| Atomic fluorine anion(F-) is a monovalent anion(or monovalent negative ion) through the attachment of an electron to atomic fluorine.As one of the important chemical intermediates,atomic fluorine anion is potentially useful in many fields such as semiconductor etching,filming,and material modifications,etc.This dissertation presents the synthesized of F- anions storage-emission material [Ca24Al28O64]4+.(F-)3.36(O2-)0.32(C12A7-F-).Its structural characteristics,anion storage and emission characteristics were observed.C12A7-F- can be used as a high pure F- anion source.The anion storage-emission mechanisms of C12A7-F- was further revealed.The high pure F- anion source was found to be useful for the etching of Si and SiO2.The major conclusions have been summarized as follows:(1) Synthesis and structure characterization of C12A7-F-.The C12A7-F- sample synthesized by sintering CaF2,CaCO3 andγ-Al2O3 at 1350℃for 8 hours under flowing Ar atmosphere,then annealing at 780℃under flowing F2/Ar mixture (F2:Ar=5:95) atmosphere for 10 hours.The field emission scanning electron microscopy(FESEM),BET and X-ray diffraction(XRD) measurements indicated that C12A7-F- belongs to I(?)3d space group with a lattice constant of 11.969±0.002(?).The BET surface area and average pore diameter are about 1.073 m2/g and 42.6(?),respectively.No obvious structural damage was found after running the emission.(2) Anions emission feature.The emission features of C12A7-F-,including temperature effects,the applied extraction field effects,the emission branch ratio and the apparent activation energy,the emission stability have been investigated by using time-of-flight mass spectrometry.It is showed that the F- is the dominating emitted anion,and its emission intensity increases with the increase of the temperature and the extraction field.The apparent activation energies of anions decrease with the increase of the extraction field which can be approximately described Schottky formula.(3) Anions storage feature.The ion chromatography(IC),electron paramagnetic resonance(EPR) and Raman spectroscopy(RS) measurements indicated that the anionic species stored in the C 12A7-F- material was dominated by the F- anions ((1.96±0.25)×1021 cm-3),accompanied by small amount of oxygen-containing anions,which also agrees with the distribution of the emitted anions via the TOF observations.The chemical formula of present material is approximately described as[Ca24Al28O64]4+·(F-)3.36(O2-)0.32(abbreviated as C12A7-F-).(4) Anions emission mechanism.In the sintered process,the encaged F- and O2- anions are formed simultaneously and the concentration of the encaged F- anions are enhanced by substituting the F- anions for O2- anions during the subsequent annealing process.The F- emission is attributed to the encaged F- anions in C12A7-F- migrating from the bulk onto the sample surface by field-enhanced thermal diffusion,and then desorbing to the gas phase.The minor O- and electron emission are mainly generated from the dissociation of residual O2-.(5) F- emission current.The emission current densities from the C12A7-F- sample are also measured.With the emission branch ration obtained by TOF-MS spectra, the emission current densities of different anions are estimated.The F- emission current density could reach aμA/cm2 level.When supplying fluorine gas and electrons,a sustainable and stable F- emission beam can be obtained.(6) Etching of Si and SiO2 by F-.Particularly,the atomic fluorine anions were found to be useful for the etching of Si and SiO2,evaluated by the morphological alterations via a field emission scanning electron microscope(FESEM),the surface composition's changes using X-ray photoelectron spectroscopy(XPS).It could be concluded that C12A7-F- can be used as a good F- anions storage and emitter material for its stability and the ability to emit high-pure F- flux,which is useful for the etching or surface modification for the semiconductor materials or other materials.
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