La-doped diamond films prepared through microwave plasma chemical vapor deposition

Abstract

La-doped diamond films were deposited through a microwave plasma chemical vapor deposition (MPCVD) system. The effects of La addition on the morphology, microstructure, and quality of the diamond films were systematically investigated. The analysis of secondary ion mass spectroscopy and X-ray photoelectron spectroscopy indicates that lanthanum atoms were incorporated into the diamond films through MPCVD with lanthanum (III) acetate as a precursor. The characterization results reveal that different lanthanum dopant flows can affect the morphology, the preferred orientation of the crystal, and the diamond phase fraction in the films. Upon the lanthanum addition with the dopant flow of 30 sccm, the intensity ratio of the (220) to (111) peaks [I(220)/I(111)] decreases from 20% to 17% and the sp3/sp2 ratio is reduced from 8.53 to 5.89. However, with the increase of the lanthanum dopant flow to 90 sccm, the intensity ratio of I(220)/I(111) rises up to 39% and the sp3/sp2 ratio increases to 8.99. Therefore, a certain amount of lanthanum addition can promote the growth of (110) orientation grains and enhances the sp3 phase fraction in the deposited diamond films. The results obtained from this study provide a hint for adjusting the morphology and microstructure of diamond films with rare earth element doping.