Infrared Radiation Properties Of Salisbury Screen Films

Thermal radiation is common phenomenon existing in nature.The control over thermal radiation in infrared spectral region is of significance in a number of emerging technologies including infrared camouflaging,thermal energy harvesting and radiative cooling etc.Electromagnetic resonant structure enables the control over light behaviors,which thus offers a promising way for manipulating thermal radiation properties of objects.In this thesis,we applied the classical microwave Salisbury screen to higher frequencies of mid-infrared region,and demonstrated structure-controlled infrared absorption and emission.Based on the wave absorption mechanism of quarter wavelength cavity,we designed and fabricated Salisbury screen multilayered films,which exhibited variable infrared absorption and emission in terms of central wavelengths and spectral bandwidth.These results are helpful for further development of artificial structured materials with tunable infrared properties.The main research results obtained in this thesis include:(1)Based on the transfer matrix method,infrared Salisbury screen multilayered films with variable infrared absorption and emission were designed and simulated.Our designed Salisbury screen multilayered films were made of 300 nm Cu,a ZnSe dielectric layer and 6nm NiCr film.The thickness of ZnSe film was used as a key parameter to control over the infrared absorption and emission.Simulation results suggested that as the ZnSe film increased from 400 nm to 900 nm,infrared absorption and emission of the multilayer was tuned within the whole range of 4~10μm.Meanwhile for a fixed wavelength of 5.1μm,as the ZnSe film thickness took the values of 1/4,3/4 and 5/4 of the wavelength,bandwidth of infrared absorption and emission of the multilayer decrease from 110.9% to 17.6% of the central wavelength,exhibiting a bandwidth-variable property.(2)Salisbury screen multilayered films were fabricated and characterized,whose variable infrared absorption and emission were demonstrated in terms of both wavelength position and spectral bandwidth.According to our theoretical designs and simulations,we fabricated a series of Salisbury screen multilayered films using electron beam deposition technique.The multilayer films are made of 300 nm Cu,a ZnSe dielectric layer and 6nm NiCr film.Thickness of the ZnSe film took four different values of 400 nm,500nm,760 nm,900nm,respectively.Infrared spectroscopy measurements indicated that as the ZnSe film thickness increased from 400 nm to 900 nm,infrared absorption and emission of the multilayer shifted from 4.38μm to 9.398μm,enabling control over the spectral position of the infrared emission.In addition,as the ZnSe thickness took the values of 500 nm,1530nm and 2550 nm,according to 1/4,3/4,5/4 of the 5.3μm wavelength,the spectral bandwidth of the infrared absorption and emission gradually decreased from 122.6% to 18.5% of the central wavelength,exhibiting a bandwidth-variable property.These measured variable infrared absorption and emission are in good agreement with simulated results,which suggests that our demonstrated Salisbury screen multilayered structure offers an effective and relatively simple way for controlling over the thermal radiation property.