SURFACE ROUGHNESS AND GRAIN SIZE CHARACTERIZATION OF ANNEALING TEMPERATURE EFFECT FOR GROWTH GALLIUM AND TANTALUM DOPED Ba0.5 Sr0.5TiO3 THIN FILM. Thin films 10 % gallium oxide doped barium strontium titanate (BGST) and 10 % tantalum oxide doped barium strontium titanate (BTST) were prepared on p-type Si (100) substrates using chemical solution deposition (CSD) method with 1.00 M precursor. The films were deposited by spin coating method with spinning speed at 3000 rpm for 30 seconds. The post deposition annealing of the films were carried out in a furnace at 200C, 240C, 280C (low temperature) for 1 hour in oxygen gas atmosphere. The surface roughness and grain size analysis of the grown thin films are described by atomic force microscope (AFM) method at 5000 nm x 5000 nm area. The rms surface roughness BGST thin films at 5000 nm x 5000 nm area are 0.632 nm, 0.564 nm, 0.487 nm for temperature 200C, 240C, 280C, respectively, whereas the grain size (mean diameter) are 238.4 nm, 219.0 nm, 185.1 nm for temperature 200C, 240C, 280C, respectively. In fact, to increase annealing temperature from 200C to 280C would result in decreasing the rms roughness and grain size. Therefore, rms roughness and grain size would have the strong correlation annealing temperature.

In this paper, the growth of GaN:Mn thin films by plasma-assisted metalorganic chemical vapor deposition (PAMOCVD) method is reported. The method used in this study, utilizes a microwave cavity as a cracking cell to produce nitrogen radicals, which in turn reduce the growth temperature. Trimethylgallium (TMGa), nitrogen (N2) and cyclopentadienyl manganese tricarbonyl (CpMnT) were used as a source of Ga, N and Mn, respectively, while hydrogen gas was used as a carrier gas for both TMGa and CpMnT. The effect of growth temperature and Mn incorporation on structural properties and surface morphology of GaN:Mn films are presented. The growth of GaN:Mn thin films were conducted at varied growth temperature in range of 625 oC to 700 oC and the Mn/Ga molar fraction in the range of 0.2 to 0.5. Energy dispersive of X-ray (EDX) and X-ray diffraction (XRD) methods were used to analyze atomic composition and crystal structure of the grown films, respectively. The surface morphology was then characterized using both atomic force microscopy (AFM) and scanning electron microscopy (SEM) images. A systematic XRD analysis reveal that maximum Mn incorporation that still produces single phase GaN:Mn (0002) is 6.4 % and 3.2 % for the film grown at 650 oC and 700 oC, respectively. The lattice constant and full width at half maximum (FWHM) of the single phase films depend on the Mn concentration. The decrease in lattice constant accompanied by the increase in FWHM is due to incorporation of substitutional Mn on the Ga sub-lattice. The maximum values of doped Mn atoms incorporated in the wurtzite structure of GaN:Mn as substitutional atoms on Ga sub-lattice are 2.0 % and 2.5 % at 650 oC and 700 oC, respectively. AFM and SEM images show that the film grown at lower growth temperature and Mn concentration has a better surface than that of film grown at higher growth temperature and Mn concentration.

Ceramic of BaxSr1-xTiO3 (BST) for x =0.3; 0.5 and 0.7 were successfully deposited by solid solution method. The BST ceramic were analyzed by x-ray diffraction (XRD). The XRD spectra was recorded on a Philips type PW 3701 diffractometer using CuKD (Oco = 1.54056 A) radiation at 30 KV and 30 mA (900 watt). The spectra shows that BST ceramic are polycrystalline with tetragonal structure. The lattice constants analysis of the grown ceramics was analyzed by visual basic program. Using Cohen’s and Cramer’s algorithms in visual basic program, , the lattice constants are a = b = 3.877 A; c = 3.970 A for Ba0.3Sr0.7TiO3 ceramic, a = b = 3.979 A; c = 3.981 A. for Ba0.5Sr0.5TiO3 ceramic and a = b = 3.965 A; c = 4.005 A for Ba0.7Sr0.3TiO3 ceramic, respectively. The reform value of the lattice constant of BST ceramic is possibly associated with the anti site defects of Ba and Sr.

Growth of GaN quantum dots on AlGaN layer using [(C2H5)4]Si [TESi] by plasma assisted metal organic chemical vapor deposition (PA-MOCVD) is reported. The surface profile of the grown GaN quantum dot was determined by atomic force microscope (AFM). The typical average density of the dots is around 4 109 cm-2, while the diameter and the height of the dots are approximately 100 and 50 nm, respectively. The density and the size of the dots significantly depend on the dose of TESi. It is found that the growth mode was changed from the two-dimensional step-flow to the three-dimensional island formation by modifying the AlGaN surface energy induced by the deposited Si.