Growth mechanism of superconducting MgB 2 films prepared by various methods
- PDF / 232,752 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 24 Downloads / 201 Views
pinella CNR-IMeTeM, Stradale Primosole 50, 95100 Catania, Italy
O. Puglisi Dipartimento di Scienze Chimiche, Universita` di Catania, Viale A. Doria 6, 95125 Catania, Italy (Received 12 March 2001; accepted 25 July 2001)
Silver nanoparticles (10–20 nm) embedded into silica thin films have been obtained through the use of a silver organometallic precursor compound dissolved in Spin-On-Glass and subsequently spinned onto suitable substrates. In this paper we present a study of the shape, size, and distribution of silver particles through the use of microscopes, x-ray diffraction, and optical extinction. It has been observed that the obtained films are stable for annealing up to 500 °C with a progressive degradation above this temperature. Furthermore it is possible to obtain high-density silver particles up to 15% in weight without affecting the cluster size and shape.
I. INTRODUCTION
Properties of composite thin films consisting of nanometer-sized metal or semiconductor particles dispersed in solid dielectric materials such as polymers or glasses have been of increasing interest for both fundamental and practical reasons. Depending on the nature of both host and guest substances, this new kind of materials possesses interesting properties (electronic, optical, magnetic,1 catalytic2,3) that can be tailored as a function of the particles dimension, size distribution, and shape.4 In particular, widely investigated are systems in which silver nanoparticles are dispersed into silica due to their optical properties that allow the use in photonic devices.5 Nonlinear glass wave guide are supposed to play a major role in the designing of all-optical switching devices6 in the picosecond range, and quantum confinement effects give rise to a strong enhancement of the nonlinear response of these composites in terms of third-order susceptibility. A huge variety of physical and chemical synthetic processes have been reported to prepare such nanocomposite materials. Ion implantation of silver ions7,8 and Na+ ↔ Ag+ ion exchange in soda lime silicate glasses,9 followed by thermal processes10 and silica xerogels11 in which silver precursor are incorporated using sol gel chemistry, are among the most used processes with
a)
e-mail: [email protected]
2934
J. Mater. Res., Vol. 16, No. 10, Oct 2001
which it is possible to obtain particles with sizes ranging from a few to tens of nanometers. Depending on the selected preparation method, different parameters (ion fluence, temperature, pore sizes, etc.) play, important roles in controlling clusters dimensions and their size distributions inside the host material and therefore in selecting the final properties of the composite. Of course each preparation method suffers from one or more limitations. Indeed ion implantation is a highly nonuniform process being strongly related to the implantation profile. On the other hand, chemical methods produce in general a material which can be hardly obtained in the form of a homogeneous thin film with a few thousand angstroms in thickness.
Data Loading...
