Preparation Of X-ray Fresnel Zone Plates With Super Large Aspect Ratio Based On Atomic Layer Deposition

X-ray has the characteristics of short wavelength,large energy and strong penetrability.X-ray microimaging technology has the characteristics of high resolution,high penetrability and rich contrast imaging mechanism,which can flexibly conduct non-destructive 3D imaging observation on the internal structure of the sample.It has a broad application prospect in the fields of biomedicine,nanomaterials,integrated circuits and environmental detection.In the X-ray micro-imaging system,Fresnel zone plates the core element of X-ray focused imaging,which is based on the diffraction principle.The structure is composed of bright and dark rings alternately,the width of the rings gradually decreases outwardly[9].The resolution is determined by the formula??=0.61?1.22?r?.The smaller the size of the outermost ring,the higher the resolution.The diffraction efficiency of focused imaging depends on the aspect ratio of the waveband,and the higher the energy of the X-ray,the larger the thickness of the waveband.At present,the traditional processing techniques such as electron beam exposure and metal plating can not achieve large aspect ratio and the processing precision is terrible and the price is high.Now,based on the traditional processing and preparation technology,we are striving to break through the technical limit and realize the preparation of high resolution and large aspect ratio wave band.In this paper,based on atomic layer deposition technology?ALD?,the transparent and opaque film structure was deposited on the central substrate with a certain diameter,and then it was cut and polished by combining with focused ion beam micro-nano processing technology?FIB?to achieve the preparation of high resolution and large aspect ratio.The main research contents and specific work are as follows:?1?The focusing imaging principle and structural characteristics of wave band plates are introduced,and the internal relations between spatial resolution and diffraction efficiency of wave band plates and structural parameters of wave band plates are derived in detail.This paper discusses the selection basis of multilayer film lamination materials of wave band plates,and gives the optimal cutting thickness of wave band plates of four different composite systems?Hf O₂/Al₂O₃,Si O₂/Al₂O₃,Ir/Al₂O₃,Ta₂O₅/Si O₂?under different X-ray energies?500e V,8 ke V,15 ke V?.According to the requirements of practical application scenarios,the structural parameters of wave band plates under the incident energy of 500 e V and 8 kev X-ray were designed.The composite of multilayer film laminae Hf O₂/Al₂O₃,the central substrate diameter was 190?m and 45?m,the number of multilayer film cycles was 382 and339,the outermost ring size?r was 25 nm and 40 nm,and the imaging focal length of waveband plates was 19.355 mm and 2.117 mm.?2?The preparation of Al₂O₃,Hf O₂and Ta₂O₅films under different technological conditions based on atomic layer deposition technology was studied.The growth characteristics of the films were characterized by SEM,AFM and XPS.The center substrate tungsten wire and optical fiber with a certain diameter and smooth surface were prepared by electrochemical etching and high stability plasma heating.A series of soft and hard X-ray band lamination structures were prepared in the center substrate by atomic layer deposition technique.?3?The focused ion beam micro-nano processing method was adopted to cut,polishing,transfer and fix 8 ke V and outermost ring 40 nm X-ray band film.X-ray band film focusing imaging test was carried out on 4W1A experimental platform of Beijing synchrotron radiation source X-ray imaging experimental station,and 50nm resolution focusing imaging was achieved.