Aluminum nitride thin films were deposited on Si (100) substrate by pulsed DC (asymmetric bipolar) reactive magnetron sputtering under variable nitrogen flow in a gas mixture of argon and nitrogen. The deposited film was characterized by grazing incidence X-ray diffraction (GIXRD), atomic force microscope (AFM), spectroscopic ellipsometry, and secondary ion mass spectroscopy (SIMS). GIXRD results have shown (100) reflection of wurtzite AlN, whereas AFM micrographs have revealed very fine grained microstructure with average roughness in the range 6–8？nm. Spectroscopic ellipsometry measurements have indicated the band gap and refractive index of the film in the range 5.0–5.48？eV and 1.58–1.84, respectively. SIMS measurement has indicated the presence of oxygen in the film. 1. Introduction Aluminum nitride, a III-V family compound, has excellent combination of physical, chemical, and mechanical properties. High-quality films of aluminum nitride have been used in various devices and sensors including the optical and optoelectronic devices. As far as the optical and optoelectronic applications are concerned, wide band gap (~6.2？eV) along with high-refractive index (~2.0) and low-absorption coefficient (<10？3) makes AlN a very attractive material for these applications [1]. In addition to this, thermal and chemical stability of AlN films make it suitable for applications in difficult environment. Today, AlN films/coatings have been grown by several methods which include pulsed laser deposition [2], reactive molecular beam epitaxy [3], vacuum arc/cathodic arc deposition [4], DC/RF reactive sputtering [5–7], ion beam sputtering [8], metal-organic chemical vapor deposition (MOCVD) [9], and miscellaneous [10] other techniques. Due to simplicity, reproducibility, ease of scaling up, and lower cost, magnetron sputtering is one of the common methods for growing AlN films for various applications. As already known, it is difficult to obtain good quality insulating films by DC magnetron sputtering, and RF magnetron sputtering has the disadvantage of lower deposition rate and higher cost of the RF power, whereas pulsed DC magnetron sputtering method has the advantage of higher deposition rate and it is suitable for producing good quality cost-effective dielectric films [11, 12]. Properties of AlN films depend upon the crystal structure, crystal orientation, microstructure, and chemical composition, which in turn depend upon the deposition conditions such as sputtering power, pulse frequency, duty cycle, growth temperature, nitrogen/argon flow ratio, and sputtering gas
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