Two-Step Growth of MgO Films on Sapphire （0001） Substrates by Radio Frequency Plasma-Assisted Molecular Beam Epitaxy

We report on the growth of rock salt MgO films on sapphire (0001) substrates by rf plasma-assisted molecular beam epitaxy.A two-step method,i.e.high temperature epilayer growth after low-temperature buffer layer growth,was adopted to obtain the single crystal MgO film.The epitaxial orientation between the MgO epilayer and the sapphire (0001) substrate was studied by using in situ reflection high energy electron diffraction and ex situ x-ray diffraction,and it is found that the MgO film grows with [111] orientation.The role of the low temperature buffer layer in the improvement of crystal quality of the MgO epilayer is discussed based on the cross-sectional scanning electron microscopy.     

电子回旋共振等离子体特性及其对生长氮化镓晶膜的影响

为了解并优化在电子回旋共振等离子体辅助化学汽相沉积GaN晶膜的工艺研究中的等离子体特性,利用朗缪尔探针及法拉第筒系统地测量了离子密度(N_i)、等离子体势(V_p)、电子温度(T_e)及离子流强(J_i)等多个等离子体参量随微波功率(P_w)及沉膜室气压(p)变化的关系.给出了在P_w＝850W,p＝0.22Pa时,上述等离子体参量的轴向及径向分布.GaN晶膜的生长速率、电学及晶体学性能 关键词：     

Review of flexible and transparent thin-film transistors based on zinc oxide and related materials

Flexible and transparent electronics enters into a new era of electronic technologies.Ubiquitous applications involve wearable electronics,biosensors,flexible transparent displays,radio-frequency identifications(RFIDs),etc.Zinc oxide(ZnO) and relevant materials are the most commonly used inorganic semiconductors in flexible and transparent devices,owing to their high electrical performances,together with low processing temperatures and good optical transparencies.In this paper,we review recent advances in flexible and transparent thin-film transistors(TFTs) based on ZnO and relevant materials.After a brief introduction,the main progress of the preparation of each component(substrate,electrodes,channel and dielectrics) is summarized and discussed.Then,the effect of mechanical bending on electrical performance is highlighted.Finally,we suggest the challenges and opportunities in future investigations.     

Sb complexes and Zn interstitials in Sb-implanted ZnO epitaxial films

In the present work, post-annealing is adopted to investigate the formation and the correlation of Sb complexes and Zn interstitials in Sb-ion implanted ZnO films, by using Raman scattering technique and electrical characterizations. The damage of Zn sublattice, produced by ion bombardment process is discerned from the unrecovered E2 (L) peak in annealed high Sb+ dose implanted samples. It is suggested that the Zn sublattice may be strongly affected by the introduction of Sb dopant because of the formation of SbZn-2VZn complex acceptor. The appearance of a new peak at 510 cm 1 in the annealed high dose Sb+ implanted samples is speculated to result from (Zn interstitials-O interstitials) Zni-Oi complex, which is in a good accordance with the electrical measurement. The p-type ZnO is difficult to obtain from the Sb+ implantation, however, which can be realized by in-situ Sb doping with proper growth conditions instead.     

氧化锌基材料、异质结构及光电器件

Ⅱ-Ⅵ族直接带隙化合物半导体氧化锌(ZnO)的禁带宽度为3.37 eV,室温下激子束缚能高达60 meV,远高于室温热离化能(26 meV),是制造高效率短波长探测、发光和激光器件的理想材料。历经10年的发展,ZnO基半导体的研究在薄膜生长、杂质调控和器件应用等方面的研究获得了巨大的进展。本文主要介绍了以国家"973"项目(2011CB302000)研究团队为主体,在上述方面所取得的研究进展,同时概述国际相关研究,主要包括衬底级ZnO单晶的生长,ZnO薄膜的同质、异质外延,表面/界面工程,异质结电子输运性质、合金能带工程,p型掺杂薄膜的杂质调控,以及基于上述结果的探测、发光和激光器件等的研究进展。迄今为止,该团队已经实现了薄膜同质外延的二维生长、硅衬底上高质量异质外延、基于MgZnO合金薄膜的日盲紫外探测器、可重复的p型掺杂、可连续工作数十小时的同质结紫外发光管以及模式可控的异质结微纳紫外激光器件等重大成果。本文针对这些研究内容中存在的问题和困难加以剖析并探索新的研究途径,期望能对ZnO材料在未来的实际应用起到一定的促进作用。     

不同硅晶面指数上的类倒金字塔结构研究与分析

晶体硅作为一种重要的半导体材料,在集成电路、太阳能电池等方面具有广泛的应用.基于各向异性的刻蚀方法,不同晶面指数的硅都可以在表面形成由{111}晶面族组成的正/倒金字塔.本文基于{111}晶面族与（abc）晶面相交构成类倒金字塔结构的特性,建立了硅的晶面指数（abc）与所形成的类倒金字塔结构的数学模型.将硅的晶面指数（abc）分成0≤a≤b<c,0≤a<b=c,a=b=c三种情况进行讨论,分别得到不同晶面指数的类倒金字塔结构.实验结果的扫描电子显微镜图证实了理论计算的准确性.晶面指数与类倒金字塔结构具有一一对应的关系,因此可以根据各向异性刻蚀后的类倒金字塔结构,进行硅的晶面指数进行检测.     

Controlled Growth of Zn-Polar ZnO Films on Al-Terminated α-Al2O3(0001) Surface by Using Wurtzite MgO Buffer

The controlled growth of Zn-polar ZnO fihns on Al-terminated α-Al203 （0001） substrates is investigated by the radio-frequency plasma-assisted molecular beam epitaxy method. Prior to the growth, α-Al2O3 （0001） surface is modified by an ultrathin MgO layer, which serves as a uniform template for epitaxy of Zn-polar ZnO films. The microstructures of ZnO/MgO/Al2O3 interface are investigated by in-situ reflection high-energy electron diffraction observations and ex-situ high-resolution transmission electron microscopy characterization. It is found that under Mg-rich condition, the achievement of the wurtzite MgO ultrathin layer plays a key role in the subsequent growth of Zn-polar ZnO. An interracial atomic model is proposed to explain the mechanism of polarity selection of both MgO and ZnO films.     

湿法刻蚀对Si基片孔点阵及ZnO外延薄膜周期形貌的影响

利用射频等离子体辅助分子束外延法,在刻有周期性孔点阵结构的Si衬底上生长了ZnO二维周期结构薄膜,系统研究了湿法化学刻蚀对孔形点阵Si(100),Si(111)基片表面形貌的影响,以及两种初底上ZnO外延薄膜的结晶质量与周期形貌的差异.X射线衍射及扫描电子显微测试结果表明：Si (111)衬底上生长出的ZnO二维周期结构薄膜具有较好的结晶质量与较好的周期性表面形貌.该研究结果为二维周期结构的制备提供了一种新颖的方法. 关键词： ZnO 分子束外延 Si 湿法刻蚀     

A Specific Case of Generalized Einstein-aether Theories

With the dark energy phenomena explored over a decade,in this present work we discuss a specific case of the generalized Einstein-aether theories,in which the modified Friedmann equation is similar to that in the Dvali-Gabadadze-Porrati(DGP) brane world model.We compute the joint statistic constraints on model parameters in this specific case by using the recent type Ia supernovae(SNe Ia) data,the cosmic microwave background(CMB) shift parameter data,and the baryonic acoustic oscillations(BAOs) data traced by the Sloan Digital Sky Survey(SDSS).Furthermore,we analyze other constrains from the observational Hubble parameter data(OHD).The comparison with the standard cosmological model(cosmological constant Λ cold dark matter(ΛCDM) model) is clearly shown;also we comment on the interesting relation between the coupling constant M in this model and the special accelerate scale in the modified Newtonian dynamics(MOND) model initially given by Milgrom with the hope for interpreting the galaxy rotation curves without introducing mysterious dark matter.