Nanostructured Gold Thin Films Prepared by Pulsed Laser Deposition
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hel Trudeau Chimie et Mate´riaux, Institut de Recherche d’Hydro-Que´bec (IREQ), Varennes, Que´bec J3X 1S1, Canada
Daniel Guaya) INRS-E´nergie, Mate´riaux et Te´le´communication, Varennes, Que´bec J3X 1S2, Canada (Received 10 July 2003; accepted 16 December 2003)
A structural and morphological study of nanostructured gold thin films prepared by pulsed laser deposition in the presence of several inert background gases (Ar, He, and N2) and at various pressures (from 10 mTorr to 1 Torr) and target-to-substrate distances (from 1 to 10 cm) is presented. Structural and morphological analyses were undertaken using semiquantitative x-ray diffraction, scanning tunneling microscopy, and transmission electron microscopy. For each set of deposition conditions, the kinetic energy of the neutral gold species [Au(I)] present in the plasma plume was determined by time-of-flight emission spectroscopy and used to characterize the plasma dynamics. It is shown that all films exhibit a transition from highly {111} oriented to polycrystalline as the Au(I) kinetic energy decreases. The polycrystalline phase ratio is close to 0% for Au(I) kinetic energy larger than approximately 3.0 eV/atom and approximately 86 ± 10% for Au(I) kinetic energy smaller than approximately 0.30 eV/atom, irrespective of the background gas atmosphere. The mean crystallite size of both phases and the mean roughness of the films also follow a unique relation with the Au(I) kinetic energy, independently of the nature of the background gas, and nanocrystalline films with crystallite size as small as 12 nm are obtained for Au(I) kinetic energy smaller than 0.3 eV/atom.
I. INTRODUCTION
Pulsed laser deposition (PLD) has become an established method for the growth of thin films from almost any kind of target materials1,2 and thin-film growth by means of PLD has extensively been studied over the past few years.1 These studies can be divided into two categories. In the first one, the dynamics of plasma expansion is the prime interest. The dynamics of the various species ejected from the target during laser ablation in background atmosphere of various compositions have been investigated with temporally and spatially resolved plasma diagnostics in several studies.3–7 In the second category, the emphasis is put on establishing meaningful correlation between the deposition parameters (composition of the background gas, pressure, target-to-substrate distance, and substrate temperature) and the properties of the deposited films.8,9 a)
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J. Mater. Res., Vol. 19, No. 3, Mar 2004 Downloaded: 16 Mar 2015
Both types of studies are obviously complementary to each other, as the former can provide meaningful information on the dynamics of the various species involved in the deposition process. However, for this synergy to occur, plasma plume studies ought to be carried out in experimental conditions (background gas, pressure, and target-to-substrate distance) relevant for t
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