Nanostructures formed by displacement of porous silicon with copper: from nanoparticles to porous membranes

Abstract

The application of porous silicon as a template for the fabrication of nanosized copper objects is reported. Three different types of nanostructures were formed by displacement deposition of copper on porous silicon from hydrofluoric acid-based solutions of copper sulphate: (1) copper nanoparticles, (2) quasi-continuous copper films, and (3) free porous copper membranes. Managing the parameters of porous silicon (pore sizes, porosity), deposition time, and wettability of the copper sulphate solution has allowed to achieve such variety of the copper structures. Elemental and structural analyses of the obtained structures are presented. Young modulus measurements of the porous copper membrane have been carried out and its modest activity in surface enhanced Raman spectroscopy is declared.

Formation Regularities of Plasmonic Silver Nanostructures on Porous Silicon for Effective Surface-Enhanced Raman Scattering

“…In case of Si-based substrates, solutions containing ions of metals with positive redox potential (Cu and noble metals) have to be used to provide the immersion deposition [ 32 ]. By nowadays, several reports have described immersion deposition of gold [ 33 ], copper [ 34 ], and silver [ 35 – 40 ] on PS at different conditions to form SERS-active substrates . Silver deposits have been mainly used to form SERS-active substrates based on PS due to the strongest plasmonic properties of this metal [ 41 ].…”

Comparative study of initial stages of copper immersion deposition on bulk and porous silicon

“…Such bimodality of the histograms means that the initially deposited Cu NPs have already coalesced into larger particles (agglomerates) - the second part of the distributions - and new NPs deposited on the reopened surface of the substrates - the first part of the distributions. This mechanism usually takes place in wet depositions [5,10]. The density of Cu particles on the Si (100) estimated as 10 9 cm −2 was an order of magnitude less than those on Si (111) and PS, which are 10 10 and 2 × 10 10 cm −2 (for the both orientations), respectively.…”

“…In particular, variation of the PS parameters without disordering pores allows the controlling of features of the final material. To understand peculiarities of Cu immersion deposition on the surface of PS, we firstly studied the process on the bulk Si because the surface of the PS pores presents Si nanoplanes of different crystal orientations [10]. Anodizing regimes used in this work provided formation of the uniform PS layers of 1-μm thick and 50% to 55% porosity.…”

“…Further growth of Cu particles resulted in the slight decrease of the potential for the samples based on PS/Si (100), Si (111), and PS/Si (111). Several peaks of the OCP time dependencies have to be related to the periodical coalescence of Cu particles during immersion deposition [10]. It is seen that Si (100) OCP demonstrates different behaviors than of the other samples.…”

“…In this case, SiO 2 removal followed by Si oxidation caused the dissolution of the PS skeleton. Proper conditions of the metal immersion deposition and PS parameters can lead to the complete conversion of PS to porous metal [10]. …”