Transport at the Epitaxial Interface between Germanium and Functional Oxides

Combining functional oxides with conventional semiconductors provides the potential for transformational advancement of microelectronic devices. Harnessing the full spectrum of oxide functionalities requires current transport between the oxide and the semiconductor. This aspect is addressed by controlling the electronic barrier at an interface between a ferroelectric oxide, BaTiO₃, and germanium. For the aligned conduction bands of germanium and BaTiO₃, as measured by spectroscopy, current transport is controlled by the barrier between the top metal electrode and the bands of the BaTiO₃. Capacitance–voltage analysis of metal–oxide–semiconductor devices further shows that the semiconductor's Fermi level can be moved by a field effect. These results demonstrate a viable approach for electronically bridging the functionalities of oxides directly with a common semiconductor.     

Epitaxial Growth and Properties of Doped Transition Metal and Complex Oxide Films

The detailed science and technology of crystalline oxide film growth using vacuum methods is reviewed and discussed with an eye toward gaining fundamental insights into the relationships between growth process and parameters, film and interface structure and composition, and electronic, magnetic and photochemical properties. The topic is approached first from a comparative point of view based on the most widely used growth methods, and then on the basis of specific material systems that have generated very high levels of interest. Emphasis is placed on the wide diversity of structural, electronic, optical and magnetic properties exhibited by oxides, and the fascinating results that this diversity of properties can produce when combined with the degrees of freedom afforded by heteroepitaxy.     

BST类铁电薄膜低温外延层状生长研究

利用激光分子束外延技术(LMBE)在SrTiO₃(100)单晶基片上外延生长SrTiO₃(STO)、BaTiO₃(BTO)、Ba_0.6Sr_0.4TiO₃(BST)铁电薄膜.通过反射高能电子衍射(RHEED)实时监测薄膜生长,并结合原子力显微镜(AFM)分析薄膜的生长模式,根据RHEED衍射强度振荡曲线及衍射图样的变化确定动态和静态控制最低晶化温度,发现STO、BTO、BST三种铁电薄膜可以分别在280、330、340℃的低温下实现外延层状生长.     

CrTe的交换耦合与磁性

用MS—Xα方法研究了过渡族硫属化物CrTe的电子结构与磁性,计算结果表明：原子之间存在负交换耦合,且随着外界压强的增加,负交换耦合增强,从而导致CrTe的铁磁性减弱。     

Full Electric Control of Exchange Bias at Room Temperature by Resistive Switching

Electric control of exchange bias (EB) is of vital importance in energy‐efficient spintronics. Although many attempts have been made during the past decade, each has its own limitations for operation and thus falls short of full direct and reversible electrical control of EB at room temperature. Here, a novel approach is proposed by virtue of unipolar resistive switching to accomplish this task in a Si/SiO₂/Pt/Co/NiO/Pt device. By applying certain voltages, the device displays obvious EB in the high‐resistance‐state while negligible EB in the low‐resistance state. Conductive filaments forming in the NiO layer and rupturing near the Co–NiO interface are considered to play dominant roles in determining the combined resistive switching and EB phenomena. This work paves a new way for designing multifunctional and nonvolatile magnetoelectric random access memory devices.     

Co1-xMnx合金的交换耦合与磁性

用MS—Xα方法研究了Co1-xMnx合金(bcc结构)的电子结构与磁性，计算结果表明：原子之间存在负交换耦合，且随着Mn含量的增加，负交换耦合增强，从而导致bcc结构的Co1-xMnx合金的铁磁性减弱，计算结果与实验符合得较好。     

P型GaN和AlGaN外延材料的制备

研究了MOVPE方法外延P型GaN和Al0.13Ga0.87N的生长工艺,包括掺杂剂量和热退火条件,对材料电学性质的影响,得到了优良的P型材料,并研制了InGaN/AlGaN双异质结蓝发光二极管。     

氧化铁微晶的生长及其应用

本文按T.Takada提供的氧化铁微晶生成相图,分别讨论了针形和纺锤形α-FeOOH微晶及Fe_3O_4超微粉的生长机制。从实验结果来看,上述微粒子的形成过程均属“溶解-析出”机制。文中还简要介绍了这些微粉的应用。     

Exchange Interactions and Ferromagnetism of Pr_(n+1)Co_(3n+5)B_(2n)-type Compounds

In present investigation exchange interactions of Pr_(n+1)Co_(3n+5)B_(2n)-type compounds have been evalu-ated in the light of molecular-field theory. The exchange interactions and ferromagnetism in thesecompounds are discussed in terms of lattice parameters and interatomic distance between Co atom.     

负衬底偏压对碳纳米管生长的影响

利用负衬底偏压增强热灯丝化学气相沉系统制备了碳纳米管，用扫描电子显微镜研究了碳纳米管的生长，结果表明碳纳米管的生长随着负衬底偏压的增大先增强，然后减弱，并且出现了部分准直的碳纳米管，分析和讨论了负衬底偏压对碳纳米管生长的影响。     

透明导电InSnGaMo氧化物薄膜光电性能研究

利用脉冲激光沉积法在石英衬底上制备出了可见光透过率高、电阻率极低的Ga,Mo共掺杂ITO基InSnGaMo复合氧化物薄膜。研究了衬底温度对薄膜结构、表面形貌、光电性能的影响。实验结果表明:衬底温度对InSnGaMo复合氧化物薄膜形貌、光电性能均有很大影响。X射线衍射、扫描电镜和霍尔测试结果表明,随着衬底温度的升高,薄膜晶粒度增大,电阻率快速下降,可见光平均透过率明显提高。当衬底温度为450℃时,InSnGaMo复合氧化物薄膜的电阻率最低为4.15×10-4Ω.cm,载流子浓度和迁移率最大分别为3×1020cm-3,45 cm2V-1s-1,在可见及近红外区平均透过率达92%,特别地,波长为362 nm时,最高透射率可达99%。     

脉冲偏压作用下MgO薄膜表面的荷电效应

采用脉冲偏压电弧离子沉积技术在玻璃基片上制备了透明的、具有择优取向的MgO薄膜。针对绝缘性薄膜表面的荷电效应,比较了脉冲偏压作用下鞘层对离子的加速时间(即鞘层的寿命)与脉冲宽度的大小以及偏压鞘层的初始厚度与离子穿越的距离的大小,讨论了不同占空比下偏压鞘层对离子的加速效应。利用X射线衍射及扫描电子显微镜对样品的观察结果表明,由于荷电效应,脉冲偏压幅值为-150 V,占空比在10%~40%的范围内,占空比的变化并不能改变MgO薄膜的微观结构和表面形貌。     

偏压技术在金刚石薄膜制备中应用的进展

近年来,用偏压技术进行异质外延单晶金刚石生长并将其尺寸增大到英寸级以上。偏压技术强大的形核能力使其也可用于制备取向金刚石薄膜、纳米金刚石薄膜和超纳米金刚石薄膜。本文综述了国内外关于偏压技术的机理以及偏压的形式和设备等方面的研究现状,以及表面反应模型、热尖峰模型和亚层注入模型的机理。常用的偏压包括直流偏压、直流脉冲偏压、脉冲叠合偏压和双极性脉冲偏压。还介绍了偏压对金刚石薄膜组织和性能的影响,详细阐述了其对取向生长,二次形核率,无定形碳-石墨-金刚石相转变以及生长速率和结合力的作用规律和机理。加偏压能改变轰击粒子能量和特定基团的浓度、影响金刚石相的转变和晶粒取向和尺寸,进而影响金刚石薄膜的光,力,热,电学性能。还讨论了目前研究工作中存在的一些不足,如偏压作用的机理仍不清晰,对电子浓度变化,氢原子刻蚀的作用尚缺少明确的解释等。最后展望了偏压技术在金刚石制备领域未来的研究和应用方向。     

Site‐Selective and van der Waals Epitaxial Growth of Rhenium Disulfide on Graphene

The surface property of growth substrate imposes significant influence in the growth behaviors of 2D materials. Rhenium disulfide (ReS₂) is a new family of 2D transition metal dichalcogenides with unique distorted 1T crystal structure and thickness‐independent direct bandgap. The role of growth substrate is more critical for ReS₂ owing to its weak interlayer coupling property, which leads to preferred growth along the out‐of‐plane direction while suppressing the uniform in‐plane growth. Herein, graphene is introduced as the growth substrate for ReS₂ and the synthesis of graphene/ReS₂ vertical heterostructure is demonstrated via chemical vapor deposition. Compared with the rough surface of SiO₂/Si substrate with dangling bonds which hinders the uniform growth of ReS₂, the inert and smooth surface nature of graphene sheet provides a lower energy barrier for migration of the adatoms, thereby promoting the growth of ReS₂ on the graphene surface along the in‐plane direction. Furthermore, patterning of the graphene/ReS₂ heterostructure is achieved by the selective growth of ReS₂, which is attributed to the strong binding energy between sulfur atoms and graphene surface. The fundamental studies in the role of graphene as the growth template in the formation of van der Waals heterostructures provide better insights into the synthesis of 2D heterostructures.     

直流负偏压对类金刚石薄膜结构和性能的影响

利用直流-射频-等离子体增强化学气相沉积技术在单晶硅表面制备了类金刚石薄膜，采用原子力显微镜、Raman光谱、X射线光电子能谱、红外光谱、表面轮廓仪和纳米压痕仪考察了直流负偏压对类金刚石薄膜表面形貌、微观结构、沉积速率和硬度等性能的影响。结果表明：无直流负偏压条件下，薄膜呈现有机类聚合结构，具有较低的SP3含量和硬度；叠加上直流负偏压后，薄膜具有典型的类金刚石结构特征，SP3含量和硬度得到了显著的提高；但随着直流负偏压的升高，薄膜的沉积速率和H含量逐渐降低，而SP3含量和硬度在直流负偏压为200V时出现最大值，此后逐渐降低。