The Si-of Tasi <sub> 2 </ Sub> Eutectic Self Composite For Field Emission

As one of the semiconductor-metal eutectic material (SEM), the rod-like eutectic in-situ composite of Si & TaSi2 has lower work function , excellent electrical transport and the schottky junctions, which was grown-in during the crystal growth step. Therefore, in this paper, two directional solidification methods, Czochralski method and electron-beam floating zone melting method, were used to obtain such material. The directional solidifition microstructures of Si-TaSi2 system was performed using NEOPHOT-1, AMRAY- 100B SEM and JEM-2000CX TEM analysis technique.The effect of the technique parameters to the microstructure of the eutectic in-situ composite was discussed firstly. On these basis, the. optimum process parameters were founded. With a seed rotation rate of 12rpm, a crucible rotation rate of 6 rpm, a seed puller rate of 12cm/h and a crucible rise rate 1.2cm/h, the average inter-rod spacing was 9-10 um, the average rod diameter was 1.79um, the average rod density was 0.925 X 106 rod/cm2 and the volume fraction was 2.3277%. These parameters all meet the requirement of field emission material. When the solidification rate was changed from 8 to 20 cm/h, with the increase of solidification rate R, the fibre diameter (d) and the inter-rod spacing (A ) both decreased. The former followed linearity rule and the latter followed the rule of λεr-0.5 The volume fraction was steadiness when the solidification rate increased. On condition of controlling solid-liquid interface preferably and keeping low directional solidification rate, there were particular phenomena in TaSi2 fibre development process. Generally, it can be divided into three typical steps. The first was star-up period, the second was competition period, the third was stabilization period. As the relationship of phase interface between Si matrix and TaSi2 fibre was studied, it resulted that the interface between the two phases was evidently. This proved that the low energy inter-face was formed. The ruleof two phase was [111]Si//[0001]TaSi2, (220) Si//(2200)Tasi2. The two coupling phasewas firstly developed in the low-energy surface. In the course of studying the fibre parameter in different development period, it was discovered that the rod density increased from the top to the middle of the boule. But it did nearly not changed from the middle to the bottom. In the same wafer, the fibre parameter was different along the radial. It was high at the edge and low in the center section. The fibre traverse section was multiplicity. The result showed that the composite had excellent fieldemission characters. The star-up field intensity was 4.4v/um and the F-Ncurve indicated that the electron emission was leaded by tunnel effect.The connection of microstructure and floating zone melting process was studied . The result indicated that the two phases in eutectic had difficulty in growing regularly on condition that the floating zone melting rate was in the scope of 0~0.3mm/min. The matrix phase was directional grown and the other phase was grown with no order. It was dispersed in the matrix phase . At the rate of 0.6mm/min, the two phases of Si-TaSi2 system was grown eutectic regularly. The fibre phase was developed in star-up process, competition process and stabilization process. Compared with the fibre distribution by CZ method and EBFZM method, it was discovered that the former was uniformity and slim, the latter was better for alignment.