Lishuan Wang

Influence of temperature and ion kinetic energy on surface morphology of CeO2 films prepared by dual plasma deposition

The effects of the substrate temperature and ion impact energy on the surface roughness and morphology of insulating cerium oxide films fabricated by dual plasma deposition were investigated. Cerium oxide films were synthesized on Si(1 0 0) substrates, and the influence of the substrate temperature and applied voltage on the surface roughness was systematically studied. Our results indicate that the roughness of the deposited films decreased when the substrate temperature was increased, probably because of enhanced surface diffusion of the adatoms. The ion kinetic energy had a similar effect as the substrate temperature, and it is believed that a higher ion kinetic energy also improves the surface diffusion of adatoms. It is found that a direct-current voltage applied to the substrate could lead to a rougher surface, whereas an appropriate alternating-current voltage gave rise to a smoother topography.

Optical and interfacial layer properties of SiO2 films deposited on different substrates.

SiO2 films were deposited on fused silica, silicon, glass, germanium, and sapphire substrates by an ion beam sputtering technique. The optical properties of SiO2 films on different substrates and interfacial layer properties between SiO2 films and different substrates were researched by the spectroscopic ellipsometry technique. The refractive indices of SiO2 films deposited on different substrates are about 1.477 at the wavelength of 632.8 nm. The optical anisotropy property of SiO2 films on fused silica substrate is the best. The impact of thermal treatment on surface roughness and interfacial layer properties between SiO2 films and Si substrates were also investigated. When the annealing temperature is 550°C, the least surface thickness and thinnest interface layer thickness between v films and silicon substrate can be achieved. The results indicate that the surface and interface layer properties between SiO2 films and silicon substrate can be greatly improved when the optimum annealing temperature is selected.

Surface modification of 2Cr13 oil pump steel by plasma immersion ion implantation-ion beam enhanced deposition (PIII-IBED)

2Cr13 martensite steel is often used as a piston material in oil pumps. In the harsh environment of an oil field, the materials and components undergo extensive and accelerated wear and tear. In this study, we employ Ti and N plasma immersion ion implantation and ion beam enhanced deposition (PIII-IBED) to enhance the surface wear resistance of 2Cr13 steel in an effort to prolong its working lifetime. To assess the technique efficacy and surface properties of the 2Cr13 steel samples treated by PIII-IBED using different voltages, the coefficient of friction, wear tracks, microhardness, anode polarization curves, chemical composition and elemental depth profiles were determined. The experimental data show that the wear resistance of the treated 2Cr13 steel samples is improved significantly by the method, and the nitride phases formed in the modified layer play an important role in the enhancement mechanism.

High duty, long lifetime, cathodic arc plasma source

We have developed a repetitively pulsed cathodic arc plasma source that can operate at high duty cycle and with long lifetime between downtimes for cathode maintenance. The arc discharge current can be up to 300 A, the arc pulse width can be varied from 0.1 to 4 ms, and the source can operate at a duty cycle of up to 30% for many hours. The cathode can be of a diameter from 20 to 40 mm, and can be easily and quickly changed. A 45° magnetic duct is used for macroparticle filtering, employing a pulsed magnetic field. We have operated the source over a wide parameter range, and we report here on the variation of plasma ion deposition current with arc current, duct magnetic field, and duct bias voltage. A momentary ion deposition current of 0.7 A was obtained with the source running stably for more than 8 h with an arc current of 100 A and duty cycle of 20%.

Correlation between properties of HfO 2 films and preparing parameters by ion beam sputtering deposition

Ion beam sputtering is one of the most important technologies for preparing hafnium dioxide thin films. In this paper, the correlation between properties of hafnium dioxide thin films and preparing parameters was systematically researched by using the orthogonal experiment design method. The properties of hafnium oxide films (refractive index, extinction coefficient, deposition rate, stress, and inhomogeneity of refractive index) were studied. The refractive index, extinction coefficient, physical thickness, and inhomogeneity of refractive index were obtained by the multiple wavelength curve-fitting method from the reflectance and transmittance of single layers. The stress of thin film was measured by elastic deformation of the thin film-substrate system. An orthogonal experimental strategy was designed using substrate temperature, ion beam voltage, ion beam current, and oxygen flow rate as the variables. The experimental results indicated that the temperature of the substrate is the key influencing parameter on the properties of hafnium oxide films, while other preparing parameters are also correlated with specific properties. The experimental results are significant for selecting proper parameters for preparing hafnium oxide films with different applications.

Insights into effects of thermal annealing on optical properties of SiO2 films

Annealing is an important method to alter the properties of thin films. The effects of thermal treatment in air on optical properties of SiO2 thin films were investigated. SiO2 thin films were deposited on Si (110) substrates by an ion beam sputtering (IBS) technique, and then annealed in air under different thermal annealing time of 16 hours, 24 hours, 36 hours, 64 hours and the temperature from 100℃ to 600℃ with 24 hours. Optical properties refractive index and thickness are studied directly after deposition and after thermal treatment, and they are measured by spectroscopic ellipsometry. When the thermal annealing temperature was fixed at 300℃, the refractive index of SiO2 films would reduce with the increase of the thermal annealing time, the optical thickness also reduced but the various quantities are almost the same. The refractive index of SiO2 films changed with the different thermal annealing temperature. As the annealing temperature increased, the refractive index of SiO2 films reduced gradually. When the selected annealing temperature is 500℃, the refractive index of SiO2 films reached minimum. It can be found that the optical properties of SiO2 thin films can be improved by an adapted annealing procedure.

Calculation and simulation of the uniformity of grinding removal in ring polishing

Ring polishing, also called continuous polishing, plays a very important role in the manufacturing of plane optical components with large aperture. This paper theoretically analyses the problem of calculation and simulation of the uniformity of grinding removal in ring polishing. By using the MATLAB software, a series of simulation figures are given. Firstly, the relative motion path on the polishing lap of a point on the workpiece is obtained by programming. From the simulation results it could draw a conclusion that the motion path is complicated when rotating speed ratio is not equal to one. Thus, its beneficial to the homogeneous material removal. Focus on the problem of the uniformity of grinding removal, then, this paper elaborates on the effect of material relative removal caused by factors such as rotating speed ratio and eccentricity theoretically. When the size of the workpiece is large enough, it will be outside of the optical polishing pitch lap, and this paper will also discuss the material removal on the whole surface in this case. All the calculation and simulation will guide practice process.

Design and manufacture of high reflective coatings deposited on metal substrate

With increasing of the laser power, higher demand for high reflective thin films in cavity is needed. Higher reflectivity is beneficial to obtaining higher output power and reducing the heat from the cavity. The reflectivity of metal substrate itself is much higher, and much higher reflectivity can be obtained through depositing thin film. Due to good thermal conductivity of metal, the thin film deposition on metal substrate is usually used in high power laser system. Due to existing absorption, we must design proper film system structure and reduce the output heat from the laser cavity. Copper was used as substrate material. Optimizing the film system can reduce the absorption. High reflective coatings were deposited on copper substrate by ion beam sputtering. When the operating angles are from 10 to 35 degrees, the obtained reflectivity reaches over 99.5% at 941nm, and the reflective band is wide.

Accuracy design of ultra-low residual reflection coatings for laser optics*

Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refractive index inhomogeneity to obtain gradient-index coating. In the normal structure of antireflection coatings for center wavelength at 532 nm, the physical thicknesses of layer H and layer L are 22.18 nm and 118.86 nm, respectively. The residual reflectance caused by refractive index inhomogeneity (the degree of inhomogeneous is between −0.2 and 0.2) is about 200 ppm, and the minimum reflectivity wavelength is between 528.2 nm and 535.2 nm. A new numerical method adding the refractive index inhomogeneity to the spectra calculation was proposed to design the laser antireflection coatings, which can achieve the design of antireflection coatings with ppm residual reflection by adjusting physical thickness of the couple layers. When the degree of refractive index inhomogeneity of the layer H and layer L is −0.08 and 0.05 respectively, the residual reflectance increase from zero to 0.0769% at 532 nm. According to the above accuracy numerical method, if layer H physical thickness increases by 1.30 nm and layer L decrease by 4.50 nm, residual reflectance of thin film will achieve to 2.06 ppm. When the degree of refractive index inhomogeneity of the layer H and layer L is 0.08 and −0.05 respectively, the residual reflectance increase from zero to 0.0784% at 532 nm. The residual reflectance of designed thin film can be reduced to 0.8 ppm by decreasing the layer H of 1.55 nm while increasing the layer L of 4.94 nm.

Study on dielectric constant of SiO 2 thin film in infrared range 400cm -1 -4000cm -1

Dielectric constant study of SiO2 films by combining the Oscillator model with factorial analysis technology was demonstrated. Provide physics meaning for the reverse data process of dielectric constant.