| 1. |
- Li, Jiantong, et al.
(författare)
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Ink-jet printed thin-film transistors with carbon nanotube channels shaped in long strips
- 2011
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 109:8, s. 084915-
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Tidskriftsartikel (refereegranskat)abstract
- The present work reports on the development of a class of sophisticated thin-film transistors (TFTs) based on ink-jet printing of pristine single-walled carbon nanotubes (SWCNTs) for the channel formation. The transistors are manufactured on oxidized silicon wafers and flexible plastic substrates at ambient conditions. For this purpose, ink-jet printing techniques are developed with the aim of high-throughput production of SWCNT thin-film channels shaped in long strips. Stable SWCNT inks with proper fluidic characteristics are formulated by polymer addition. The present work unveils, through Monte Carlo simulations and in light of heterogeneous percolation, the underlying physics of the superiority of long-strip channels for SWCNT TFTs. It further predicts the compatibility of such a channel structure with ink-jet printing, taking into account the minimum dimensions achievable by commercially available printers. The printed devices exhibit improved electrical performance and scalability as compared to previously reported ink-jet printed SWCNT TFTs. The present work demonstrates that ink-jet printed SWCNT TFTs of long-strip channels are promising building blocks for flexible electronics.
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| 2. |
- Li, Jiantong, et al.
(författare)
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Distinguishing self-gated rectification action from ordinary diode rectification in back-gated carbon nanotube devices
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:133111
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Tidskriftsartikel (refereegranskat)abstract
- Self-gating leading to rectification action is frequently observed in two-terminal devices built from individual or networked single-walled carbon nanotubes (SWCNTs) on oxidized Si substrates. The current-voltage (I-V) curves of these SWCNT devices remain unaltered when switching the measurement probes. For ordinary diodes, the I-V curves are symmetric about the origin of the coordinates when exchanging the probes. Numerical simulations suggest that the self-gated rectification action should result from the floating semiconducting substrate which acts as a back gate. Self-gating effect is clearly not unique for SWCNT devices. As expected, it is absent for devices fabricated on insulating substrates.
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| 3. |
- Li, Jiantong, et al.
(författare)
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Improved electrical performance of carbon nanotube thin film transistors by utilizing composite networks
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:133103
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a simple scheme of using composite carbon nanotube networks (c-CNNs) to significantly improve the electrical performance of long-channel thin film transistors based on single-walled carbon nanotubes (SWCNTs). Such c-CNNs comprise two sets of SWCNTs. A primary set consists of dense arrays of perfectly aligned long SWCNTs along the transistor channel direction. A secondary set is composed of short SWCNTs either randomly orientated or perpendicularly aligned with respect to the channel. While retaining a high on/off current ratio, the drive current in such c-CNNs is much higher than that in currently studied systems with single CNNs or SWCNT arrays.
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| 4. |
- Hållstedt, Julius, et al.
(författare)
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A robust spacer gate process for deca-nanometer high-frequency MOSFETs
- 2006
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 83:3, s. 434-439
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Tidskriftsartikel (refereegranskat)abstract
- This paper, presents a robust spacer technology for definition of deca-nanometer gate length MOSFETs. Conformal deposition, selective anisotropic dry-etching and selective removal of sacrificial layers enabled patterning of an oxide hard mask with deca-nanometer lines combined with structures defined with I-line lithography on a wafer. The spacer gate technology produces negligible topographies on the hard mask and no residual particles could be detected on the wafer. The line-width roughness of 40 nm poly-Si gate lines was 4 nm and the conductance of 200 pm long lines exhibited a standard deviation of 6% across a wafer. nMOSFETs with 45 nm gate length exhibited controlled short-channel effects and the average maximum transconductance in saturation was 449 mu S/mu m with a standard deviation of 3.7% across a wafer. The devices exhibited a cut-off frequency above 100 GHz at a drain current of 315 mu A/mu m. The physical and electrical results show that the employed spacer gate technology is robust and can define deca-nanometer nMOSFETs with high yield and good uniformity.
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| 5. |
- Jablonka, Lukas, et al.
(författare)
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Formation of nickel germanides from Ni layers with thickness below 10 nm
- 2017
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Ingår i: Journal of Vacuum Science & Technology B. - : A V S AMER INST PHYSICS. - 1071-1023 .- 1520-8567. ; 35:2
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Tidskriftsartikel (refereegranskat)abstract
- The authors have studied the reaction between a Ge (100) substrate and thin layers of Ni ranging from 2 to 10 nm in thickness. The formation of metal-rich Ni5Ge3 was found to precede that of the monogermanide NiGe by means of real-time in situ x-ray diffraction during ramp-annealing and ex situ x-ray pole figure analyses for phase identification. The observed sequential growth of Ni5Ge3 and NiGe with such thin Ni layers is different from the previously reported simultaneous growth with thicker Ni layers. The phase transformation from Ni5Ge3 to NiGe was found to be nucleationcontrolled for Ni thicknesses < 5 nm, which is well supported by thermodynamic considerations. Specifically, the temperature for the NiGe formation increased with decreasing Ni (rather Ni5Ge3) thickness below 5 nm. In combination with sheet resistance measurement and microscopic surface inspection of samples annealed with a standard rapid thermal processing, the temperature range for achieving morphologically stable NiGe layers was identified for this standard annealing process. As expected, it was found to be strongly dependent on the initial Ni thickness.
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| 6. |
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| 7. |
- Lindgren, A. C., et al.
(författare)
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Characterization of strained Si/Si1-xGex/Si heterostructures annealed in oxygen or argon
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:5, s. 2708-2712
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Tidskriftsartikel (refereegranskat)abstract
- The strained Si/Si1-xGex/Si layer heterostructure heat treated from 700 degreesC to 950 degreesC in Ar (annealing) or O-2-C2H2Cl2 (oxidation) was characterized using high-resolution x-ray diffraction in combination with Rutherford backscattering. Only small changes to the structure are observed up to 800 degreesC, within the resolution limits of diffraction and backscattering. Severe strain relaxation occurs at 950 degreesC and the heterostructure tends to relax more during annealing in Ar than during oxidation in O-2-C2H2Cl2. The strain relaxation is mainly caused by interdiffusion of Si and Ge rather than formation of misfit dislocations. Diffusion of Si interstitials generated during oxidation into the heterostructure is suggested as the cause responsible for the less pronounced interdiffusion of Si and Ge in the oxidized samples.
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| 8. |
- Luo, Jun, et al.
(författare)
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Effects of Carbon on Schottky Barrier Heights of NiSi Modified by Dopant Segregation
- 2009
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Ingår i: IEEE Electron Device Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 0741-3106 .- 1558-0563. ; 30:6, s. 608-610
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Tidskriftsartikel (refereegranskat)abstract
- The presence of carbon at the interface between NiSi and Si has been found to participate in the process of modification of effective Schottky barrier heights using the dopant segregation (DS) method. Carbon alone results in an increased phi(bn) from 0.7 to above 0.9 eV. Boron diffusion in NiSi is inhibited by carbon, and no B-DS at the NiSi/Si interface occurs below 600 degrees C. Above this temperature, B-DS at this interface is evident thus keeping phi(bn) high. The presence of interfacial carbon leads to an increased interfacial As concentration resulting in beneficial effects in tuning phi(bn) above 1.0 eV by As-DS.
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| 9. |
- Luo, Jun, et al.
(författare)
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Effects of carbon pre-silicidation implant into Si substrate on NiSi
- 2014
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Ingår i: Microelectronic Engineering. - : Elsevier BV. - 0167-9317 .- 1873-5568. ; 120, s. 178-181
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the effects of carbon pre-silicidation implant into Si(1 0 0) substrate on NiSi were investigated. NiSi films with carbon pre-silicidation implant to different doses were characterized by means of sheet resistance measurements, X-ray diffraction, scanning electron microscopy (SEM), planar view transmission electron microscopy (TEM) and second ion mass spectroscopy (SIMS). The presence of C is found to indeed significantly improve the thermal stability of NiSi as well as tends to change the preferred orientations of polycrystalline NiSi. The homogeneously distributed C at NiSi grain boundaries and C peak at NiSi/Si interface is ascribed to the improved thermal stability of NiSi. More importantly, the dose of carbon pre-silicidation implant also plays a key role in the formation of NiSi, which is suggested not to exceed a critical value about 5 x 10(15) cm(-2) in practical application in accordance with the results achieved in this work. (C) 2013 Elsevier B.V. All rights reserved.
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| 10. |
- Luo, Jun, et al.
(författare)
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Interaction of NiSi with dopants for metallic source/drain applications
- 2010
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Ingår i: Journal of Vacuum Science & Technology B. - : American Vacuum Society. - 1071-1023 .- 1520-8567. ; 28:1, s. C1I1-C1I11
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Tidskriftsartikel (refereegranskat)abstract
- This work has a focus on NiSi as a possible metallic contact for aggressively scaled complementary metal oxide semiconductor devices. As the bulk work function of NiSi lies close to the middle of Si bandgap, the Schottky barrier height (SBH) of NiSi is rather large for both electron (similar to 0.65 eV) and hole (similar to 0.45 eV). Different approaches have therefore been intensively investigated in the literature aiming at reducing the effective SBH: dopant segregation (DS), surface passivation (SP), and alloying, in order to improve the carrier injection into the conduction channel of a field-effect transistor. The present work explores DS using B and As for the NiSi/Si contact system. The effects of C and N implantation into Si substrate prior to the NiSi formation are examined, and it is found that the presence of C yields positive effects in helping reduce the effective SBH to 0.1-0.2 eV for both conduction polarities. A combined use of DS or SP with alloying could be considered for more effective control of effective SBH, but an examination of undesired compound formation and its probable consequences is necessary. Furthermore, an analysis of the metal silicides that have a small "intrinsic" SBH reveals that only a very small number of them are of practical interest as most of the silicides require either a high formation temperature or possess a high specific resistivity.
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