Fabrication and Characterization of Patterned Single-Crystal Silicon Nanolines

Abstract

This letter demonstrates a method for fabricating single-crystal Si nanolines, with rectangular cross sections and nearly atomically flat sidewalls. The high quality of these nanolines leads to superb mechanical properties, with the strain to fracture measured by nanoindentation tests exceeding 8.5% for lines of 74 nm width. A large displacement burst before fracture was observed, which is attributed to a buckling mechanism. Numerical simulations show that the critical load for buckling depends on the friction at the contact surface.

Indentation of single-crystal silicon nanolines: Buckling and contact friction at nanoscales

“…Figure 2 shows two sets of force-displacement curves obtained from the nanoindentation tests. Similar to the indentation response of the 74 nm wide SiNLs reported in our previous work, [5] a large displacement burst was observed at a critical indentation load, which was attributed to buckling instability of the SiNLs.…”

“…[5,13] It is found from the present study that, for the high-aspect-ratio 24 nm SiNLs, variation in the local friction property can lead to two drastically different buckling modes (see Fig. 3).…”

“…In a previous study of SiNLs with a line width of 74 nm and an aspect ratio of 6.9, the load-displacement curves from the indentation tests showed an instability with large displacement bursts at a critical load ranging from 480 µN to 700 µN. [5] This phenomenon was attributed to a transition of the buckling mode of the SiNLs under indentation, which occurred preceeding the final fracture of the nanolines. In our earlier work, the onset of buckling instability and the mode transition were found to depend on the friction at the contact between the indenter tip and the SiNLs as well as the relative tip location and the aspect ratio of the SiNLs .…”

“…[5] On the other hand, the maximum indentation displacement for the 24 nm SiNLs was larger, up to 220 nm. This displacement is about 58% of the line height.…”

“…[5][6][7][8][9][10][11][12] By combining electron-beam lithography (EBL) and anisotropic wet etching (AWE), a top-down fabrication process was developed to obtain singlecrystal, parallel SiNLs on a silicon (110) wafer. [5] Under indentation, the singlecrystal SiNLs showed mechanical properties that are distinctly different from those of bulk silicon. In a previous study of SiNLs with a line width of 74 nm and an aspect ratio of 6.9, the load-displacement curves from the indentation tests showed an instability with large displacement bursts at a critical load ranging from 480 µN to 700 µN.…”