立方氮化硼的振动光谱及反射光谱的研究

 将黑色、黄色、棕色三种小于50 μm立方氮化硼粉末为样品，研究了其红外光谱、拉曼光谱、反射光谱，结果表明：（1）样品的红外光谱中，1 818 cm^-1和1 548 cm^-1属于cBN的晶格本征振动，而立方氮化硼的晶格本征振动外的晶体缺陷吸收则发生在~800 cm^-1，1 580 cm^-1~1 740 cm^-1和大于2 400 cm^-1处。（2）拉曼光谱测试表明，在1 052 cm^-1和1 304 cm^-1附近出现的散射与cBN不具有反演中心及cBN具有立方结构这样的事实相一致，并且这种散射伴随着布里渊区中心声子的横向和纵向发射。144 cm^-1附近出现的散射，被认为是由于局部振荡模式的出现，在反斯托克斯区造成的信号，这与晶格中杂质缺陷有关。（3）依据得到的反射光谱，计算了cBN单晶禁带宽度，发现这三种cBN都具有大于金刚石的禁带宽度值，分别为：E_g(黑)=6.21 eV，E_g(黄)=5.73 eV，E_g(棕)=5.71 eV。

VIBRATIONAL AND REFLECTIONAL SPECTRA OF cBN

Spectra of synthesized cBN crystal (black, yellow, brown in color and <50 μm) were measured by using IR, Raman and UV. The results are described in the following sections: (1) According to the infrared absorption spectrum, the sharp 1 818 cm^-1 and 1 548 cm^-1 absorption spectrum bands is intrinsic vibration of cBN, while the defect absorption appears at 800 cm^-1, 1 560 cm^-1~1 740 cm^-1 and >2 400 cm^-1. (2) The Raman scattering spectrum shows that two lines appeared at 1 052 cm^-1 and 1 034 cm^-1 are in agreement with the fact the cBN possesses cubic symmetry without inversion center. The lines in the spectrum correspond to the Stokes components of first modes Raman scattering with the emission of transverse and longitudinal optical phonons in the center of the Brillouin zone. The presence of line 144 cm^-1 can be accounted for by the emergence of local oscillation modes connected with the presence of impurity-defect complexes in the lattice. (3) The result of cBN reflection at spectrum indicates that three types of cBN crystals possess greater values of band gap which are E_g=6.12 eV (black), E_g=5.73 eV (yellow), E_g=5.71 eV (brown), respectively.