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novel method was developed for low-temperature preparation of thin films. Pulsed laser ablation was combined with electron cyclotron resonance microwave discharge, constituting a novel hybrid film preparation method called electron cyclotron resonance plasma–assisted reactive pulsed laser deposition. We demonstrated the feasibility of the method by preparing compound films of silicon nitride, silicon dioxide, and aluminum nitride from elemental starting materials. The mechanisms responsible for efficient compound formation and film growth are discussed, together with characterization of the prepared films, analysis of the plasma composition, and comparison of the films prepared with and without assistance of the plasma. The unique features of the method make it suitable for one-step preparation of compound thin films at low temperatures.

I. INTRODUCTION

Pulsed laser deposition (PLD) of thin films is one of the most important applications of lasers. Since the successful preparation of high-temperature superconducting (HTSC) thin films, PLD has attracted great attention and has been developed as a versatile technique for preparing a variety of thin films ranging from elemental to multicomponent materials including metals, HTSC, semiconductors, nitrides, oxides, buckminsterfulleres, and organic and biological materials.1 PLD is probably the simplest and most versatile thin film preparation technique. One of the most important features of the PLD method is its capability for reactive deposition of thin films when performed in a low-pressure reactive gaseous environment. For the formation of compound thin films such as oxides and nitrides, the interaction of the ablated target material with a reactive ambient gas plays an important role in producing the atomic and molecular precursors required for growth of the compound phase.2 Therefore, the various novel approaches developed in which an additional source was attached to the basic PLD setup, constituting hybrid ion beam- or plasma-assisted PLD. The

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Address all correspondence to this author. J.D. Wu, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, People’s Republic of China. Fax: 86-21-65641344 e-mail: [email protected]

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http://journals.cambridge.org

J. Mater. Res., Vol. 17, No. 7, Jul 2002 Downloaded: 13 Mar 2015

combination of PLD with ion beam or plasma techniques makes the PLD method more efficient in thin film preparation and makes it possible to grow thin films at reduced substrate temperatures. We have recently developed a film deposition method named electron cyclotron resonance (ECR) plasma– assisted reactive pulsed laser ablation (RPLD), or ECRRPLD in short, which combines pulsed laser ablation of a target with ECR microwave discharge in a gas. ECR microwave discharges are capable of producing highdensity plasmas with low temperature at low pressures.3,4 Significant amounts of highly activated species, such as excited ionized and neutral particles, can be generated in the ECR plasma. The activated species in the E