Materials & Thin films
2019, 48(S2): 68-74.
doi: 10.3788/IRLA201948.S217001
As an alternative to 3He neutron detectors, boron-coated neutron detectors have been a current focus for researchers worldwide. For the boron-coated neutron detectors, a B4C film with low stress and good adhesion to the Al substrate is required. To enhance adhesion of the B4C films on Al substrates, a B4C film with low stress was fabricated by direct current sputtering technique without substrate-heating. The Mg-Al alloy thin film was introduced between the B4C film and its substrate for enhancing the adhesion. The effect of sputtering pressure on the stress of B4C films during deposition was studied. Additionally, the adhesion of B4C films using Mg-Al films as adhesive layers and effects of sputtering pressure and alloy film thickness on adhesion were studied. Scanning and transmission electron microscopies were used to characterize the microstructure. Experimental results show that the stress of B4C films decreases and stabilizes when sputtering pressure increases during deposition. Thin and porous Mg-Al films react well with both B4C films and Al2O3 on Al substrates to enhance adhesion of the B4C films, without substrate-heating.
2019, 48(S2): 75-80.
doi: 10.3788/IRLA201948.S217002
A thorough research of the optical properties of structural color generation based on grating/colloidal crystal was reported in terms of structural design, experimental preparation and spectral color rendering performance testing. Around realizing wide color gamut, narrow band gap, high brightness and anisotropic structure photonic crystal color control problems, the color mechanism of grating/colloidal crystal microsphere composite photonic crystals was explored by gravity deposition and vertical deposition.Taking the gravity sedimentation method, when the concentration of the dispersion was 1%, the colloidal microspheres were uniformly attached to the grating. When the concentration of the solution was 5%, the PS beads can be closely arranged, but cannot form a single layer or double. The layer structure would precipitate multiple layers and the grating structure was not observed. With the vertical settlement assembly method, when the concentration of the dispersion liquid was 1%, the assembly effect was not good and a dense structure couldn't be formed. When the solution concentration was 5%, the composite structure was assembled well, and the colloidal crystal was assembled in the grating groove. The spectral performance was tested and its color properties were evaluated, which laid a theoretical and practical foundation for its effective application in the field of anti-counterfeiting printing.
2019, 48(8): 817001.
doi: 10.3788/IRLA201948.0817001
Using transfer matrix and equivalent principle, the Tamm state on the surface of the symmetric photonic crystal was investigated in the new point of energy levels. The result shows that when the symmetric system is an infinite periodic structures for photonic crystal, there is impedance mismatch between incident medium and photonic crystal, thus the optical Tamm state on the surface doesn't exist. When the photonic crystals is truncated to finite period structure, it supports the appearance of the optical Tamm state on the surface, and the doubly degenerated energy level of TE and TM polarization appears in the energy band. In optical off-axis transmission, the optical Tamm state form the passband edge non-degenerated energy which is restricted on on the surface of photonic crystal. When the truncation parameter is matched with the high refractive index of outmost layer, it is easy to form a strong optical Tamm state. But when it is matched with the lower refractive index of outmost layer, it is difficult to realize the surface state. When the surface state of photonic crystal is excited by the ATR total reflection technique, the coupled resonance absorption can be observed. The properties of optical Tamm state on the surface of photonic crystal can provide guidance for research and design of optical waveguide or surface wave sensor.
2019, 48(8): 817002.
doi: 10.3788/IRLA201948.0817002
An experimental platform capable of continuously controlling the polarization angle of the 1 and 2 lights was constructed, and a series of all-optical poling of the silicon germanium glass sample was realized. The poling effectiveness and poled direction, which were determined by the magnitude and direction of internal electric field, correlations of which with the poling polarization state and intensity were studied. Basically the experimental results were consistent with the classic model and its derivation, but quantitative inconsistencies were found as well, including local tendency, angle size, etc, which further proved the complexity of the all-optical poling process. It was experimentally found that the effectiveness of the poling process was the best when 1 and 2 lights were polarized parallel, and the poling process was also very sensitive to the poling intensity.
2019, 48(11): 1117001.
doi: 10.3788/IRLA201948.1117001
Evaporation characteristics and optical constants of LaF3 materials in 2.5-12 m infrared band were investigated. With low refractive index LaF3 materials, high-durability antireflection (AR) coatings in 3.7-4.8 m medium-wavelength infrared bands were designed and fabricated on Ge substrate. SEM image of the AR coatings with the LaF3 shows that the surface nanocrystals is uniform and densified. The measured optical properties by Fourier tranform infrared spectrometer indicate that the peak transmittance is as high as 99.4%, and the average transmittance increases to 98.8% from 47.7% in 3.7-4.8 m after double-sided coating. The firmness and durability environmental tests signify that this AR coating can work in harsh environment while maintaining good optical properties.
2019, 48(11): 1117002.
doi: 10.3788/IRLA201948.1117002
The technology of magnet-assistant pulsed laser deposition was advanced. A magnetic field whose magnetic lines pointed to the substrate was fixed around the silicon substrate when the diamondlike carbon(DLC) film was prepared by pulsed laser deposition(PLD), so that the ions those flied outside of the substrate were drove to fly to the substrate potentially and participate in the course of filming. The concentration of the ions increased based on the centralization of the ions, and the content of the non-electriferous granule reduced indirectly. Compared with the DLC film prepared without magnetic field, not only the deposition velocity of the DLC film prepared under magnetic field increased sharply, but also the mechanical hardness improved. Of the most importance, this research testified to the high efficiency of the ionization by the laser to the target, offering the base of the feasibility to the combinability between the technologies of the PLD and filtration by magnetic field.
2019, 48(10): 1017001.
doi: 10.3788/IRLA201948.1017001
Short-medium wave infrared detectors can work both in the low light night vision band and medium band at the same time, which can meet the requirement of complex detection environment. Infrared detector are widely used in military and civil fields. In order to improve the precision of infrared detector and shorten the response time, it is necessary to develop a wide band film with high transmittance that meets the system requirements in the short-medium band. The evaluation function of the variable scale algorithm was optimized based on the Baumesiter anti-reflection membrane design theory. A new weighted evaluation function model was established to design the membrane system structure with low sensitivity and high tolerance in the water absorption band of 2.6-3.3 m. The influence of different ion source assisted deposition parameters on the spectral characteristics of MgF2 was studied by optimizing the preparation technology for the water absorption band. Meanwhile,a step annealing process was used to obtain an effective method to reduce the water absorption. Finally,the spectral transmittance of the prepared film was greater than 96.5%.
2019, 48(10): 1017002.
doi: 10.3788/IRLA201948.1017002
Theoretical thermal desorption and in situ temperature programmed desorption(TPD) were developed to study the degassing of contaminants adsorbed in III-nitride photocathodes assembly. In the frame of Malev'sadsorption-diffusion outgassing theory, one dimensional slab was used to model the photocathodes assembly. By using the first and the second Fick'slaw, the expressions of the special gas concentration, the specific gas outgassing rate and the amount of degased specific gas over the time in the degassing process were obtained. To make it more intuitional, these parameters were ploted over time within different diffusion coefficient magnitude at the approximation of fourth order. In the TPD method for III-nitride photocathodes assembly, residual gas mass spectrum was thoroughly studiedat different constant temperature stage to determine which gases were desorbed into the vacuum. The least square method was employed to fit the expression of the specific outgassing rate at the constant temperature of 1 000 K, and the diffusion coefficient D for outgassing N2 was 510-5 cm2/s in the dynamic method of degassing process. By combining theoretical analysis with TPD experiments, the heating up temperature for sufficient outgassing the contaminants from the III-nitride photocathodes assembly was evaluated and verified.
2019, 48(10): 1017003.
doi: 10.3788/IRLA201948.1017003
Aiming at the shortcomings of traditional hyperspectral imaging system, such as large volume and weight, complicated structure of optical machine and high cost, it was urgent to meet the needs of miniaturization. The research on the design and preparation of distributed Bragg reflector(DBR) in hyperspectral imaging chip was carried out, and the simulator of multilayer film structure was developed. The fabrication of 5-layer film DBR and 7-layer film DBR were completed according to the structural design. The visible/near-infrared spectrophotometer was used to measure the reflectivity of the DBR, and the simulator for comparison, due to the existence of flaw in the actual preparation of the DBR, resulting in a error of 3%, The multilayer film structure simulator can guide the preparation of the actual DBR and lay the foundation for the hyperspectral imaging chip.
2019, 48(10): 1017004.
doi: 10.3788/IRLA201948.1017004
Microbial aerosols, as an important component of atmospheric aerosols, can affect atmospheric radiation characteristics through absorption or scattering. At present, the research on the optical properties of microbial aerosols is mostly limited to single-band or single germplasm. It is impossible to generalize the generality and particularity of microscopic aerosol optical properties, which is not conducive to comprehensively analyze the effects of microbial aerosols on atmospheric radiation characteristics. Herein, the spectral reflectances of three eukaryotic microbe and three prokaryotic microbes in the waveband from 0.25 to 15 m were measured. Based on the Kramers-Kroning algorithm, the complex refractive index (CRI) m was calculated and the FTIR spectra of microbes were analysed. The similarities and differences between the optical properties of the 0.25-15 m band of eukaryotic and prokaryotic microorganisms were compared. The conclusion can help to comprehensively understand and quantitatively calculate atmospheric radiation characteristics, provide theoretical support for microbial aerosol remote sensing detection and type identification, and provide new ideas for the development of new functional materials.
2019, 48(10): 1017005.
doi: 10.3788/IRLA201948.1017005
The vanadium oxide thin film with high quality was prepared on c-Al2O3 substrate for the first time by magnetron sputtering with rapid thermal process(RTP). Firstly, the surface particle size of the film was uniform, the surface root mean square roughness was about 16.75 nm, the major components of the film were VO2 and V2O5, V4+ content was about 78.59%. The prepared vanadium oxide thin films had the stable property of thermal-excited phase transition; Secondly, the terahertz transmission modulation was characterized by terahertz time-domain spectroscopy system(THz-TDS). The result indicated that the transmission ratios of the film increased with increasing optical excitation power; Finally, the amplitudes of the THz waves for vanadium oxide without any obvious fluctuation after the optimized process conditions of preparation and transmission ratios were nearly stable within repeated testing by in-site test, could be widely used for THz devices such as modulators and switches.
