Fabrication of vertically aligned Si nanowires on Si (100) substrates utilizing metal-assisted etching

Abstract

Vertically aligned Si nanowires were fabricated utilizing a metal-assisted chemical etching scheme using a thin anodic aluminum oxide (AAO) template formed on (100) Si substrate. The diameter and length of the obtained Si nanowires were about 55 and 340 nm, respectively, when the thickness of the AAO template was about 600 nm. The diameters and shapes of the Si nanowires were determined by the hole size and shape of the Ag mesh on the AAO template. In addition, the lengths of the vertical Si nanowires depended on both the AAO thickness and the Ag film thickness.

Silicon nanowires with controlled sidewall profile and roughness fabricated by thin-film dewetting and metal-assisted chemical etching

“…Porous anodized aluminum oxide (AAO) [18] with monodispersed pores has also been used to produce SiNWs, with the advantage of having highly tunable diameter control in the sub-200 nm range. AAO is grown on a bulk aluminum foil [19,20] or thin-film [21] by a two-step anodization with the pore depth and size controlled by the anodization time and the pore opening step. Multiple approaches [6,21,19] may be used to open up the bottoms of the pores so that the membrane can be used as a template.…”

“…AAO membranes-transferred via this method-are covered with a Au film and immersed in MacEtch solution to produce SiNWs. Even though this process integration has been shown to produce SiNW arrays, the areal coverage of SiNWs produced by this method is limited by the template wall thickness and pore closure effects [19,20]. Moreover, the process requires a number of delicate manual steps in the transfer of the template, thus limiting the size of the patterned surface and the yield.…”

Characterization of vertical Si nanowire p-n diodes fabricated by metal-assisted etching and AAO templates

“…The small round images (2-10 nm) found on Si nanowire surfaces are Pt particles, which were deposited to minimize the damage during focused ion beam milling. This phenomenon usually occurred whenever the length of Si nanowires was greater than 1.2 lm (see our previous report to understand this phenomenon 15 ). 8(b) was taken from the marked area of the Si nanowire and indicates that the wire consists of nonporous single crystals formed along the [100] direction, which is identical to the Si (100) substrate.…”

“…[12][13][14][15] The first anodization was conducted in 0.3 M oxalic acid with a 40 V bias at 4 C for 3700 s. The anodization time was selected in an attempt to achieve a desired unoxidized Al film thickness of $180 nm. Then, a well-known two-step anodizing process was applied to the Al films on the Si substrate.…”

“…After the first anodization, partially formed anodic aluminum oxide was removed by immersion in a mixture of 1.8 wt. 15 Each sample was widened for varying etching times of 1, 3, 5, or 7 min using metal-assisted etching. % H 3 PO 4 at 75 C for 90 min.…”