Highly (002)-oriented ZnO film grown by ultrasonic spray pyrolysis on ZnO-seeded Si (100) substrate
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ao-Min Lia) State Key Laboratory of High-Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, People’s Republic of China
Sam Zhangb) School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798
Chang Yang State Key Laboratory of High-Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, People’s Republic of China; and Graduate School of Chinese Academy of Sciences, Beijing 100039, People’s Republic of China
Xiang-Dong Gao and Wei-Dong Yu State Key Laboratory of High-Performance Ceramics and Superfine Microstructures, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, People’s Republic of China (Received 12 December 2005; accepted 23 January 2006)
ZnO films are grown by the ultrasonic spray pyrolysis method on ZnO seeding layer deposited on Si (100) by pulsed laser deposition. The resultant film possesses a columnar microstructure perpendicular to the substrate and exhibits smooth, dense, and uniform morphology. The preferred orientation along the c-axis of the film is significantly enhanced compared to that without the seeding layer. ZnO film grown on ZnO-seeded silicon exhibits higher hall mobility, lower resisitivity, and higher photoluminescence intensity. I. INTRODUCTION
ZnO film has received extensive attention because of its notable properties1–3 such as a direct wide band gap of 3.37eV and a high exciton bonding energy of 60 meV at room temperature (which is much higher than the 20 meV of ZnSe or 21–25 meV of GaN). Furthermore, ZnO can grow at lower temperatures than GaN and ZnSe—a preferred property in realizing integration of ZnO-based optoelectronic devices into a silicon-based process. As such, ZnO is expected to be a promising candidate for replacing GaN in blue and ultraviolet (UV) optoelectronic applications, such as UV laser diodes, blue-to-UV light emitting diodes, and UV detectors.4,5
a)
Address all correspondence to this author. e-mail: [email protected] b) This author was an editor of this journal during the review and decision stage. For the JMR policy on review and publication of manuscripts authored by editors, please refer to http://www.mrs.org/ publications/jmr/policy.html. DOI: 10.1557/JMR.2006.0291 J. Mater. Res., Vol. 21, No. 9, Sep 2006
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Many techniques have been used to deposit ZnO films, including pulsed laser deposition (PLD),5–7 metalorganic vapor-phase epitaxy,8 magnetron sputtering,9 chemical vapor deposition,10 sol-gel,11 and ultrasonic spray pyrolysis (USP).12–15 USP is a simple and inexpensive method for large-area deposition. The atmospheric growth environment of USP also improves stoichiometry, thus reducing intrinsic defects such as oxygen vacancies that, in turn, improve luminescence properties. This has been demonstrated in preparation of p-type ZnO films.13–15 However, ZnO films of high crystallin
