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Kong, Lingping

Publications and source records attributed to Kong, Lingping.

High-throughput manufacturing of epitaxial membranes from a single wafer by 2D materials-based layer transfer process

Layer transfer techniques have been extensively explored for semiconductor device fabrication as a path to reduce costs and to form heterogeneously integrated devices. These techniques entail isolating epitaxial layers from an expensive donor wafer to form freestanding membranes. However, current layer transfer processes are still low-throughput and too expensive to be commercially suitable. Here we report a high-throughput layer transfer technique that can produce multiple compound semiconductor membranes from a single wafer. We directly grow two-dimensional (2D) materials on III–N and III–V substrates using epitaxy tools, which enables a scheme comprised of multiple alternating layers of 2D materials and epilayers that can be formed by a single growth run. Each epilayer in the multistack structure is then harvested by layer-by-layer mechanical exfoliation, producing multiple freestanding membranes from a single wafer without involving time-consuming processes such as sacrificial layer etching or wafer polishing. Moreover, atomic-precision exfoliation at the 2D interface allows for the recycling of the wafers for subsequent membrane production, with the potential for greatly reducing the manufacturing cost.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

Highly tunable properties in pressure-treated two-dimensional Dion–Jacobson perovskites

Significance Two-dimensional Dion–Jacobson (2D D-J) lead-halide perovskite is a cutting-edge material paradigm that has realized high-efficiency photovoltaic applications and synergetic chemical stability. With the addition of the pressure dimension, this material provides a crucial platform for studying both pressure-tailored physical properties and pressure-driven novel phenomena. Here, we demonstrate that 2D D-J perovskites experience various transitions under pressure, such as crystalline-amorphous and 2D–three-dimensional structural transformation, and the probable metallization are strongly suggested. Moreover, the fundamental changes in the material properties are observed at ambient conditions after pressure treatment, which is crucial for achieving the desired characteristics for viable applications.

36 MATERIALS SCIENCE↗

Diffused morphotropic phase boundary in relaxor-PbTiO 3 crystals: High piezoelectricity with improved thermal stability

Solid solution ferroelectrics are the most widely used piezoelectric material for numerous electromechanical applications, including sensors, actuators, and transducers. A milestone in ferroelectric research is the discovery of the morphotropic phase boundary that was first reported in Pb(Zr x Ti 1–x )O 3 , which has been extensively solicited to improve the performance of various solid solution ferroelectrics, including those having the highest piezoelectricity known today. However, due to the inherent correlation between phase transition and thermodynamic imbalance, the efforts of building the phase boundary encounter the challenge that high performance materials are generally accompanied by property instability. In this paper, we report a comprehensive study on the crystalline symmetry and polar nano-regions in relaxor-PbTiO 3 crystals by synchrotron measurements and property characterizations. In contrast to the common belief that the morphotropic phase boundary is a narrow composition region, the morphotropic phase boundary in ternary Pb(In 1/2 Nb 1/2 )O 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 is demonstrated as an extensive region covering at least 9% of the PbTiO 3 content. Such a diffused morphotropic phase boundary is associated with the intensive interaction of polar nano-regions, leading to high piezoelectricity (>1500 pC/N) with greatly improved thermal stability, where the piezoelectric variation is ~90% over the temperature range of 273–373 K, which is about a factor of 3 lower compared to its binary counterpart Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 . This work sheds light on the fundamental understanding of nanoscale inhomogeneity and macroscopic symmetry in relaxor-PbTiO 3 , and successfully interlinks the structure and properties in complex solid solutions. The existence of a diffused morphotropic phase boundary is also expected to benefit other ferroic systems beyond ferroelectrics, such as ferromagnetic and multiferroic materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

Pressure-induced polyamorphism by quantitative structure factor and pair distribution function analysis in two Ce-based metallic glasses

We utilized the pair distribution function method to characterize the pressure-induced polyamorphic transition in Ce60Al20Cu20 and Ce55Al45 metallic glass at room temperature. Using synchrotron high-energy x-ray diffraction we collected scattering information from a large Q-space coverage, which in turn gave a high resolution g(r) that provided accurate local structure information. We observed a sudden change in compressibility and the nearest neighbor distance at 3.50–6.32 GPa for Ce60Al20Cu20 and 2.20–6.89 GPa for Ce55Al45. The origin of the volume collapse seemed to be pressure-induced qualitative changes in bond shortening that corresponded to different coordination spheres. The polyamorphic transitions in these two systems from low-density glass (LDG) to high-density glass (HDG) are associated with local atomic rearrangements.

36 MATERIALS SCIENCE↗

Pressure-Induced Bandgap Optimization in Lead-Based Perovskites with Prolonged Carrier Lifetime and Ambient Retainability

Bond length and bond angle exhibited by valence electrons is essential to the core of chemistry. Using lead-based organic–inorganic perovskite compounds as an exploratory platform, it is demonstrated that the modulation of valence electrons by compression can lead to discovery of new properties of known compounds. Yet, despite its unprecedented progress, further efficiency boost of lead-based organic–inorganic perovskite solar cells is hampered by their wider bandgap than the optimum value according to the Shockley–Queisser limit. By modulating the valence electron wavefunction with modest hydraulic pressure up to 2.1 GPa, the optimized bandgap for single-junction solar cells in lead-based perovskites, for the first time, is achieved by narrowing the bandgap of formamidinium lead triiodide (HC(NH 2 ) 2 PbI 3 ) from 1.489 to 1.337 eV. Strikingly, such bandgap narrowing is partially retained after the release of pressure to ambient, and the bandgap narrowing is also accompanied with double-prolonged carrier lifetime. With First-principles simulation, this work opens a new dimension in basic chemical understanding of structural photonics and electronics and paves an alternative pathway toward better photovoltaic materials-by-design.

14 SOLAR ENERGY↗