Thermoelectric Properties of Li-Intercalated ZrSe2 Single Crystals

Zirconium diselenide (ZrSe₂) is one of many members of the layer-structured transition-metal dichalcogenide family. The structure of these materials features a weakly bonded van der Waals gap between covalently bonded CdI₂-type atomic layers that may host a wide range of intercalants. Intercalation can profoundly affect the structural, thermal, and electronic properties of such materials. While the thermoelectric potential of layer-structured transition-metal dichalcogenides has been formerly studied by several groups, to our best knowledge, neither the thermoelectric properties of ZrSe₂ nor the impact of intercalation on its thermoelectric properties have been reported (specifically, the full evaluation of the dimensionless figure of merit, ZT, which includes the thermal conductivity). In this proof-of-principle study, ZrSe₂ single crystals have been synthesized using an iodine-assisted vapor transport method, followed by a wet-chemistry lithium intercalation process. The results of resistivity, thermopower, and thermal conductivity measurements between 10 K and 300 K show that Li intercalation induced additional charge carriers and structural disorder that favorably affected the thermoelectric properties of the material. As a result, a dimensionless figure of merit ZT ≈ 0.26 has been attained at room temperature in a Li-intercalated sample, representing nearly a factor of three improvement compared with the pristine sample. These improvements, along with the abundance, relatively low toxicity, and low cost of such materials, merit further thermoelectric investigations of intercalated zirconium diselenide, especially in conjunction with a substitutional doping approach.     

Reduction of Inclusions in (CdZn)Te and CdTe:In Single Crystals by Post-Growth Annealing

(CdZn)Te with the composition of 3% Zn and In-doped CdTe single crystals were annealed at various annealing temperatures and under various Cd or Te pressures with the aim of eliminating Te or Cd inclusions. Te inclusions were reduced by Cd-saturated annealing at temperatures above 660°C. Only small (<1 μm) residual dark spots, located at the original position of as-grown inclusions, were observed after annealing. The size of Cd inclusions was reduced by Te-rich annealing at temperatures higher than 700°C. A specific cooling regime was used to eliminate new small Te precipitates (∼1 μm) concurrently formed on dislocations during Te-rich annealing. Poor infrared transmittance of samples with Cd inclusions was detected after Te-rich annealing; therefore, Cd-saturated re-annealing of annealed samples was used for increasing infrared transmittance to a value above 60%. Alternative models explaining the formation of star-shaped corona-surrounding inclusions are discussed.     

生长条件及退火处理对磷化铟单晶结构完整性的影响

利用X射线双晶衍射(XRD)技术研究了原生及退火处理后的磷化铟单晶的晶格完整性.原生磷化铟单晶中由于存在着大量的位错和高的残留热应力,导致晶格产生很大的畸变,表现为XRD半峰宽的值较高并且分布不均匀,甚至有些原生的磷化铟单晶片出现XRD双峰等.通过降低晶体生长过程的温度梯度,降低位错密度并减小晶体中的残留热应力可以提高晶体的完整性.利用高温退火处理也可有效地降低磷化铟晶体中的残留热应力.对磷化铟晶体生长过程中熔体的配比、掺杂浓度等条件对结构完整性的影响进行了分析.     

生长条件及退火处理对磷化铟单晶结构完整性的影响

利用X射线双晶衍射(XRD)技术研究了原生及退火处理后的磷化铟单晶的晶格完整性.原生磷化铟单晶中由于存在着大量的位错和高的残留热应力,导致晶格产生很大的畸变,表现为XRD半峰宽的值较高并且分布不均匀,甚至有些原生的磷化铟单晶片出现XRD双峰等.通过降低晶体生长过程的温度梯度,降低位错密度并减小晶体中的残留热应力可以提高晶体的完整性.利用高温退火处理也可有效地降低磷化铟晶体中的残留热应力.对磷化铟晶体生长过程中熔体的配比、掺杂浓度等条件对结构完整性的影响进行了分析.     

Effects of In Substitution for Ga on the Thermoelectric Properties of Type-VIII Clathrate Ba8Ga16Sn30 Single Crystals

We have prepared single crystals of type-VIII clathrate Ba₈Ga_15.9?x In _x Sn_30.1 for x ≤ 0.60 by the Sn-flux method. As x is increased from 0 to 0.60, the lattice parameter increases by 0.2%, which is consistent with the larger covalent diameter for In than for Ga. The Seebeck coefficient α, electrical resistivity ρ, and thermal conductivity κ were measured in the temperature range from 300 K to 600 K. For all samples, α is negative, indicating the dominant charge carriers are electrons. With increasing x from 0 to 0.20, ρ and \(\left| \alpha \right|\) decrease by 50% and 30%, respectively. As a result, the lattice thermal conductivity at 300 K decreases from 0.58 W/Km to 0.41 W/Km, which is ascribed to enhancement of rattling of the guest atoms. It is found that the maximum of the dimensionless figure of merit ZT reaches 1.05 at 540 K for x = 0.20.     

生长条件及退火处理对磷化铟单晶结构完整性的影响

利用X射线双晶衍射（XRD）技术研究了原生及退火处理后的磷化铟单晶的晶格完整性. 原生磷化铟单晶中由于存在着大量的位错和高的残留热应力，导致晶格产生很大的畸变，表现为XRD半峰宽的值较高并且分布不均匀，甚至有些原生的磷化铟单晶片出现XRD双峰等. 通过降低晶体生长过程的温度梯度，降低位错密度并减小晶体中的残留热应力可以提高晶体的完整性. 利用高温退火处理也可有效地降低磷化铟晶体中的残留热应力. 对磷化铟晶体生长过程中熔体的配比、掺杂浓度等条件对结构完整性的影响进行了分析.     

Preparation and Transport Properties of Bi2O2Se Single Crystals

Bi₂O₂Se single crystals were grown by a gas-phase transport reaction with a temperature gradient. X-ray diffraction revealed that the products crystallized in a tetragonal-type lattice with lattice parameters a?=?0.38866?nm and c?=?1.22001?nm. The samples were characterized by measuring the electrical conductivity, Hall coefficient, and Seebeck coefficient as functions of temperature between 80?K and 470?K. The obtained experimental data allowed us to calculate the reduced Fermi level, provided that the single-valley parabolic model applied. The corresponding value of the electron effective mass proved to be m _ef????0.29. Free electron mobility is governed by the scattering of carriers by acoustic phonons.     

退火处理对二氧化锡纳米线性能的影响

采用化学气相沉积法在硅衬底上生长二氧化锡(SnO2)纳米线,并对其进行热处理.扫描电子显微镜、X射线衍射仪和拉曼光谱测试分析表明所合成的SnO2蚋米线为单一四方金红石相,且结晶性能良好.光致发光测试显示在576 nm附近有明显的黄色发光峰,但在氧气氛环境退火处理后该发光峰逐渐减弱,表明576 nm处的发光峰为氧空位缺陷引起的发光.同时,退火处理能有效提高材料的场发射性能,SnO2纳米线的最低开启和阚值电场分别约为4.6和6.2 V/μm.     

热处理气氛对直拉硅单晶中体缺陷的影响

研究了五种不同的热处理气氛对直拉硅中氧沉淀及其诱生缺陷的影响.实验结果表明,经过低-高退火处理的硅片继续在五种不同的气氛中高温退火,氧沉淀会部分溶解,其溶解量与热处理气氛没有明显的关系,但不同气氛中处理的硅片中体缺陷(BMDs)的分布不同.并对此现象的机理进行了讨论,认为热处理气氛影响了硅片中点缺陷的分布从而影响到BMDs的分布.此研究对集成电路生产中内吸杂工艺的保护气氛的选择有指导意义.     

热处理气氛对直拉硅单晶中体缺陷的影响

研究了五种不同的热处理气氛对直拉硅中氧沉淀及其诱生缺陷的影响.实验结果表明,经过低-高退火处理的硅片继续在五种不同的气氛中高温退火,氧沉淀会部分溶解,其溶解量与热处理气氛没有明显的关系,但不同气氛中处理的硅片中体缺陷(BMDs)的分布不同.并对此现象的机理进行了讨论,认为热处理气氛影响了硅片中点缺陷的分布从而影响到BMDs的分布.此研究对集成电路生产中内吸杂工艺的保护气氛的选择有指导意义.     

Perovskite Single Crystals: Synthesis,Properties, and Applications

Perovskite single crystals have gained enormous attention in recent years due to their facile synthesis and excellent optoelectronic properties including the long carrier diffusion length, high carrier mobility, low trap density, and tunable absorption edge ranging from ultra-violet (UV) to near-infrared (NIR), which offer potential for applications in solar cells, photodetectors (PDs), lasers, etc. In this review, we summarized the synthesis, properties, and applications of organic-inorganic mixed and all-inorganic perovskite single crystals, particularly those through the solution synthesis approach. Challenges towards the crystal growth and stability with future perspectives were also briefly described at the end of this paper.     

二次大气退火对于非晶铟镓锌氧化物薄膜晶体管电学特性的影响

介绍了非晶铟镓锌氧化物薄膜晶体管(a-IGZO TFT)的制备,并在不同环境下进行了退火.其中,经过一次退火冷却后再进行第二次退火的器件表现出了最佳的电学性能,相比其他器件有较小的亚阈值摆幅(～1.43V/decade)和更好的磁滞稳定性.通过对比其他退火条件下的器件表现与工艺,发现在一次退火基础上增加的较短时间(30min)退火是这些显著提高的主要原因.这说明,在a-IGZO TFT进行了一次退火并冷却后,通过引入二次退火使得a-IGZO薄膜表面平整化和结构密实化,器件性能仍然有提高的空间.     

On the Growth and Properties of FeIn2S3.6Se0.4 Single Crystals

Semiconductors - FeIn2S3.6Se0.4 single crystals are grown by planar crystallization of the melt (the vertical Bridgman method). The composition and crystal structure of the crystals are determined....     

热处理温度对片状ZnO晶体结构和光学性质的影响

采用均匀沉淀法,在无任何催化剂的条件下,两步合成片状ZnO晶体。105℃干燥得到ZnO晶体前驱物,400℃煅烧得到纯ZnO晶体。通过XRD、SEM、TEM、UV-vis和PL光谱等测试手段对ZnO晶体在两个不同热处理温度下的结构和光学性质进行表征。结果显示:ZnO晶体为六方纤锌矿结构,(0001)面形貌为规则的片状正六边形。热处理温度由105℃升至400℃,样品直径增加,透射率降低,禁带宽度减小,光致发光近带边发射峰强度减弱,位置红移。实验结果表明,热处理温度对均匀沉淀法合成ZnO晶体的光学性质存在一定影响。     

Ca0.28Ba0.72Nb2O6单晶的光学性质的研究

研究了室温下铌酸钙钡单晶的光学性质。分别用分光光度计和椭偏光谱仪测量了铌酸钙钡晶体的透射率和折射率随波长的变化关系，结果表明铌酸钙钡晶体具有正常色散关系，且寻常光折射率‰大于异常光折射率ne，说明该晶体为负的单轴晶。折射率之差在短波区达到0．12。透射率光谱显示该晶体在400～900nm波段是透明的。根据透射率计算了该波段晶体的吸收系数以及它的平方根。通过对该曲线的研究，发现铌酸钙钡晶体吸收边以下对应的跃迁为间接跃迁，计算出间接跃迁的禁带宽度E为2．94eV以及声子能量E为0．17eV。此外，通过改变系统光路中偏振片的透振方向，获得了寻常光和异常光的透射率，并进一步计算了它们的吸收系数。     

Perovskite Single Crystals: Synthesis,Optoelectronic Properties,and Application

Recently, lead halide perovskite (PVSK) polycrystalline films have drawn much attention as photoactive material and scored tremendous achievements in solar cells, photodetectors, light-emitting diodes, and lasers owing to their engrossing optoelectronic properties and facile solution-processed fabrication. However, large amounts of grain boundaries unfavorably induce ion migration, surface defect, and poor stability, impeding PVSK polycrystalline film-based optoelectronic devices from practical application. In comparison with the polycrystalline counterparts, PVSK single crystals (SCs) with lower trap density serve as a better platform for not only fundamental research but also device applications. In light of this, the idea of using PVSK single crystals (SCs) to construct the optoelectronic devices is then proposed. Since then, a series of synthesis methods of PVSK SCs have emerged. In this review, recent progress of synthesis method of PVSK SCs is tried to be summarized and their advantages and limitations are analyzed. And then, the optoelectronic properties including carrier dynamic, defects, ion migration, and instability issues in these 3D and 2D PVSK SCs are overviewed and accordingly the proper device configurations of corresponding solar cells, photodetectors, X-ray, γ-ray detectors, etc., are proposed. It is believed that this review can provide the guidance for the further development of PVSK SCs and their applications.     

高质量InAs单晶材料的制备及其性质

利用液封直拉法(LEC)生长了直径50mm〈100〉和〈111〉晶向的InAs单晶.分析研究了n型杂质Sn,S和p型杂质Zn,Mn的分凝特性、晶格硬化作用、掺杂效率等.利用X射线双晶衍射分析了晶体的完整性.对InAs晶片的抛光、化学腐蚀和清洗进行了分析,在此基础上实现了抛光晶片的开盒即用(EPI-READY).     

退火对大剂量Al离子注入GaN发光特性的影响

首次报道了用不同浓度的Al离子注入于蓝宝石衬底上的GaN薄膜（注入能量为500keV、注入浓度为10^14-10^15cm^-2），在做了不同温度和不同时间的快速热退火处理以及常规热退火处理后，在12K下用He-Cd激光（325nm）激发得到其发射谱。结果显示，经大剂量Al注入后的样品，其光致发光谱中3.45eV的带边激子发光以及2．9－3．3eV的4个声子伴随峰消失，此表明大剂量Al注入对GaN的晶体结构造成严重的损伤，以致本征发光消失。经10^14cm^-2剂量Al注入后的样品，在N2气氛中退火处理后，2．2eV缺陷发光峰得到了一定程度的恢复。而且，经常规退火处理后，此发射峰比快速退火处理的样品发射峰恢复得更好（其积分光强高3倍）。相似的结果亦显示于10^15cm^-2浓度的Al注入的样品。2.2eV黄色荧光源于GaN的缺陷(如Ga空位VGa)，或VGa-H2,或VGa-ON复合体），其能级位于价带顶以上约1.1eV处。荧光发射可以来自“导带－缺陷能级”的跃迁，也可能来自浅施主（如N位O，能有位于导带下－10meV）至上述缺陷能级之间的跃迁。I－V测量显示，Al的注入区成为－10^12Ω.cm^-1高阻膜，这表明Al的注入可能产生了某种深的电子陷阱，由于电子陷阱可俘获导带电子，导致发光猝灭，而退火可使与黄色荧光相关的缺陷得到部分恢复，因而2.2eV发射峰有所恢复。     

不同退火氛围对TiN/HfO2/SiO2/Si结构电荷分布的影响

热退火技术是集成电路制造过程中用来改善材料性能的重要手段。系统分析了两种不同的退火条件(氨气氛围和氧气氛围)对TiN/HfO₂/SiO₂/Si结构中电荷分布的影响,给出了不同退火条件下SiO₂/Si和HfO₂/SiO₂界面的界面电荷密度、HfO₂的体电荷密度以及HfO₂/SiO₂界面的界面偶极子的数值。研究结果表明,在氨气和氧气氛围中退火会使HfO₂/SiO₂界面的界面电荷密度减小、界面偶极子增加,而SiO₂/Si界面的界面电荷密度几乎不受退火影响。最后研究了不同退火氛围对电容平带电压的影响,发现两种不同的退火条件都会导致TiN/HfO₂/SiO₂/Si电容结构平带电压的正向漂移,基于退火对其电荷分布的影响研究,此正向漂移主要来源于退火导致的HfO₂/SiO₂界面的界面偶极子的增加。     

高质量InAs单晶材料的制备及其性质

利用液封直拉法(LEC)生长了直径50mm〈100〉和〈111〉晶向的InAs单晶.分析研究了n型杂质Sn,S和p型杂质Zn,Mn的分凝特性、晶格硬化作用、掺杂效率等.利用X射线双晶衍射分析了晶体的完整性.对InAs晶片的抛光、化学腐蚀和清洗进行了分析,在此基础上实现了抛光晶片的开盒即用(EPI-READY).