摘要
由聚硼硅氮烷前驱体在高温常压下热裂解得到氮化硅纳米纤维,确定了样品结构为α相,讨论了纳米纤维的生长模式属于气-液-固生长机制。在室温下用488 nm激光对样品激发,观察到样品有很宽的强光致发光带,并有两个发光中心,这种强的可见光致发光主要来自氮化硅的内禀S i和N的悬键。测量了纳米纤维的室温吸收光谱,得到氮化硅纳米纤维的光学带隙为4.80 eV。
A method to prepare crystal silicon nitride nanofibers by polysis of polymer with the assistant of FeCl2 catalyst has been presented in this paper. Scanning electronic microscopy（SEM） showed that the size of the nanofibers mostly are 100 -200 nm in diameter and up to several microns in length. The growth mechanism can be explained by vapor-liquid-solid （VLS） model. The XRD pattern of the nanofibers indicated that the fiber belongs to α phase and no other crystalline phases were detected. The optical properties of the single crystalline α-Si3N4 were characterized by absorption and photoluminescence （PL）. The optical absoorption spectrum showed the relationship between absorption coefficient a verse photo energy hv. In order to investigate the optical band gap of α-Si3 N4 nanofibers, we plot the relationship between （ahv）2 and photon energy hr. A linear relationship was observed. That the nanofibers exhibited direct-gap semiconductor behavior with band gap of -4.80 eV, which is different from pure Si3 N4 （ 5.0 - 5.3 eV）. This is possible because the catalyst of Fe is dopped and the Fe element affects the silicon-nitrogen molecular vibration and the states within the band gap of the silicon nitride. Intensive luminescence was observed by bare-eye. The broad emission band can be divided into two discrete broad peak by gaussian type peak fitting. The intensive optical emission are at 1.71 eV and 2.18 eV in PL spectrum at room temperature. It is believed that there exists Si dangling bonds between N3 and Si （called K center） and another point defect identified as the N dangling bonds between Si2 and N （called N center）. These point defects consist of an unpaired electron largely localized on a two-coordinated N and on a three coordinated Si atom, respectively. The two defects give rise to different states, the N center corresponds to a level in the valence band, while the K center is associated to a state in the middle of the gap. The PL emission associates to the inherently imperfect α
出处
《发光学报》
EI
CAS
CSCD
北大核心
2005年第6期794-798,共5页
Chinese Journal of Luminescence
基金
中国科学院"百人计划"资助项目
