Search Results

You searched for all publications:

with publication states 'Published (Approved)'

Search Again...

These results only include publications that have been reviewed and processed by Diamond Light Source. To also view papers that have not yet been processed click here.

You can use the folder icon under Actions to collate papers as required. You can then click on View Folder in the left-hand navigation to review and/or download your folder.

Exact matches
Related results

8 items found (0 items not approved), displaying all items.1

Instruments / Technical Area	Publication Details	Published
I06-Nanoscience	Manipulating the metal-to-insulator transition and magnetic properties in manganite thin films via epitaxial strain Dong Li , Bonan Zhu , Dirk Backes , Larissa S. I. Veiga , Tien-Lin Lee , Hongguang Wang , Qian He , Pinku Roy , Jiaye Zhang , Jueli Shi , Aiping Chen , Peter A. Van Aken , Quanxi Jia , Sarnjeet S. Dhesi , David O. Scanlon , Kelvin H. L. Zhang , Weiwei Li Physical Review B 105 DOI: 10.1103/PhysRevB.105.165426 Diamond Proposal Number(s): [25425, 26901, 29616] Show Abstract ▼ Abstract: Strain engineering of epitaxial transition metal oxide heterostructures offers an intriguing opportunity to control electronic structures by modifying the interplay between spin, charge, orbital, and lattice degrees of freedom. Here, we demonstrate that the electronic structure, magnetic and transport properties of La 0.9 Ba 0.1 MnO 3 thin films can be effectively controlled by epitaxial strain. Spectroscopic studies and first-principles calculations reveal that the orbital occupancy in Mn e g orbitals can be switched from the d 3 z 2 − r 2 orbital to the d x 2 − y 2 orbital by varying the strain from compressive to tensile. The change of orbital occupancy associated with Mn 3 d -O 2 p hybridization leads to dramatic modulation of the magnetic and electronic properties of strained La 0.9 Ba 0.1 MnO 3 thin films. Under moderate tensile strain, an emergent ferromagnetic insulating state with an enhanced ferromagnetic Curie temperature of 215 K is achieved. These findings not only deepen our understanding of electronic structures, magnetic and transport properties in the La 0.9 Ba 0.1 MnO 3 system, but also demonstrate the use of epitaxial strain as an effective knob to tune the electronic structures and related physical properties for potential spintronic device applications.	Apr 2022
I09-Surface and Interface Structural Analysis	Modulation of the Bi3+ 6S2 lone pair state in perovskites for high-mobility p-type oxide semiconductors Jueli Shi , Ethan A. Rubinstein , Weiwei Li , Jiaye Zhang , Ye Yang , Tien-Lin Lee , Changdong Qin , Pengfei Yan , Judith L. Macmanus-Driscoll , David O. Scanlon , Kelvin H.l. Zhang Advanced Science DOI: 10.1002/advs.202104141 Diamond Proposal Number(s): [24219] Open Access Show Abstract ▼ Abstract: Oxide semiconductors are key materials in many technologies from flat-panel displays，solar cells to transparent electronics. However, many potential applications are hindered by the lack of high mobility p-type oxide semiconductors due to the localized O-2p derived valence band (VB) structure. In this work, the VB structure modulation is reported for perovskite Ba2BiMO6 (M = Bi, Nb, Ta) via the Bi 6s2 lone pair state to achieve p-type oxide semiconductors with high hole mobility up to 21 cm2 V−1 s−1, and optical bandgaps widely varying from 1.5 to 3.2 eV. Pulsed laser deposition is used to grow high quality epitaxial thin films. Synergistic combination of hard x-ray photoemission, x-ray absorption spectroscopies, and density functional theory calculations are used to gain insight into the electronic structure of Ba2BiMO6. The high mobility is attributed to the highly dispersive VB edges contributed from the strong coupling of Bi 6s with O 2p at the top of VB that lead to low hole effective masses (0.4–0.7 me). Large variation in bandgaps results from the change in the energy positions of unoccupied Bi 6s orbital or Nb/Ta d orbitals that form the bottom of conduction band. P–N junction diode constructed with p-type Ba2BiTaO6 and n-type Nb doped SrTiO3 exhibits high rectifying ratio of 1.3 × 104 at ±3 V, showing great potential in fabricating high-quality devices. This work provides deep insight into the electronic structure of Bi3+ based perovskites and guides the development of new p-type oxide semiconductors.	Jan 2022
I09-Surface and Interface Structural Analysis	Ni3+-induced semiconductor-to-metal transition in spinel nickel cobaltite thin films X. C. Huang , W.-W. Li , S. Zhang , F. E. Oropeza , G. Gorni , V. A. De La Pena-O'Shea , T.-L. Lee , M. Wu , L.-S. Wang , D.-C. Qi , L. Qiao , J. Cheng , K. H. L. Zhang Physical Review B 104 DOI: 10.1103/PhysRevB.104.125136 Diamond Proposal Number(s): [24219] Show Abstract ▼ Abstract: In this paper, we report insights into the local atomic and electronic structure of NiCo 2 O 4 epitaxial thin films and its correlation with electrical, optical, and magnetic properties. We grew structurally well-defined NiCo 2 O 4 epitaxial thin films with controlled properties on Mg Al 2 O 4 ( 001 ) substrates using pulsed laser deposition. Films grown at low temperatures ( < 400 ∘ C ) exhibit a ferrimagnetic and metallic behavior, while those grown at high temperatures are nonmagnetic semiconductors. The electronic structure and cation local atomic coordination of the respective films were investigated using a combination of resonant photoemission spectroscopy, x-ray absorption spectroscopy, and ab initio calculations. Our results unambiguously reveal that the Ni 3 + valence state promoted at low growth temperature introduces delocalized Ni 3 d -derived states at the Fermi level ( E F ), responsible for the metallic state in NiCo 2 O 4 , while the Co 3 d -related state is more localized at higher binding energy. In the semiconducting films, the valence state of Ni is lowered and ∼ + 2 . Further structural and defect chemistry studies indicate that the formation of oxygen vacancies and secondary CoO phases at high growth temperature are responsible for the Ni 2 + valence state in NiCo 2 O 4 . The Ni 3 d -related state becomes localized away from E F , opening a band gap for a semiconducting state. The band gap of the semiconducting NiCo 2 O 4 is estimated to be < 0.8 eV , which is much smaller than the quoted values in the literature ranging from 1.1 to 2.58 eV. Despite the small band gap, its optical transition is d − d dipole forbidden, and therefore, the semiconducting NiCo 2 O 4 still shows reasonable transparency in the infrared-visible light region. The present insights into the role of Ni 3 + in determining the electronic structure and defect chemistry of NiCo 2 O 4 provide important guidance for use of NiCo 2 O 4 in electrocatalysis and opto-electronics.	Sep 2021
	Colloidal synthesis and optical properties of perovskite-inspired cesium zirconium halide nanocrystals Anna Abfalterer , Javad Shamsi , Dominik J. Kubicki , Christopher N. Savory , James Xiao , Giorgio Divitini , Weiwei Li , Stuart Macpherson , Krzysztof Gałkowski , Judith L. Macmanus-Driscoll , David O. Scanlon , Samuel D. Stranks Acs Materials Letters DOI: 10.1021/acsmaterialslett.0c00393 Open Access Show Abstract ▼ Abstract: Optoelectronic devices based on lead halide perovskites are processed in facile ways, yet are remarkably efficient. There are extensive research efforts investigating lead-free perovskite and perovskite-related compounds, yet there are challenges to synthesize these materials in forms that can be directly integrated into thin film devices rather than as bulk powders. Here, we report on the colloidal synthesis and characterization of lead-free, antifluorite Cs2ZrX6 (X = Cl, Br) nanocrystals that are readily processed into thin films. We use transmission electron microscopy and powder X-ray diffraction measurements to determine their size and structural properties, and solid-state nuclear magnetic resonance measurements reveal the presence of oleate ligand, together with a disordered distribution of Cs surface sites. Density functional theory calculations reveal the band structure and fundamental band gaps of 5.06 and 3.91 eV for Cs2ZrCl6 and Cs2ZrBr6, respectively, consistent with experimental values. Finally, we demonstrate that the Cs2ZrCl6 and Cs2ZrBr6 nanocrystal thin films exhibit tunable, broad white photoluminescence with quantum yields of 45% for the latter, with respective peaks in the blue and green spectral regions and mixed systems exhibiting properties between them. Our work represents a critical step toward the application of lead-free Cs2ZrX6 nanocrystal thin films into next-generation light-emitting applications.	Nov 2020
I07-Surface & interface diffraction	Efficient light-emitting diodes from mixed-dimensional perovskites on a fluoride interface Baodan Zhao , Yaxiao Lian , Linsong Cui , Giorgio Divitini , Gunnar Kusch , Edoardo Ruggeri , Florian Auras , Weiwei Li , Dexin Yang , Bonan Zhu , Rachel A. Oliver , Judith L. Macmanus-Driscoll , Samuel D. Stranks , Dawei Di , Richard H. Friend Nature Electronics 26 DOI: 10.1038/s41928-020-00487-4 Diamond Proposal Number(s): [17223] Show Abstract ▼ Abstract: Light-emitting diodes based on halide perovskites have recently reached external quantum efficiencies of over 20%. However, the performance of visible perovskite light-emitting diodes has been hindered by non-radiative recombination losses and limited options for charge-transport materials that are compatible with perovskite deposition. Here, we report efficient, green electroluminescence from mixed-dimensional perovskites deposited on a thin (~1 nm) lithium fluoride layer on an organic semiconductor hole-transport layer. The highly polar dielectric interface acts as an effective template for forming high-quality bromide perovskites on otherwise incompatible hydrophobic charge-transport layers. The control of crystallinity and dimensionality of the perovskite layer is achieved by using tetraphenylphosphonium chloride as an additive, leading to external photoluminescence quantum efficiencies of around 65%. With this approach, we obtain light-emitting diodes with external quantum efficiencies of up to 19.1% at high brightness (>1,500 cd m−2).	Oct 2020
I06-Nanoscience	Atomic‐scale control of electronic structure and ferromagnetic insulating state in perovskite oxide superlattices by long‐range tuning of BO6 octahedra Weiwei Li , Bonan Zhu , Ruixue Zhu , Qiang Wang , Ping Lu , Yuanwei Sun , Clodomiro Cafolla , Zhimin Qi , Aiping Chen , Peng Gao , Haiyan Wang , Qing He , Kelvin H. L. Zhang , Judith L. Macmanus‐driscoll Advanced Functional Materials 114 DOI: 10.1002/adfm.202001984 Diamond Proposal Number(s): [17284] Open Access Show Abstract ▼ Abstract: Control of BO6 octahedral rotations at the heterointerfaces of dissimilar ABO3 perovskites has emerged as a powerful route for engineering novel physical properties. However, its impact length scale is constrained at 2–6 unit cells close to the interface and the octahedral rotations relax quickly into bulk tilt angles away from interface. Here, a long‐range (up to 12 unit cells) suppression of MnO6 octahedral rotations in La0.9Ba0.1MnO3 through the formation of superlattices with SrTiO3 can be achieved. The suppressed MnO6 octahedral rotations strongly modify the magnetic and electronic properties of La0.9Ba0.1MnO3 and hence create a new ferromagnetic insulating state with enhanced Curie temperature of 235 K. The emergent properties in La0.9Ba0.1MnO3 arise from a preferential occupation of the out‐of‐plane Mn d 3z 2−r 2 orbital and a reduced Mn eg bandwidth, induced by the suppressed octahedral rotations. The realization of long‐range tuning of BO6 octahedra via superlattices can be applicable to other strongly correlated perovskites for exploring new emergent quantum phenomena.	Aug 2020
I06-Nanoscience	Interface engineered room‐temperature ferromagnetic insulating state in ultrathin manganite films Weiwei Li , Bonan Zhu , Qian He , Albina Y. Borisevich , Chao Yun , Rui Wu , Ping Lu , Zhimin Qi , Qiang Wang , Aiping Chen , Haiyan Wang , Stuart A. Cavill , Kelvin H. L. Zhang , Judith L. Macmanus‐driscoll Advanced Science 5 DOI: 10.1002/advs.201901606 Diamond Proposal Number(s): [17284] Open Access Show Abstract ▼ Abstract: Ultrathin epitaxial films of ferromagnetic insulators (FMIs) with Curie temperatures near room temperature are critically needed for use in dissipationless quantum computation and spintronic devices. However, such materials are extremely rare. Here, a room‐temperature FMI is achieved in ultrathin La0.9Ba0.1MnO3 films grown on SrTiO3 substrates via an interface proximity effect. Detailed scanning transmission electron microscopy images clearly demonstrate that MnO6 octahedral rotations in La0.9Ba0.1MnO3 close to the interface are strongly suppressed. As determined from in situ X‐ray photoemission spectroscopy, O K‐edge X‐ray absorption spectroscopy, and density functional theory, the realization of the FMI state arises from a reduction of Mn eg bandwidth caused by the quenched MnO6 octahedral rotations. The emerging FMI state in La0.9Ba0.1MnO3 together with necessary coherent interface achieved with the perovskite substrate gives very high potential for future high performance electronic devices.	Nov 2019
I09-Surface and Interface Structural Analysis	Electronic and transport properties of Li-doped NiO epitaxial thin films Jia-Ye Zhang , Weiwei Li , Robert L. Z. Hoye , Judith Macmanus-Driscoll , Melanie Budde , Oliver Bierwagen , Le Wang , Yingge Du , Matthew Wahila , Louis F. J. Piper , Tien-Lin Lee , Holly Edwards , Vinod R. Dhanak , Hongliang Zhang Journal Of Materials Chemistry C DOI: 10.1039/C7TC05331B Diamond Proposal Number(s): [16005] Show Abstract ▼ Abstract: NiO is a p-type wide bandgap semiconductor of use in various electronic devices ranging from solar cells to transparent transistors. Understanding and improving its optical and transport properties have been of considerable interest. In this work, we have investigated the effect of Li doping on the electronic, optical and transport properties of NiO epitaxial thin films grown by pulsed laser deposition. We show that Li doping significantly increases the p-type conductivity of NiO, but all the films have relatively low room-temperature mobilities (< 0.05 cm2 V−1s−1). The conduction mechanism is better described by small-polaron hoping model in the temperature range of 200 K < T <330 K, and variable range hopping at T <200 K. A combination of x-ray photoemission and O K-edge x-ray absorption spectroscopic investigations reveal that the Fermi level gradually shifts toward the valence band maximum (VBM) and a new hole state develops with Li doping. Both the VBM and hole states are composed of primarily Zhang-Rice bound states, which accounts for the small polaron character (low mobility) of hole conduction. Our work provides guidelines for the search for p-type oxide materials and device optimization.	Jan 2018

Publications Database

Search Results

You searched for all publications:

Search Again...

Subject Areas (check all that apply) select all

Instruments used to collect data (check all that apply) select all

Collaborations involved (check all that apply) select all

Diamond Offline Facilities used

Relevant Technical Areas (check all that apply) select all

Menu for Anonymous User