衬底取向对 Al 掺杂3C-SiC 薄膜微结构的影响

采用低压化学气相沉积(LPCVD)法分别在 Si(100)和 Si(111)衬底上制备了 Al 掺杂的3C-SiC 薄膜。采用 X 射线衍射、扫描电子显微镜、Raman 光谱对所制备薄膜的微结构、形貌以及内部应力的演变进行分析。结果表明：在 Si(100)衬底上制备的 Al 掺杂 SiC 薄膜具有较好的结晶质量,而且结晶质量受 Al 掺杂浓度的影响比较大。Al 掺杂 SiC 薄膜的生长模式为二维层状生长模式。Si(100)衬底上所制备的 Al 掺杂 SiC 薄膜表面为层状的四边形结构,而 Si(111)衬底上的 Al 掺杂 SiC 薄膜表面为层状的截角三角形结构。Si(100)衬底上的薄膜厚度略大于 Si(111)衬底上的。由于 Al 离子的掺入和薄膜厚度的增加,Si(100)衬底上所制备的 Al 掺杂 SiC 薄膜内部的应力得到很好的释放。Si(111)衬底上的 Al 掺杂 SiC 薄膜内部的应力则由张应力模式转为压应力模式,而且纵光学声子(LO)、横光学声子(TO)特征峰分离变大,出现这种现象的原因可能与 Al3+替代 Si4+使 SiC离子性增强和生长模式的转变有关。     

宽带隙半导体材料SiC研究进展及其应用

SiC是第3代宽带隙半导体的核心材料之一，具有极为优良的物理化学性能，应用前景十分广阔，本文综合介绍SiC的基本特性，材料的生长技术（包括体单晶生长和薄膜外延生长技术），SiC基器件的研发现状，应用领域及发展前景，同时还介绍了作者用脉冲激光淀积法在Si衬底上制备出单晶4H-SiC薄膜的研究结果。     

物理气相传输法SiC衬底上生长AlN单晶的研究进展

氮化铝(AlN)是直接带隙半导体，具有超宽禁带宽度(6.2 eV)、高热导率[3.2 W/(cm·K)]、高表面声波速率(V_L=10.13×10⁵ cm/s,V_T=6.3×10⁵ cm/s)、高击穿场强和稳定的物理化学性能，是紫外/深紫外发光材料的理想衬底，由此制作的Al_xGa_1–xN材料，还可以实现200～365 nm波段内的连续发光；可以制作耐高压、耐高温、抗辐射和高频的电子器件，是具有巨大潜力的新一代半导体材料。本文介绍了物理气相传输法异质外延生长AlN单晶的原理，并从碳化硅(Si C)衬底上AlN单晶生长研究历程、Al N/SiC衬底生长AlN晶体以及偏晶向SiC衬底生长AlN晶体3个方面综述了SiC衬底上异质外延生长AlN晶体的研究进展。最后简述了SiC衬底上生长AlN单晶面临的挑战和机遇，展望了AlN材料的未来发展前景。     

衬底取向对Al掺杂3C-SiC薄膜微结构的影响（英文）

采用低压化学气相沉积(LPCVD)法分别在Si(100)和Si(111)衬底上制备了Al掺杂的3C-Si C薄膜。采用X射线衍射、扫描电子显微镜、Raman光谱对所制备薄膜的微结构、形貌以及内部应力的演变进行分析。结果表明:在Si(100)衬底上制备的Al掺杂Si C薄膜具有较好的结晶质量,而且结晶质量受Al掺杂浓度的影响比较大。Al掺杂Si C薄膜的生长模式为二维层状生长模式。Si(100)衬底上所制备的Al掺杂Si C薄膜表面为层状的四边形结构,而Si(111)衬底上的Al掺杂Si C薄膜表面为层状的截角三角形结构。Si(100)衬底上的薄膜厚度略大于Si(111)衬底上的。由于Al离子的掺入和薄膜厚度的增加,Si(100)衬底上所制备的Al掺杂Si C薄膜内部的应力得到很好的释放。Si(111)衬底上的Al掺杂Si C薄膜内部的应力则由张应力模式转为压应力模式,而且纵光学声子(LO)、横光学声子(TO)特征峰分离变大,出现这种现象的原因可能与Al3+替代Si4+使Si C离子性增强和生长模式的转变有关。     

专利技术

低温相偏硼酸钡单晶薄膜的制备方法一种低温相偏硼酸钡单晶薄膜的制备方法 ,其特征在于它是采用电阻加热的液相外延炉 ,将高温相的偏硼酸钡 (α -BBO)单晶衬底作为大面积的籽晶 ,在 β -BBO单晶的结晶温度下 (低于相变温度 92 5℃ ) ,在高速旋转的α -BBO单晶衬底与BBO多晶料的     

衬底温度对Al2O3(0001)表面外延6H-SiC薄膜的影响

采用固源分子束外延技术,以α-Al2O3(0001)为衬底,在不同衬底温度下制备了6H-SiC薄膜.利用反射式高能电子衍射,原子力显微镜、X射线衍射对生长样品的结构和结晶质量进行了表征.结果表明:在衬底温度为1100℃时生长的薄膜质量较好,在较低温度(1000℃)和较高温度(1200℃)条件下生长的薄膜质量较差.同时发...     

金刚石/氧化锌透明异质结的研制

利用化学气相沉积和磁控溅射方法制备了透明金刚石薄膜／氧化锌异质结。首先,在金刚石单晶表面外延生长1层透明p型半导体金刚石薄膜,然后在金刚石薄膜上利用反应磁控溅射方法制备出n型透明氧化锌半导体薄膜;进而利用溅射、光刻等方法制备出欧姆接触电极,获得了金刚石／氧化锌透明异质pn结。该结呈现典型的二极管伏安特性曲线,开启电压为1．0V。在500～700nm波长范围内,该结的透过率达到20％。     

Ba(Zr0.3Ti0.7)O3薄膜的结构及性能

用溶胶-凝胶法分别在Pt/Ti/SiO2/Si和LaNiO3/Pt/Ti/SiO2/Si衬底上制备了锆钛酸钡[Ba(Zr0.3Ti0.7)O3,BZT]薄膜.相结构及介电性能研究表明:衬底和薄膜厚度对BZT薄膜性能具有显著影响.制备在LaNiO3/Pt/Ti/SiO2/Si衬底上的BZT薄膜具有(100)面的择优取向,其介电常数及介电损耗则随着薄膜厚度的增加而降低.对制备在Pt/Ti/SiO2/Si衬底上的BZT薄膜,在薄膜厚度低于500nm时,其介电常数随薄膜厚度增加而增加,大于500nm时又有所减小.     

在大晶格失配的MgO衬底上生长SrNb_(0.2)Ti_(0.8)O_3薄膜

采用脉冲激光沉积技术(PLD),在MgO单晶平衬底上制备了SrNb0.2Ti0.8O3(SNTO)薄膜,两者的失配度约为5.7%。X射线衍射分析表明:在沉积温度为850℃,沉积氧压为50 Pa,沉积速度为2Hz/s的情况下,薄膜可以近外延的生长;实验还发现,随着退火氧压的减小,薄膜的电阻减小,(002)特征峰的强度也随之变弱,至1×10-3Pa时,薄膜的(002)特征峰消失。从而摸索出在MgO衬底上制备SNTO导电薄膜的最佳条件。     

雾化学气相外延法异质外延Ga2O3薄膜的生长特性

氧化镓各晶相的应用广泛,亚稳相只能通过外延的手段获得。选择合适的生长方法和提高异质外延水平仍是学术界一直探讨的问题。采用雾化学气相沉积(Mist-CVD)法在蓝宝石衬底上异质外延生长了氧化镓薄膜,通过优化工艺条件实现了物相调控,系统研究了外延膜的结晶质量、组分和表面形貌,以及生长速率变化规律。同时,探究了Mist-CVD生长系统中,Ga₂O₃外延膜的晶体成核及晶相控制机理。在原有α-Ga₂O₃生长工艺的基础上,制备了α/ε混相薄膜、ε-Ga₂O₃纯相薄膜,呈三维岛状生长模式。在ε-Ga₂O₃纯相薄膜的基础上,随着氧气流量的增加,结晶质量先稳定后下降,生长速率先增加后降低,最高达到3μm/h。通过退火,获得了β-Ga₂O₃纯相薄膜,表面粗糙度由10.80 nm降低至5.42 nm。在利用Mist-CVD法进行不同晶相外延调控及其生长机理研究方面具有一定借鉴意义。     

Micro-Raman Mapping of 3C-SiC Thin Films Grown by Solid–Gas Phase Epitaxy on Si (111)

A series of 3C-SiC films have been grown by a novel method of solid–gas phase epitaxy and studied by Raman scattering and scanning electron microscopy (SEM). It is shown that during the epitaxial growth in an atmosphere of CO, 3C-SiC films of high crystalline quality, with a thickness of 20 nm up to few hundreds nanometers can be formed on a (111) Si wafer, with a simultaneous growth of voids in the silicon substrate under the SiC film. The presence of these voids has been confirmed by SEM and micro-Raman line-mapping experiments. A significant enhancement of the Raman signal was observed in SiC films grown above the voids, and the mechanisms responsible for this enhancement are discussed.     

Heteroepitaxial growth of thick 3C-SiC (110) films by Laser CVD

Previously, we found 3C-SiC films favor to grow in <111> orientation on Si (110) ( https://doi.org/10.1111/jace.15260 ). However, epitaxial growth of thick <110>-3C-SiC is still a big challenge. In this study, thick 3C-SiC (110) epitaxial films were prepared on Si (110) substrate by laser chemical vapor deposition (LCVD) using hexamethyldisilane (HMDS) in H₂ atmosphere. The investigation of growth mechanism showed that the laser of LCVD played an important role during the depositions. Observation by high-resolution transmission electron microscopy (HRTEM) revealed that the interface of 3C-SiC (110)/Si (110) exhibited rough texture at atomic level. The atomic roughness on Si (110) surface could be a key factor for 3C-SiC (110) nucleation. The growth of thick 3C-SiC (110) epitaxial films could be very promising for new development in power electronics applications.     

Structural defects in (100) 3C-SiC heteroepitaxy: Influence of the buffer layer morphology on generation and propagation of stacking faults and microtwins

Growth of 3C-SiC on (100) Si has been performed via chemical vapor deposition under two pressure regimes (low and atmospheric pressure) in the early stage of growth. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) have been conducted to study the initial stage of growth while X-ray diffractometry (XRD) and TEM have been used to analyze thicker films and to detect and quantify defects, resulting in a comprehensive and detailed investigation of 3C-SiC structural defects. We have found out that the secondary nucleation of 3C-SiC island growth leads to a higher defect generation rate and, at the same time, to a more effective defect elimination rate. Hillocks found on the surface of thin samples grown under reduced pressure conditions are more pronounced as they seem to be a consequence of twins created in the early stage of growth. Finally, a different initial nucleation density (in the two pressure regimes considered) does not strongly influence stacking fault and microtwin density when growth of thick 3C-SiC films is performed. A very strong influence is indeed observed when 3C-SiC thickness is limited to hundreds of nanometers.     

Surface Chemistry Involved in Epitaxy of Graphene on 3C-SiC(111)/Si(111)

Surface chemistry involved in the epitaxy of graphene by sublimating Si atoms from the surface of epitaxial 3C-SiC(111) thin films on Si(111) has been studied. The change in the surface composition during graphene epitaxy is monitored by in situ temperature-programmed desorption spectroscopy using deuterium as a probe (D₂-TPD) and complementarily by ex situ Raman and C1s core-level spectroscopies. The surface of the 3C-SiC(111)/Si(111) is Si-terminated before the graphitization, and it becomes C-terminated via the formation of C-rich (6√3 × 6√3)R30° reconstruction as the graphitization proceeds, in a similar manner as the epitaxy of graphene on Si-terminated 6H-SiC(0001) proceeds.     

Microstructural analysis of single crystal SiC prepared by novel liquid phase epitaxy

Single crystal SiC has been synthesized by a novel liquid phase epitaxy using mixture of (Sm:Co) as unique solvent. The synthesized high quality crystals have been characterized by field emission gun scanning electron microscopy and field emission gun transmission electron microscopy. The above analysis shows the epitaxial growth of single crystal SiC along [1 1 1] direction parallel to the Si wafer, followed by polycrystalline 3C-SiC and 6H-SiC whiskers. The formation mechanisms of single crystal SiC and SiC whiskers have been proposed.     

A quantitative assessment of nanometric machinability of major polytypes of single crystal silicon carbide

The influence of polymorphism on nanometric machinability of single crystal silicon carbide (SiC) has been investigated through molecular dynamics (MD) simulation. The simulation results are compared with silicon as a reference material.Cutting hardness was adopted as a quantifier of the machinability of the polytypes of single crystal SiC. 3C-SiC offered highest cutting resistance (～2.9 times that of silicon) followed by the 4H-SiC (～2.8 times that of silicon) whereas 6H-SiC (～2.1 times that of silicon) showed the least. Despite its high cutting resistance, 4H-SiC showed the minimum sub-surface crystal lattice deformed layer depth, in contrast to 6H-SiC. Further analysis of temperatures in the cutting zone and the percentage tool wear indicated that single point diamond turning (SPDT) of single crystal SiC could be limited to either 6H-SiC or 4H-SiC depending upon quality and cost considerations as these were found to be more responsive and amenable to SPDT compared to single crystal 3C-SiC.     

C/C多孔体对C/C-SiC复合材料微观结构和弯曲性能的影响

以4种纤维含量相同(32%,体积分数,下同),用化学气相渗透(chemical vapor infiltration,CVI)法制备了4种密度的碳纤维增强碳(carbon fiber reinforced carbon,C/C)多孔体,基体炭含量约20%～50%.利用液相渗硅法(liquid silicon infiltration,LSI)制备了C/C-SiC复合材料,研究了C/C多孔体对所制备的C/C-SiC复合材料微观结构和弯曲性能的影响.结果表明:不同密度的C/C多孔体反应渗硅后,复合材料的物相组成均为SiC,C及单质Si;随着C/C多孔体中基体炭含量的增加,C/C-SiC复合材料中SiC含量逐渐减少而热解炭含量逐渐增加.C/C-SiC复合材料弯曲强度随着材料中残留热解炭含量增加而逐渐增加,热解炭含量为约42%的C/C多孔体所制备的C/C-SiC复合材料的弯曲强度最大,达到320 MPa.     

Heteroepitaxy of Diamond on Cubic Boron Nitride

The epitaxial growth process of diamond from the gas phase on a cubic boron nitride (c-BN) {111} surface has been investigated. At the initial growth stage, carbon adsorption progressed on a boron-terminated surface of c-BN ({111}_B). The coordination of the carbon atoms was found to be the same as that observed in diamond, as confirmed by electron energy loss spectroscopy (EELS). The epitaxial growth of diamond particles has been observed after formation of the carbon layer. On the other hand, on the nitrogen-terminated surface ({111}_N), neither stable adsorption of carbon nor nucleation of diamond has been observed. The stability of adsorbed carbon atoms in the chemical vapor deposition (CVD) ambient, in which large amounts of atomic hydrogen are supplied to the substrate heated at high temperature, is quite important for the nucleation of diamond. Using cross-sectional transmission electron microscopy (TEM), numerous crystal defects were observed, both in c-BN and diamond. Formation of the epitaxial diamond particles has been observed especially at defect sites on c-BN. The misfit dislocation has been observed near the interface with the diamond particle. Even though there exist misfit dislocations that relieve the stress caused by the lattice mismatch between diamond and c-BN, the epitaxial film involved retains a tensile strain of about 0.29% for a film thickness of about 200 nm.     

Formation of qualified epitaxial graphene on Si substrates using two-step heteroexpitaxy of C-terminated 3C-SiC(-1-1-1) on Si(110)

Formation of epitaxial graphene (EG) on 3C–SiC films heteroepitaxially grown on Si substrates, otherwise known as graphene-on-silicon (GOS) technology, has a high potential in future nanocarbon-based electronics. The EG's quality in GOS however remains mediocre due mostly to the high density of crystal defects in the 3C–SiC/Si films caused by the large (~ 20%) lattice-mismatch between Si and 3C–SiC crystals. Resultant Si out-diffusion along the planar defects during the high-temperature (~ 1525 K) graphitization annealing can also account for the degradation. Here we propose a two-step growth technique that consists of seeding of rotated 3C-SiC(-1-1-1) crystallites on the Si(110) substrate, conducted in the high-temperature-low-pressure regime, followed by a rapid growth of SiC films in the low-temperature-high-pressure regime. We succeeded in forming an almost lattice-relaxed 3C-SiC(-1-1-1) film on Si(110), having a sufficient thickness (~ 200 nm) that we believe is able to suppress the Si out-diffusion during graphitization. A graphitization annealing applied to this epi-film yields an EG, whose domain size is increased by 60% as compared to that of conventional GOS films.     

Formation of <111> fiber texture in β-SiC films deposited on Si(100) substrates

The evolution of the morphology and the texture of 3C-SiC films grown by chemical vapor deposition (CVD), using 1,3-disilabutane as precursor, on Si(100) substrates is investigated by transmission electron microscopy. Films were found to exhibit a columnar grain structure with a strong <111> fiber texture and a high density of stacking faults and twins. The columnar grains do not originate at the substrate surface but on a buffer layer about 3 to 5 nm thick, consisting of interconnected 3D-islands that initiate as epitaxial nuclei. The change from <100> epitaxial islands to <111> columnar grains can be understood in terms of anisotropic growth rates and multiple twinning. The observed <111> fiber texture, faulted substructure, faceted surface morphology and carbon enrichment of the growth surface are in agreement with the proposed growth model.