First-principles Calculations Of Se-doped Diamond And Preparation Of Porous Diamond Films

In order to explore the electrical properties of selenium(Se)doped diamond and its formation mechanism,as well as preparate porous diamond films,we proceeded from theoretical calculations and experimental preparations.In the theoretical calculation aspect,the first-principles calculations method was used to calculate and analyze the formation energy and electrical properties of Se-doped diamond,and the adsorption and migration behaviors of Se atoms on a hydrogen terminated diamond(001)surface.In the experiment aspect,diamond film and silicon(Si)doped diamond film were prepared by MPCVD method.The silicon substrate of Si-doped diamond film was removed by wet chemical method.The preparation of porous diamond films by etching holes in Si-doped diamond films was studied.The prepared films were examined by SEM and AFM.The research results are as follows:(1)The calculation results of defect formation energy show that Se-doped diamond is difficult to prepare in experiments.1Se1 V doped diamond and selenium,boron(B)co-doped diamond can be prepared in experiments,and the presence of B atom promotes the incorporation of Se atoms into diamond.After the doping of the Se or 1Se1 B atoms,the diamond changed from an insulator to an n-type semiconductor,and it is a direct band gap.The analyses of different electron density maps and Bader charge showed that the Se atom lost electrons and showed as donors.The ionization energy calculations show that the Se atom and the 1Se1 B atoms are deep donors.(2)On the fully hydrogen terminated diamond(001)surface,the Se atom can not bond with the surface carbon atoms or hydrogen atoms.When active sites appear on the diamond(001)surface,the deposited Se atom can bond to the surface carbon atoms.On the diamond(001)surface,Se atoms can easily diffuse.On the diamond(001)surface with two active sites,a Se atom bonded to two surface carbon atoms can be combined by a newly deposited carbon atom to form a C-Se molecule.The C-Se molecule tends to desorb from the surface.(3)Based on the preparation of the(111)crystal phase diamond film,we conducted a silicon doping experiment.After the Si atom was doped,the films first exhibited a cauliflower shape.With the incrasing of hydrogen flux,the Si-doped diamond films gradually showed a distinct(110)crystal phase and silicon carbide(SiC)appeared.Silicon substrates of Si-doped diamond films were removed by wet chemical method.Since SiC and diamond are dispersed,only the surface layer of SiC could be etched away,and no holes formed.In order to prepare porous diamond films by etching Si-doped diamond films,it is necessary to prepare a Si-doped diamond film in which diamond and SiC are interphased and SiC crosses the entire film from bottom to top.