Nano-structuring, surface and bulk modification with a focused helium ion beam

Daniel Fox,Colm C Faulkner,Yanhui Chen,Hongzhou Zhang

doi:10.3762/bjnano.3.67

Abstract

We investigate the ability of a focused helium ion beam to selectively modify and mill materials. The sub nanometer probe size of the helium ion microscope used provides lateral control not previously available for helium ion irradiation experiments. At high incidence angles the helium ions were found to remove surface material from a silicon lamella leaving the subsurface structure intact for further analysis. Surface roughness and contaminants were both reduced by the irradiation process. Fabrication is also realized with a high level of patterning acuity. Implantation of helium beneath the surface of the sample is visualized in cross section allowing direct observation of the extended effects of high dose irradiation. The effect of the irradiation on the crystal structure of the material is presented. Applications of the sample modification process are presented and further prospects discussed.

Highlights

Ion beams are widely used to modify the physical and chemical properties of the surface of materials with a high degree of control
We have demonstrated that a focused helium ion beam can modify a surface’s physical properties, such as crystallinity, roughness and thickness, in a controlled manner. 35 keV helium ions were used to produce a surface which was smoother than could be achieved by 30 keV focused ion beam (FIB)
Thickness dimensions can be reduced to just a few tens of nanometers. This is critical for techniques in aberration corrected transmission electron microscopy (TEM) such as atomically resolved energy loss spectroscopy (EELS) [30]

Summary

Introduction

Ion beams are widely used to modify the physical and chemical properties of the surface of materials with a high degree of control. The extended high frequency information in the diffraction pattern recorded from the HIM modified region in Figure 2d indicates that this area of the sample is thinner, while still retaining its high quality crystalline structure.

Results

Conclusion