinction coefficients are smaller than 1×10(-4). The Fourier transform infrared spectroscopy and x-ray diffractometry measurements reveal the amorphous structure of the Si3N4 films with extremely low hydrogen content and very low absorption between the near IR and middle IR ranges. Compared to other deposition techniques, Si3N4 films deposited by the combined HIPIMS/UBMS deposition technique possess the highest refractive index, the lowest extinction coefficient, and excellent structural properties. Finally a four-layer coating is deposited on both sides of a silicon substrate. The average transmittance from 3200 to 4800 nm is 99.0%, and the highest transmittance is 99.97% around 4200 nm.

Infrared interference coating by use of Si3N4 and SiO2 films with ion-assisted deposition

Silicon nitride (Si(3)N(4)) and silicon dioxide (SiO(2)) films were prepared by ion-assisted deposition, and a higher deposition rate was achieved for both films. The results of x-ray diffraction and transmission electron microscopy measurements showed that the films have amorphous structures. As measured by infrared (IR) spectrometry and x-ray photoelectron spectrometry, both stoichiometric films have extremely low hydrogen content. The IR optical constants of the films were determined by spectroscopic ellipsometry. Both films exhibited a low extinction coefficient at wavelengths from 2 to 7 microm. The application of Si(3)N(4) and SiO(2) films on the IR interference coating is demonstrated.

Effect of high-energy electron-beam irradiation on the optical properties of ion-beam-sputtered silicon oxynitride thin films

Silicon oxynitride thin films are prepared by ion-beam sputtering, and the optical properties and surface chemical composition are studied by spectrophotometric and x-ray photoelectron spectroscopy, respectively. It is seen that the films sputtered by use of nitrogen alone as the sputtering species from a silicon nitride target are completely transparent (k < 0.005) and have a refractive-index dispersion from 1.85 to 1.71 over the visible and near-infrared spectral regions, and the films show distinct spectral lines that are due to silicon, Si(2s), nitrogen, N(1s), and oxygen, O(1s). Sputter deposition of argon and of argon and nitrogen produces silicon-rich silicon oxynitride films that are absorbent and have high refractive indices. These films have a direct electronic transition, with a threshold energy of 1.75 eV. Electron irradiation transforms optically transparent silicon oxynitride films into silicon-rich silicon oxynitride films that have higher refractive indices and are optically absorbing owing to the presence of nonsaturated silicon in the irradiated films. The degradation in current responsivity of silicon photodetectors, under electron irradiation, is within 3% over the wavelength region from 450 to 750 nm, which is entirely due to the degradation of optical properties of silicon oxynitride antireflection coatings.

Optical and structural properties of Ag-Si3N4 nanocermets prepared by means of ion-beam sputtering in alternate and codeposition modes

Ion-beam sputtering deposition has been used in two ways, as granular multilayers and as cosputtered film, to elaborate Ag-Si3N4 nanocermets. Multilayer deposition creates slightly oblate clusters, and cosputtering produces two cluster families: elongated clusters within the Si3N4 matrix and larger ones at the film surface. The transmittance spectra of these nanocermets are characterized by a surface plasmon resonance. In the reported research the position of this resonance is related to the morphological properties of silver nanoclusters, which are studied by transmission-electron microscopy, grazing-incidence small-angle x-ray scattering, and atomic-force microscopy.