Nonlithographic Patterning and Metal-Assisted Chemical Etching for Manufacturing of Tunable Light-Emitting Silicon Nanowire Arrays

Abstract

Semiconductor nanowires have potential applications in photovoltaics, batteries, and thermoelectrics. We report a top-down fabrication method that involves the combination of superionic-solid-state-stamping (S4) patterning with metal-assisted-chemical-etching (MacEtch), to produce silicon nanowire arrays with defined geometry and optical properties in a manufacturable fashion. Strong light emission in the entire visible and near infrared wavelength range at room temperature, tunable by etching condition, attributed to surface features, and enhanced by silver surface plasmon, is demonstrated.

Fabrication of ultrahigh aspect ratio silicon nanostructures using self-assembled gold metal-assisted chemical etching

“…One of these samples was a metal pattern on a h100i wafer etched in a high HF concentration solution (6∶1) while the other was on a h111i wafer etched in low HF concentration solution (1∶2). This data is in agreement with Chern et al, 6 who suggest the formation of slanted etched profiles of h100i wafers for high HF concentration solutions as well for h111i wafers with low HF concentration solutions. Because these two samples were the only two which appeared to be influenced primarily by the solution stoichiometry rather than metal pattern morphology, we conclude that the pattern morphology is the primary influence over etch direction for the metal pattern size regime and solution stoichiometry tested; while a secondary influence can be attributed to solution stoichiometry, particularly at the extreme ends of the solution ratios tested.…”

“…Even a slight rate of undercut would limit the maximum depth that could be achieved and cause structures to collapse; the density of the nanostructures could also dramatically decrease as many of the structures would be lifted off due to the undercut. While MacEtch is known to have a crystalline dependency, 6,7,9,17 the role of solution ratio has conflicting reports 4,6,7,9,12 and the role of metal geometry has not been studied extensively. 5,12 Furthermore, it should also be noted that previous studies have generally been limited to metal patterns that are significantly larger than the patterns we have examined.…”

“…5,12 Furthermore, it should also be noted that previous studies have generally been limited to metal patterns that are significantly larger than the patterns we have examined. [5][6][7][8][9]12,13,[16][17][18] To test the impact of solution ratio, we performed the etch at six different ratios (by volume): 6∶1, 3∶1, 2∶1, 3∶2, 1∶1, and 1∶2 HF∶H 2 O 2 for 1 min. This grouping of ratios straddles what was reported by Chartier et al 4 to be the optimal concentration of 80% HF to 20% H 2 O 2 by mol corresponding to a volumetric ratio of nearly 3∶2 for maximum metal penetration rate.…”

“…It has been reported previously that the remaining silicon structures can be crystalline or porous in nature depending on the etchant solution stoichiometry, substrate doping, and metal catalyst type. [6][7][8][9][10] MacEtch has been demonstrated on lithographically patterned 6,11,12 and self-assembled metal patterns. 4,5,7,8,[13][14][15] With self-assembly, it is possible to reach geometrical features far smaller than what can be realized by lithographic patterning.…”

Fabrication and characterisation of GaAs nanopillars using nanosphere lithography and metal assisted chemical etching

“…However, our nanopillars satisfy the asymptotic criterion (r [ 100 nm); therefore we plot in Fig. 5 our measured SO peak frequency (281.8 cm À1 ) and the expected SO phonon dispersion for the a-As/GaAs interface using eqn (2). A value of 3 m ¼ 11.1 for a-As 29 is in excellent agreement with our asymptotic limit for large r and supports a model where an amorphous phase of elemental arsenic aggregates at the GaAs surface, as shown in the inset of Fig.…”