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筛选条件 : Chunlan MA
Zenghua Cai; Chunlan Ma
Applied Physics Letters, 2025 126 (2) - EI SCIE

摘要 : SrTiO3 (STO) displays a broad spectrum of physical properties, including superconductivity, ferroelectricity, and photoconductivity, making it a standout semiconductor material. Despite extensive research, the oxygen partial pressure-dependent conductivity in STO has remained elusive. This study leverages first-principles calculations and systematically investigates the intrinsic defect properties of STO. The results reveal that VO, VSr, and TiSr are the dominant intrinsic defects, influencing STO's conductivity under varying O chemical potentials (oxygen partial pressures). Under O-poor condition, VO is the predominant donor, while VSr is the main acceptor. As the oxygen pressure increases, TiSr emerges as a critical donor defect under O-rich conditions, significantly affecting the conductivity. Additionally, the study elucidates the abnormal phenomenon where VTi, typically an acceptor, exhibits donor-like behavior due to the formation of O-trimer. This work offers a comprehensive understanding of how intrinsic defects tune the Fermi level, thereby altering STO's conductivity from metallic to n-type and eventually to p-type across different O chemical potentials. These insights resolve the long-standing issue of oxygen partial pressure-dependent conductivity and explain the observed metallic conductivity in oxygen-deficient STO.

Huan Zheng; Bingjie Liu; Can Huang; Kaifeng Li; Shuhao Wang; Chunlan Ma
Applied Surface Science, 2024 672 - EI SCIE

摘要 : We have studied the structural, electrical, and optical properties of La 0.05 Sr 0.95 SnO 3 thin films, which exhibited a strong dependence upon the substrate's orientation and strain. X-ray diffraction results show that the LSSO films grow epitaxially on (0 0 1) and (0 1 1)-oriented LaAlO 3 substrates, and the in-plane compressive strain decreases gradually upon increasing film thickness. Room-temperature resistivity varies from 4.23 (13.0) to 1.37 (4.76) mΩ cm as the film thickness increases for (0 0 1) orientation ((0 1 1) orientation). Temperature dependent resistivity curves of all the samples show a metal–semiconductor transition (MST), which can be explained by the electron–electron interactions below MST rather than weak localization. Both reducing the in-plane compressive strain and transferring the orientation from (0 1 1) to (0 0 1) can drive the MST point shifts toward lower temperature, indicative of the enhancement of the metallic transport in the films. The band gap increases upon increasing film thickness due to Burstein-Moss effect. The charge distributions of Sn and O from density functional theory (DFT) calculations illustrate that (0 0 1)-plane has a better conductivity. Furthermore, our DFT results also demonstrate that decreasing the in-plane strain will lead to a smaller electron effective mass, thus the increased carrier mobility can be obtained. These comprehensive investigations advance our knowledge of the optoelectronic characteristics and provide valuable insights for future research in related transparent materials.

Zan Du; Wei Liu; Aina Wang; Azizur Rahman; Yuyan Han; Wei Tong
Applied Physics Letters, 2024 125 (13) - EI SCIE

摘要 : Chromium-intercalated Cr1/3TaS2 is well known for hosting a nontrivial chiral magnetic soliton lattice (CSL) with the reported highest Curie temperature (⁠ TC∼151 K) and strongest spin–orbit coupling, which has significant applications in gigahertz and high-speed spintronic devices. Herein, we thoroughly investigate the magneto-electrical transport properties of Cr1/3TaS2 single crystals. For H//ab⁠, our magnetoresistance (MR) measurements reveal distinctive step-like behaviors, which are attributed to the formation and annihilation of chiral magnetic solitons. When under an oblique field, similar but weaker MR behaviors are observed compared to H//ab⁠, indicating the appearance of an inclination-field-induced tilted-CSL. A topological Hall effect is observed under an oblique field, which is suggested to be induced by a nonzero topological charge density resulting from the tilted chiral states. The Cr1/3TaS2 offers an intriguing platform for studying the impact of chiral magnetic structures on magneto-electrical properties, which holds promise for both future spintronic device applications and fundamental investigation.

Chuanjun Zhang; Ruihao Jiang; Yonghui Zheng; Yaozhen Li; Zenghua Cai; Chunlan Ma
Advanced Energy Materials, 2024 -1 - EI SCIE

摘要 : Quasi-1D antimony selenide (Sb2Se3) is known for its stable phase structure and excellent light absorption coefficient, making it a promising material for high-efficiency light harvesting. However, the (Sb4Se6)n ribbons align horizontally, increasing defect interference and limiting vertical carrier transport. Herein, a novel strategy of burying selenium (Se) seed layers to reduce lattice mismatch at the heterojunction interface, promote crystal orientation, mitigate deep donor defects, increase P-type carrier concentration, and purify the PN junction, is proposed. Admittance spectroscopy reveals that Sb2Se3 solar cells with Se seed layers have higher activation energies for defect states and significantly lower defect densities (1.2 × 1014, 2.7 × 1014, and 1.3 × 1015 cm−3 for D1, D2, and D3) compared to an order of magnitude higher densities in Sb2Se3 solar cells without a Se seed layer. First-principles calculations support these findings, showing that Se seed layers create a Se-rich environment, reducing selenium vacancies (VSe), antimony on selenium sites (SbSe), and interface defects. This dual passivation mechanism suppresses defect formation and activation, increasing carrier concentration and open-circuit voltage (VOC). Ultimately, employing this novel method, a VOC of 498.3 mV and an efficiency of 8.42%, the highest performance reported for Sb2Se3 solar cells prepared via vapor transport deposition (VTD), are achieved.

Hao Liu; Yamei Wang; Chunlan Ma; Yuzhou Xiao; Ruirui Deng; Fengjiao Qian
Applied Surface Science, 2024 657 - EI SCIE

摘要 : The research of high-speed photodetector and high-speed optical receiver garners significant attention due to their indispensable properties in many fields including high-temperature event monitoring, security, and ad hoc network wireless communication. Inorganic perovskite oxides LaCoO 3 films showcase an extensive prospect in this area owing to their remarkable photoconductive effect. Up to present, however, LaCoO 3 films are mostly grown on rigid instead of flexible substrates, greatly limiting their applications to wearable optoelectronic sensors. In this work, we fabricated some flexible LaCoO 3 thin films to study their photoresponse. By inserting SrTiO 3 and BaTiO 3 as buffer layers, we find that LaCoO 3 thin films could epitaxially grow on the fluorphlogopite surface and show a stable photoresponse to visible-light. Nevertheless, we also found that the epitaxial strain and the content of surface-adsorbed oxygen could impact the photoconductivity. The mechanical strain generated by bending the fluorphlogopite substrate has been confirmed to has a tunable effect on the photoresponse. Moreover, with the fatigue tests of 10 5 bending cycles, the flexible LaCoO 3 thin films maintain a good photoresponse without any essentially weakening, proving a superior mechanical durability and stability. This work not only indicates the feasibility of the LaCoO 3 films applied for flexible photodetectors but also opens a path for other perovskite films applications for flexible substrate.

Zhenqi Liu; Lin Wang; Tong Tong; Hang Xu; Yue Xue; Yaping Qi
Applied Physics Letters, 2024 124 (21) - EI SCIE

摘要 : Two-dimensional electron gas (2DEG) has drawn significant attention due to its intriguing properties. Recent advances have encouraged the use of one-dimensional electron gas for high-performance functional devices. Here, we develop a universal method of atomic force microscope tip etching to construct a quasi-one-dimensional (Q1D) channel on the STO surface. Ar+ ion beam is used to bombard the SrTiO3 surface for inducing the Q1D electron gas (Q1DEG). Compared with 2DEG, Q1DEG exhibits a significant enhancement in terms of photoconductivity. At room temperature, it exhibits ultrahigh sensitivity to ambient light with increase in photocurrent by over five orders of magnitude. A slow response to the ON/OFF light indicates persistent photoconductivity (PPC), originating from the defect levels. Furthermore, we investigate the wavelength dependence of PPC in Q1DEG. It is found that decreasing wavelength favors photoresponsivity and prolongs the response time. Based on the electron diffusion process in the oxygen-deficient region, a mechanism has been proposed to explain the advantages of Q1DEG over 2DEG in regard to photoelectric response. This work paves a path for the development of high-performance photoelectric devices based on Q1D electronic systems.

Bingjiao Yu; Rui Zhao; Zhen Lu; Hangbo Su; Binye Liang; Bingjie Liu
Nanomaterials, 2024 14 (7) - SCIE

摘要 : Amorphous alloys or metallic glasses (MGs) thin films have attracted extensive attention in various fields due to their unique functional properties. Here, we use in situ heating transmission electron microscopy (TEM) to investigate the thermal stability and crystallization behavior of Pd-Au-Si thin films prepared by a pulsed laser deposition (PLD) method. Upon heating treatment inside a TEM, we trace the structural changes in the Pd-Au-Si thin films through directly recording high-resolution images and diffraction patterns at different temperatures. TEM observations reveal that the Pd-Au-Si thin films started to nucleate with small crystalline embryos uniformly distributed in the glassy matrix upon approaching the glass transition temperature Tg=625K, and subsequently, the growth of crystalline nuclei into sub-10 nm Pd-Si nanocrystals commenced. Upon further increasing the temperature to 673K, the thin films transformed to micro-sized patches of stacking-faulty lamellae that further crystallized into Pd9Si2 and Pd3Si intermetallic compounds. Interestingly, with prolonged thermal heating at elevated temperatures, the Pd9Si2 transformed to Pd3Si. Simultaneously, the solute Au atoms initially dissolved in glassy alloys and eventually precipitated out of the Pd9Si2 and Pd3Si intermetallics, forming nearly spherical Au nanocrystals. Our TEM results reveal the unique thermal stability and crystallization processes of the PLD-prepared Pd-Au-Si thin films as well as demonstrate a possibility of producing a large quantity of pure nanocrystals out of amorphous solids for various applications.

Yue Xue; Yaping Qi; Tong Tong; Hang Xu; Zhenqi Liu; Cheng Ji
Applied Physics Letters, 2024 124 (18) - EI SCIE

摘要 : The zero-bandgap properties of graphene (Gr) limit its various applications. Fluorination is an alternative strategy to open the bandgap to broaden its applications. However, traditional fluorination methods are detrimental to human health and contribute extensively to environmental pollution. Here, we develop a simple and safe process of weak fluorination that introduces fluorine atoms into Gr, breaking its zero-bandgap structure. This strategy is more environmentally friendly, risk-free, and harmless to humans, making it suitable for large-scale production. Through this highly controllable weak fluorination process, micro-area selective fluorination is achieved and induces excellent photoluminescence characteristics but maintains a high mobility, compared to the pristine Gr with zero bandgap. The degree of fluorination determines the photoelectric and transport properties of Gr. This work provides an experimental foundation for developing materials based on fluorinated graphene and designing high-performance functional devices.

Hang Xu; Yue Xue; Zhenqi Liu; Qing Tang; Tianyi Wang; Xichan Gao
Small science, 2024 4 (4) - ESCI

摘要 : A van der Waals (vdW) heterostructure is formed by combining multiple materials through vdW bonds. It can combine the advantages of electronic, optical, thermal, and magnetic properties of different 2D materials and has the potential to develop into the next generation of high-performance functional devices. Herein, the current research advances of vdW heterostructures are reviewed. First, current fabrication methods and physical structures of vdW heterostructures are summarized. The 2D/nD (n = 0, 1, 2, 3) mixed-dimensional heterostructures are discussed in detail. Second, a new type of vdW heterostructure is introduced based on two-dimensional electron gas with a nanoscale junction interface. Finally, the application prospects of vdW heterostructures in photoelectric and memory devices are further outlined by combing new applications in the neural networks. This review shows that vdW heterostructures have great advantages in high integration, energy harvesting, and logical operations, and it provides directions and suggestions for the future research and application of environmentally friendly, high-performance, and smart functional devices.

Hang Xu; Yue Xue; Zhenqi Liu; Qing Tang; Tianyi Wang; Xichan Gao
Small science, 2024 4 (4) - ESCI