| 1. |
- Dong, Yu, et al.
(författare)
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Observation of a Ubiquitous (π, π)-Type Nematic Superconducting Order in the Whole Superconducting Dome of Ultra-Thin BaFe2–xNixAs2 Single Crystals
- 2021
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Ingår i: Chinese Physics Letters. - : Institute of Physics Publishing (IOPP). - 0256-307X .- 1741-3540. ; 38:9
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Tidskriftsartikel (refereegranskat)abstract
- In iron-based superconductors, the (0, pi) or (pi, 0) nematicity, which describes an electronic anisotropy with a four-fold symmetry breaking, is well established and believed to be important for understanding the superconducting mechanism. However, how exactly such a nematic order observed in the normal state can be related to the superconducting pairing is still elusive. Here, by performing angular-dependent in-plane magnetoresistivity using ultra-thin flakes in the steep superconducting transition region, we unveil a nematic superconducting order along the (pi, pi) direction in electron-doped BaFe2 - x Ni x As2 from under-doped to heavily overdoped regimes with x = 0.065-0.18. It shows superconducting gap maxima along the (pi, pi) direction rotated by 45 degrees from the nematicity along (0, pi) or (pi, 0) direction observed in the normal state. A similar (pi, pi)-type nematicity is also observed in the under-doped and optimally doped hole-type Ba1 - y K y Fe2As2, with y = 0.2-0.5. These results suggest that the (pi, pi) nematic superconducting order is a universal feature that needs to be taken into account in the superconducting pairing mechanism in iron-based superconductors.
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| 2. |
- Duan, Ningyuan, et al.
(författare)
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Reduction of NiGe/n- and p-Ge Specific Contact Resistivity by Enhanced Dopant Segregation in the Presence of Carbon During Nickel Germanidation
- 2016
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Ingår i: IEEE Transactions on Electron Devices. - : IEEE. - 0018-9383 .- 1557-9646. ; 63:11, s. 4546-4549
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Tidskriftsartikel (refereegranskat)abstract
- This brief explores the specific contact resistivity (rho(c)) of NiGe/n- and p-Ge contacts with and without carbon pregermanidation implantation. It is found that in the presence of carbon, not only the thermal stability of NiGe films is improved, but also the rho(c) of the NiGe/n- and p-Ge contacts is reduced remarkably due to enhanced phosphorus (P) and boron (B) dopant segregation (DS) at the NiGe/Ge interface after nickel germanidation. At 500 degrees C germanidation temperature, the.c values are reduced from 1.1 x 10(-4) Omega-cm(2) and 2.9 x 10(-5) Omega-cm(2) for NiGe/n- and p-Ge contacts without carbon to 7.3 x 10(-5) Omega-cm(2) and 1.4 x 10(-5) Omega-cm(2) for their counterparts with carbon, respectively.
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| 3. |
- Li, Junjie, et al.
(författare)
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A Novel Dry Selective Isotropic Atomic Layer Etching of SiGe for Manufacturing Vertical Nanowire Array with Diameter Less than 20 nm
- 2020
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Ingår i: Materials. - : MDPI AG. - 1996-1944 .- 1996-1944. ; 13:3
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Tidskriftsartikel (refereegranskat)abstract
- Semiconductor nanowires have great application prospects in field effect transistors and sensors. In this study, the process and challenges of manufacturing vertical SiGe/Si nanowire array by using the conventional lithography and novel dry atomic layer etching technology. The final results demonstrate that vertical nanowires with a diameter less than 20 nm can be obtained. The diameter of nanowires is adjustable with an accuracy error less than 0.3 nm. This technology provides a new way for advanced 3D transistors and sensors.
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| 4. |
- Guo, Pengzhi, et al.
(författare)
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Twisted Alkylthiothien-2-yl Flanks and Extended Conjugation Length Synergistically Enhanced Photovoltaic Performance by Boosting Dielectric Constant and Carriers Kinetic Characteristics
- 2021
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Ingår i: Macromolecular Chemistry and Physics. - : Wiley. - 1022-1352 .- 1521-3935. ; 222:12
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Tidskriftsartikel (refereegranskat)abstract
- Alternating conjugated polymers (CPs), derived from 2-ethylhexylthiothiophen-2-yl (TS) or 2-ethylhexylthiophen-2-yl (T) flanked dithieno[3,2-d:3,2-d ']benzo[1,2-b:4,5-b ']dithiophene (DTBDT) and diketopyrrolo-pyrrole (DPP) termed as PDTBDT-TS-DPP and PDTBDT-T-DPP, are prepared and characterized. It is found that the PDTBDT-TS-DPP not only exhibits slightly deepening the highest occupied molecular orbital energy levels, and similar absorption, etc., but also presents higher dielectric constant (epsilon(r)) of 6.7 at 1 kHz in contrast to 3.2 for PDTBDT-T-DPP, which are even higher than those of 4.3 and 3.0 for PBDT-TS-DPP/PBDT-T-DPP generated from TS and T flanked benzo[1,2-b:4,5-bMODIFIER LETTER PRIME]dithiophene and DPP. Beyond that, the power conversion efficiency of 8.17% for the inverted photovoltaic devices from DPP-based CPs, is achieved from PDTBDT-TS-DPP. The alkylthio side chains are used in the DTBDT of the larger twisting angles of TS flanks and longer conjugation length, synergistically contribute to the highest dipole moments, and then lead to the enhancement of epsilon(r), thus devoted the modification exciton dissociation and charge carriers kinetic characteristics. To the authors' knowledge, it is the first time to report that epsilon(r) of the CPs is connected with the twisting angle of flanks and conjugation length of the building blocks, besides the use of functional side chains and atoms.
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| 5. |
- Liu, Yi, et al.
(författare)
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Effect of fluorine atoms on optoelectronic, aggregation and dielectric constants of 2,1,3-benzothiadiazole-based alternating conjugated polymers
- 2021
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Ingår i: Dyes and Pigments. - : Elsevier BV. - 0143-7208 .- 1873-3743. ; 193
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Tidskriftsartikel (refereegranskat)abstract
- Three 2,1,3-benzothiadiazole-based conjugated copolymers named PBDT-0F-BTs, PBDT-2F-BTs and PBDT-6F-FBTs, which were derived from 4,8-bis(4,5-dioctylthiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene and (3,4′-bis(2-hexyl- decyl)-2,2′-dithiophene-5-yl) substituted 2,1,3-benzothiadiazole and/or 5,6-difluoro- 2,1,3-benzothiadiazole derivatives with 2,2′-dithiophene and/or 3,3′-difluoro- 2,2′-dithiophene as π-linkers, were prepared and characterized. The copolymers PBDT-0F-BTs, PBDT-2F-BTs and PBDT-6F-FBTs exhibited the highest occupied molecular orbital (HOMO) and lowest unoccupied orbital (LUMO) energy levels of −5.38 eV/−3.57 eV, −5.45 eV/−3.65 eV and −5.55 eV/−3.78 eV, with the light response from 300 nm to 720–750 nm, alongside with the similar aggregation, except that the charge transporting mobilities were successively increased, and the dielectric constants were gradually improved from 3.3 to 4.8 to 5.9 at 1 KHz, while the fluorine atoms in the each repeat unit of polymers were varied from 0 to 2 and then up to 6, respectively. Beyond that, it has also been found that the power conversion efficiencies and exciton dissociation probability (P(E,T)) of the bulk heterojunction organic photovoltaic cells (BHJ-OPVs) from the blend films of polymers paired with Y6 (2,2'-((2Z,2'Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl12,13-dihydro[1,2,5]thia- diazolo[3,4-e]thieno[2'',3'':4',5']thieno[2',3':4,5]pyrrolo[3,2-g]thieno[2',3':4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H-ind-ene-2,1-diylidene))dimalononitrile), were varied from 7.83% and 85.9%, to 9.22% and 90.2% and then up to 12.34% and 91.4%. The results indicated that the continuous insertion of the fluorine atoms into the repeat units of the conjugated polymers would result in the consecutively deepening the HOMO energy levels, increase dielectric constants and charge mobilities, thus devote to the enhancement of the P(E,T) and the performance of the BHJ-OPVs.
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| 6. |
- Wang, Guilei, et al.
(författare)
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Growth of SiGe layers in source and drain regions for 10 nm node complementary metal-oxide semiconductor (CMOS)
- 2020
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 31, s. 26-33
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the integration of Si 1−x Ge x (50% ≤ x ≤ 60%) selective epitaxy on source/drain regions in 10 nm node FinFET has been presented. One of the major process issues was the sensitivity of Si-fins’ shape to ex- and in-situ cleaning prior to epitaxy. For example, the sharpness of Si-fins could easily be damaged during the wafer washing. The results showed that a DHF dip before the normal cleaning, was essential to clean the Si-fins while in-situ annealing in range of 780–800 °C was needed to remove the native oxide for high epitaxial quality. Because of smallness of fins, the induced strain by SiGe could not be directly measured by X-ray beam in a typical XRD tool in the lab or even in a Synchrotron facility. Further analysis using nano-beam diffraction technique in high-resolution transmission electron microscope also failed to provide information about strain in the FinFET structure. Therefore, the induced strain by SiGe was simulated by technology computer-aided design program and the Ge content was measured by using energy dispersive spectroscopy. Simulation results showed 0.8, 1 and 1.3 GPa for Ge content of 40%, 50% and 60%, respectively. A kinetic gas model was also introduced to predict the SiGe profile on Si-fins with sharp triangular shape. The input parameters in the model includes growth temperature, partial pressure of the reactant gases and the exposed Si coverage in the chip area.
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| 7. |
- Wang, Guilei, et al.
(författare)
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Study of SiGe selective epitaxial process integration with high-k and metal gate for 16/14 nm nodes FinFET technology
- 2016
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Ingår i: Microelectronic Engineering. - : Elsevier. - 0167-9317 .- 1873-5568. ; 163, s. 49-54
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the process integration of SiGe selective epitaxy on source/drain regions, for 16/14 nm nodes FinFET with high-k & metal gate has been presented. Selectively grown Si1-xGex (0.35 <= x <= 0.40) with boron concentration of 1 x 10(20) cm(-3) was used to elevate the source/drain of the transistors. The epi-quality, layer profile and strain amount of the selectively grown SiGe layers were also investigated by means of various characterizations. A series of prebaking experiments were performed for temperatures ranging from 740 to 825 degrees C in order to in situ clean the Si fins prior to the epitaxy. The results showed that the thermal budget needs to be limited to 780-800 degrees C in order to avoid any damages to the shape of Si fins but to remove the native oxide effectively which is essential for high epitaxial quality. The Ge content in SiGe layers on Si fins was determined from the strain measured directly by reciprocal space mappings using synchrotron radiation. Atomic layer deposition technique was applied to fill the gate trench with W using WF6 and B2H6 precursors. By such an AID approach, decent growth rate, low resistivity and excellent gap filling capability of W in pretty high aspect-ratio gate trench was realized. The as-fabricated FinFETs demonstrated decent electrical characteristics.
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| 8. |
- Wang, Xiaolin, et al.
(författare)
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Comprehension of the Effect of a Hydroxyl Group in Ancillary Ligand on Phosphorescent Property for Heteroleptic Ir(III) Complexes : A Computational Study Using Quantitative Prediction
- 2017
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 56:15, s. 8986-8995
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Tidskriftsartikel (refereegranskat)abstract
- A new Ir(III) complex (dfpypya)(2)Ir(pic-OH) (2) is theoretically designed by introduction of a simple hydroxyl group into the ancillary ligand on the basis of (dfpypya)(2)Ir(pic) (1) with the aim to get the high efficiency and stable blue-emitting phosphors, where dfpypya is 3-methyl-6-(2',4'-difluoro-pyridinato)pyridazine, pic is picolinate, and pic OH is 3-hydroxypicolinic acid. The other configuration (dfpypya)(2)Ir(pic OH)' (3) is also investigated to compare with 2. The difference between 2 and 3 is whether the intramolecular hydrogen bond is formed in the (dfpypya)(2)Ir(pic OH). The quantum yield is determined by three different methods including the semiquantitative and quantitative methods. To quantitatively determine the quantum yield is still not an easy task to be completed. This work would provide some useful advices to select the suitable method to reliably evaluate the quantum yield. Complex 2 has larger quantum yield and more stability as compared with 1 and 3. The formation of intramolecular hydrogen bond would become a new method to design new phosphor with the desired properties.
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| 9. |
- Xiong, Wenjuan, et al.
(författare)
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SiNx films and membranes for photonic and MEMS applications
- 2020
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 31, s. 90-97
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a novel process to form SiN x films and process for membranes with excellent mechanical properties for micro-electro-mechanical systems application as well as integration as IR waveguide for photonic application. The SiN x films were fabricated in SiNgen apparatus which is a single wafer chamber equipment compared to conventional low pressure chemical vapor deposition furnace process. The films showed low stress, good mechanical properties, but the synthesis also eradicates the issues of particle contamination. Through optimizing of the growth parameters and post annealing profile, low stress (40 Mpa) SiN x film could be finally deposited when annealing temperature rose up to 1150 °C. The stress relaxation is a result of more Si nano-crystalline which was formed during annealing, according to the FTIR results. The mechanical properties, Young’s modulus and hardness, were 210 Gpa and 20 Gpa respectively. For the waveguide application, a stack of three layers, SiO 2 /SiN x /SiO 2 was formed where the optimized layer thicknesses were used for minimum optical loss according to simulation feedback. After deposition of the first two layers in the stack, the samples were annealed in range of 900–1150 °C in order to release the stress. Chemical mechanical polish technique was applied to planarize the nitride layer prior to the oxide cladding layer. Such wafers can be used to bond to Si or Ge to manufacture advanced substrates.
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| 10. |
- Bao, Qinye, et al.
(författare)
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Regular Energetics at Conjugated Electrolyte/Electrode Modifier for Organic Electronics and Their Implications of Design Rules
- 2015
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Ingår i: Advanced Materials Interfaces. - : John Wiley & Sons. - 2196-7350. ; 2:12, s. 1-6
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Tidskriftsartikel (refereegranskat)abstract
- Regular energetics at a conjugated electrolyte/electrode modifier are found and controlled by equilibration of the Fermi level and an additional interface double dipole step induced by ionic functionality. Based on the results, design rules for conjugated electrolyte/electrode modifiers to achieve the smallest charge injection/exaction barrier and break through the current thickness limitation are proposed.
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