Gold Nanocomposites Prepared by Reactive Sputtering
- PDF / 1,213,485 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 62 Downloads / 199 Views
ABSTRACT Reactive sputtering of gold and selected gold alloys in oxygen and nitrogen plasmas generated in a DC glow discharge was studied. Gold alloys examined were various compositions with gallium, aluminum and silicon. Gold is transported unreacted from a gold target to the substrate in a nitrogen plasma to form polycrystalline films, but gold alloys produce fine dispersions of gold in the corresponding ceramic nitride matrix which was crystalline for gallium and amorphous for silicon and aluminum. This contrasts with the behavior in an oxygen plasma which produces pure gold oxide, Au2 O3, from a gold target and gold oxide-silicon oxide nanocomposites from Au/Si alloys. Gold oxide is thermally labile and reverts to the elements at 350 0C. Stress in gold oxide films was detected in the decomposition profile, volatile evolution versus temperature, as an event occurring at a lower temperature. The thermal lability of gold oxide was utilized to generate gold nanocomposites in silica with different metal loading through pyrolysis of the corresponding precursor gold oxide-silica films. The properties of gold oxide and gold nanocomposites are described. INTRODUCTION Interest in nanostructured materials has grown considerably in the recent past because of technological applications stemming from size effects associated with the presence of particles a few nanometer in diameter. Such nanostructured materials may display optical, electric, magnetic or mechanical properties that depart from those of the corresponding bulk materials. A particular subset ofnanostructured materials is that of granular solids which are truly nanocomposites of a very fine dispersion of a metallic phase within an insulating phase or within a secondary inmiscible metallic phase. Work on these materials has its beginning with the studies of Abeles et al[l] who examined transport properties as a function of metal loading in nanocomposites. Preparation of nanocomposite films has been accomplished most commonly through sputtering of homogeneous targets or co-sputtering of separate or segmented targets. Also used, more recently, are sol-gel techniques[2,3] and ion implantation[4]. In the specific case of gold nanocomposites the effects observed include non-linear optical effects[4,5] and high dielectric constant materials[6]. EXPERIMENT In the present study films, about one gim in thickness, were deposited by reactive sputtering of gold alloys in nitrogen or argon/oxygen plasmas generated in a simple parallel plate DC glow discharge apparatus previously described[7]. Pure gold foil was also sputtered, for comparison purposes, and in the case of the oxygen plasma to better characterize the precursor gold oxide formed. Sputtering was typically conducted for a 20 h period using a voltage drop of about 500 V and a current density of 1.8 mA/cm2 ', while passing 10 cm 3 of high purity gas, either 529 Mat. Res. Soc. Symp. Proc. Vol. 405 01996 Materials Research Society
nitrogen or oxygen in argon at a 40 vol % concentration. Films were deposited on a varie
Data Loading...
