激光蒸发产生的GaxAsy—,GaxPy—与InxPy—及其质谱

在自制的激光等离子体源飞行时间质谱计上,以脉冲激光束轰击砷化镓、磷化镓、磷化铟等由Ⅲ A族和Ⅴ A族元素组成的半导体材料,可以产生Ga_xAs_y~-、Ga_xP_y~-与In_xP_y~-等二元原子簇负离子,质谱分析发现,在这些负离子中,所有含奇数个原子的簇离子的信号强度相对较高,说明这些原子簇均具有特殊的电子构型。

Mass Spectrometry of Laser Generated Ions Ga_xAs_y-, Ga_xP_y- and In_xP_y-

Both positive and negative cluster ions of GaxAsy, Gax,Py and InxPy were generated on a self-built laser probe time-of -flight mass spectrometer. Cluster ions only consist of the metal atoms in the samples were found in the positive mass spectra. While the negative mass spectra showed an alternation of the cluster ion intensities with the odd/even total number of atoms (metal and non-metal)in the clusters. This result is attributed to that all the valence electrons in the clusters of odd atom number are paired, thus stable. Besides, in the mass spectra of gallium phosphide and indium phosphide, it is observed that the x value in MxPy(M = Ga,In) can be quite large, while the y value is small,with those peaks of y=2 comparately stronger. Pn- ions are also observed, and P2- is the most abundant. It is proposed that, based on the above result, these cluster ions are formed by adding the metal atoms to the Pn- ions, which are easier and earlier formed. Further studies on both theoritical computation and experimentation are being carried on.