Synthesis of GaN nanorods on Si substrates with assistance of the volatilization of ZnO middle layers

GaN nanorods have successfully been synthesized on Si(111) substrates via ammoniating ZnO/Ga2O3 films at 950℃. Ga2O3 thin films and ZnO middle layers were deposited in turn on Si(111) substrates by r.f. magnetron sputtering system. ZnO volatilized at 950℃ in the ammonia ambience and Ga2O3 reacted to NH3 to fabricate GaN nanorods in the later ammoniating process. The volatilization of ZnO layers played an important role in the fabrication. The structure and composition of the GaN nanorods were studied by X-ray diffraction (XRD) and Fourier transform infrared spectrophotometer (FTIR). The orphology ofGaN nanorods was investigated using scanning electron microscopy (SEM) and transmission electronic microscope (TEM). The analyses of measured results revealed that GaN nanorods with hexagonal wurtzite stxucture were prepared by this method.     

Fabrication of hexagonal gallium nitride films on silicon (111) substrates

Hexagonal gallium nitride films were successfully fabricated through ammoniating Ga2O3 films deposited on silicon (111) substrates by electrophoresis. The structure, composition, and surface morphology of the formed films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The measurement results reveal that the polycrystalline GaN films with hexagonal wurtzite structure were successfully grown on the silicon (111) substrates. Preliminary results suggest that varying the ammoniating temperature has obvious effect on the quality of the GaN films formed with this method.     

Synthesis of GaN films on porous silicon substrates

A novel and simple method was employed to synthesize GaN films on porous silicon (PS) substrates. GaN films were obtained through the reaction between NH3 and Ga2O3 films deposited on the substrates with magnetron sputtering. Since GaN and PS are all good materials for luminescence, it is expected to obtain some new properties from GaN on PS. The samples were analyzed with X-ray diffraction (XRD) to identify crystalline structure. Fourier transmit infrared (FTIR) spectrum was used to analyze the chemical state of the samples. The films were observed with scanning electron microscopy (SEM) and were found to consist of many big crystal grains. Photoluminescence (PL) spectrum was used to illuminate the optical property of the GaN films.     

（Short communication） Synthesis of GaN films on porous silicon substrates

A novel and simple method was employed to synthesize GaN films on porous silicon （PS） substrates, GaN films were obtained through the reaction between NH3 and Ga2O3 films deposited on the substrates with magnetron sputtering. Since GaN and PS are all good materials for luminescence, it is expected to obtain some new properties from GaN on PS. The samples were analyzed with X-ray diffraction （XRD） to identify crystalline structure. Fourier transmit infrared （FFIR） spectrum was used to analyze the chemical state of the samples. The films were observed with scanning electron microscopy （SEM） and were found to consist of many big crystal grains. Photoluminescence （PL） spectrum was used to illuminate the optical property of the GaN films.     

Microstructure and magnetic properties of NiZn ferrite thin films prepared by sol-gel method

Ti^4＋ substitution for Fe^3＋ in Ni0.5Zn0.5Fe2O4 （NZF） ferrite thin films were realized by sol-gel method and annealing at 600℃for 30 min in the air. Crystal structure and lattice constant determination was performed by X-ray diffractometer （XRD）. Surface microstructure was observed by scanning electron microscope （SEM） and atomic force microscope （AFM）, and the magnetic properties were measured by vibrating sample magnetometer （VSM）. XRD analyses of the samples show that Ni0.5＋xZn0.5TixFe2-2xO4 （NZTF） films with x varing from 0 to 0.15 in steps of 0.05 are composed of single phase with spinel structure. And the lattice parameter, particle size and the diffraction intensity of the films increase with substitution of Ti as the result of the larger radius ions entering the lattice. SEM and AFM show homogeneous grain size of each sample, but there is a few differences in grain size with different Ti-substitution contents. As the nonmagnetic Ti^4＋ substitutes Fe^3＋, both the saturation magnetization and coercivity decrease.     

Effect of substrate temperature on structural properties and photocatalytic activity of TiO2 thin films

Titanium dioxide （TiO2） films with anatase structure were prepared on quartz glass substrates by pulse laser ablating titanium （99.99%） target under oxygen pressure of 10 Pa at substrate temperature of 500-800 ℃. The structural properties of the films were characterized by X-ray difffactometry（XRD）, X-ray photoelectron spectroscopy（XPS） and field emission scan electron microscopy（FESEM）. The results show that, as the substrate temperature is increased from 600 ℃ to 800 ℃, the anatase structure of the films changes from random growth to （211）-oriented growth. The absorption edge tested by UV-Vis Spectrometer has a blue shift. The photocatalytic activity of the films was tested on the degradation of methyl orange. It is found that the film with random growth structure exhibits better photo-degradation efficiency than that with （211）-oriented growth structure.     

PECVD OF HARD AND ELASTIC BCN COATINGS

Compounds of the B-C-N system are very promising to produce superhard coatings with good tribological, chemical and thermal properties. Consequently, BCN films were prepared by plasma enhanced chemical vapor deposition (PECVD). The films were deposited from gaseous mixtures of BCl3-C2H4-N2-H2-Ar in different unipolar and bipolar pulsed glow discharges at 550℃ and analyzed with respect to composition, electronic structure and mechanical properties. The micro structure and composition of the BCN films were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and reflection electron energy loss spectroscopy (REELS). Mechanical properties were characterized using both the traditional Vickers method and nanoindentation. The films, that were deposited using a bipolar pulsed generator, were weak and had a sponge-like structure, whereas the films prepared using an unipolar generator were well adherent, had a hardness of more than 11GPa and very high e     

Fabrication of ZnO films by radio frequency magnetron sputtering and annealing

ZnO thin films were deposited on Si（111） substrates through a radio frequency （rf） magnetron sputtering system. Then the samples were annealed at different temperatures in air ambience and ammonia ambience respectively. The structure and composition of the ZnO films were studied by X-ray diffraction （XRD） and X-ray photoelectron spectroscopy （XPS）. The morphology of the samples was studied by scanning electron microscopy （SEM）. Measured results show that ZnO films with hexagonal wurtzite structure were grown on Si（111） substrates when annealed in the two ambiences. The volatilization process of ZnO in the ammonia ambience at high temperature was discussed and the mechanism of the reaction was analyzed.     

Microstructure of Nitrided Aluminum Alloys Using an Electron-Beam-Excited-Plasma （EBEP）

Nitriding of surface of aluminum alloys was carried out with using an electron-beam-excited-plasma (EBEP) technique. The EBEP is sustained by electron impact ionization with energetic electron beam. Two kinds of substrates,aluminum alloys AA5052 and AA5083, were exposed to the down flow of EBEP source at 843 K for 45min. The specimens were characterized with respect to following properties: crystallographic structure (XRD), morphology (SEM) and the cross sectional microstructures of the nitrided layer was observed using a scanning electron microscopy (SEM). There are some Al2O3 particles on the surface of the nitrided AA5052 and AA5083. The AlN layers were formed on the substrates with the thickness of 4.5μm for AA5052 and 0.5μm for AA5083. A relatively uniform nitrided surface layer composed of AlN can be observed on the AA5052 substrate. The grains size near the interfaces between the substrate and AlN layer were smaller than that near the surface. On the surface of AlN layer, the concentration of nitrogen was high and in the middle of AlN layer it had a constant concentration like the aluminum and the concentration was decreased with approaching to the interface. On the surface of nitrided AA5083, a uniform AlN layer was not formed as the reason for the high nitriding temperature.     

Induced effects of Cu underlayer on（111） orientation of Fe50 Mn50 thin films

Effects of Cu underlayer on the structure of Fe50 Mn50 films were studied. Samples with a structure of Fe50 Mn50 (200 nm)/Cu(tcu) were prepared by rnagnetron sputtering on thermally oxidized silicon substrates at room temperature. The thickness of Cu underlayer varied from 0 to 60 nm in the intervals of 10 nm. High-vacuum annealing treatments, at different temperatures of 200, 300 and 400℃ for 1 h, respectively, on the Fe50Mn50 (200 nm)/Cu(20 nm) thin films were performed. The surface morphologies and textures of the samples were measured by field emission scan electronic microscope (FE-SEM) and X-ray diffraction(XRD). Energy dispersive X-ray spectroscopy (EDX) and Auger electron spectroscopy(AES) were used to analyze the compositional distribution. It is found that Cu underlayer has an obvious induce effect on (111) orientation of Fe50 Mn50 thin films. The induce effects of Cu on (111) orientation of Fe50 Mn50 changed with the increase of Cu layer thickness and the best effect was obtained at the Cu layer thickness of 20 nm. High-vacuum annealing treatments cause the migration of Mn atoms towards surface of the film and interface between Cu layer and substrate. With the increasing annealing temperature, migration of Mn atoms is more obvious, which leads to a Fe-riched Fe-Mn alloy film.     

Preparation and Properties of GaN Micro-Ribbons on Ga-Diffused Si （111） Substrates

用射频磁控溅射工艺在室温扩镓硅衬底上沉积Ga2O3膜,然后在氨气气氛下氮化Ga2O3膜得到GaN微米带,用X射线衍射(XRD)、扫描电镜(SEM)、选区电子衍射(SAED)、X射线光电子能谱(XPS)及光致发光谱(PL)对薄膜样品进行了结构、表面形貌、组分及发光特性分析.SEM图像显示直径约为100 nm～300 nm微米带随机分布在GaN薄膜表面.XRD、XPS及SAED分析表明GaN微米带呈六方闪锌矿多晶结构,择优沿[001]方向生长.P1显示了可能由量子限制效应引起的发光峰,其相对于报道的GaN晶体发光峰有显著蓝移.     

ZnO／Ga2O3膜的氨化温度对制作硅基GaN纳米材料的影响

通过在不同温度下氨化ZnO／Ga2O3膜，在Si衬底上成功制备了GaN纳米结构材料。氨化前，ZnO层和Ga2O3膜分别通过射频磁控溅射法依次溅射到Si衬底上。用X射线衍射(XRD)、红外傅里叶变换光谱(FTIR)分析了GaN晶体的结构和组分，利用扫描电子显微镜(SEM)观察了样品的形貌。通过对测试结果的分析可知在Si衬底上由ZnO挥发辅助生长出六方纤锌矿GaN纳米结构晶体，并且ZnO／Ga2O3的氨化温度对形成GaN纳米材料具有明显的影响。     

氨化Ga2O3 /Nb膜制备的GaN纳米线的光学和微观结构特性的研究

采用射频磁控溅射技术在硅衬底上制备Ga2O3/Nb薄膜,然后在900℃下于流动的氨气中进行氨化制备GaN纳米线.用X射线衍射(XRD)、透射电子显微镜(TEM)和高分辨透射电子显微镜详细分析了GaN纳米线的结构和形貌.结果表明:采用此方法得到的GaN纳米线有直的形态和光滑的表面,其纳米线的直径大约50nm,纳米线的长约几个微米.室温下以325nm波长的光激发样品表面,只显示出一个位于367 nm的很强的紫外发光峰.最后,简单讨论了GaN纳米线的生长机制.     

氨化Si基Ga2O3／Al2O3制备GaN薄膜

研究了Ga2O3／Al2O3膜反应自组装制备GaN薄膜。首先利用磁控溅射法在硅衬底上制备Ga2O3／Al2O3膜，再将Ga2O3／Al2O3膜在高纯氨气气氛中氨化反应得到了GaN薄膜。用X射线衍射(XRD)，X光光电子能谱(XPS)、扫描电镜(SEM)、透射电镜(TEM)和荧光光谱(PL)对样品进行结构、组分、形貌和发光特性的分析。测试结果表明：用此方法得到了六方纤锌矿结构的GaN晶体膜。     

钽催化磁控溅射法制备GaN纳米线

利用磁控溅射技术通过氮化Ga2O3/Ta薄膜,合成大量的一维单晶纤锌矿型氮化镓纳米线.用X射线衍射、扫描电子显微镜、高分辨透射电子显微镜,选区电子衍射和光致发光谱对制备的氮化镓进行了表征.结果表明;制备的GaN纳米线是六方纤锌矿结构,其直径大约20～60 nm,其最大长度可达10 μm左右.室温下光致发光谱测试发现363 nm处的较强紫外发光峰.另外,简单讨论了氮化镓纳米线的生长机制.     

Preparation of GaN Nanorods by Rare Earth Metal Tb Catalyst-Assisted Process

利用稀土金属Tb作为催化剂,通过氨化磁控溅射在Si(111)衬底上的Ga203/Tb薄膜制备出GaN纳米棒.X射线衍射和傅里叶红外吸收谱测试结果表明,制备的样品为六方结构的GaN.利用扫描电子显微镜、透射电子显微镜和高分辨透射电子显微镜对样品进行测试,结果显示样品为单晶结构的纳米棒,直径为80～200 nm,长度达几十微米.最后简单地讨论了GaN纳米棒的生长机制.     

氨化Si基Ga2O3/V膜制备GaN纳米线

氨化硅基钒应变层氧化镓膜制备了大量氮化镓纳米线,X射线衍射、扫描电子显微镜和透射电子显微镜观察发现,纳米线具有十分光滑且干净的表面,其直径为20～60 nm左右,长度达到十几微米.高分辨透射电子显微镜和选区电子衍射分析结果表明,制备的氮化稼纳米线为六方纤锌矿结构.光致发光谱显示制备的氮化稼纳米线有良好的发光特性.另外,简单讨论了氮化稼纳米线的生长机制.