Si基氨化ZnO/Ga2O3薄膜制备GaN纳米线

利用射频磁控溅射法在Si(111)衬底上溅射ZnO中间层和Ga2O3薄膜,然后在管式炉中常压下通氨气对ZnO/Ga2O3薄膜进行氨化,高温下ZnO层在氨气气氛中挥发,而Ga2O3薄膜和氨气反应合成出GaN纳米线.X射线衍射测量结果表明利用该方法制备的GaN纳米线具有沿c轴方向择优生长的六角纤锌矿结构.利用扫描电子显微镜、透射电子显微镜、傅里叶红外透射谱、能量弥散谱及选区电子衍射观测并分析了样品的形貌、成分和晶格结构.研究发现ZnO层的挥发有利于Ga2O3和NH3反应合成GaN纳米线.     

Si基ZnO/Ga2O3氨化反应制备GaN薄膜

利用射频磁控溅射法在Si(111)衬底上先溅射ZnO缓冲层，接着溅射Ga2O3薄膜，然后ZnO／Ga2O3膜在开管炉中850℃常压下通氨气进行氨化，反应自组装生成GaN薄膜。XRD测量结果表明利用该方法制备的GaN薄膜是沿c轴方向择优生长的六角纤锌矿多晶结构的薄膜，利用傅里叶红外吸收光谱仪测量了薄膜的红外吸收谱，利用SEM和TEM观测了薄膜形貌，PL测量结果发现了位于350nm和421nm处的室温光致发光峰。     

Si基氨化ZnO／Ga2O3薄膜制备GaN纳米线

利用射频磁控溅射法在Si(111)衬底上溅射ZnO中间层和Ga2O3薄膜，然后在管式炉中常压下通氨气对ZnO/Ga2O3薄膜进行氨化，高温下ZnO层在氨气气氛中挥发，而Ga2O3薄膜和氨气反应合成出GaN纳米线．X射线衍射测量结果表明利用该方法制备的GaN纳米线具有沿c轴方向择优生长的六角纤锌矿结构．利用扫描电子显微镜、透射电子显微镜、傅里叶红外透射谱、能量弥散谱及选区电子衍射观测并分析了样品的形貌、成分和晶格结构．研究发现ZnO层的挥发有利于Ga2O3和NH3反应合成GaN纳米线．     

竹叶状GaN纳米带的制备

为了制备GAN纳米带,用射频磁控溅射法在Si(111)衬底上先溅射ZnO中间层,接着溅射Ga2O3,然后ZnO/Ga2O3膜在开管炉中1000℃下常压通氨气进行氨化。在氨气气氛中ZnO在高温下挥发,借助于ZnO挥发的帮助,Ga2O3与NH3反应自组装生成GaN纳米带。XRD分析结果表明GaN纳米带为六方纤锌矿结构,利用SEM观测GaN纳米带具有竹叶状形貌,PL谱测量发现了位于370nm处和460nm处的室温光致发光峰。     

RF磁控溅射和氨化法制备GaN纳米棒和纳米颗粒

利用射频磁控溅射法分别溅射ZnO中间层和Ga2O3薄膜到Si(111)衬底上,然后ZnO/Ga2O3薄膜在管式石英炉中常压下通氨气进行氨化,高温下ZnO在氨气气氛中被还原生成Zn而升华,而在不同的氨化时间下Ga2O3和氨气反应合成出GaN纳米棒和纳米颗粒。X射线衍射(XRD)测量结果表明,利用该方法制备GaN纳米棒和颗粒具有沿c轴择优取向生长的六方纤锌矿结构。利用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、傅里叶红外透射谱(FTIR)及选区电子衍射(SAED)观测和分析了样品的形貌、成分和晶格结构。研究分析了此种方法合成GaN纳米结构的反应机制。     

RF磁控溅射和氮化法制备GaN纳米棒和纳米颗粒

利用射频磁控溅射法分别溅射ZnO中间层和Ga2O3薄膜到Si（111）衬底上，然后ZnO／Ga2O3薄膜在管式石英炉中常压下通氨气进行氨化，高温下ZnO在氨气气氛中被还原生成Zn而升华，而在不同的氨化时间下Ga2O3和氨气反应合成出GaN纳米棒和纳米颗粒。X射线衍射（XRD）测量结果表明，利用该方法制备GaN纳米棒和颗粒具有沿c轴择优取向生长的六方纤锌矿结构。利用扫描电子显微镜（SEM）、透射电子显微镜（TEM）、傅里叶红外透射谱（FTIR）及选区电子衍射（SAED）观测和分析了样品的形貌、成分和晶格结构。研究分析了此种方法合成GaN纳米结构的反应机制。     

合成GaN粗晶体棒的研究

利用磁控溅射系统,在Si(111)衬底上的SiC缓冲层上溅射Ga2O3纳米颗粒薄膜。然后令该薄膜在NH3中高温退火,在产物中发现直径为数百纳米的GaN棒。直径如此大的GaN棒在国内外鲜有报道。该晶体棒被认为是在Ga2O3薄膜与NH3自组装反应过程中形成。该工艺可为合成大尺寸GaN一维结构提供一条新的途径。     

溅射气压对氧化镓薄膜光学特性的影响

采用射频磁控溅射法在石英衬底上制备了氧化镓(Ga2O3)薄膜.利用X射线衍射仪和紫外-可见-红外分光光度计分别对Ga2O3薄膜的晶体结构和光学带隙进行了表征,并在室温下测量了 Ga2O3薄膜的光致发光(PL)谱.结果表明:制备的Ga2O3薄膜呈非晶态.吸收边随着溅射气压的增加先蓝移后红移,光学带隙值范围为5.06～5.37 eV,溅射气压为1 Pa时,制备的Ga2O3薄膜具有最大的光学带隙.在325 nm激光激发下,400 nm附近和525 nm附近处出现与缺陷能级相关的发光峰.     

氧化物缓冲层制备Si(111)基GaN纳米线

采用氧化物缓冲层,通过射频磁控溅射系统依次在n型Si(111)衬底上沉积Ga2O3/ZnO(Ga2O3/MgO)薄膜,然后将薄膜于950℃氨化合成GaN纳米结构,氨化时间为15min。采用X射线衍射(XRD)、傅里叶红外吸收谱(FTIR)和高分辨透射电镜(HRTEM)对样品的结构进行了分析,结果显示两种缓冲层下制备的样品均为六方纤锌矿单晶GaN纳米结构,且缓冲层的取向对纳米线的生长方向有很大影响;采用扫描电镜(SEM)对样品的形貌进行了测试,发现纳米线表面光滑,长度可达几十微米,表明采用氧化物缓冲层制备了高质量的GaN线。同时对GaN纳米线的生长机理进行了简单讨论。     

ZnAl2O4/α-Al2O3衬底上GaN的生长

研究了直接在ZnAl2O4/α-Al2O3衬底上用MOCVD法一步生长GaN薄膜．利用脉冲激光淀积法在α-Al2O3衬底上淀积了高质量ZnO薄膜,对ZnO/α-Al2O3样品在1100℃退火得到了具有ZnAl2O4覆盖层的α-Al2O3衬底,并在此复合衬底上利用光加热低压MOCVD法直接生长了纤锌矿结构GaN．X射线衍射谱表明反应得到的ZnAl2O4层为（111）取向．扫描电子显微镜照片显示随退火时间从小于30min增加到20h,ZnAl2O4表面由均匀的岛状结构衍变为突起的线状结构,相应的GaN X 射线衍射谱表明GaN由c轴单晶变为多晶,单晶GaN的摇摆曲线半高宽为0.4°．结果表明薄ZnAl2O4覆盖层的岛状结构有利于GaN生长初期的成核,从而提高了GaN的晶体质量．     

纳米Al夹层Ga_2O_3深紫外透明导电膜的研究

用磁控溅射法在室温条件下制备了Al膜、Ga2O3膜及Ga2O3/Al/Ga2O3三层膜,对其光学和电学性能进行了表征。单层Al膜厚度大于7nm时,光学透射率在近紫外光区域大于可见光区域;Ga2O3膜在深紫外光区域(<300nm)透明,光学带隙4.96eV;Ga2O3/Al/Ga2O3三层膜透射率截止波长在245nm左右,随着顶层Ga2O3厚度增加,电导率减小,紫外光透射率峰位、吸收边、截止波长红移,透射率峰值先稍微增加,然后逐渐降低。顶层Ga2O3厚度为34nm时,Ga2O3/Al/Ga2O3三层膜在275nm处的透射率达70%,电导率为3346S.cm–1。     

P-type ZnO thin films prepared by in situ oxidation of DC sputtered Zn3N2:Ga

The feasibility of a new fabrication route for N and Ga codoped p-type ZnO thin films on glass substrates, consisting of DC sputtering deposition of Zn3N2:Ga precursors followed by in situ oxidation in high purity oxygen, has been studied. The effects of oxidation temperature on the structural, optical and electrical properties of the samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), optical transmittance and Hall effect measurements. The results were compared to a control film without Ga. XRD analyses revealed that the Zn3N2 films entirely transformed into ZnO films after annealing Zn3N2 films in oxygen over 500 ℃ for 2 h. Hall effect measurements confirmed p-type conduction in N and Ga codoped ZnO films with a low resistivity of 19.8 Ω·cm, a high hole concentration of 4.6 × 1018 cm-3 and a Hall mobility of 0.7 cm2/(V·s). These results demonstrate a promising approach to fabricate low resistivity p-type ZnO with high hole concentration.     

Electrical and optical properties of deep ultraviolet transparent conductive Ga2O3/ITO films by magnetron sputtering

Ga2O3/ITO films were prepared by magnetron sputtering on quartz glass substrates. The transmittance and sheet resistance of ITO films and Ga2O3/ITO films were measured by using a double beam spectrophotometer and four point probes. The effect of the ITO layer and Ga2O3 layer thickness on the electrical and optical properties of Ga2O3/ITO bi-layer films were investigated in detail. Ga2O3 (50 nm)/ITO (23 nm) films exhibited a low sheet resistance of 323 Ω/□ and high deep ultraviolet transmittance of 77.6% at a wavelength of 280 nm. The ITO layer controls the ultraviolet transmittance and sheet resistance of Ga2O3/ITO films. The Ga2O3 layer thickness has a marked effect on the transmission spectral shape of Ga2O3/ITO films in the violet spectral region.     

Growth and characterization of ZnO thin films on GaN epilayers

Dense ZnO(0001) films formed at 500°C via coalescence of islands grown via metalorganic vapor phase epitaxy (MOVPE) either on GaN/AlN/SiC(0001) substrates or on initial, coherent ZnO layers. Conical crystallites formed due to thermal expansion-induced stresses between the ZnO and the substrate. Interfaces between the ZnO films on GaN epilayers exposed either simultaneously to diethylzinc and oxygen or only to diethylzinc at the initiation of growth were sharp and epitaxial. Interfaces formed after the exposure of the GaN to O₂ were less coherent, though an interfacial oxide was not observed by cross-sectional transmission electron microscopy (TEM). Threading dislocations and stacking faults were observed in all films.     

Investigation of Ga oxide films directly grown on n-type GaN by photoelectrochemical oxidation using He-Cd laser

By using a He-Cd laser in a chemical solution of H₃PO₄ with a pH value of 3.5, Ga oxide films were directly grown on n-type GaN. From the energy-dispersive spectrometer (EDS) measurement and x-ray diffraction (XRD) measurement, the grown Ga oxide film was identified as (104) α-Ga₂O₃ structure. A small amount of phosphors existed and bonded with oxygen on the grown films. The as-grown films were amorphous. From the XRD analysis, it is evident that annealing of the α-Ga₂O₃ films led to a change in the microstructure from an amorphous to a polycrystalline phase. In addition, the as-grown low-density films gradually became dense films during the annealing process. Furthermore, the surface roughness of the annealed films also gradually decreased. Hexagonal pinholes on the grown films were observed. The density of the hexagonal pinholes was similar to the defect density of the n-type GaN. From the cross-sectional transmission electron microscopy (TEM) micrographs, it is evident that the hexagonal pinholes originated from defects in the n-type GaN.     

Structure of GaN films grown by molecular beam epitaxy on (0001) sapphire

GaN films grown by electron-cyclotron resonance plasma-assisted molecular beam epitaxy were studied by transmission electron microscopy and x-ray diffraction (XRD). Two sets of films were compared that were grown under identical conditions except for the ratio of the Ga to N flux. Films with a 30% higher Ga to N ratio (A films) were found to contain inversion domains (IDs). No IDs were found in films grown with a lower Ga to N ratio (B films), but instead the zinc-blende GaN was found near the film substrate interface. A narrower XRD rocking curve width along the (0002) direction and a broader rocking curve width along the asymmetric (1102) axis were found for A films compared to B films.