Materials Science Forum Vol. 725

Abstract: We performed first-principle calculations to investigate the effects of F, Cl and Sb impurities on the electronic properties of SnO₂. We obtained, firstly, the electronic structure of SnO₂, a valence band maximum of SnO₂ is an O 2p orbital and a conduction band minimum was an antibonding Sn 5s and O 2p orbitals dominantly. Secondly, those impurites doped SnO₂ was obtained the electronic structure. The F, Cl and Sb impurities as n-type dopants exhibited shallow donors. This calculation results were in good agreement with our prvious experiment that we obtained the low resistivity SnO₂.

Abstract: For the purpose of increasing the conductivity of β-Ga₂O₃ films, Sn doping in the β-Ga₂O₃ films has been explored using co-sputtering. Growth of β-Ga₂O₃ was confirmed by the XRD pattern for the undoped sample. However, it is shown that the Ga₂O₃ phase is transformed from the β to the γ phase by Sn doping, because of the increase of the phase transition temperature from the γ to the β phase. To improve the crystalline quality, additional annealing at 900°C for 60 min is performed to the Sn doped film. The XRD peaks corresponding with β-Ga₂O₃ could be confirmed after the additional annealing.

Abstract: For the purpose of improving the crystalline quality of undoped and Si doped β-Ga₂O₃ films, high temperature annealing at 900°C was performed. The crystalline quality of the films investigated using scanning electron microscopy and X-ray diffraction. Also the conductivity of the films is compared before and after the annealing. After the 900°C annealing, the XRD peaks intensity corresponding to β-Ga₂O₃ is increased. This result indicates that the crystalline quality improves by the high temperature annealing.

Abstract: A novel precursor for ZnO film deposition with Zn-O structure was synthesized by the reaction of diethylzinc and water in some ether solvents. The novel precursor was characterized by 1H-NMR spectroscopy and differential scanning calorimetry (DSC). Nondoped and In-doped ZnO films on a glass substrate have been successfully grown by conventional spin coating using nondoped and In added novel precursor solution. The samples have an optical transmittance of more than 85%, and a smooth surface determined from optical transmittance and scanning electron microscopy, respectively. The sheet resistivity of In-doped ZnO films is lower than that of nondoped ZnO film.

Abstract: Low resistivity, fluorine-doped tin dioxide thin films were deposited on glass substrates by spray pyrolysis. These films were prepared with different F-doping concentrations from 0 to 33 mol%. The structure of these films was investigated by X-ray diffraction and the surface morphology by Scanning Electron Microscopy. Sample compositions were evaluated using X-ray Photoemission Spectroscopy. According to these results, the films were all polycrystalline with tetragonal crystal structures. Hall measurements were used to probe the dependence of the resistivity on temperature for un-doped SnO₂ and F-doped SnO₂. The resistivity of un-doped SnO2 slightly increased with increasing temperature. Conversely, the resistivity of F-doped SnO₂ slightly decreased with increasing temperature.

Abstract: Boron Phosphide (BP) layers have been grown on Si (100) as a substrate for cubic GaN heteroepitaxy. Si heavy doping was attempted to reduce the threading dislocation density in the BP. To observe the effect on dislocations in BP by Si doping, we used cross-sectional transmission electron microscopy (XTEM). Also, Glow Discharge-Optical Emission Spectroscopy (GDOES) were used to evaluate the effect of Si doping. For the samples under the conditions (a) and (e), we found the formation of pits at BP surface and an increasing in the proportion of threading dislocations with an angle of 90 ° to the surface. We could not see a significant change in the threading dislocation density by Si doping under the conditions used in this paper.

Abstract: This paper describes structure evaluation of GexSbyTez (GST) film fabricated by chemical vapor deposition (CVD). We successfully established composition controlled GST CVD with smooth surface by applying appropriate deposition conditions. By increasing Ge flow rate or reducing substrate temperature, the average grain size was reduced and the film flatness was improved. As the results, we succeeded to obtain the extremely smooth surface, and also to fill a finite hole with conformal film deposition. All GexSbyTez films showed FCC or amorphous crystalline structures, both are utilized in the proposed phase change random access memory (PRAM), in spite of the wide range of composition control. We believe these CVD-GST films are useful for PRAM applications.