Mechanical Properties of Ferro-Electric Composite Thin Films
- PDF / 1,941,900 Bytes
- 6 Pages / 414.72 x 648 pts Page_size
- 12 Downloads / 188 Views
the broad acceptance for thin films produced by physical vapor deposition (PVD) process has been presented by Movchan and Demchishin [1]. They proposed three zones to describe the microstructures than can develop in deposits produced by vacuum evaporation as a function of [T, /Tm], where T, is the absolute substrate temperature and Tm is the absolute melting temperature of the deposited material. Thornton [2] elaborated on the approach of Movchan and Demchishin extending it to typical sputtering. Thornton also concluded that the structure and physical properties of films produced by sputtering could be represented as a function of T, /Tn, where Tm is the absolute melting temperature of the film material, in terms of four zones as shown in Fig. 1, each with its own characteristic structure and physical properties. The general features of Thornton's model were based on the examination of 25- to 250-jtm-thick coatings deposited at argon pressures of 1.33 X 10-4 (1 mTorr) to 3.9 X 10-3 Pa (30 mTorr) using cylindrical-post and hollow cathode magnetron sputtering sources. Fountzoulas and Nowak [3] further elaborated on the approach of Movchan and Thornton, extending them to ion plating. We have initiated a detailed investigation of the adhesive and cohesive properties of dielectric thin films of barium strontium titanium oxide (BSTO) thin films deposited on crystalline substrates by the Pulsed Laser Deposition method (PLD) [4-6]. This paper presents the initial results of this study of these mechanical properties of BSTO thin films as a function of deposition temperature. 337 Mat. Res. Soc. Symp. Proc. Vol. 505 0 1998 Materials Research Society
20'
Jill
!hl~l
PRESSURE
(mTor).
Fig. 1. Thornton's structure zone model for coatings produced by sputtering. [2] EXPERIMENTAL PROCEDURE In this work, thin films of BSTO were deposited by the PLD technique on single crystal sapphire substrates at temperatures varying from R.T. (30 'C) to 700 'C. The details of this deposition technique can be found elsewhere [7]. The fracture cross sections of the films were observed by scanning electron microscopy (SEM). Crystallinity, crystal orientation and composition of the films were determined by FTRAMAN spectroscopy and Glancing Angle X-ray Diffraction (GAXRD). The adhesive and cohesive failure loads of the films were evaluated with the aid of a CSEM-Revetest instrument (Centre Suisse d' Electronique et de Microtechnique, CSEM, CH-20007, Neuch tel, Switzerland). Specimen evaluation The material properties of the BSTO thin films deposited at various substrate temperatures were evaluated by FT-Raman spectroscopy and are reported elsewhere [7]. The Knoop microhardness of the coatings, uncorrected for substrate hardness effects, was measured using a 0.25 N applied load and a dwell time of 15 s. Even at this low load the maximum indenter penetration exceeded by far the critical value of 1/10 of the coating thickness considered sufficient for the substrate not to have a significant effect on hardness values. The cohesion and adhesion value
Data Loading...
