Jian Cui

Bio: Jian Cui is an academic researcher from Shaanxi Normal University. The author has contributed to research in topics: Perovskite (structure) & Molecular beam epitaxy. The author has an hindex of 16, co-authored 34 publications receiving 816 citations. Previous affiliations of Jian Cui include Xi'an Jiaotong University & Fudan University.

Inch-Size 0D-Structured Lead-Free Perovskite Single Crystals for Highly Sensitive Stable X-Ray Imaging

Abstract: Summary Ion migration in perovskite materials accelerates its decomposition—deteriorating device performance, causing baseline drift, and lowering imaging resolution. In particular, in X-ray detectors, the effect of ion migration is more obvious under the necessary high working bias. Here, we report an effective strategy to grow superior inch-sized, high-quality, zero-dimensional (0D)-structured, lead-free (CH3NH3)3Bi2I9 perovskite single crystals. These crystals have significantly lower ion migration, reduced dark current, and better environmental stability compared with other perovskites, enabling us to fabricate a type of 0D-structured perovskite X-ray detector. The X-ray detector shows high sensitivity of 1,947 μC Gyair−1 cm−2, low detection limit of 83 nGyair s−1, short response time of 23.3 ms, the lowest baseline drift of 5.0 × 10−10 nA cm−1 s−1 V−1, and the best long-term stability among all perovskites reported. The combination of large crystal size and excellent X-ray response allows us to fabricate the first 0D-structured perovskite X-ray imaging system.

Visible band-gap ZnCdO heterostructures grown by molecular beam epitaxy

Abstract: Single-phase ZnCdO alloys with a band gap extending from the violet to yellow spectral range are fabricated by molecular beam epitaxy using extremely low growth temperatures in conjunction with O-rich growth conditions. The Cd concentration can be systematically adjusted via the Cd∕Zn beam pressure ratio. Despite growth temperatures as low as 150°C, layer-by-layer growth is accomplished allowing for the preparation of ZnCdO∕ZnO quantum well structures. Both epilayers and quantum wells exhibit strong band-gap-related emission at room temperature in the whole composition range.

Growth of high-quality ZnMgO epilayers and ZnO/ZnMgO quantum well structures by radical-source molecular-beam epitaxy on sapphire

Abstract: We report on a specific growth procedure combining low-temperature growth of ZnMgO and postgrowth annealing at intermediate temperatures. Despite the large lattice misfit induced by the sapphire substrate, layer-by-layer growth is accomplished up to the phase-separation limit found at a c-lattice constant of 0.5136nm and Mg mole fraction of 0.40. The procedure allows us to grow quantum wells with atomically smooth interfaces in a wide range of structural designs exhibiting prominent emission features up to room temperature.

Fast parallel algorithms for short-range molecular dynamics

Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

ZnO : From basics towards applications

Abstract: Several hundred thousands of tons of ZnO are used by per year, e.g. as an additive to concrete or to rubber. In the field of optoelectronics, ZnO holds promises as a material for a blue/UV optoelectronics, alternatively to GaN, as a cheap, transparent, conducting oxide, as a material for electronic circuits, which are transparent in the visible or for semiconductor spintronics. The main problem is presently, however, a high, reproducible and stable p-doping. We review in this contribution partly critically the material growth, fundamental properties of ZnO and of ZnO-based nanostructures, doping as well as present and future applications, with emphasis on the electronic and optical properties including stimulated emission. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Ultrastrong ductile and stable high-entropy alloys at small scales.

Abstract: Refractory high-entropy alloys (HEAs) are a class of emerging multi-component alloys, showing superior mechanical properties at elevated temperatures and being technologically interesting. However, they are generally brittle at room temperature, fail by cracking at low compressive strains and suffer from limited formability. Here we report a strategy for the fabrication of refractory HEA thin films and small-sized pillars that consist of strongly textured, columnar and nanometre-sized grains. Such HEA pillars exhibit extraordinarily high yield strengths of ∼ 10 GPa--among the highest reported strengths in micro-/nano-pillar compression and one order of magnitude higher than that of its bulk form--and their ductility is considerably improved (compressive plastic strains over 30%). Additionally, we demonstrate that such HEA films show substantially enhanced stability for high-temperature, long-duration conditions (at 1,100 °C for 3 days). Small-scale HEAs combining these properties represent a new class of materials in small-dimension devices potentially for high-stress and high-temperature applications.

Transition states between pyramids and domes during Ge/Si island growth

Abstract: Real-time observations were made of the shape change from pyramids to domes during the growth of germanium-silicon islands on silicon (001). Small islands are pyramidal in shape, whereas larger islands are dome-shaped. During growth, the transition from pyramids to domes occurs through a series of asymmetric transition states with increasing numbers of highly inclined facets. Postgrowth annealing of pyramids results in a similar shape change process. The transition shapes are temperature dependent and transform reversibly to the final dome shape during cooling. These results are consistent with an anomalous coarsening model for island growth.