Raman scattering of tetrahedrally-bonded amorphous carbon deposited at oblique angles

Amorphous carbon (t(x)a-C1-x) films were prepared by filtered cathodic are deposition (FCAD). The films were deposited on p-type Si (111). The angle of beam incidence was varied from 0 degrees to 75 degrees with respect to the substrate normal. Micro-Raman spectroscopy, electron energy loss spectroscopy (EELS), and transmission electron microscopy (TEM) were carried out for sample analysis. It was found that the position of the G peak shifts to a higher wave number region as the angle of incidence increases. This means that the sp(2)/sp(3) ratio increases with increasing angle. This conclusion is supported by EELS. The film deposited at an angle of 75 degrees exhibits a columnar structure with alternating high and low carbon density regions. (C) 1999 Elsevier Science B.V. All rights reserved.