Influence of Processing Conditions on Mechanical and Structural Properties of DLC Produced by FIB-CVD Method
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Influence of Processing Conditions on Mechanical and Structural Properties of DLC Produced by FIB-CVD Method Naomichi Sakamoto1, Yusai Akita2, Hiroyuki Harada2, Takuya Yasuno1, Yasuo Kogo2 1 Department of Science and Engineering, Iwaki Meisei University, 5-5-1 Chuodai-Iino Iwaki, Fukushima, Japan 2 Department of Materials Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda 278-8510, Japan ABSTRACT Influence of processing condition on mechanical and structural properties of diamondlike carbon (DLC) by focused ion-beam chemical vapor deposition (FIB-CVD) method was investigated. The DLC specimens were produced under conditions of varying supplied amount of material gas and probe current of FIB. Volume determination results of DLC structures indicated that a deposition rate was increased with both the amount of gas and the probe current. To evaluation of mechanical property, indentation hardness was measured by a nano-indentation tester. From evaluation of mechanical property, it was found that the indentation hardness was sensitive to the processing condition, showing in the range of 8-13 GPa. The hardness of DLC structures was seemed to be lower when etching process higher contributed for formation process. Crystallographic structure of DLC remained amorphous even though the mechanical properties varied widely. Results of hydrogen concentration measurement indicated that increase of hydrogen concentration might lead to decrease of hardness. INTRODUCTION Focused ion-beam chemical vapor deposition (FIB-CVD) method is one of the techniques to realize production of three-dimensional micro/nanometer-order structures with complex shapes. With this method, micro/nanometer-order diamond-like carbon (DLC) structures can be produced using phenanthrene (C14H10) gas as source material. Since DLC is widely used as coating material because of its superior mechanical and tribological properties, a combination of FIB-CVD method with phenathrene source gas to produce DLC must have potential for producing nano-machine parts for MEMS/NEMS. Actually, device application with this combination has been reported and excellent geometric properties of DLC structure by FIBCVD has been demonstrated [1]. In FIB-CVD method, it is widely accepted that DLC are deposited by chemical decomposition of phenanthrene gas due to interaction with secondary electron generated by ionbeam irradiation on substrate and/or the DLC itself. In addition, it was experimentally revealed that etching process occurred simultaneously with deposition process during DLC formation [2]. However, mechanism of DLC deposition using FIB-CVD method remains to be fully elucidated. To clarify the deposition mechanism, it is believe that investigation on influence of processing condition on several properties of deposited DLC structures is valid. In this study, therefore, relationships between processing conditions of FIB-CVD and mechanical/structural properties of DLC were investigated. In production of DLC specimens, supplied amount of
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material gas and
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