Focused Ion Beam Induced Surface Damage Effect on the Mechanical Properties of Silicon Nanowires

Abstract

¡n this paper, the effect ofswface damage induced by focused ion beam (FIB) fabrication on the mechanical properties of silicon (Si) nanowires (NWs) was investigated. Uniaxial tensile testing of the NWs was performed using a reusable on-chip tensile test device with 1000 pairs of comb structures working as an electrostatic force actuator, a capacitive displacement sensor, and a force sensor. Si NWs were made from silicon-on-nothing (SON) membranes that were produced by deep reactive ion etching hole fabrication and ultrahigh vacuum annealing. Micro probe manipulation and film deposition functions in a FIB system were used to bond SON membranes to the device's sample stage and then to directly fabricate Si NWs on the device. All the NWs showed brittle fracture in ambient air. The Young's modulus of 57nm-wide NW was 107.4 GPa, which was increased to 144.2 GPa with increasing the width to 221 nm. The fracture strength ranged from 3.9 GPa to 7.3 GPa. By assuming the thickness of FIB-induced damage layer, the Young's modulus of the layer was estimated to be 96.2 GPa, which was in good agreement with the literature value for amorphous Si.

Mechanical reliability of FIB-fabricated WC–Co cemented carbide nanowires evaluated by MEMS tensile testing

“…The produced device consists of many sets of comb structures used as electrostatic actuator for tensile force application and capacitive sensor for displacement and force measurements [4]. The NW's elongation during the test is basically measured from the difference in displacement between the two sensors equipped in both ends of a specimen.…”

“…3 shows developed MEMS tension test device made from a silicon-on-insulator (SOI) wafer. The SOI wafer was composed of a 35 lm-thick p-type device layer of 0.05 X cm, a 2 lm-thick buried oxide layer, and a 300 lm-thick handle layer [3,4]. The device was produced by using conventional micro fabrication techniques.…”

“…For the micron-sized specimens like sputtered films, many types of tensile test techniques have been developed so far [9][10][11][12][13][14][15][16][17][18][19]. We have several types of mechanical testing techniques for thin films and NWs [3,4,[9][10][11][20][21][22][23]. By adopting them to evaluating size effect phenomena within the nano-millimeter size range, investigating the limit size showing its excellent mechanical characteristics is of significance, for realization of future strong MEMS components made of hard metals.…”

“…For the nano-and submicron-sized specimens, MEMS-based on-chip tensile test devices that have been proposed by many researchers are used very often [2][3][4][5][6][7][8]. By using electrostatic actuator or thermal actuator, tension force can be applied to Si NWs [2][3][4], C NWs [5,6], and other metallic, semiconductor, and insulator NWs [7,8]. For the micron-sized specimens like sputtered films, many types of tensile test techniques have been developed so far [9][10][11][12][13][14][15][16][17][18][19].…”

“…Uniaxial tensile test is most popular method to study mechanical characteristics for minute specimens. For the nano-and submicron-sized specimens, MEMS-based on-chip tensile test devices that have been proposed by many researchers are used very often [2][3][4][5][6][7][8]. By using electrostatic actuator or thermal actuator, tension force can be applied to Si NWs [2][3][4], C NWs [5,6], and other metallic, semiconductor, and insulator NWs [7,8].…”