The Research On Preparation And Field Emission Properties Of Lanthanum Hexaboride Nanostructure Arrays Film

Lanthanum hexaboride?LaB₆?is an ideal field emission candidate material,which combines the characteristics required by excellent field emission cathode materials.It has a broad application prospect in transmission electron microscope,high frequency electronic equipment,sensor and display.The cathode of field emission with nanostructure arrays is an excellent field emission cathode structure.However,it is a great challenge to fabricate LaB₆ nanostructure arrays at present.In this paper,LaB₆ nanostructure arrays were prepared by magnetron sputtering LaB₆ on anodic alumina templates.The effects of anodic alumina template morphology on the morphology and field emission properties of the nanostructure arrays were systematically studied,and the effects of ion beam treatment on the morphology and field emission properties of nanostructure arrays were further investigated.The main research work and results are as follow:Three kinds of anodic alumina templates were prepared by anodic oxidation.In oxalic acid solution,U-shaped and V-shaped templates were prepared by adjusting the steps of anodic oxidation,and the pore size with 130 nm and 180 nm characteristics templates were prepared at different anodic oxidation voltages by optimizing hard anodic oxidation.The pore depth characteristic templates with pore depths of 240 nm,620 nm and 1600 nm were prepared by controlling the time of the second anodization.The highly ordered and vertically arranged LaB₆ nanostructure arrays can be fabricated by AAO template assisting method.U-shaped and V-shaped cross-section characteristic templates can assist in the preparation of nanotube arrays and nanorod arrays,and partially open-end nanotube arrays and cap-end nanotube arrays can be fabricated with pore size characteristic templates of 130 nm and 180 nm.The pore depth characteristic templates of 240 nm and 1600 nm can be used to fabricate cap-end nanotube arrays,cap-end nanotube arrays and open-end nanotube arrays.The open nanotube arrays prepared by hole depth characteristic template have good field emission properties,low opening field strength of 6.8 V/?m and high field enhancement factor 496.Both the oblique angle of ion beam and the vertical bombardment can effectively adjust the morphology of LaB₆ nanostructure arrays and enhance its field emission performance.With the prolongation of ion bombardment time,the cap-end nanotube arrays gradually changed into open-end.When the oblique ion bombardment time is90 s and the vertical ion bombardment time is 30 s,all the cap-end nanotube arrays turned into open-end with sharp edges.With the prolongation of ion beam bombardment time,the ratio of B/La atoms on the surface of LaB₆ nanostructure arrays decreases gradually.The enrichment of La atoms on the surface is conducive to reducing the vacuum barrier of electron escape,thus reducing the work function.Combined with the change of morphology and atomic ratio,when the angle of oblique bombardment time is 90 s,the turn on filed decreases from 8.2 to 6.8 V/?m,and the emission current density increases 5.5 times at 11V/?m.When the vertical bombardment time is 30 s,the turn on filed decreases from 8.2 to 6.9 V/?m,and the emission current density increases 6.2 times at 11V/?m.The cap-end nanotube arrays turn into open-end and the enrichment of La atoms on the surface play an important role in improving the field emission properties of nanotube arrays.