| 1. |
- Yin, X., et al.
(författare)
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Vertical Sandwich Gate-All-Around Field-Effect Transistors with Self-Aligned High-k Metal Gates and Small Effective-Gate-Length Variation
- 2020
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers Inc.. - 0741-3106 .- 1558-0563. ; 41:1, s. 8-11
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Tidskriftsartikel (refereegranskat)abstract
- A new type of vertical nanowire (NW)/nanosheet (NS) field-effect transistors (FETs), termed vertical sandwich gate-all-around (GAA) FETs (VSAFETs), is presented in this work. Moreover, an integration flow that is compatible with processes used in the mainstream industry is proposed for the VSAFETs. Si/SiGe epitaxy, isotropic quasi-atomic-layer etching (qALE), and gate replacement were used to fabricate pVSAFETs for the first time. Vertical GAA FETs with self-aligned high-k metal gates and a small effective-gate-length variation were obtained. Isotropic qALE, including Si-selective etching of SiGe, was developed to control the diameter/thickness of the NW/NS channels. NWs with a diameter of 10 nm and NSs with a thickness of 20 nm were successfully fabricated, and good device characteristics were obtained. Finally, the device performance was investigated and is discussed in this work. © 2019 IEEE.
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| 2. |
- Li, J., et al.
(författare)
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Study of silicon nitride inner spacer formation in process of gate-all-around nano-transistors
- 2020
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 10:4
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Tidskriftsartikel (refereegranskat)abstract
- Stacked SiGe/Si structures are widely used as the units for gate-all-around nanowire transistors (GAA NWTs) which are a promising candidate beyond fin field effective transistors (FinFETs) technologies in near future. These structures deal with a several challenges brought by the shrinking of device dimensions. The preparation of inner spacers is one of the most critical processes for GAA nano-scale transistors. This study focuses on two key processes: Inner spacer film conformal deposition and accurate etching. The results show that low pressure chemical vapor deposition (LPCVD) silicon nitride has a good film filling effect; a precise and controllable silicon nitride inner spacer structure is prepared by using an inductively coupled plasma (ICP) tool and a new gas mixtures of CH2F2/CH4/O2/Ar. Silicon nitride inner spacer etch has a high etch selectivity ratio, exceeding 100:1 to Si and more than 30:1 to SiO2. High anisotropy with an excellent vertical/lateral etch ratio exceeding 80:1 is successfully demonstrated. It also provides a solution to the key process challenges of nano-transistors beyond 5 nm node. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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| 3. |
- Du, Y., et al.
(författare)
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Strain modulation of selectively and/or globally grown ge layers
- 2021
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 11:6
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Tidskriftsartikel (refereegranskat)abstract
- This article presents a novel method to grow a high-quality compressive-strain Ge epilayer on Si using the selective epitaxial growth (SEG) applying the RPCVD technique. The procedures are composed of a global growth of Ge layer on Si followed by a planarization using CMP as initial process steps. The growth parameters of the Ge layer were carefully optimized and after cycle-annealing treatments, the threading dislocation density (TDD) was reduced to 3 × 107 cm−2 . As a result of this process, a tensile strain of 0.25% was induced, whereas the RMS value was as low as 0.81 nm. Later, these substrates were covered by an oxide layer and patterned to create trenches for selective epitaxy growth (SEG) of the Ge layer. In these structures, a type of compressive strain was formed in the SEG Ge top layer. The strain amount was −0.34%; meanwhile, the TDD and RMS surface roughness were 2 × 106 cm−2 and 0.68 nm, respectively. HRXRD and TEM results also verified the existence of compressive strain in selectively grown Ge layer. In contrast to the tensile strained Ge layer (globally grown), enhanced PL intensity by a factor of more than 2 is partially due to the improved material quality. The significantly high PL intensity is attributed to the improved crystalline quality of the selectively grown Ge layer. The change in direct bandgap energy of PL was observed, owing to the compressive strain introduced. Hall measurement shows that a selectively grown Ge layer possesses room temperature hole mobility up to 375 cm2/Vs, which is approximately 3 times larger than that of the Ge (132 cm2/Vs). Our work offers fundamental guidance for the growth of high-quality and compressive strain Ge epilayer on Si for future Ge-based optoelectronics integration applications.
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| 4. |
- Li, J., et al.
(författare)
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Study of selective isotropic etching Si1−xGex in process of nanowire transistors
- 2020
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Ingår i: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 31:1, s. 134-143
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Tidskriftsartikel (refereegranskat)abstract
- On approach towards the end of technology roadmap, a revolutionary approach towards the nanowire transistors is favorable due to the full control of carrier transport. The transistor design moves toward vertically or laterally stacked Gate-All-Around (GAA) where Si or SiGe can be used as channel material. This study presents a novel isotropic inductively coupled plasma (ICP) dry etching of Si1−xGex (0.10 ≤ x ≤ 0.28) in SiGe/Si multilayer structures (MLSs) with high selectivity to Si, SiO2, Si3N4 and SiON which can be applied in advanced 3D transistors and Micro-Electro-Mechanical System (MEMS) in future. The profile of SiGe etching for different thicknesses, compositions and locations in MLSs using dry or wet etch have been studied. A special care has been spent for layer quality of Si, strain relaxation of SiGe layers as well as residual contamination during the etching. In difference with dry etching methods (downstream remote plasma), the conventional ICP source in situ is used where CF4/O2/He gas mixture was used as the etching gas to obtain higher selectivity. Based on the reliability of ICP technique a range of etching rate 25–50 nm/min can be obtained for accurate isotropic etching of Si1−xGex, to form cavity in advanced 3D transistor processes in future.
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| 5. |
- Huang, Ivy, et al.
(författare)
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High performance dual-electrolyte magnesium-iodine batteries that can harmlessly resorb in the environment or in the body
- 2022
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Ingår i: Energy & Environmental Science. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 15:10, s. 4095-4108
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Tidskriftsartikel (refereegranskat)abstract
- Batteries represent the dominant means for storing electrical energy, but many battery chemistries create waste streams that are difficult to manage, and most possess toxic components that limit their use in biomedical applications. Batteries constructed from materials capable of complete, harmless resorption into the environment or into living organisms after a desired period of operation bypass these disadvantages. However, previously reported eco/bioresorbable batteries offer low operating voltages and modest energy densities. Here, we introduce a magnesium-iodine chemistry and dual (ionic liquid/aqueous) electrolyte to overcome these limitations, enabling significant improvements in voltage, areal capacity, areal energy, areal power, volumetric energy, and volumetric power densities over any alternative. Systematic studies reveal key materials and design considerations. Demonstrations of this technology include power supplies for cardiac pacemakers, wireless environmental monitors, and thermal sensors/actuators. These results suggest strong potential for applications where commercial battery alternatives pose risks to the environment or the human body.
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| 6. |
- Chodankar, N. R., et al.
(författare)
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Solution-free self-assembled growth of ordered tricopper phosphide for efficient and stable hybrid supercapacitor
- 2021
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Ingår i: Energy Storage Materials. - : Elsevier B.V.. - 2405-8289 .- 2405-8297. ; 39, s. 194-202
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Tidskriftsartikel (refereegranskat)abstract
- Herein, a solution-free dry strategy for the growth of self-assembled ordered tricopper phosphide (Cu3P) nanorod arrays is developed and the product is employed as a high-energy, stable positive electrode for a solid-state hybrid supercapacitor (HSC). The ordered Cu3P nanorod arrays grown on the copper foam deliver an excellent specific capacity of 664 mA h/g with an energy efficiency of 88% at 6 A/g and an ultra-long cycling stability over 15,000 continuous charge–discharge cycles. These electrochemical features are attributed to the ordered growth of the Cu3P nanorod arrays, which offers a large number of accessible electroactive sites, a reduced number of ion transfer paths, and reversible redox activity. The potential of the Cu3P nanorod arrays is further explored by engineering solid-state HSCs in which the nanorods are paired with an activated carbon-based negative electrode. The constructed cell is shown to convey a specific energy of 76.85 Wh/kg at a specific power of 1,125 W/kg and an 88% capacitance retention over 15,000 cycles. Moreover, the superior energy storing and delivery capacity of the cell is demonstrated by an energy efficiency of around 65%. The versatile solution-free dry strategies developed here pave the way towards engineering a range of electrode materials for next-generation energy storage systems. © 2021 Elsevier B.V.
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