| Hexagonal boron nitride?h BN?is a synthetic wide bandgap semiconductor material with a band gap of 6 eV,which is a quasi-direct bandgap material.It has many excellent physical and chemical properties,because it is well-matched to the lattice of graphene?the mismatch rate is less than 1.7%?,it is considered to be the best substrate material for the preparation of graphene,which is very promising to play an important role in graphene electronic devices.However,due to the very harsh preparation conditions of hBN,it is still very difficult to obtain a thin film material with good crystal quality and large size,and because the intrinsic resistivity of hBN material is very high,its application in the field of microelectronics and optoelectronics is limited.Therefore,how to improve the crystal quality and stability of hBN materials and regulate the electrical properties of hBN materials is particularly important.In view of the two aspects above,in this paper,we studied the effect of the growth atmosphere on the quality of hBN films and the in-situ doping of hBN films.The main results obtained are as follows:1.The effect of working atmosphere on the quality of hBN thin films was studied.The RF magnetron sputtering technique was used to prepare hBN thin films with working atmospheres of pure Ar gas and Ar/N2 mixing ratio of 1:1 respectively.The XPS results that the prepared film in a pure Ar atmosphere has a large number of N vacancies,and the B/N ratio is about 2:1.The excess B atoms in the film will combine with O atoms in the air to cause a large amount of boron oxide compounds,which induced the film unstable.The film prepared in the mixed atmosphere,due to the introduction of N2,effectively compensated for the N vacancies.The B/N ratio was1.07:1,which exhibits in a better crystalline quality of the hBN film and a more stable film.2.The Zn in-situ doping technique for hBN thin films was studied.In-situ doping of Zn was performed in RF magnetron sputtering processes using a zinc bar method and a dual-target co-sputtering method respectively.The XPS results showed that the atomic percentage of Zn impurity in the film reached to 6.36%by the zinc bar method.The optical band gap of the film was found to be 5.15 eV by UV-Vis spectroscopy.However,there are some problems that the film has a poor crystal quality,the percentage of Zn dopants cannot be controlled during the doping process,and the film is easily contaminated.The crystal quality of the hBN thin film prepared by the dual-target co-sputtering method is very good,the XPS results show that the atomic percentage of Zn impurities is 0.19%,and the calculated impurity concentration is2.43×1020cm-3.The results of UV-Vis spectroscopy indicated that the absorption edge of the film was red-shifted,at about 250 nm,and the optical band gap was to be calculated about 4.7 eV.The Hall-effect test showed that the film was P-type and the Hall mobility was 186cm2/V·s,the hole concentration was 1.3×1015/cm3.The measured ionization energy was 0.071 eV.Although the impurity ionization energy is very small,the Zn impurities in the hBN film are not fully activated.The probable reason is that a part of the Zn atoms are present as interstitials and they do not bond with N atoms.so the hole concentration is not high.3.The in-situ Mg doping of h BN thin films was studied.In the RF magnetron sputtering processes,dual-target co-sputtering and mixed target sputtering were used.However,since the nature of Mg is very active,when the dual-target co-sputtering method was used,the Mg atoms sputtered from the high-purity Mg target may react with N2 in the mixed working gas,resulting in the production of Mg3N2.When doping with a mixed target,in order to prevent producing Mg3N2,pure Ar was used as the working gas.The XPS test results showed that there were a large number of N vacancies in the film,resulting in deterioration of the crystal quality of the film,and Mg impurities may not effectively activated.This experiment needs further improvement. |
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