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Focused Ion Beam Milling of Crystalline Diamonds Rustin Golnabi1, Won I. Lee1, Deok-Yang Kim1, and Glen R. Kowach2 Bergen County Academies, 200 Hackensack Avenue, Hackensack, NJ 07601, U.S.A. 2 Department of Chemistry, The City College of New York, 160 Convent Avenue, New York, NY 10031, U.S.A. 1

ABSTRACT Recently, a wide range of new applications of diamond materials such as spintronics, field emission, and bio-sensing have been proposed. These applications often require the precise patterning of diamonds, which is not trivial because diamonds are the hardest materials known in nature. Among various patterning techniques, the focused ion beam milling method has been proven to provide flexibility as well as high resolution in the pattern design. In this study, a focused beam of 30 kV Ga+ ions was utilized to create sub-micrometer size patterns out of crystalline diamonds. The sputtering rate, re-deposition, and surface roughening of diamond structure have been closely monitored with various milling parameters during the milling process. Our study revealed a low milling yield of 0.02 m3/nC, high Ga content re-deposition, and the formation of sub-micron scale terracing on the sidewall of patterned diamonds. INTRODUCTION Focused ion beam (FIB) milling has recently found many applications in a variety of nanoscale patterning and fabrication. It is often utilized in the maskless micromachining and patterning of materials [1], especially metal alloys, due to the high level of precision provided by the technique [2]. Furthermore, the application of FIB to microfabrication has become increasingly popular, due to the lack of necessity for a mask, high resolution to microscale features, and versatility in numerous geometric patterns [3]. In particular, this study involves the use of gallium (Ga+) ion milling, commonly used in FIB systems. Previously, gallium FIB has also been used in ion beam-induced deposition with various precursors [4]. For diamond, one of the only viable ways to fabricate microscale patterns is by focused ion beam. Recently, several applications of diamond materials such as spintronics, field emission, and bio-sensing have been studied [5-7]. These functions often require the precise pattering of diamond, which is difficult because diamond is such a hard material; consequently, FIB is one of the few methods by which diamond can be precisely patterned [8]. However, a number of additional effects makes the process rather unpredictable and arduous. Re-deposition of both the milled carbon and Ga+ ions from the FIB results in unintended structural formations, while nanoterracing ("ripple") effects often disrupt clean milling patterns [9]. Consequently, it is necessary to determine methods by which to minimize such detrimental effects for the efficient milling of diamond materials for a number of significant applications. In this study, several varying conditions are used in milling diamond in order to observe the effects of re-deposition and nano-terracing on single-crystal milling, as well as determine the a