Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 25Citation - Scopus: 26Structural and Optical Characteristics of Tantalum Oxide Grown by Pulsed Nd:yag Laser Oxidation(AVS Science and Technology Society, 2006) Atanassova, Elenada A.; Aygün, Gülnur; Turan, Raşit; Babeva, T.Tantalum pentoxide (Ta2 O5) thin films (20-50 nm) have been grown by 1064 nm Nd:YAG laser oxidation of Ta film deposited on Si. The chemical bonding, structure, and optical properties of the films have been studied by Fourier transform infrared spectroscopy, x-ray diffraction, and reflectance measurements at normal light incidence in the spectral range of 350-800 nm. The effect of the substrate temperature (250-400 °C) during oxidation and its optimization with respect to the used laser beam energy density (3.2-3.4 J cm2 per pulse) is discussed. It is established that the substrate temperature is a critical factor for the effectiveness of the oxidation process and can be used to control the composition and amorphous status of the films. The film density explored by refractive index is improved with increasing film thickness. The refractive index of the layers grown under the higher laser beam energy density and at substrate temperature of 350-400 °C was found to be close to the value of bulk Ta2 O5. The films are amorphous at substrate temperature below 350 °C and possessed an orthorhombic (Β- Ta2 O5) crystal structure at higher temperatures. The thinner layers crystallize at a little higher temperature.Article Citation - WoS: 14Citation - Scopus: 18Xps Study of Pulsed Nd:yag Laser Oxidized Si(Elsevier Ltd., 2006) Özyüzer, Gülnur Aygün; Aygün, Gülnur; Atanassova, Elenada A.; Kostov, K.; Turan, RaşitX-ray photoelectron spectra (XPS) of thin SiO2 layers grown by pulsed Nd:YAG laser at a substrate temperature of 748 K are presented. The peak decomposition technique combined with depth profiling is employed to identify the composition and chemical states of the film structure. It is established that the oxide is non-stoichiometric, and contains all oxidation states of Si in different amounts throughout the film. The interface Si/laser-grown oxide is not abrupt, and the coexistence of Si2O3 and Si2O suboxides in a relatively wide interfacial region is found. It is concluded that post-oxidation annealing is necessary in order to improve the microstructure of both oxide and near interface region.Article Citation - WoS: 22Citation - Scopus: 22Oxidation of Si Surface by a Pulsed Nd: Yag Laser(IOP Publishing Ltd., 2004) Özyüzer, Gülnur Aygün; Atanassova, Elenada A.; Alaçakır, Ali; Özyüzer, Lütfi; Turan, RaşitSiO2 thin films have been obtained by 1064 nm Nd: YAG laser oxidation of p-Si in the presence of O2. The thickness uniformity, dielectric and electrical properties of the layers have been studied. The effect of both the laser beam energy density and the substrate temperature on the oxide growth is also discussed. It was established that there exists an interval of laser beam energy density in which the oxidation occurs without surface melting. The oxidation process is controlled by the laser beam energy density rather than by the substrate temperature (673-748 K) and the higher laser power results in a thicker oxide. X-ray photoelectron spectroscopy (XPS) was used to provide information on the oxide composition. XPS results revealed that the as-grown oxide is a mixed layer of SiO2 and Si2O, which are distributed nonuniformly through the depth. MOS capacitors fabricated on the grown oxide exhibited typical capacitance-voltage, conductance-voltage characteristics. However, the density of interface states and oxide charge density were found to be higher than the typical values of thermally grown oxides. The quality of the oxide layers can be further improved by optimization of the process parameters and/or by post-processing of the grown films. It is concluded that the SiO2 films formed by the technique of Nd: YAG laser-enhanced oxidation at low temperature are potentially useful for device applications.