| 1. |
- Zhao, Jie, et al.
(författare)
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A Sequential Process of Graphene Exfoliation and Site-Selective Copper/Graphene Metallization Enabled by Multifunctional 1-Pyrenebutyric Acid Tetrabutylammonium Salt
- 2019
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 11:6, s. 6448-6455
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports a procedure leading to shear exfoliation of pristine few-layer graphene flakes in water and subsequent site-selective formation of Cu/graphene films on polymer substrates, both of which are enabled by employing the water soluble 1-pyrenebutyric acid tetrabutylammonium salt (PyB-TBA). The exfoliation with PyB-TBA as an enhancer leads to as-deposited graphene films dried at 90 °C that are characterized by electrical conductivity of ∼110 S/m. Owing to the good affinity of the tetrabutylammonium cations to the catalyst PdCl42–, electroless copper deposition selectively in the graphene films is initiated, resulting in a self-aligned formation of highly conductive Cu/graphene films at room temperature. The excellent solution-phase and low-temperature processability, self-aligned copper growth, and high electrical conductivity of the Cu/graphene films have permitted fabrication of several electronic circuits on plastic foils, thereby indicating their great potential in compliant, flexible, and printed electronics.
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| 2. |
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| 3. |
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| 4. |
- Zhang, Da
(författare)
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On the Low Frequency Noise in Ion Sensing
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ion sensing represents a grand research challenge. It finds a vast variety of applications in, e.g., gas sensing for domestic gases and ion detection in electrolytes for chemical-biological-medical monitoring. Semiconductor genome sequencing exemplifies a revolutionary application of the latter. For such sensing applications, the signal mostly spans in the low frequency regime. Therefore, low-frequency noise (LFN) present in the same frequency domain places a limit on the minimum detectable variation of the sensing signal and constitutes a major research and development objective of ion sensing devices. This thesis focuses on understanding LFN in ion sensing based on both experimental and theoretical studies.The thesis starts with demonstrating a novel device concept, i.e., ion-gated bipolar amplifier (IGBA), aiming at boosting the signal for mitigating the interference by external noise. An IGBA device consists of a modified ion-sensitive field-effect transistors (ISFET) intimately integrated with a bipolar junction transistor as the internal current amplifier with an achieved internal amplification of 70. The efficacy of IGBA in suppressing the external interference is clearly demonstrated by comparing its noise performance to that of the ISFET counterpart.Among the various noise sources of an ISFET, the solid/liquid interfacial noise is poorly studied. A differential microelectrode cell is developed for characterizing this noise component by employing potentiometry and electrochemical impedance spectroscopy. With the cell, the measured noise of the TiN/electrolyte interface is found to be of thermal nature. The interfacial noise is further found to be comparable or larger than that of the state-of-the-art MOSFETs. Therefore, its influence cannot be overlooked for design of future ion sensors.To understand the solid/liquid interfacial noise, an electrochemical impedance model is developed based on the dynamic site-binding reactions of surface hydrogen ions with surface OH groups. The model incorporates both thermodynamic and kinetic properties of the binding reactions. By considering the distributed nature of the reaction energy barriers, the model can interpret the interfacial impedance with a constant-phase-element behavior. Since the model directly correlates the interfacial noise to the properties of the sensing surface, the dependencies of noise on the reaction rate constants and binding site density are systematically investigated.
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| 5. |
- Chen, Si, et al.
(författare)
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A graphene field-effect capacitor sensor in electrolyte
- 2012
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 101:15, s. 154106-
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Tidskriftsartikel (refereegranskat)abstract
- The unique electronic properties of graphene are exploited for field-effect sensing in both capacitor and transistor modes when operating the sensor device in electrolyte. The device is fabricated using large-area graphene thin films prepared by means of layer-by-layer stacking. Although essentially the same device, its operation in the capacitor mode is found to yield more information than in the transistor mode. The capacitor sensor can simultaneously detect the variations of surface potential and electrical-double-layer capacitance at the graphene/electrolyte interface when altering the ion concentration. The capacitor-mode operation further facilitates studies of the molecular binding-adsorption kinetics by monitoring the capacitance transient
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| 6. |
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| 7. |
- Miao, Fengjuan, et al.
(författare)
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Inkjet printing of electrochemically-exfoliated graphene nano-platelets
- 2016
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 220, s. 318-322
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report on a facile method of inkjet printing of graphene nano-platelets (GNPs). The GNPs are exfoliated from graphite by means of an electrochemical process in an inorganic salt based electrolyte. The electrochemically exfoliated GNPs with oxygen-bearing functional groups exhibit spectroscopic features similar to those of reduced graphene oxides. As a result, ink formulation with such GNPs for inkjet printing readily accomplishes without using stabilizer and various conductive objects are easily fabricated on different substrates by inkjet printing. The as-printed films of the electrochemically exfoliated GNPs deliver an electrical conductivity of 44 S/m, a typical value for as-printed pristine GNP films in the literature. A simple thermal treatment results in an improved DC conductivity by two orders of magnitude to ~2.5 × 103 S/m.
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| 8. |
- Zhang, Shili, et al.
(författare)
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Metal Silicides in Advanced CMOS Technology
- 2014
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Ingår i: Metallic films: structure, processing and properties. - UK : Woodhead Publishing Limited.
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Östling, Mikael, et al.
(författare)
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Device integration issues towards 10 nm MOSFETs
- 2006
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Ingår i: 2006 25TH INTERNATIONAL CONFERENCE ON MICROELECTRONICS, VOLS 1 AND 2, PROCEEDINGS. - NEW YORK, NY : IEEE. - 142440116X ; , s. 25-30
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Konferensbidrag (refereegranskat)abstract
- An overview of critical integration issues for future generation MOSFETs towards 10 nm gate length is presented. Novel materials and innovative structures are discussed. Implementation of high K gate dielectrics is presented and device performance is demonstrated for TiN metal gate surface channel SiGe MOSFETs with a gate stack based on ALD-formed HfO(2)/Al(2)O(3). Low frequency noise properties for those devices are also analyzed. A selective SiGe epitaxy process for low resistivity source/drain contacts has been developed and implemented in pMOSFETs. A spacer pattering technology using optical lithography to fabricate sub 50 nm high-frequency MOSFETs and nanowires is demonstrated, Finally ultra thin body Sol devices with high mobility SiGe channels are demonstrated.
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| 10. |
- Chen, Si, 1982-
(författare)
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Electronic Sensors Based on Nanostructured Field-Effect Devices
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Point-of-care (POC) diagnostics presents a giant market opportunity with profound societal impact. In particular, specific detection of DNA and protein markers can be essential for early diagnosis of e.g. cancer, cardiovascular disease, infections or allergies. Today, identification of these markers often requires extensive laboratory work and hence is expensive and time consuming. Current methods for recognition and detection of specific biomolecules are mostly optics based and thus impose severe limitations as to convenience, specificity, sensitivity, parallel processing and cost reduction.Electronic sensors based on silicon nanowire field-effect transistors have been reported to be able to detect biomolecules with concentrations down to femtomolar (fM) level with high specificity. Although the reported capability needs further confirmation, the CMOS-compatible fabrication process of such sensors allows for low cost production and high density integration, which are favorable for POC applications. This thesis mainly focuses on the development of a multiplex detection platform based on silicon nanowire field-effect sensors integrated with a microfluidic system for liquid sample delivery. Extensive work was dedicated to developing a top-down fabrication process of the sensors as well as an effective passivation scheme. The operation mechanism and coupling efficiencies of different gate configurations were studied experimentally with the assistance of numerical simulation and equivalent circuits. Using pH sensing as a model system, large effort was devoted to identifying sources for false responses resulting from the instability of the inert-metal gate electrode. In addition, the drift mechanism of the sensor operating in electrolyte was addressed and a calibration model was proposed. Furthermore, protein detection experiments were performed using small-sized Affibody molecules as receptors on the gate insulator to tackle the Debye screening issue. Preliminary results showed that the directionality of the current changes in the sensors was in good agreement with the charge polarities of the proteins. Finally, a graphene-based capacitor was examined as an alternative to the nanowire device for field-effect ion sensing. Our initial attempts showed some attractive features of the capacitor sensor.
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