Browsing by Author "Cakmak, M."
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Item Open Access Effects of thermal annealing on the morphology of the AlxGa(1x)N films(Elsevier, 2010-01-08) Corekci, S.; Tekeli, Z.; Cakmak, M.; Ozcelik, S.; Dinc, Y.; Zeybek, O.; Özbay, EkmelEffects of thermal annealing on the morphology of the AlxGa(1-x)N films with two different high Al-contents (x=0.43 and 0.52) have been investigated by atomic force microscopy (AFM). The annealing treatments were performed in a nitrogen (N-2) gas ambient as short-time (4 min) and long-time (30 min). Firstly, the films were annealed as short-time in the range of 800-950 degrees C in steps of 50-100 degrees C. The surface root-mean-square (rms) roughness of the films reduced with increasing temperature at short-time annealing (up to 900 degrees C), while their surface morphologies were not changed. At the same time, the degradation appeared on the surface of the film with lower Al-content after 950 degrees C. Secondly, the Al0.43Ga0.57N film was annealed as long-time in the range of 1000-1200 degrees C in steps of 50 degrees C. The surface morphology and rms roughness of the film with increasing temperature up to 1150 degrees C did not significantly change. Above those temperatures, the surface morphology changed from step-flow to grain-like and the rms roughness significantly increased.Item Open Access The influence of thickness and ammonia flow rate on the properties of AIN layers(Elsevier, 2012) Corekci, S.; Ozturk, M. K.; Cakmak, M.; Ozcelik, S.; Özbay, EkmelUndoped AlN layers have been grown on c-plane sapphire substrates by metal-organic chemical vapor deposition in order to study the effects of ammonia (NH3) flow rate and layer thickness on the structural quality and surface morphology of AlN layers by high-resolution X-ray diffraction, scanning electron microscopy, and atomic force microscopy. Lower NH3 flow rate improves crystallinity of the symmetric (0 0 0 2) plane in AlN layers. Ammonia flow rate is also correlated with surface quality; pit-free and smooth AlN surfaces have been obtained at a flow rate of 70 standard cm(3) per minute. Thicker AlN films improve the crystallinity of the asymmetric (1 0 1 (1) over bar 2) plane.