不同金属缓冲层对GaN薄膜的光学及电学性能的影响

本文以金属Ga和NH₃为原料,Al、Ni和Fe为金属缓冲层,采用化学气相沉积法(CVD)在Si(100)衬底上合成了GaN微米薄膜。利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、能量弥散X射线谱(EDS)、光致发光光谱(PL)和霍尔效应测试仪(HMS-3000)等对GaN微米薄膜进行表征。结果表明,所有样品均为六方纤锌矿结构;样品均出现了很强的近带边紫外发射峰和半峰宽较大的中心波长为672nm红光发射峰;不同样品的电学性能差异较大。最后对合成的GaN微米薄膜的可能形成机理进行了简单分析。     

N2流量对GaN的形貌及光学和电学性能的影响

采用化学气相沉积法(CVD)在Si(100)衬底上以Ni为催化剂,金属Ga和NH3为原料合成了GaN微纳米结构,并研究了N2流量对产物GaN的形貌及光学和电学性能的影响。利用场发射扫描电子显微镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)、Xray能谱仪(EDS)、光致发光谱(PL)和霍尔效应测试仪(HMS-3000)等测试手段对样品的形貌、结构、成分、光学和电学性能进行了分析。结果表明,随着N2流量的增加,产物GaN的形貌发生了由微米棒到蠕虫状线再到光滑纳米线的转变;生成的GaN均为六方纤锌矿结构;样品均表现出383 nm的近带边紫外发射峰和470 nm左右的蓝光发射峰;所有样品均为p型;并对产物GaN的形貌转变机理进行了分析。     

N2流量对GaN的形貌及光学和电学性能的影响

采用化学气相沉积法(CVD)在Si(100)衬底上以Ni为催化剂, 金属Ga和NH₃为原料合成了GaN微纳米结构, 并研究了N₂流量对产物GaN的形貌及光学和电学性能的影响。利用场发射扫描电子显微镜(SEM)、透射电镜(TEM)、X射线衍射仪(XRD)、X-ray能谱仪(EDS)、光致发光谱(PL)和霍尔效应测试仪(HMS-3000)等测试手段对样品的形貌、结构、成分、光学和电学性能进行了分析。结果表明, 随着N₂流量的增加, 产物GaN的形貌发生了由微米棒到蠕虫状线再到光滑纳米线的转变;生成的GaN均为六方纤锌矿结构;样品均表现出383 nm的近带边紫外发射峰和470 nm左右的蓝光发射峰;所有样品均为n型;并对产物GaN的形貌转变机理进行了分析。     

利用Pd催化合成单晶GaN纳米线的光学特性(英文)

基于金属元素钯具有的催化特性,采用射频磁控溅射方法,在Si(111)衬底上沉积Pd:Ga2O3薄膜,然后在950℃下对薄膜进行氨化,制备出大量GaN纳米线.采用扫描电子显微镜(SEM)、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(HRTEM)等技术手段对样品的结构、形貌和成分进行分析.结果表明,制备的样品为具有六方纤锌矿结构的单晶GaN纳米线,直径在20-60nm范围内,长度为几十微米,表面光滑无杂质,结晶质量较高.用光致发光光谱对样品的发光特性进行测试,分别在361.1、388.6和426.3nm处出现三个发光峰,且与GaN体材料相比近带边紫外发光峰发生了较弱的蓝移.对GaN纳米线的生长机制也进行了简单的讨论.     

Mg掺杂GaN纳米线的结构及其特性

利用类似Delta掺杂技术在硅衬底上沉积Mg:Ga2O3薄膜, 然后在850 ℃下对薄膜进行氨化, 反应后制备出大量Mg掺杂GaN纳米线. 采用扫描电子显微镜(SEM)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱和高分辨透射电子显微镜(HRTEM)对样品进行分析.结果表明, Mg掺杂GaN纳米线具有六方纤锌矿单晶结构, 纳米线的直径在30-50 nm范围内, 长度为几十微米.     

Ag作催化剂制备的GaN的形貌及其性能

用化学气相沉积法(CVD)在Si(100)衬底上以Ag纳米颗粒为催化剂制备了微纳米结构的GaN,原料是熔融态的金属Ga和气态的NH3。采用X射线衍射仪(XRD)、透射电镜(TEM)、X-ray能谱仪(EDS)、场发射扫描电子显微镜(SEM)、光致发光能谱(PL)和霍尔效应测试对样品进行了结构、成分、形貌和发光、电学性能分析。结果表明:生成的自组装GaN为六方纤锌矿的类似小梯子的微纳米单晶结构,且在不同的温度下,GaN的发光性能和电学性能也有所不同,相对于强的紫外发光峰,其它杂质发光峰很微弱,且均呈p型导电。对本实验所得到的GaN微纳米结构的可能形成机理进行了探讨。     

扩镓硅基GaN晶体膜质量的电镜分析

采用射频磁控溅射工艺在扩镓硅基上溅射Ga2O3薄膜,氮化反应组装GaN晶体膜,并对其生长条件进行研究．用扫描电镜(SEM)和X射线衍射(XRD)对样品进行结构、形貌分析．观测结果表明：采用此方法得到的在预沉积扩镓硅基上生长的GaN晶体膜,随着扩镓时间的增加,薄膜的晶化程度得到明显提高,而氮化时间对构成GaN薄膜的颗粒形态影响不大．     

GaN薄膜的两步法制备及其物性转变的研究

本实验通过水浴加热和简单化学气相氨化两步法,在旋涂有ZnO的Si衬底上成功合成了由排列整齐纺锤体形貌的GaOOH构成的薄膜,然后在950℃下对样品进行氨化得到由排列整齐纺锤体组成的GaN薄膜。然后对氨化前后样品的形貌,结构和光学性能分别通过FESEM、EDS、TEM、XRD和PL谱进行了表征。结果表明:水热生成的GaOOH薄膜是由纺锤体形状GaOOH紧密排列形成,该纺锤体形状GaOOH有直径大约600 nm,长约为1.5~2μm。氨化前后样品的形貌没发生太大的变化;但晶体结构由正交晶系相GaOOH转变为六方纤锌矿GaN;而且发光峰也由较宽的绿光峰转变为中心为365 nm的蓝光峰,这主要是由于样品由正交晶系相GaOOH转变为六方纤锌矿GaN引起的。最后对排列整齐的锤体形构成的GaOOH薄膜的形成机理以及GaOOH向GaN的转变过程发生的化学反应做了简单的探讨和分析。     

退火对MgxZn1-xO薄膜特性的影响

采用MOCVD法在c面蓝宝石衬底上生长出了高质量的MgxZn1-xO薄膜. 研究了退火对MgxZn1-xO薄膜各种特性的影响. 将样品分别在真空和氧气中退火1 h. X射线衍射研究发现, 在真空中, 尤其是在氧气中退火的样品的(002)峰均增强. 由原子力显微镜观察发现, 在真空中退火样品的表面与未退火样品的表面几乎相同, 而在氧气中退火后样品的表面变得光滑了很多. 从光致发光光谱中发现, 真空退火后的样品的紫外光谱峰显著增强, 而深能级发射峰几乎消失. 在氧气中退火后样品的紫外光谱峰减弱而深能级发射峰显著增强. 所以退火对MgxZn1-xO薄膜的各种性质具有重要的影响, 通过退火可调节MgxZn1-xO的晶体质量与光学质量.     

利用高分辨X射线衍射仪表征GaN薄膜的结构特性

使用高分辨X射线衍射法（HRXRD）对金属有机物化学气相沉积（MOCVD）外延生长GaN薄膜进行微结构表征．首先采用绝对测量法精确测试了GaN薄膜的晶格常数,由此获得该GaN薄膜的应变与弛豫的信息．采用面内掠入射（IP—GID）法测定了GaN薄膜的位错密度以及位错扭转角．     

X-ray absorption fine structure study of amorphous metal oxide thin films prepared by photochemical metalorganic deposition

The oxidation state and local geometry of the metal centers in amorphous thin films of Fe₂O₃ (Fe³⁺ oxidation state), CoFe₂O₄ (Co²⁺/Fe³⁺ oxidation states), and Cr₂O₃ (Cr³⁺ oxidation state) are determined using K edge X-ray absorption near-edge structure (XANES) spectroscopy and extended X-ray absorption fine structure (EXAFS) spectroscopy. The metal oxide thin films were prepared by the solid-state photochemical decomposition of the relevant metal 2-ethylhexanoates, spin cast as thin films. No peaks are observed in the X-ray diffraction patterns, indicating the metal oxides are X-ray amorphous. The oxidation state of the metals is determined from the edge position of the K absorption edges, and in the case of iron-containing samples, an analysis of the pre-edge peaks. In all cases, the EXAFS analysis indicates the first coordination shell consists of oxygen atoms in an octahedral geometry, with a second shell consisting of metals. No higher shells are observed beyond 3.5 Å for all samples, indicating the metal oxides are truly amorphous, consistent with X-ray diffraction results.     

Room Temperature Ferromagnetism in Ga1-xHoxN (x=0.0 and 0.05) Diluted Magnetic Semiconductor Thin Films

Holmium doped GaN diluted magnetic semiconductor thin films have been prepared by thermal evaporation technique and subsequent ammonia annealing. X-ray diffraction mea-surements reveal all peaks belong to the purely hexagonal wurtzite structure. Surface mor-phology and composition analysis were carried out by scanning electron microscopy and energy dispersive spectroscopy respectively. The room temperature ferromagnetic proper-ties of Ga_1-xHo_xN(x=0.0, 0.05) films were analyzed using vibrating sample magnetometer at room temperature. Magnetic measurements showed that the undoped films (i.e. GaN) exhibited diamagnetic behavior, while the Ho-doped (Ga_0.95Ho_0.05N) film exhibited a ferro-magnetic behavior.     

Low Pressure Chemical Vapor Deposition of III/V-Nitrides Using Organometallics and Hydrazoic Acid Precursors

In and Ga nitride films have been deposited on various substrates using organometallics and hydrazoic acid (HN₃) as nitrogen precursor. The film deposition was carried out under low pressure (10^?510 ^?6 Torr) and low V/III ratios (1-10). XPS analysis indicated that the ln(Ga):N atomic ratio of unity can be easily achieved by adjusting the experimental conditions. For the growth of InN on Si(100) substrate, 308-nm photon beam is needed to speed up the film deposition rate. He(II) UPS spectra of InN films are in good agreement with the result of a pseudo-potential calculation for InN valence band, while the spectra of GaN compare favorably with a recent semi-ab-initio calculation and with the UPS results of GaN single crystal films. The bandgap of our GaN films is ～ 3.3 cV as determined by photoluminescence and UV-VIS absorption spectra. Raman spectra taken from GaN Films showed peaks at 66 and 88 meV for TO and LO phonons, respectively, indicating a wurtzite structure of the GaN. In a corresponding X-ray diffraction spectrum, the (002) peak is about 400 times more intense than that of the (101) peak, suggesting that the GaN layers are highly oriented with the c-axis normal or nearly so to the Al₂O₃ substrate.     

不同条件对扩镓硅基GaN晶体膜质量影响的XRD分析

采用射频磁控溅射工艺在扩镓硅基上溅射Ga2O3薄膜氮化反应组装GaN晶体膜,并对其生长条件进行研究。用XRD对样品进行了结构分析,测试结果表明：采用此方法得到的预沉积的扩镓硅基生长GaN晶体膜随着扩镓时间和氮化时间的增加,薄膜的晶化程度得到明显提高。