- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Misfit-Dislocation Distributions in Heteroepitaxy: From Mesoscale Measurements to Individual Defects and Back
摘要： We provide an in-depth characterization of the dislocation distribution in partially relaxed Si0.92Ge0.08/Si(001) films. This is achieved by an innovative and general method, combining two state-of-the-art characterization techniques through suitable modeling. After having inferred the dislocation positions from transmission-electron-microscopy images, we theoretically reproduce scanning-x-ray-diffraction-microscopy tilt maps measured on the very same region of the sample. We obtain a nearly perfect match between model predictions and experimental data. As a result, we claim that it is possible to establish a local, direct correlation between the dislocations revealed by the transmission-electron-microscopy analysis and the measured lattice tilt distribution.
关键词： heteroepitaxy,dislocation distribution,scanning x-ray diffraction microscopy,transmission electron microscopy,lattice tilt distribution
更新于2025-09-23 15:21:01
-
Orientational competition in quantum dot growth in Si-Ge heteroepitaxy on pit-patterned Si(001) substrates
摘要： Towards precisely controlled nanostructure growth, patterned substrates are used as templates to direct heteroepitaxial self–assembly. This affects the size, shape and ordering of nanostructures which are formed as a consequence of the mismatch strain. In the well–studied case of Si–Ge heteroepiaxy on Si, the lattice mismatch leads to spontaneous formation of quantum dots. On patterned substrates, the competition between the length scale of the pattern and the intrinsic quantum dot size leads to rich behavior where the localization of dots can be modi?ed with respect to the features of the patterns. We show by continuum modeling that, in cubic elastic materials such as silicon and germanium, there is also a competition between the pattern orientation and the elastically soft directions of the ?lm which affects the precise location of quantum dots on the surface. When the pattern is between the elastically soft directions, the quantum dots can form purely in the narrow region directly between two neighboring pits, referred to as the saddle region. On the other hand, when the pattern is along the elastically soft directions, the quantum dots prefer to form in the region at the centre of four pits, referred to as the crown region. This resolves a discrepancy between theory and experiments and gives another dimension to control quantum dot formation in strained nanocrystalline systems.
关键词： elastic anisotropy,Si–Ge,quantum dots,patterned substrates,heteroepitaxy
更新于2025-09-23 15:19:57
-
How to Grow Fully (100) Oriented SiC/Si/SiC/Si Multi-Stack
摘要： This paper reports on the successful elaboration of fully (100) oriented SiC/Si/SiC/Si multi-stack using chemical vapor deposition. Si(100) heteroepitaxy on 3C-SiC(100) is identified as the critical step which is solved by pulse insertion of precursors during cooling. It lead to the roughening of the 3C-SiC surface which in turn lead to the quasi-exclusive nucleation of (100) oriented islands at the expanse of (110) ones. Subsequent Si epitaxy on such modified surface allows growing fully (100) oriented Si layer, as confirmed by structural characterization of the layers. The 3C-SiC grown on top of such Si(100) layer is again of (100) orientation, forming thus a fully (100) oriented stack. Due to the high lattice mismatch, each interface of the stack is characterized by a high density of crystalline defects which are shown to recombine along with thickness. Antiphase domains present inside the 3C-SiC seed are shown to have no detrimental influence on the Si layer quality. Without the surface modification step, the Si layers grown on 3C-SiC are always polycrystalline with a mixture of (110) and (100) orientations.
关键词： CVD,3C-SiC,surface modification,multilayers,Si heteroepitaxy
更新于2025-09-19 17:15:36
-
Transferable High-Quality Inorganic Perovskites for Optoelectronic Devices by Weak Interaction Heteroepitaxy
摘要： Transferable semiconductors with superior light-emitting properties are important for developing flexible and integrated optoelectronics. However, finding such a qualified candidate remains challenging. Here, we report the fabrication of transferable high-quality CsPbBr3 single-crystals on highly oriented pyrolytic graphite (HOPG) substrate via weak-interaction heteroepitaxy for the first time. Semi-quantitative kinetic analysis based on classical nucleation theory well accounts for the van der Waals (vdW) epitaxial growth process of perovskite on the HOPG substrate. The density functional theory (DFT) calculations illustrate the bonding nature of the interface and predict the Volmer-Weber growth mode in vdW epitaxy, which is consistent with our experimental observations. Importantly, the extremely weak vdW interaction between perovskite and HOPG not only enables the high quality of the crystals, but also endows them with the facile transferability to any foreign substrate by the mechanical exfoliation technique. Leveraging on the transferred CsPbBr3 single-crystals, the low-threshold microlasers and monolithic perovskite light-emitting diode (LED) devices are demonstrated. Our results represent a significant step towards advanced optoelectronic devices relying on the emerging perovskite semiconductors.
关键词： high quality,optoelectronic devices,heteroepitaxy,Transferable semiconductor,halide perovskite
更新于2025-09-19 17:13:59
-
Quantum dot molecule formation in Si-Ge heteroepitaxy on pita??patterned Si(001) substrate : A theoretical study
摘要： Quantum dot molecules refer to nanostructures consisting of four quantum dots around a central pit. These are observed to form in Si-Ge heteroepitaxy and are considered an alternative to quantum dots for strain relaxation. Here we use numerical simulations of a continuum model of strained heteroepitaxy to show the spontaneous formation of quantum dot molecules in thick Si0:5Ge0:5 films grown on pit–patterned Si substrates. The route to their formation first involves a quantum dot in the pit, followed by removal of material from the pit to form quantum dot molecules. These molecules are formed for smaller pit widths, whereas larger pit widths tend to create a ridged surface. A mature single–walled quantum dot molecule has a typical size of about 220 nm. On reducing the wavelength of the original pit–pattern, we notice that multiple–walled quantum dot molecules form, due to the interactions with other nearby molecules. Our results broadly agree with experiment and suggest that QDM formation on patterned substrates does not necessarily have a nucleation barrier and can take place following the usual evolution of the Asaro–Tiller–Grinfeld instability.
关键词： Heteroepitaxy,Quantum Dot Molecule,Patterned substrate
更新于2025-09-16 10:30:52
-
Gallium Oxide || MBE growth and characterization of gallium oxide
摘要： Gallium oxide (Ga2O3) is an ultrawide bandgap (UWBG) oxide semiconductor with an indirect bandgap of 4.5–5.2 eV. The beta-phase (β-Ga2O3) is the commonly regarded as most stable of the several crystalline phases (or polymorphs) of Ga2O3. Because of its wide bandgap, it is transparent from ultraviolet to visible wavelengths. It had first been widely explored as a transparent conductive oxide (TCO) for optical devices such as light-emitting diodes. Also, it has been used as a gate dielectric in metal oxide semiconductor (MOS) structures in GaAs. The β-Ga2O3 can be synthesized by melt growth techniques such as Czochraski, floating zone (FZ), and edge-defined film-fed growth (EFG) at atmospheric pressure which can provide inexpensive large area bulk substrates. The commercial availability of large area Ga2O3 substrates is an important advantage over GaN and similar group III-N compound semiconductors in many potential electrical and optical device applications. Besides material benefit of UWBG, these substrates provide a high-quality crystalline platform for power electronics devices that require higher crystalline quality, low-defect density material with precise doping control capabilities.
关键词： β-Ga2O3,MBE growth,Gallium oxide,ultrawide bandgap,heteroepitaxy,homoepitaxy
更新于2025-09-09 09:28:46
-
Fabrication of Metal–Organic Framework Thin Films Using Programmed Layer‐by‐Layer Assembly Techniques
摘要： Metal–organic frameworks (MOFs) are a rather new class of crystalline, nanoporous solids that are self-assembled from inorganic, metal or metal-oxo nodes and organic linkers. Powder MOFs are originally developed for gas storage and catalyst applications, but more recently, more advanced applications have used well-defined MOF thin films in electronic, photonic, and sensing devices. MOF thin films for targeted applications can be fabricated on appropriately functionalized substrates using a programmed layer-by-layer (LbL) assembly technique, which yields oriented, highly crystalline MOF thin films (surface-mounted MOFs, SURMOFs). The LbL assembly technique as well as the huge potential of SURMOFs is presented herein. Emerging SURMOF properties related to their heteroepitaxy, postsynthetic modification/crosslinking, lithography, and photoswitching are highlighted.
关键词： lithography,photoswitching,MOF thin film,layer-by-layer assembly,heteroepitaxy
更新于2025-09-04 15:30:14