Deposition of ZnO Films on Freestanding CVD Thick Diamond Films

For ZnO/diamond structured surface acoustic wave （SAW） filters, performance is sensitively dependent on the quality of the ZnO films. In this paper, we prepare highly-oriented and fine grained polycrystalline ZnO thin films with excellent surface smoothness on the smooth nucleation surfaces of freestanding CVD diamond films by metal organic chemical vapour deposition （MOCVD）. The properties of the ZnO films are characterized by x-ray diffraction （XRD）, scanning electron microscopy （SEM）, and photoluminescence （PL） spectrum. The influences of the deposition conditions on the quality of ZnO films are discussed briefly. ZnO/freestanding thick-diamond-film layered SAW devices with high response frequencies are expected to be developed.     

自持金刚石厚膜上沉积生长ZnO薄膜及发光特性

采用磁控溅射在自持CVD金刚石厚膜的成核面上制备了ZnO薄膜,并实验研究了其生长特性和发光特性随O2和Ar流量的变化。利用X射线衍射(XRD)、光致发光(PL)光谱、电子探针(EPMA)和霍尔测量对样品进行了检测。结果表明,在O2/Ar比值约为1时沉积得到的ZnO薄膜取向较一致,呈现高阻的状态并且发光性能最好。     

Growth and Characteristics of Freestanding Hemispherical Diamond Films by Microwave Plasma Chemical Vapor Deposition

Freestanding hemispherical diamond films have been fabricated by microwave plasma chemical vapor deposition using graphite and molybdenum （Mo） as substrates. Characterized by Raman spectroscopy and scanning electron microscopy, the crystalline quality of the films deposited on Mo is higher than that on graphite, which is attributed to the difference in intrinsic properties of the two substrates. By decreasing the methane concentration, the diamond films grown on the Mo substrate vary from black to white, and the optical transparency is enhanced. After polishing the growth side, the diamond films show an infrared transmittance of 35-60% in the range 400-4000 cm^- 1.     

Laser Induced Damage in CVD Diamond Films

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金刚石厚膜的微结构研究

 采用直流辉光等离子体化学气相沉积金刚石厚膜,利用氢的微波等离子体对抛光的金刚石厚膜截面进行刻蚀,用扫描电子显微镜、激光拉曼光谱仪研究了金刚石厚膜的微结构及杂质、缺陷的分布。结果表明：杂质、空洞主要富集在晶界处;在金刚石膜的生长过程中,随着甲烷流量的增加,晶界密度、空洞、晶粒内部缺陷、杂质含量逐渐增加,晶界的排列从以纵向为主过渡到网状结构。     

Characterization of Thick GaN Films Directly Grown on Wet-Etching Patterned Sapphire by HVPE

Thick GaN films of high quality are directly grown on wet-etching patterned sapphire in a vertical hydride vapour phase epitaxy reactor. The optical and structural properties of GaN films are studied using scanning electronic microscopy and cathodoluminescence. Test results show that initial growth of hydride vapour phase epitaxy GaN occurs not only on the mesas but also on the two asymmetric sidewalls of the V-shaped grooves without selectivity. After the two-step coalescence near the interface, the GaN films near the surface keep on growing along the direction perpendicular to the long sidewall. Based on Raman results, GaN of the coalescence region in the grooves has the maximum residual stress and poor crystalline quality over the whole GaN film, and the coalescence process can release the stress. Therefore, stress-free thick GaN films are prepared with smooth and crack-free surfaces by this particular growth mode on wet-etching patterned sapphire substrates.     

Columnar Structures and Stress Relaxation in Thick GaN Films Grown on Sapphire by HVPE

Thick GaN films with high quality are directly grown on sapphire in a home-built vertical hydride vapour phase epitaxy （HVPE） reactor. The optical and structural properties of large scale columnar domains near the interface are studied using cathodoluminescence and micro-Raman scattering. These columnar domains show a strong emission intensity due to extremely high free carrier concentration up to 2 × 10^19 cm^-3, which are related with impurities trapped in structural defects. The compressive stress in GaN film clearly decreases with increasing distance from interface. The quasi-continuous columnar domains play an important role in the stress relaxation for the upper high quality layer.     

CVD金刚石薄膜探测器性能研究

通过实验测量和理论分析, 从载流子动力学角度研究了用于脉冲辐射探测的CVD金刚石薄膜探测器的适用结构、电荷收集效率和时间响应性能. 结果表明, CVD金刚石薄膜可以制成均匀型结构的探测器; 薄膜中的缺陷会降低探测器的电荷收集效率, 探测器的电荷收集效率随场强增大而增大直至饱和. 已研制的CVD金刚石探测器电荷收集时间可达719ps, 在2.5V/μm场强下达到饱和, 电荷收集效率 达60.5%; 晶格散射是影响探测器时间响应的主要因素, 选用大晶粒甚至单晶金刚石薄膜可以提高探测器时间响应.     

Influence of the Diamond Layer on the Electrical Characteristics of AlGaN/GaN High-Electron-Mobility Transistors

The thermal management is an important issue for AlGaN/GaN high-electron-mobility transistors(H/EMTs).In this work,the influence of the diamond layer on the electrical characteristics of AlGaN/GaN HEMTs is investigated by simulation. The results show that the lattice temperature can be effectively decreased by utilizing the diamond layer. With increasing the drain bias, the diamond layer plays a more significant role for lattice temperature reduction. It is also observed that the diamond layer can induce a negative shift of threshold voltage and an increase of transconductance. Furthermore, the influence of the diamond layer thickness on the frequency characteristics is investigated as well.By utilizing the 10-μm-thickness diamond layer in this work, the cutoff frequency f_T and maximum oscillation frequency f_(max) can be increased by 29% and 47%, respectively. These results demonstrate that the diamond layer is an effective technique for lattice temperature reduction and the study can provide valuable information for HEMTs in high-power and high-frequency applications.     

MOCVD生长的GaN和GaN:Mg薄膜的拉曼散射

通过显微拉曼散射对用金属有机化学气相沉积(MOCVD)法在Al2O3衬底上生长的六方相CaN和掺Mg的P型GaN薄膜进行了研究。在两个样品的拉曼散射谱中同时观察到位于640,660cm^-1附近的两个峰。640cm^-1的峰归因于布里渊区边界(L点)最高声学声子的二倍频,而660cm^-1的峰为布里渊区边界的光学声子支或缺陷诱导的局域振动模。掺Mg的GaN在该处的峰型变宽是Mg诱导的缺陷引起的加宽或Mg的局域模与上述两峰叠加的结果。在掺Mg的样品中还观察到276,376cm^-1几个局域模并给予了解释。同时掺Mg的GaN中出现了应力弛豫的现象,掺Mg引起的失配位错和电子-声子相互作用都有可能对E2模的频率产生影响。     

富勒烯作为过渡层生长金刚石薄膜研究

采用微波等离子体化学气相淀积法，以Ｃ６０膜过渡层，在光滑的单晶Ｓｉ衬底（１００）表面的研磨的石英衬底表面等光学衬底上，首次在无衬底负偏压条件下生长出多晶金刚石薄膜，通过扫描电镜观察到生长膜晶粒呈莱花状，生长表面为金刚石（１００）界面。     

Observation of Substitutional Fe in CEMS Measurements on Synthetic CVD Diamond

Hyperfine Interactions - Conversion electron Mössbauer spectroscopy measurements have been made on a diamond sample synthesized by chemical vapour deposition. The sample was implanted with 70...     

GaN及AlGaN薄膜透射光谱的研究

利用透射光谱矩阵光学原理,对三种GaN或AlGaN外延薄膜的透射光谱进行了分析.在传统的透射光谱拟合方法的基础上,添加了表征材料表面粗糙度、膜内散射情况的拟合参量,拟合曲线与实验曲线达到了准确的吻合.结果表明:外延薄膜透射光谱的拟合可以准确提取出材料的消光系数、表面状况、散射情况、折射率及厚度,从而对样品质量作出详细的分析.     

GaN及AlGaN薄膜透射光谱的研究

利用透射光谱矩阵光学原理,对三种GaN或AlGaN外延薄膜的透射光谱进行了分析.在传统的透射光谱拟合方法的基础上,添加了表征材料表面粗糙度、膜内散射情况的拟合参量,拟合曲线与实验曲线达到了准确的吻合.结果表明：外延薄膜透射光谱的拟合可以准确提取出材料的消光系数、表面状况、散射情况、折射率及厚度,从而对样品质量作出详细的分析.     

金刚石膜/多孔硅复合材料的性能表征

提出了一种新颖的多孔硅表面钝化技术,即采用微波等离子体辅助的化学气相沉积（MPCVD）方法在多孔硅上沉积金刚石薄膜。采用原子力显微镜（AFM）、扫描电子显微镜（SEM）、X射线衍射仪（XRD）、拉曼光 谱仪和荧光分光度计对多孔硅及金刚石膜的表面形貌、结构和发光特性进行了表征。结果表明采用微波等离子体化学气相沉积法可在多孔硅基片上形成均匀、致密、性能稳定且对可见光具有全透性的金刚石膜。金刚石膜与多孔硅的复合,大大稳定了多孔硅的发光波长和强度,同时增强了多孔硅的机械强度。     

MPCVD金刚石的Raman光谱分析

用微波等离子体化学气相淀积法（MPCVD）在Si基片上生长了金刚石薄膜，通过对其进行Raman光谱分析，一次表征了金刚石的结构，纯度及应力状况等材料性能，同时并研究了生长过程中微波功率与金刚石性质的关系。研究表明，微波等离子体化学气相溶积法生长的金刚石薄膜，除了金刚石成分的生长外，还会有部分非金刚石成分的生长，金刚石的纯度与微波功率的关系不明显，另外此种方法生长的金刚石薄膜主要表现为张应力。     

Eu掺杂GaN薄膜的阴极荧光特性

通过MOCVD方法在蓝宝石衬底上生长GaN薄膜,利用离子注入方法将Eu³⁺离子注入到GaN基质中。X射线衍射结果表明：经过退火处理后,修复了部分离子注入所导致的晶格损伤。利用阴极荧光光谱可得到GaN∶Eu³⁺材料在623 nm处有很强的红光发射,该发射峰来源于Eu³⁺离子的内部4f能级跃迁。另外,Eu³⁺离子注入会在样品中引入电荷转移态,产生408 nm附近的发光。退火处理有助于获得更强的电荷转移态发光和Eu离子特征发光。GaN基质的黄光峰与Eu离子之间存在能量交换,将能量传递给Eu离子,促进Eu离子发光。     

Fe掺杂的GaN薄膜的结构和铁磁性（英文）

本文通过高温氨化由磁控溅射方法制备的Ga₂O₃:Fe薄膜,成功地在单晶硅(100)基底上制备了Fe掺杂的GaN薄膜.X射线衍射结果显示Fe掺杂浓度为0%～7%的GaN薄膜均未发现第二相.磁性测量表明所有Fe掺杂的样品均显示出室温铁磁性,而且每个Fe原子的磁矩随Fe浓度的增加而减小,Fe的浓度为1%时每个Fe的磁矩最大,最大值为1.92μ_B/Fe.     

硅基二氧化硅厚膜材料的快速生长

采用火焰水解法在Si片上快速淀积SiO₂厚膜材料,材料膜厚达到40μm以上,生长速率达8μm/min.然后将该材料分别在真空中/空气气氛中高温致密化处理,获得了各种形态的二氧化硅厚膜材料,包括平整度好、光滑透明的玻璃态SiO₂厚膜材料.并利用XRD、电子显微镜等仪器对SiO₂膜的表面和膜厚进行了测试分析.