Two-dimensional (2D) palladium ditelluride (PdTe2) and platinum ditelluride (PtTe2) are two Dirac semimetals which demonstrate fascinating quantum properties such as superconductivity, magnetism and topological order, illustrating promising applications in future nanoelectronics and optoelectronics. However, the synthesis of their monolayers is dramatically hindered by strong interlayer coupling and orbital hybridization. In this study, an efficient synthesis method for monolayer PdTe2 and PtTe2 is demonstrated. Taking advantages of the surface reaction, epitaxial growth of large-area and high quality monolayers of PdTe2 and patterned PtTe2 is achieved by direct tellurization of Pd(111) and Pt(111). A well-ordered PtTe2 pattern with Kagome lattice formed by Te vacancy arrays is successfully grown. Moreover, multilayer PtTe2 can be also obtained and potential excitation of Dirac plasmons is observed. The simple and reliable growth procedure of monolayer PdTe2 and patterned PtTe2 gives unprecedented opportunities for investigating new quantum phenomena and facilitating practical applications in optoelectronics.
CoFe${}_{2}$O${}_{4}$ (CFO)-BiFeO${}_{3}$ (BFO) nanocomposites are an intriguing option for future memory and logic technologies due to the magnetoelctric properties of the system. However, these nanocomposites form with CFO pillars randomly located within a BFO matrix, making implementation in devices difficult. To overcome this, we present a technique to produce patterned nanocomposites through self-assembly. CFO islands are patterned on Nb-doped SrTiO${}_{3}$ to direct the self-assembly of epitaxial CFO-BFO nanocomposites, producing square arrays of CFO pillars.
Epitaxy of semiconductors is a process of tremendous importance in applied science and optoelectronic industry. Controlling of defects introduced during epitaxial growth is a key point in manufacturing devices of high efficiency and durability. In this work, we demonstrate how useful hybrid reflections are on the study of epitaxial structures with anisotropic strain gradients due to patterned substrates. High accuracy to detect and distinguish elastic and plastic relaxations are one of the greatest advantages of measuring this type of reflection, as well as the fact that it can be exploited in…
Top and side gated epitaxial graphene field effect transistors
介绍了三种第一代外延石墨烯场效应晶体管（FET），并讨论了它们的优缺点。石墨烯外延生长在六方碳化硅的碳和硅表面上，并用电子束光刻法进行图案化。通道具有霍尔条几何形状以便于磁阻测量。在Si面上图案化的FET表现出超过30的关-导通沟道电阻比。C面FET具有较低的关-开电阻比，但其迁移率（高达5000 cm 2/Vs）比Si面晶体管大得多。对全石墨烯侧栅FET结构的初步研究是有希望的。
We report the growth of high-quality triangular GaN nanomesas, 30-nm thick, on the C-face of 4H-SiC using nano selective area growth (NSAG) with patterned epitaxial graphene grown on SiC as an embedded mask. NSAG alleviates the problems of defective crystals in the heteroepitaxial growth of nitrides, and the high mobility graphene film can readily provide the back low-dissipative electrode in GaN-based optoelectronic devices. The process consists in first growing a 5-8 graphene layers film on the C-face of 4H- SiC by confinement-controlled sublimation of silicon carbide. The graphene film is t…
We present a method for growing bit patterned magnetic recording media using directed growth of sputtered granular perpendicular magnetic recording media. The grain nucleation is templated using an epitaxial seed layer which contains Pt pillars separated by amorphous metal oxide. The scheme enables the creation of both templated data and servo regions suitable for high density hard disk drive operation. We illustrate the importance of using a process that is both topographically and chemically driven to achieve high quality media.
A perfectly compliant substrate would allow the monolithic integration of high-quality semiconductor materials such as Ge and III-V on Silicon (Si) substrate, enabling novel functionalities on the well-established low-cost Si technology platform. Here, we demonstrate a compliant Si substrate allowing defect-free epitaxial growth of lattice mismatched materials. The method is based on the deep patterning of the Si substrate to form micrometer-scale pillars and subsequent electrochemical porosification. The investigation of the epitaxial Ge crystalline quality by X-ray diffraction, transmission …
Graphene's original promise to succeed silicon faltered due to pervasive edge disorder in lithographically patterned deposited graphene and the lack of a new electronics paradigm. Here we demonstrate that the annealed edges in conventionally patterned graphene epitaxially grown on a silicon carbide substrate (epigraphene) are stabilized by the substrate and support a protected edge state. The edge state has a mean free path that is greater than 50 microns, 5000 times greater that the bulk states and involves a theoretically unexpected Majorana-like zero-energy non-degenerate quasiparticle that…
Surfaces and interfaces of ferroelectric oxides exhibit enhanced functionality, and therefore serve as a platform for novel nano and quantum technologies. Experimental and theoretical challenges associated with examining the subtle electro-chemo-mechanical balance at metal-oxide surfaces have hindered the understanding and control of their structure and behavior. Here, we combine advanced electron-microscopy and first-principles thermodynamics methods to reveal the atomic-scale chemical and crystallographic structure of the surface of the seminal ferroelectric BaTiO3. We show that the surface …
We employed graphene as a patternable template to protect the intrinsic surface states of thin films of topological insulators (TIs) from environment. Here we find that the graphene provides high-quality interface so that the Shubnikov de Haas (SdH) oscillation associated with a topological surface state could be observed at the interface of a metallic Bi2Se3 film with a carrier density higher than ~10^19 cm-3. Our in situ X-ray diffraction study shows that the Bi2Se3 film grows epitaxially in a quintuple layer-by-layer fashion from the bottom layer without any structural distortion by interfa…
