Fabrication and orientation control of diamond nanotips by broad ion beam etching

Well-aligned diamond nanotips are fabricated by etching as-grown diamond thin films using a Kaufman type broad ion beam source. The nanotips have nanometre-size heads, micrometre-size roots and the same apex angle. All of the nanotips consistently point in the direction against the incident ion beam. The orientation of diamond nanotips can be controlled by adjusting the incident direction of the ion beam. The Raman spectrum does not show a significant increase in graphitic peak intensity after etching, indicating that the quality of diamond is barely degraded by ion beam etching. Near-edge x-ray absorption fine structure spectra show that the diamond sp(3) structure is dominant in the spectra of both as-grown and ion etched diamond. The sp(2) fraction is found to increase by about 12% at the surface layer of the diamond nanotips as compared with as-grown diamond. The formation of diamond nanotips is explained by Sigmund's sputtering theory and the angle-dependent sputtering mechanism. This method to produce diamond nanotips has the advantage of excellent orientation control and the capability to produce nanotip arrays on a large area.