Growth of ZnO nanocrystals in silica by rf co-sputter deposition and post-annealing V.V. Siva Kumar * , F. Singh, Amit Kumar, D.K. Avasthi Nuclear Science Centre, P.O. Box 10502, Aruna Asaf Ali Marg, New Delhi 110 067, India Available online 20 December 2005 Abstract Thin films with ZnO nanocrystals in silica were synthesized by rf reactive magnetron co-sputter deposition and post-annealing. The films were deposited from a ZnO/Si composite target in an rf oxygen plasma. The deposited films were annealed in air/vacuum at high temperatures to grow ZnO nanocrystals. The deposited and annealed films were characterized by X-ray diffraction (XRD), fourier trans- form infrared spectroscopy (FT-IR), uv–vis spectroscopy (UV–VIS) and photoluminescence (PL) measurements. FT-IR results of the films show the vibrational features of Si–O–Si and Zn–O bonds. UV–VIS spectra of the deposited film shows the band edge of ZnO. The XRD results of the films annealed at 750 °C and 1000 °C indicate the growth of ZnO nanocrystals with average crystallite sizes between 7 nm and 26 nm. PL measurements of the deposited film show a broad visible luminescence peak which can be due to ZnO. These results suggest the growth of ZnO nanocrystals in silica matrix. Ó 2005 Elsevier B.V. All rights reserved. PACS: 81.15.C; 81.40.G Keywords: ZnO; Nanostructures; Silica; Thin films; Co-sputtering; Annealing 1. Introduction ZnO (zincite) is a wide band gap semiconductor (E g = 3.3 eV at RT) which has great potential in many acoustic, electronic and optical applications [1,2]. ZnO nanocrystals are studied for ultraviolet laser emission [3], luminescence [4] and gas sensor applications [5]. Nanocrystals grown in a host matrix have attracted wide attention due to the stability of their size and properties [6–8]. Growth of ZnO/ SiO 2 nanocomposite material is reported using chem- ical methods [9,10]. Recently co-sputter deposition was used to grow ZnS nanocrystals [11] and Er doped Ge nanoclus- ters in Silica [12]. However to the best of our knowledge there are no reports on the growth of ZnO nanocrystals in a silica matrix by sputter deposition. This work reports on the growth of thin films of ZnO nanocrystals in a SiO x matrix by co-sputter deposition and annealing. Co-sputter deposition has the advantage of easy control on the amount of material to be dispersed in a host matrix. 2. Experimental details Thin films were deposited by reactive rf magnetron sput- tering using an rf sputtering set-up, developed in-house. A 100 mm dia. ZnO/Si (1:8 ratio) target was used for the film deposition. The substrates were placed on a grounded anode which is separated by 40 mm from the target. A base vacuum of 1.06 · 10 5 mbar was produced in the chamber. The chamber was flushed with oxygen gas for 30 min before the thin film deposition. The films were deposited with an rf power of 175 W and a process pressure of 9.2 · 10 2 mbar. Before deposition on the substrates, the target was pre-sputtered for 10 min with oxygen ions with the substrates covered by a shutter. For comparison, thin films from the pure Si target were also deposited in identi- cal deposition conditions. 0168-583X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.nimb.2005.11.013 * Corresponding author. Tel.: +91 11 26893955; fax: +91 11 26893666. E-mail address: vvsk@nsc.res.in (V.V. Siva Kumar). www.elsevier.com/locate/nimb Nuclear Instruments and Methods in Physics Research B 244 (2006) 91–94 NIM B Beam Interactions with Materials & Atoms