Investigation of stress and morphology in electrodeposited copper nanofilms by cantilever beam method and in situ electrochemical atomic force microscopy

Abstract

Both stress and atomic force microscopy (AFM) measurements were carried out in situ during potentiostatic electrodeposition of copper on gold in 0.05moldm−3 CuSO4 in 0.1moldm−3 H2SO4 with and without additives. With no additives, compressive stress generally developed initially and films subsequently underwent a compressive-to-tensile (C-T) transition. With increasing negative potential, the time for the C-T transition decreased rapidly as the rate of coalescence of nuclei (measured by AFM) increased rapidly. This is consistent with models that attribute the C-T transition to increasing tensile stress due to coalescence of nuclei. Furthermore, at a potential of −75mV (Cu∕Cu2+), where AFM showed very little coalescence of nuclei, no C-T transition was observed, again consistent with these models. The nucleation density measured by AFM increased from 2.7×107cm−2 at −75mVto2.5×109cm−2 at −300mV. Stress measurements with a combination of three additives [1×10−3moldm−3 Cl−, 8.82×10−5moldm−3 polyethylene glycol, and 1×10−5moldm−3 3-mercapto-1-propanesulfonic acid sodium salt (MPSA)] also showed that compressive stress generally developed initially and its magnitude was greater than in additive-free electrolyte. At less negative potentials, even though the rate of coalescence of nuclei was rapid, as observed by AFM, the stress continued to evolve in the compressive direction. At intermediate potentials (−90to−150mV), classical compressive-tensile-compressive (C-T-C) behavior was observed, while at more negative potentials the stress continued to evolve in the tensile direction. Similar results were obtained with a combination of two additives (1×10−3moldm−3 Cl− and 1×10−5moldm−3 MPSA), but in that case the compressive stress appeared to be greater, and consequently the T-C transition was observed even at −500mV. The results are consistent with enhancement of a compressive component of stress in the presence of additives.

On the electrochemical deposition of metal–organic frameworks

“…A compressive stress arises from the rst instants when the potential is applied. The compressive stress is partially due to the dissolution of the copper lm which contains tensile stress 28,29 and to the deposition of HKUST-1 crystals. A compressive stress is in good agreement with the appearance of most MOF layers and HKUST-1 ones in particular: the layers appear to be constituted by continuous lms of intergrown crystals with good adhesion to each other, and while buckling of the layers can be observed, cracks have not been reported for this MOF.…”

“…To determine stresses in MOF lms, rst a 2 mm layer of copper was electrodeposited on the cantilever's gold-coated face causing tensile stress to arise. 29 As a blank, thin lm stress was measured during dissolution of copper in an ethanol/water (67 : 33 vol%) electrolyte without H 3 BTC but with 10 g L À1 methyltributylammonium methyl sulphate (32 mM, MTBS, Sigma-Aldrich, 95%) to enhance the conductivity. The same experiment was repeated with the same electrolyte with 10 g L À1 of H 3 BTC (48 mM) and 10 g L À1 of MTBS (32 mM).…”

In Situ Stress Measurements during Cobalt Electrodeposition on (111)-Textured Au

“…For example, cantilever curvature has been used to quantify the surface stress induced by surface charge (electrocapillarity) [25][26][27][28] and adsorption processes [29][30][31][32] as well as the growth stress associated with upd 25,[33][34][35][36][37][38][39][40][41][42][43][44] and the electrodeposition of bulk thin film. [45][46][47][48][49][50][51][52][53][54][55] This method is particularly useful in identifying structural changes, such as surface alloying, that may proceed without any electrochemical or nanogravimetric signature. 39,42 In the case of Co deposition, Cammarata 53,56 reported that Co, galvanostatically electrodeposited onto amorphous NiTi, shows compressive-tensile-compressive (CTC) stress transitions that are typically observed for Volmer-Weber growth.…”

Surface Morphology and Stress in Electrodeposited Copper Nanofilms

“…5,[15][16][17] The use of these additives in electrodeposited copper thin films is also known to lead to smaller, more dense grains during film growth 18 . Additives are proposed to decrease surface diffusivity and reduce the number of vacant sites for adatom adsorption 19 .…”

“…These stresses are found to evolve during film growth and can consist of a compressive-to-tensile (CT) or (CTC) behaviour in high mobility films during vapour-phase deposition [1][2][3] or tensile behaviour during room-temperature electrodeposition in low-mobility films [4][5][6] .…”