| 51. |
- Qin, Leiqiang, et al.
(författare)
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A flexible semitransparent photovoltaic supercapacitor based on water-processed MXene electrodes
- 2020
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 8:11, s. 5467-5475
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Tidskriftsartikel (refereegranskat)abstract
- Solar energy, although it has the highest power density available in terms of renewable energy, has the drawback of being erratic. Integrating an energy harvesting and storage device into photovoltaic energy storage modules is a viable route for obtaining self-powered energy systems. Herein, an MXene-based all-solution processed semitransparent flexible photovoltaic supercapacitor (PSC) was fabricated by integrating a flexible organic photovoltaic (OPV) with Ti3C2Tx MXene as the electrode and transparent MXene supercapacitors with an organic ionogel as the electrolyte in the vertical direction, using Ti3C2Tx thin film as a common electrode. In the quest for a semitransparent flexible PSC, Ti3C2Tx MXene was first used as a transparent electrode for OPV with a high power conversion efficiency of 13.6%. The ionogel electrolyte-based transparent MXene supercapacitor shows a high volumetric capacitance of 502 F cm(-3) and excellent stability. Finally, a flexible PSC with a high average transmittance of over 33.5% was successfully constructed by all-solution processing and a remarkable storage efficiency of 88% was achieved. This strategy enables a simple route for fabricating MXene based high-performance all-solution-processed flexible PSCs, which is important for realizing flexible and printable electronics for future technologies.
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| 52. |
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| 53. |
- Tholander, Christopher, et al.
(författare)
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Ab initio calculations and experimental study of piezoelectric YxIn1-xN thin films deposited using reactive magnetron sputter epitaxy
- 2016
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 105, s. 199-206
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Tidskriftsartikel (refereegranskat)abstract
- By combining theoretical prediction and experimental verification we investigate the piezoelectric properties of yttrium indium nitride (YxIn1-xN). Ab initio calculations show that the YxIn1-xN wurtzite phase is lowest in energy among relevant alloy structures for 0≤x≤0.5. Reactive magnetron sputter epitaxy was used to prepare thin films with Y content up to x=0.51. The composition dependence of the lattice parameters observed in the grown films is in agreement with that predicted by the theoretical calculations confirming the possibility to synthesize a wurtzite solid solution. An AlN buffer layer greatly improves the crystalline quality and surface morphology of subsequently grown YxIn1-xN films. The piezoelectric response in films with x=0.09 and x=0.14 is observed using piezoresponse force microscopy. Theoretical calculations of the piezoelectric properties predict YxIn1−xN to have comparable piezoelectric properties to ScxAl1-xN.
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| 54. |
- Thorsteinsson, E. B., et al.
(författare)
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Room temperature ferromagnetism in the nanolaminated MAX phase (Mn1−xCrx)2GaC
- 2023
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Ingår i: APL Materials. - : AIP Publishing. - 2166-532X. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- MAX phases are a class of intrinsically nanolaminated materials, which combine features of metals and ceramics, owing to the alternating metallic and covalent bonding between atomic layers. Magnetic MAX phases have been known for a decade, but ferromagnetism at room temperature in this highly anisotropic system has been elusive, limiting their value as magnets in practice. Here, we show that a MAX phase with a strong ferromagnetic response is obtained by substituting Mn with Cr on the M-site in the well-known Mn2GaC. The ferromagnetic response is observed in (Mn1-xCrx)(2)GaC with 0.06 < x < 0.29 up to temperatures well exceeding room temperature (489 K). The strongest magnetization is achieved with x = 0.12, reaching a saturation moment of 1.25 mu B and a remanence of 0.67 mu(B) per M-atom at 3 K and maintaining 0.90 and 0.44 mu(B) per M-atom, respectively, at 300 K. This is the first experimental report of a significant ferromagnetic response in a MAX phase at room temperature. The results open the door to the use of MAX phases in a broad range of applications, from bulk magnets in power electronics to spintronic devices.(c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license(http://creativecommons.org/licenses/by/4.0/).
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| 55. |
- Tunca, B., et al.
(författare)
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In situ He+ irradiation of the double solid solution (Ti-0.5,Zr-0.5)(2)(Al-0.5,Sn-0.5)C MAX phase: Defect evolution in the 350-800 degrees C temperature range
- 2021
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Ingår i: Acta Materialia. - : PERGAMON-ELSEVIER SCIENCE LTD. - 1359-6454 .- 1873-2453. ; 206
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Tidskriftsartikel (refereegranskat)abstract
- Thin foils of the double solid solution (Zr-0.5,Ti-0.5)(2)(Al-0.5,Sn-0.5)C MAX phase were in situ irradiated in a transmission electron microscope (TEM) up to a fluence of 1.3 x 10(17) ions.cm(-2) (similar to 7.5 dpa), using 6 keV He+ ions. Irradiations were performed in the 350-800 degrees C temperature range. In situ and post-irradiation examination (PIE) by TEM was used to study the evolution of irradiation-induced defects as function of dose and temperature. Spherical He bubbles and string-like arrangements thereof, He platelets, and dislocation loops were observed. Dislocation loop segments were found to lie in non-basal-planes. At irradiation temperatures >= 450 degrees C, grain boundary tearing was observed locally due to He bubble segregation. However, the tears did not result in transgranular crack propagation. The intensity of specific spots in the selected area electron diffraction patterns weakened upon irradiation at 450 and 500 degrees C, indicating an increased crystal symmetry. Above 700 degrees C this was not observed, indicating damage recovery at the high end of the investigated temperature range. High-resolution scanning TEM imaging performed during the PIE of foils previously irradiated at 700 degrees C showed that the chemical ordering and nanolamination of the MAX phase were preserved after 7.5 dpa He+ irradiation. The size distributions of the He platelets and spherical bubbles were evaluated as function of temperature and dose. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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| 56. |
- Wu, D., et al.
(författare)
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A novel strained Si0.7Ge0.3 surface-channel pMOSFET with an ALD TiN/Al2O3/HfAlOx/Al2O3 gate stack
- 2003
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 24:3, s. 171-173
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Tidskriftsartikel (refereegranskat)abstract
- Proof-of-concept pMOSFETs with a strained-Si0.7Ge0.3 surface-channel deposited by selective epitaxy and a TiN/Al2O3/HfAIO(x)/Al2O3 gate stack grown by atomic layer chemical vapor deposition (ALD) techniques were fabricated. The Si0.7Ge0.3 pMOSFETs exhibited more than 30% higher current drive and peak transconductance than reference Si pMOSFETs with the same gate stack. The effective mobility for the Si reference coincided with the universal hole mobility curve for Si. The presence of a relatively low density of interface states, determined as 3.3x10(11) cm(-2) eV(-1), yielded a subthreshold slope of 75 mV/dec. for the Si reference. For the Si0.7Ge0.3 pMOSFETs, these values were 1.6x10(12) cm(-2) eV(-1) and 110 mV/dec., respectively.
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| 57. |
- Zhang, Hengfang, et al.
(författare)
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On the polarity determination and polarity inversion in nitrogen-polar group III-nitride layers grown on SiC
- 2022
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 131:5
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the interfaces and polarity domains at the atomic scale in epitaxial AlN and GaN/AlN grown by hot-wall metal organic chemical vapor epitaxy on the carbon face of SiC. X-ray diffraction, potassium hydroxide (KOH) wet chemical etching, and scanning transmission electron microscopy combined provide an in-depth understanding of polarity evolution with the film thickness, which is crucial to optimize growth. The AlN grown in a 3D mode is found to exhibit N-polar pyramid-type structures at the AlN-SiC interface. However, a mixed N-polar and Al-polar region with Al-polarity domination along with inverted pyramid-type structures evolve with increasing film thickness. We identify inclined inversion domain boundaries and propose that incorporation of oxygen on the & lang;40-41 & rang; facets of the N-polar pyramids causes the polarity inversion. We find that mixed-polar AlN is common and easily etched and remains undetected by solely relying on KOH etching. Atomic scale electron microscopy is, therefore, needed to accurately determine the polarity. The polarity of GaN grown on mixed-polar AlN is further shown to undergo complex evolution with the film thickness, which is discussed in the light of growth mechanisms and polarity determination methods.
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| 58. |
- Zhang, Hengfang, et al.
(författare)
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Polarity Control by Inversion Domain Suppression in N-Polar III-Nitride Heterostructures
- 2023
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Ingår i: Crystal Growth and Design. - : American Chemical Society (ACS). - 1528-7483 .- 1528-7505. ; 23:2, s. 1049-1056
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogen-polar III-nitride heterostructures offer advantages over metal-polar structures in high frequency and high power applications. However, polarity control in III-nitrides is difficult to achieve as a result of unintentional polarity inversion domains (IDs). Herein, we present a comprehensive structural investigation with both atomic detail and thermodynamic analysis of the polarity evolution in low- and high-temperature AlN layers on on-axis and 4° off-axis carbon-face 4H-SiC (0001̅) grown by hot-wall metal organic chemical vapor deposition. A polarity control strategy has been developed by variation of thermodynamic Al supersaturation and substrate misorientation angle in order to achieve the desired growth mode and polarity. We demonstrate that IDs are completely suppressed for high-temperature AlN nucleation layers when a step-flow growth mode is achieved on the off-axis substrates. We employ this approach to demonstrate high quality N-polar epitaxial AlGaN/GaN/AlN heterostructures.
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| 59. |
- Zhou, Jie, et al.
(författare)
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Boridene: Two-dimensional Mo4/3B2-x with ordered metal vacancies obtained by chemical exfoliation
- 2021
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 373:6556, s. 801-
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Tidskriftsartikel (refereegranskat)abstract
- Extensive research has been invested in two-dimensional (2D) materials, typically synthesized by exfoliation of van der Waals solids. One exception is MXenes, derived from the etching of constituent layers in transition metal carbides and nitrides. We report the experimental realization of boridene in the form of single-layer 2D molybdenum boride sheets with ordered metal vacancies, Mo4/3B2-xTz (where T-z is fluorine, oxygen, or hydroxide surface terminations), produced by selective etching of aluminum and yttrium or scandium atoms from 3D in-plane chemically ordered (Mo2/3Y1/3)(2)AlB2 and (Mo2/3Sc1/3)(2)AlB2 in aqueous hydrofluoric acid. The discovery of a 2D transition metal boride suggests a wealth of future 2D materials that can be obtained through the chemical exfoliation of laminated compounds.
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| 60. |
- Zhou, Jie, et al.
(författare)
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Two-Dimensional Hydroxyl-Functionalized and Carbon-Deficient Scandium Carbide, ScCxOH, a Direct Band Gap Semiconductor
- 2019
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Ingår i: ACS Nano. - : AMER CHEMICAL SOC. - 1936-0851 .- 1936-086X. ; 13:2, s. 1195-1203
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Tidskriftsartikel (refereegranskat)abstract
- Two-dimensional (2D) materials have attracted intense attention in nanoscience and nanotechnology due to their outstanding properties. Among these materials, the emerging family of 2D transition metal carbides, carbonitrides, and nitrides (referred to as MXenes) stands out because of the vast available chemical space for tuning materials chemistry and surface termination, offering opportunities for property tailoring. Specifically, semiconducting properties are needed to enable utilization in optoelectronics, but direct band gaps are experimentally challenging to achieve in these 2D carbides. Here, we demonstrate the fabrication of 2D hydroxyl-functionalized and carbon-deficient scandium carbide, namely, ScCxOH, by selective etching of a layered parent ScAI(3)C(3) compound. The 2D configuration is determined as a direct band gap semiconductor, with an experimentally measured band gap approximated at 2.5 eV. Furthermore, this ScCxOH-based device exhibits excellent photoresponse in the ultraviolet-visible light region (responsivity of 0.125 A/W at 360 nm/10 V, and quantum efficiency of 43%). Thus, this 2D ScCxOH direct band gap semiconductor may find applications in visible light detectors, photocatalytic chemistry, and optoelectronic devices.
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