Si(111)衬底上HVPE GaN厚膜生长

在Si(111)衬底上,以MOCVD方法高温外延生长的AIN为缓冲层,使用氮化物气相外延(HVPE)方法外延生长了15Km的c面GaN厚膜.并利用X射线衍射(XRD)、光致发光谱(PL)、拉曼光谱(Raman)等技术研究了GaN厚膜的结构和光学性质.分析结果表明,GaN厚膜具有六方纤锌矿结构,外延层中存在的张应力较小,...     

图形化SOI衬底上侧向外延生长GaN研究

采用MOCVD系统,在图形化的绝缘体上硅(SOI:silicon-on-insulator)衬底上侧向外延生长了GaN薄膜。利用SEM、TEM和Raman光谱对生长的GaN薄膜的质量进行了分析研究。研究发现,在GaN的侧向外延生长区域,侧向生长的GaN能够完全合并,GaN薄膜内的残余应力减小,穿透位错密度大幅度降低。     

Si(001)衬底上方形3 C-SiC岛的LPCVD生长

Si衬底上SiC的异质外延生长深受关注,为了了解Si衬底上的成核及长大过程,采用PLCVD方法在Si(001)衬底上生长出了方形3C-SiC岛,利用Nomarski光学显微镜和扫描电子显微镜（SEM）观察了SiC岛的形状,尺寸,密度和界面形貌,结果表明,3C－SiC岛生长所需的Si原子来自反应气源,衬底上的Si原子不发生迁移或外扩散,气相中C原子浓度决定了SiC岛的生长过程。     

GaN材料的横向外延过生长(LEO)及其特性研究

对用LEO技术生长GaN材料的选择生长和横向生长速率进行了实验研究。结果表明，作为LEO生长基板的GaN层的表面质量是实现选择生长的关键，而图形方向对横向生长速率与纵向生长速率之比（L／V）也有重要的影响。通过选择合适的工艺条件，实现了GaN材料的LEO外延生长，所得样品的X射线衍射峰宽比用常规MOCVD法生长的样品减小了1／3。     

Si(111) 衬底上3C-SiC的超低压低温外延生长

研究了发展一种Si衬底上低温外延生长3C－SiC的方法。采用LPCVD生长系统，以SiH4和C2H4为气源，在超低压（30Pa) ,低温（900℃）的条件下，在Si(111衬底上外延生长出高质量的3C－SiC薄膜材料。采用俄歇能谱（AES），X射线衍射（XRD）和原子力显微镜（AFM）等分析手段研究了SiC薄膜的外延层组分，晶体结构及其表面形貌。AES结果表明薄膜中的Si/C的原子比例符合SiC的理想化学计量比，XRD结果显示了3C－SiC外延薄膜的良好晶体结构，AFM揭示了3C－SiC薄膜的良好的表面形貌。     

Si衬底GaN基LED理想因子的研究

首次报道Si衬底GaN LED的理想因子.通过GaN LEDI-V曲线与其外延膜结晶性能相比较,发现理想因子的大小与X射线双晶衍射摇摆曲线(102)面半峰宽有着对应关系:室温时Si衬底GaN LED的理想因子为6.6,对应着半峰宽707arcsec;理想因子为4.5时,对应半峰宽530arcsec.蓝宝石衬底GaN LED理想因子为3.0,其对应半峰宽401arcsec.硅衬底GaN LED理想因子大的原因可以归结为高缺陷密度所致,高缺陷密度使电流隧穿更容易进行.     

硅基GaN外延层的SIMS及XPS研究

采用真空反应法在硅基上制备出ＧａＮ外延层。利用二次离子质谱和Ｘ射线光电子能谱对ＧａＮ外延层进行了深度剖析和表面分析,结果表明,外延层中Ｇａ和Ｎ分布均匀;在表面处Ｇａ发生了偏聚,外延层中还存在Ｓｉ,Ｏ等杂质,但这些并未影响到ＧａＮ外延层的物相及发生性能,实验还表明,在外延生长前采用原位清洗可去除Ｓｉ衬底表面的氧。     

衬底温度对Si(111)衬底上MBE异质外延3C-SiC薄膜的影响

利用固源分子束外延(SSMBE)技术, 在Si(111)衬底上异质外延生长3C-SiC单晶薄膜, 通过RHEED、XRD、AFM、XPS等实验方法研究了衬底温度对薄膜结构、形貌和化学组分的影响. 研究结果表明, 1000℃生长的样品具有好的结晶质量和单晶性. 在更高的衬底温度下生长, 会导致大的孔洞形成, 衬底和薄膜间大的热失配使降温过程中薄膜内形成更多位错, 从而使晶体质量变差. 在低衬底温度下生长, 由于偏离理想的化学配比也会导致薄膜的晶体质量降低.     

α－Al_2O_3衬底上生长的GaN膜的光学性质

采用金属有机化学气相淀积（ＭＯＣＶＤ）方法生长了α－Ａｌ２Ｏ３衬底上外延的高质量的单晶ＧａＮ薄膜。Ｘ射线衍射光谱与喇曼散射光谱表征了ＧａＮ外延薄膜的单晶结构和单晶质量。透射光谱和光调制反射光谱定出了六角单晶ＧａＮ薄膜的直接带隙宽度和光学参数。     

Si基片上Ag膜的微结构及光学常数研究

用真空蒸镀法在室温Si基片上制备了Ag薄膜，并用X射线衍射及反射式椭偏光谱技术对薄膜的微结构和光学常数进行了测试分析。结构分析表明：制备的Ag膜晶体仍为面心立方结构，呈多晶状态，晶粒择优取向于[111]，平均晶粒尺寸约为22.7nm，晶格常数（0.40860nm)比标准值（0.40862nm)略小。在250－830nm波长范围椭偏光谱测量结果表明：Ag膜的折射率和消光系数分别在0.15-1.49和0.31-5.77之间。与块材相比，在块材的折射率大于一定值（1.00-1.33)时，Ag膜的折射率比块材的小，其余范围则增大；Ag膜的消光系数减小。并给出了一套较为可靠的、具有实用价值的Ag薄膜光学常数。     

基片温度对微晶硅薄膜微观结构和光学性能的影响

以Ar＋SiH_4作为反应气体,采用电子回旋共振等离子体增强化学气相沉积（ECR-PECVD）方法制备微晶硅薄膜,研究了基片温度对薄膜微观结构、吸收系数、光学禁带宽度的影响。结果表明,随着基片温度的升高,薄膜的微观组织逐渐由非晶转化为微晶,薄膜的粗糙度单调增大,而H含量则单调减小。薄膜的光学吸收系数随基片温度的升高而增...     

以TiO_2为缓冲层在GaN上外延生长PZT铁电薄膜

采用脉冲激光沉积技术在(0001)取向的GaN基片上以TiO2为缓冲层外延生长了PZT(111)单晶薄膜。X射线衍射分析表明PZT(111)衍射峰的摇摆曲线半高宽为0.4°,说明薄膜结晶性能良好。PZT薄膜疲劳特性测试结果表明,在经过107次翻转后PZT薄膜的剩余极化强度开始出现下降。P-E电滞回线和I-V测试表明PZT薄膜矫顽场(2Ec)为350 kV/cm,剩余极化(2Pr)约为96μC/cm2,在1 V电压下薄膜的漏电流密度为1.5×10-7A/cm2。以上性能测试结果表明,在半导体GaN上外延生长的PZT铁电薄膜性能基本满足铁电随机存储器的需要。     

Optical properties of GaN epilayers grown on Si (111) and Si (001) substrates

We report the observation of bright photoluminescence (PL) emission from two types of GaN epilayers grown by molecular beam epitaxy (MBE). Wurtzite phase GaN/Si (111) epilayers are grown by gas source MBE process, whereas cubic phase GaN epilayers are grown on (001) Si covered by thin SiC film in the process of Si annealing in propane prior to the GaN growth. PL emissions are identified based on the results of detailed PL and time-resolved PL investigations. For the wurtzite phase GaN we observe an efficient up in the energy transfer from bound to free excitons. This process is explained by a large difference in the PL decay times for two types (free and bound (donor, acceptor)) of excitonic PL emissions. For cubic phase GaN we confirm recent suggestion that acceptors have smaller thermal ionization energies than those in the wurtzite phase GaN.     

基体温度对气相沉积聚氯代对二甲苯膜结构与性能的影响

用化学气相沉积法制备的聚氯代对二甲苯膜具有优异的耐溶剂腐蚀及气体阻隔性能。文中采用X射线衍射(XRD)、扫描电镜(SEM)表征了不同基体温度下制备聚氯代对二甲苯膜的微观组织结构;采用MOCON透湿仪测试了其水汽渗透率。结果表明,随基体温度升高,膜内聚合物分子链取向度先升高、后降低,且在较高温度下聚合物苯环基团更倾向于垂直基体表面。水汽在膜内渗透速率随基体温度升高先降低、后升高,且在约30℃～45℃处达到最低值。     

Thermal Properties of GaN Films Grown on Si Substrates

GaN films grown on Si substrates by molecular beam epitaxy with different nitridation times have been investigated. The GaN/Si structural and optical properties were evaluated by transmission electron microscopy, X-ray diffraction, atomic force microscopy, and photoluminescence. The effective thermal conductivity of the GaN/Si system was obtained using the photoacoustic technique, and from these results the nitridation time dependence of the interface thermal conductivity (η) can be evaluated using a two-layer model. An optimal nitridation time for which the GaN crystal quality can be improved was obtained. The variation of the parameter η for different nitridation times can be related to the interface phonon scattering process by the presence of disorder at the GaN/Si interface.     

Si(111)衬底上多层石墨烯薄膜的外延生长

利用固源分子束外延(SSMBE)技术, 在Si(111)衬底上沉积碳原子外延生长石墨烯薄膜, 通过反射式高能电子衍射(RHEED)、红外吸收谱(FTIR)、拉曼光谱(RAMAN)和X射线吸收精细结构谱(NEXAFS)等手段对不同衬底温度(400、600、700、800℃)生长的薄膜进行结构表征. RAMAN和NEXAFS结果表明: 在800℃下制备的薄膜具有石墨烯的特征, 而 400、600和700℃生长的样品为非晶或多晶碳薄膜. RHEED和FTIR结果表明, 沉积温度在600℃以下时C原子和衬底Si原子没有成键, 而衬底温度提升到700℃以上, 沉积的C原子会先和衬底Si原子反应形成SiC缓冲层, 且在800℃沉积时缓冲层质量较好. 因此在Si衬底上制备石墨烯薄膜需要较高的衬底温度和高质量的SiC缓冲层.     

Optical,surface and magnetic properties of the Ti-doped GaN nanosheets on glass and PET substrates by thermionic vacuum arc (TVA) method

Room-temperature ferromagnetism of GaN and doped GaN materials has been reported in nanostructured form. Especially, nanoparticles show ferromagnetic properties at room temperature. In this paper, Ti-doped effects on GaN were deposited on glass and Polyethylene terephthalate (PET) substrates by thermionic vacuum arc and their room temperature magnetic properties are presented for the first time. The structure of the Ti-doped GaN was crystallized in a novel form, nano honeycomb formation. Optical and surface properties of the nano honeycombs and honeycomb nanosheets were determined. GaN and TiN phases were detected in X-ray diffraction patterns. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) device were used for imaging of the crystal structure. According to FESEM images, hexagonal crystal formations were detected for all samples. Crystal formations are very good oriented on PET substrates materials according to glass samples. The band gap value of the sample is changed by crystallization dimension. It was found that increasing crystallizations and decreasing crystal dimensions were increased the band gap of the Ti-doped GaN approximately 50?meV. Fourier transform infrared spectra and a vibrating sample magnetometer results were presented. These results confirm the Ti doped GaN honeycomb nanosheets and nano honeycombs show the room temperature ferromagnetic properties.     

衬底温度对Sn掺杂ZnO薄膜结构、电学和光学性能的影响

采用射频磁控溅射技术在石英衬底上制备了掺杂浓度为0.5％(原子分数)的ZnO∶Sn(TZO)薄膜,研究了不同衬底温度下薄膜的结构、形貌、电学和光学的性能.研究发现,TZO薄膜沿着C轴择优生长,在400℃时结晶度最好,最低电阻率为2.619×10-2Ω·cm,在可见光范围内具有较好的透光率.     

Si(111)衬底上六方YMnO3薄膜的制备与铁电性质

采用化学溶液法在Si(111)衬底上制备了YMnO3薄膜.XRD结果表明,所制备的薄膜为六方纯相YMnO3,且具有部分择优取向生长.以Pt为顶电极,测试了YMnO3薄膜的电滞回线,结果表明,所制备的YMnO3薄膜具有良好的铁电性质.