Applied Surface Science 273 (2013) 315–323 Contents lists available at SciVerse ScienceDirect Applied Surface Science j our nal ho me p age: www.elsevier.com/loc ate/apsusc Electron scattering at surfaces and grain boundaries in thin Au films Ricardo Henriquez a , Marcos Flores b , Luis Moraga b , German Kremer c , Claudio González-Fuentes a , Raul C. Munoz b,∗ a Departamento de Física, Universidad Técnica Federico Santa María, Av. Espa˜ na 1680, Casilla 110-V, Valparaíso, Chile b Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Blanco Encalada 2008, Casilla 487-3, Santiago 8370449, Chile c Bachillerato, Universidad de Chile, Las Palmeras 3425, Santiago 7800024, Chile a r t i c l e i n f o Article history: Received 14 December 2012 Accepted 8 February 2013 Available online 24 February 2013 PACS: 73.50.-h 73.61.-r Keywords: Resistivity Electron-surface scattering Electron-grain boundary scattering a b s t r a c t The electron scattering at surfaces and grain boundaries is investigated using polycrystalline Au films deposited onto mica substrates. We vary the three length scales associated with: (i) electron scattering in the bulk, that at temperature T is characterized by the electronic mean free path in the bulk ℓ 0 (T ); (ii) electron-surface scattering, that is characterized by the film thickness t; (iii) electron-grain boundary scattering, that is characterized by the mean grain diameter D. We varied independently the film thickness from approximately 50 nm to about 100 nm, and the typical grain size making up the samples from 12 nm to 160 nm. We also varied the scale of length associated with electron scattering in the bulk by measuring the resistivity of each specimen at temperatures T, 4 K < T < 300 K. Cooling the samples to 4 K increases ℓ 0 (T ) by approximately 2 orders of magnitude. Detailed measurements of the grain size distribution as well as surface roughness of each sample were performed with a Scanning Tunnelling Microscope (STM). We compare, for the first time, theoretical predictions with resistivity data employing the two theories available that incorporate the effect of both electron-surface as well as electron-grain boundary scattering acting simultaneously: the theory of A.F. Mayadas and M. Shatzkes, Phys. Rev. 1 1382 (1970) (MS), and that of G. Palasantzas, Phys. Rev. B 58 9685 (1998). We eliminate adjustable parameters from the resistivity data analysis, by using as input the grain size distribution as well as the surface roughness measured with the STM on each sample. The outcome is that both theories provide a fair representation of both the temperature as well as the thickness dependence of the resistivity data, but yet there are marked differences between the resistivity predicted by these theories. In the case of the MS theory, when the average grain diameter D is significantly smaller than ℓ 0 (300) = 37 nm, the electron mean free path in the bulk at 300 K, the effect of electron-grain boundary scattering dominates the increase in resistivity of the film over the bulk, and the electronic mean free path, ℓ D (4), computed from Drude’s model at 4 K, is similar to the grain diameter D. The increase in resistivity attributable to electron-grain boundary scattering can be as large as 220 at low temperatures, for samples made out of 12 nm grains. On the contrary, when D is significantly larger than ℓ 0 (300), then electron-surface scattering dominates the increase in resistivity. When D is comparable to ℓ 0 (300), there is a cross over where both electron-surface and electron-grain boundary scattering do contribute to increasing the resistivity of the film over that of the bulk. These predictions are in sharp contrast with those based upon the theory of Palasantzas, that predicts an increase in resistivity—attributable to electron-grain boundary/surface scattering—that turns out to be essentially unity regardless of the size of the grains making up the sample. © 2013 Elsevier B.V. All rights reserved. 1. Introduction The question of how electron scattering by rough surfaces and/or grain boundaries influences the charge transport process in metallic nanostructures, when one of the dimensions character- izing the nanostructure becomes comparable to or smaller than the electron mean free path in the bulk, has sparked a debate over the ∗ Corresponding author. Tel.: +56 2978 4335. E-mail address: ramunoz@ing.uchile.cl (R.C. Munoz). last decade within the semiconductor industry [1]. Current interest is growing rapidly, as illustrated by several experiments concerning this problem published over the last three years [2–11]. However, after more than a century of research, the understanding of size effects in thin metallic films today still seems fragmentary and incomplete. There are many hundreds of papers published regarding the resistivity of thin metallic films where the increase in resistivity over the bulk is interpreted as arising solely from electron- surface scattering, and significantly fewer papers that interpret the increase in resistivity as arising from both electron-surface and 0169-4332/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsusc.2013.02.037