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Showing papers on "Contact resistance published in 2021"


Journal ArticleDOI
12 May 2021-Nature
TL;DR: In this paper, the metal-induced gap states (MIGS) were suppressed and degenerate states in the metal dichalcogenides (TMDs) spontaneously formed in contact with bismuth.
Abstract: Advanced beyond-silicon electronic technology requires both channel materials and also ultralow-resistance contacts to be discovered1,2. Atomically thin two-dimensional semiconductors have great potential for realizing high-performance electronic devices1,3. However, owing to metal-induced gap states (MIGS)4–7, energy barriers at the metal–semiconductor interface—which fundamentally lead to high contact resistance and poor current-delivery capability—have constrained the improvement of two-dimensional semiconductor transistors so far2,8,9. Here we report ohmic contact between semimetallic bismuth and semiconducting monolayer transition metal dichalcogenides (TMDs) where the MIGS are sufficiently suppressed and degenerate states in the TMD are spontaneously formed in contact with bismuth. Through this approach, we achieve zero Schottky barrier height, a contact resistance of 123 ohm micrometres and an on-state current density of 1,135 microamps per micrometre on monolayer MoS2; these two values are, to the best of our knowledge, the lowest and highest yet recorded, respectively. We also demonstrate that excellent ohmic contacts can be formed on various monolayer semiconductors, including MoS2, WS2 and WSe2. Our reported contact resistances are a substantial improvement for two-dimensional semiconductors, and approach the quantum limit. This technology unveils the potential of high-performance monolayer transistors that are on par with state-of-the-art three-dimensional semiconductors, enabling further device downscaling and extending Moore’s law. Electric contacts of semimetallic bismuth on monolayer semiconductors are shown to suppress metal-induced gap states and thus have very low contact resistance and a zero Schottky barrier height.

350 citations


Journal ArticleDOI
06 Jan 2021-ACS Nano
TL;DR: In this article, the authors show that low-temperature (2 × 1013 cm-2, sheet resistance as low as ∼7 kΩ/□, and good contact resistance ∼480 Ω·μm in transistors from monolayer MoS2 grown by chemical vapor deposition.
Abstract: Semiconductors require stable doping for applications in transistors, optoelectronics, and thermoelectrics. However, this has been challenging for two-dimensional (2D) materials, where existing approaches are either incompatible with conventional semiconductor processing or introduce time-dependent, hysteretic behavior. Here we show that low-temperature ( 2 × 1013 cm-2, sheet resistance as low as ∼7 kΩ/□, and good contact resistance ∼480 Ω·μm in transistors from monolayer MoS2 grown by chemical vapor deposition. We also reach record current density of nearly 700 μA/μm (>110 MA/cm2) along this three-atom-thick semiconductor while preserving transistor on/off current ratio >106. The maximum current is ultimately limited by self-heating (SH) and could exceed 1 mA/μm with better device heat sinking. With their 0.1 nA/μm off-current, such doped MoS2 devices approach several low-power transistor metrics required by the international technology roadmap.

71 citations


Journal ArticleDOI
TL;DR: In this article, the fabrication and characterization of 2D Ruddlesden-Popper perovskites (2D PVK) single crystal FETs are reported, which exhibit reliable field effect electrical characteristics at low temperatures.
Abstract: 2D Ruddlesden–Popper perovskites (2D PVKs) have attracted huge interest because of their excellent optoelectronic properties, yet the understanding of their electrical properties is inadequate due to the difficulties in obtaining 2D PVK field‐effect transistors (FETs) with decent performance. Herein, the fabrication and characterization of 2D PVK ((BA)2(MA)n−1PbnI3n+1) single crystal FETs are reported, which exhibit reliable field effect electrical characteristics at low temperatures. Kelvin probe force microscopy (KPFM) results reveal that both ion migration and contact resistance seriously degrade device performance. While ion migration can be suppressed at low temperatures, contact resistance seems to fundamentally determine device performance. On one hand, Schottky contacts are observed to form at the metal/2D PVK interface because of Fermi level pinning, resulting in significant charge injection resistance, although this can be remarkably improved by replacing Au electrodes with Ca. On the other hand, the out‐of‐plane mobility is found to be three orders of magnitude lower than the in‐plane mobility in 2D PVKs, causing large interlayer transport resistance. Thus, a low work‐function metal and a thin crystal are important for achieving high device performance. This work provides important experimental insights into fabrication and electrical properties of 2D PVK FETs.

50 citations


Journal ArticleDOI
TL;DR: In this article, the CrN, CrAlN and multilayer CrN/CrAlN coatings were deposited on 316L SS to increase the corrosion resistance and decrease the interfacial contact resistance.

37 citations


Journal ArticleDOI
TL;DR: In this article, the authors explored the possible explanations for these observations, including the prevalence of Fermi-level pinning and the difficulties in forming optimized interfaces with organic semiconductors.
Abstract: To take full advantage of recent and anticipated improvements in the performance of organic semiconductors employed in organic transistors, the high contact resistance arising at the interfaces between the organic semiconductor and the source and drain contacts must be reduced significantly. To date, only a small portion of the accumulated research on organic thin-film transistors (TFTs) has reported channel-width-normalized contact resistances below 100 Ωcm, well above what is regularly demonstrated in transistors based on inorganic semiconductors. A closer look at these cases and the relevant literature strongly suggests that the most significant factor leading to the lowest contact resistances in organic TFTs so far has been the control of the thin-film morphology of the organic semiconductor. By contrast, approaches aimed at increasing the charge-carrier density and/or reducing the intrinsic Schottky barrier height have so far played a relatively minor role in achieving the lowest contact resistances. Herein, the possible explanations for these observations are explored, including the prevalence of Fermi-level pinning and the difficulties in forming optimized interfaces with organic semiconductors. An overview of the research on these topics is provided, and potential device-engineering solutions are discussed based on recent advancements in the theoretical and experimental work on both organic and inorganic semiconductors.

35 citations


Journal ArticleDOI
TL;DR: In order to improve the conductivity of titanium bipolar plate under the premise of ensuring its corrosion resistance for the proton exchange membrane fuel cell (PEMFC), the nitride coatings are deposited on the surface of the plate via a powder immersion reaction assisted coating (PIRAC) method as discussed by the authors.

27 citations


Journal ArticleDOI
08 Jan 2021
TL;DR: In this paper, the authors report the fabrication of ultraclean Ohmic van der Waals (vdW) contacts between indium (In) and molybdenum disulfide (MoS2) and the clarification of the atomistic origins of its Ohmic-like transport properties.
Abstract: The achievement of ultraclean Ohmic van der Waals (vdW) contacts at metal/transition-metal dichalcogenide (TMDC) interfaces would represent a critical step for the development of high-performance electronic and optoelectronic devices based on two-dimensional (2D) semiconductors Herein, we report the fabrication of ultraclean vdW contacts between indium (In) and molybdenum disulfide (MoS2) and the clarification of the atomistic origins of its Ohmic-like transport properties Atomically clean In/MoS2 vdW contacts are achieved by evaporating In with a relatively low thermal energy and subsequently cooling the substrate holder down to ~100 K by liquid nitrogen We reveal that the high-quality In/MoS2 vdW contacts are characterized by a small interfacial charge transfer and the Ohmic-like transport based on the field-emission mechanism over a wide temperature range from 24 to 300 K Accordingly, the contact resistance reaches ~600 Ω μm and ~1000 Ω μm at cryogenic temperatures for the few-layer and monolayer MoS2 cases, respectively Density functional calculations show that the formation of large in-gap states due to the hybridization between In and MoS2 conduction band edge states is the microscopic origins of the Ohmic charge injection We suggest that seeking a mechanism to generate strong density of in-gap states while maintaining the pristine contact geometry with marginal interfacial charge transfer could be a general strategy to simultaneously avoid Fermi-level pinning and minimize contact resistance for 2D vdW materials

27 citations


Journal ArticleDOI
08 Mar 2021-ACS Nano
TL;DR: In this article, the authors report the direct measurement of electrical and optical responses of 2D semiconductor-metal buried interfaces using a recently developed metal-assisted transfer technique to expose the buried interface, which is then directly investigated using scanning probe techniques.
Abstract: The semiconductor-metal junction is one of the most critical factors for high-performance electronic devices. In two-dimensional (2D) semiconductor devices, minimizing the voltage drop at this junction is particularly challenging and important. Despite numerous studies concerning contact resistance in 2D semiconductors, the exact nature of the buried interface under a three-dimensional (3D) metal remains unclear. Herein, we report the direct measurement of electrical and optical responses of 2D semiconductor-metal buried interfaces using a recently developed metal-assisted transfer technique to expose the buried interface, which is then directly investigated using scanning probe techniques. We characterize the spatially varying electronic and optical properties of this buried interface with <20 nm resolution. To be specific, potential, conductance, and photoluminescence at the buried metal/MoS2 interface are correlated as a function of a variety of metal deposition conditions as well as the type of metal contacts. We observe that direct evaporation of Au on MoS2 induces a large strain of ∼5% in the MoS2 which, coupled with charge transfer, leads to degenerate doping of the MoS2 underneath the contact. These factors lead to improvement of contact resistance to record values of 138 kΩ μm, as measured using local conductance probes. This approach was adopted to characterize MoS2-In/Au alloy interfaces, demonstrating contact resistance as low as 63 kΩ μm. Our results highlight that the MoS2/metal interface is sensitive to device fabrication methods and provide a universal strategy to characterize buried contact interfaces involving 2D semiconductors.

24 citations


Journal ArticleDOI
TL;DR: In this paper, an intrinsic Ohmic contact between a wide band gap semiconductor MgS and semimetal graphene is predicted theoretically by using density functional theory, and a comprehensive investigation of the modulation in the electronic contact properties is conducted under the application of vertical compressive strain and a perpendicular electric field to understand their role in the transport mechanism.
Abstract: The development of low contact resistance at metal-semiconductor interfaces in next-generation transistors is being prioritized to improve device performance. By using density functional theory, an intrinsic Ohmic contact between a wide band gap semiconductor MgS and semimetal graphene is predicted herewith theoretically. The zero Schottky barriers in graphene/MgS van der Waals heterostructure (vdWH) can facilitate a high charge injection efficiency, whereas Ohmic contact can be induced in graphene/MgSe under small external perturbation. A comprehensive investigation of the modulation in the electronic contact properties is conducted under the application of vertical compressive strain and a perpendicular electric field to understand their role in the transport mechanism. Under vertical compressive strain, a band gap of \ensuremath{\sim}0.62 eV in graphene has been opened up. While under perpendicular electric field, the hole carrier concentration in graphene is found to be increased up to $\ensuremath{\sim}{10}^{14}\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{--2}$. Moreover, this work circumvents the prevalent approaches in inducing an Ohmic contact and addresses solutions to very fundamental challenges in pristine graphene, i.e., band gap opening and its tunability, and modulation of carrier concentration. These interesting properties of vdWHs can open up new avenues for constructing these heterojunctions for multifunctional graphene-based field-effect transistors.

23 citations


Journal ArticleDOI
TL;DR: In this paper, an amorphous carbon (α-C) film was prepared using DC balanced magnetron sputtering, and the defect density and corrosion resistance of SS316L and TA2 were analyzed by electrochemical and Mott-Schottky tests.

22 citations


Journal ArticleDOI
TL;DR: In this article, the influence of bias voltage on surface microstructure of TiN films deposited on Ti substrate by multi-arc ion plating was systematically investigated and it was shown that the surface micro-structure depends strongly on the bias voltages.

Journal ArticleDOI
TL;DR: This study demonstrated that the Ohmic-like behaviors obtained after area-selective UV/ozone treatment improved the electrical properties of the 2D WSe2-based FETs such as the field-effect mobility and current on/off ratio, while maintaining the p-type normally-off characteristics.
Abstract: Development of two-dimensional (2D) semiconductor devices with good Ohmic contact is essential to utilize their full potential for nanoelectronics applications. Among the methods that have been introduced to reduce the Schottky barrier in 2D material-based electronic devices, charge transfer doping has attracted significant interest because of its efficiency, simplicity, and compatibility with the microelectronic fabrication process. In this study, 2D WSe2-based field-effect transistors (FETs) were subjected to selective UV/ozone treatment to improve the Ohmic contact by forming WOX with a high work function, which induced hole doping in the neighboring WSe2 via electron transfer. The atomic force microscopy, cross-sectional transmission electron microscopy, and micro-Raman spectroscopy analyses confirmed the self-limiting formation of WOX while maintaining the crystallinity of the underlying WSe2. The channel layer of the back-gated 2D WSe2 FETs was encapsulated using 2D hexagonal boron nitride to prevent the UV/ozone-induced oxidation. By contrast, the regions that were in contact with the underlying metal electrodes were open, which allowed area-selective p-doping in the 2D WSe2. Our study demonstrated that the Ohmic-like behaviors obtained after area-selective UV/ozone treatment improved the electrical properties of the 2D WSe2-based FETs such as the field-effect mobility (improvement of 3-4 orders of magnitude) and current on/off ratio (improvement of five orders of magnitude), while maintaining the p-type normally-off characteristics. These results provide useful insights into an effective and facile method to reduce contact resistance in 2D semiconductor materials, thereby enhancing the electrical performances of 2D material-based electronic devices.

Journal ArticleDOI
05 Aug 2021-ACS Nano
TL;DR: In this paper, a one-step growth approach was proposed to synthesize Nb-doped WSe2 with controllable doping concentration and metal/doped-semiconductor vdWHs.
Abstract: van der Waals heterostructures (vdWHs) of metallic (m-) and semiconducting (s-) transition-metal dichalcogenides (TMDs) exhibit an ideal metal/semiconductor (M/S) contact in a field-effect transistor. However, in the current two-step chemical vapor deposition process, the synthesis of m-TMD on pregrown s-TMD contaminates the van der Waals (vdW) interface and hinders the doping of s-TMD. Here, NbSe2/Nb-doped-WSe2 metal-doped-semiconductor (M/d-S) vdWHs are created via a one-step synthesis approach using a niobium molar ratio-controlled solution-phase precursor. The one-step growth approach synthesizes Nb-doped WSe2 with a controllable doping concentration and metal/doped-semiconductor vdWHs. The hole carrier concentration can be precisely controlled by controlling the Nb/(W + Nb) molar ratio in the precursor solution from ∼3 × 1011/cm2 at Nb-0% to ∼1.38 × 1012/cm2 at Nb-60%; correspondingly, the contact resistance RC value decreases from 10 888.78 at Nb-0% to 70.60 kΩ.μm at Nb-60%. The Schottky barrier height measurement in the Arrhenius plots of ln(Isat/T2) versus q/KBT demonstrated an ohmic contact in the NbSe2/WxNb1-xSe2 vdWHs. Combining p-doping in WSe2 and M/d-S vdWHs, the mobility (27.24 cm2 V-1 s-1) and on/off ratio (2.2 × 107) are increased 1238 and 4400 times, respectively, compared to that using the Cr/pure-WSe2 contact (0.022 cm2 V-1 s-1 and 5 × 103, respectively). Together, the RC value using the NbSe2 contact shows 2.46 kΩ.μm, which is ∼29 times lower than that of using a metal contact. This method is expected to guide the synthesis of various M/d-S vdWHs and applications in future high-performance integrated circuits.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate high performance "all-PtSe2" field effect transistors (FETs) completely free from Fermi level pinning and the absence of an effective doping method.
Abstract: Achieving a high-quality metal contact on two-dimensional (2D) semiconductors still remains a major challenge due to the strong Fermi level pinning and the absence of an effective doping method. Here, we demonstrate high performance "all-PtSe2" field-effect transistors (FETs) completely free from those issues, enabled by the vertical integration of a metallic thick PtSe2 source/drain onto the semiconducting ultrathin PtSe2 channel. Owing to its inherent thickness-dependent semiconductor-to-metal phase transition, the transferred metallic PtSe2 transforms the underlying semiconducting PtSe2 into metal at the junction. Therefore, a fully metallized source/drain and semiconducting channel could be realized within the same PtSe2 platform. The ultrathin PtSe2 FETs with PtSe2 vdW contact exhibits excellent gate tunability, superior mobility, and high ON current accompanied by one order lower contact resistance compared to conventional Ti/Au contact FETs. Our work provides a new device paradigm with a low resistance PtSe2 vdW contact which can overcome a fundamental bottleneck in 2D nanoelectronics.


Journal ArticleDOI
Baosen Mi1, Chen Zhuo1, Wang Quan1, Li Yifeifei1, Qin Ziwei1, Wang Hongbin1 
TL;DR: In this paper, C doped CrTiN films were deposited on 316L stainless steel by magnetron sputtering technology to investigate corrosion resistance and electrical conductivity, and the result of the potentiodynamic polarization test in the simulate PEMFC environment reveals that C-6A has the lowest current density, 6.09 × 10−7 A/cm2.

Journal ArticleDOI
TL;DR: In this paper, the position of the Fermi level on either side of the junction was modified by a systematic doping variation of the amorphous silicon and the transparent conductive oxide.
Abstract: Resistive losses in silicon heterojunction (SHJ) solar cells are partly linked to transport barriers at the amorphous silicon/crystalline silicon (a-Si:H/c-Si) and transparent conductive oxide (TCO)/a-Si:H interfaces. A key parameter is the position of the Fermi-level on either side of the junction which we modify by a systematic doping variation of the amorphous silicon and the transparent conductive oxide. We identify the charge carrier concentration to be the main driver for low contact resistance. For a-Si:H, this is achieved by using a sufficient but not too high doping gas concentration during deposition. For indium tin oxide (ITO) and aluminum zinc oxide (AZO), no or only a very low oxygen (O2) gas concentration during deposition is needed. We show that a stack of low-oxygen ITO interlayer and an oxygen-rich ITO “bulk” layer is not only an effective means to combine efficient transport and low TCO absorption but also to improve the thermal stability of the a-Si:H/TCO/metal contact resistivity ( ρc ). Such a layer stack helps to relax the constraints regarding the optoelectrical performance and improves the efficiency of SHJ solar cells.

Journal ArticleDOI
TL;DR: In this article, the top-contacted polypyrrole (PPy) electrodes are directly patterned on hydrophobic surfaces of organic semiconductors by microchannel templates.
Abstract: Conductive polymers are considered promising electrode materials for organic transistors, but the reported devices with conductive polymer electrodes generally suffer from considerable contact resistance. Currently, it is still highly challenging to pattern conductive polymer electrodes on organic semiconductor surfaces with good structure and interface quality. Herein, we develop an in situ polymerization strategy to directly pattern the top-contacted polypyrrole (PPy) electrodes on hydrophobic surfaces of organic semiconductors by microchannel templates, which is also applicable on diverse hydrophobic and hydrophilic surfaces. Remarkably, a width-normalized contact resistance as low as 1.01 kΩ·cm is achieved in the PPy-contacted transistors. Both p-type and n-type organic field-effect transistors (OFETs) exhibit ideal electrical characteristics, including almost hysteresis-free, low threshold voltage, and good stability under long-term test. The facile patterning method and high device performance indicate that the in situ polymerization strategy in confined microchannels has application prospects in all-organic, transparent, and flexible electronics.

Journal ArticleDOI
Hui Yang1, Sa Cai1, Yifei Zhang1, Dongping Wu1, Xiaosheng Fang1 
TL;DR: In this article, an e-beam lithography-free method to fabricate MoS2 FETs by employing maze-like source/drain electrodes was introduced, and an ohmic contact was achieved without annealing.
Abstract: Molybdenum disulfide (MoS2) as a two-dimensional semiconductor material has been actively explored for field-effect-transistors (FETs). The current prevailing method for MoS2 FET fabrication involves multiple complex steps, including electron beam (e-beam) lithography, annealing, etc., which are time-consuming and require polymer resists. As a consequence, the MoS2 exposed to chemicals during the patterning process may be unfavorably affected by residues and the performance of the final FET could be impaired while the annealing limits materials for FETs. Therefore, there is an urgent need to free the fabrication of FETs from e-beam lithography and annealing. In this study, we introduce an e-beam lithography-free method to fabricate MoS2 FETs by employing maze-like source/drain electrodes. In addition, an ohmic contact in multilayer MoS2 FETs using chromium (Cr) as source/drain electrodes is achieved without annealing. The underlying mechanism for contact performance is studied, and the tightness of the contact and the type of metal are found to be responsible because they determine the contact resistance. Furthermore, the long-term device degradation is explored, in which the oxidation of metal dominates. The facile fabrication process and mechanism explanation in this work might provide a new platform for future electronic devices.

Journal ArticleDOI
TL;DR: In this paper, the scaling behavior of large-area grown MoS2 material with channel length down to 30nm and capacitive effective oxide thickness (CET) down to 1.9nm was investigated.
Abstract: Two-dimensional semiconducting materials are considered as ideal candidates for ultimate device scaling. However, a systematic study on the performance and variability impact of scaling the different device dimensions is still lacking. Here we investigate the scaling behavior across 1300 devices fabricated on large-area grown MoS2 material with channel length down to 30 nm, contact length down to 13 nm and capacitive effective oxide thickness (CET) down to 1.9 nm. These devices show best-in-class performance with transconductance of 185 μS/μm and a minimum subthreshold swing (SS) of 86 mV/dec. We find that scaling the top-contact length has no impact on the contact resistance and electrostatics of three monolayers MoS2 transistors, because edge injection is dominant. Further, we identify that SS degradation occurs at short channel length and can be mitigated by reducing the CET and lowering the Schottky barrier height. Finally, using a power performance area (PPA) analysis, we present a roadmap of material improvements to make 2D devices competitive with silicon gate-all-around devices.

Journal ArticleDOI
TL;DR: In this article, a 2.3kW high-power diode laser was used to alloy a commercially pure copper (cp Cu) with NiTi powder to attain higher corrosion and electrical wear resistances.
Abstract: With a 2.3-kW high-power diode laser, laser surface alloying of a commercially pure copper (cp Cu) with NiTi powder was carried out to attain higher corrosion and electrical wear resistances. Potentiodynamic polarization was conducted in simulated acid rain (SAR) at 25 °C for simulating the corrosive environment. In the SAR, corrosion potentials of all laser-alloyed samples are found to be nobler than those of cp Cu and NiTi alloy and their corrosion current densities are lower than that of cp Cu although their oxide layers are less uniform. Electrical wear tests were also carried out in both dry and wet conditions with a pin-on-disc tribometer. The electrical wear resistances of the laser-alloyed samples in wet condition are higher than in dry condition due to lubrication effect and reduction in frictional heat. The electrical wear resistances of all laser-alloyed samples were improved as compared with cp Cu owing to the presence of pseudo-plasticity of B19′ and hard IMPs, and work hardening effect during electrical wear. The contribution of electrical wear in SAR is mainly mechanical wear, and wear-corrosion synergism up to 36.1%, while corrosion is negligible. Compared with cp Cu, the interfacial contact resistance of the laser-alloyed samples at 50 N/cm2 has increased from 3.5 to 7.2 times.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a simple and efficient numerical model to account for thermal contact resistance at immersed interfaces in multi-material heat transfer, which was validated through different test cases, including steady and unsteady conduction, and applied to simulation of chill cooling and solidification of a steel sample on board the International Space Station.

Journal ArticleDOI
TL;DR: In this paper, high temperature brazing material is used as a filler that enables direct bonding of TE legs to the copper electrode without metallizing legs, which improves the TEG performance and stability at high temperatures by minimizing the contact resistance and diffusion at TE leg/electrode interface.

Journal ArticleDOI
15 Oct 2021-Carbon
TL;DR: In this article, the authors demonstrate metal-induced doping of graphene in graphene-ruthenium hybrid structures, which provides a viable and practical basis for integrating graphene as a conductor in advanced interconnects.

Journal ArticleDOI
TL;DR: In this article, the authors demonstrate the lateral metal-oxidesemiconductor field effect transistors (MOSFETs) with β-Ga2O3 film (thickness) grown on a c-plane sapphire substrate by a hydride vapor phase epitaxy (HVPE) method using a CF4-based plasma treatment.

Journal ArticleDOI
Wurui Ta1, Suming Qiu1, Yulong Wang1, Jinyu Yuan1, Yuanwen Gao1, Youhe Zhou1 
TL;DR: In this paper, a volumetric contact theory is developed that is valid for investigating electro-mechanical contact properties between random rough surfaces, including the contact resistance formula and the elastic and elastoplastic electrical contact models.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate a method to mitigate current crowding, by engineering the interface layer properties and geometry, based on a self-consistent transmission-line model, and show that the distribution of the contact current greatly depends on the properties of the interfacial layer between two contacting members.
Abstract: Highly conductive nanoscale electrical contacts suffer from strong current crowding at the contact edges, which can lead to nonuniform heat deposition; the formation of local hot spots, aggravation of electromigration; and, in the worst-case scenario, lead to thermal runaway and breakdown of the device. These effects severely affect the overall device properties, reliability, and lifetime. Devices based on thin-film junctions, nanotubes or nanowires, and two-dimensional (2D) materials are especially sensitive to current transport at electrical contacts, due to their reduced dimensions and increased geometrical confinement for current flow. Here, we demonstrate a method to mitigate current crowding, by engineering the interface layer properties and geometry. Based on a self-consistent transmission-line model, we show that the distribution of the contact current greatly depends on the properties of the interfacial layer between two contacting members. Current steering and redistribution can be realized by strategically designing the specific contact resistivity, ${\ensuremath{\rho}}_{c}$, along the contact length. For similar contact members, parabolically varying ${\ensuremath{\rho}}_{c}$ along the contact interface significantly reduces the edge-current crowding in ohmic contacts. Similarly, the nonuniform current distribution of 2D semiconductor-3D metal contacts can be decreased, and the current-transfer length can be increased by varying the Schottky barrier height along the interface. It is also found that introducing a nanometer- or subnanometer-scale thin insulating tunneling gap between contact members can greatly reduce current crowding, while maintaining a similar total contact resistance.

Journal ArticleDOI
TL;DR: In this paper, the intrinsic quantum limit of width-normalized contact resistance with 1D edge metal contacts was calculated and the authors showed that the limit depends on GNR dimensions, decreasing with width downscaling to ~3 Ω∙µm in 0.4 nm-wide GNRs, and increasing with length downcaling up to ~30 Ω ∼30 µm in 5 nm-long GNRs.
Abstract: Graphene has attracted a lot of interest as a potential replacement for silicon in future integrated circuits due to its remarkable electronic and transport properties. In order to meet technology requirements for an acceptable bandgap, graphene needs to be patterned into graphene nanoribbons (GNRs), while one-dimensional (1D) edge metal contacts (MCs) are needed to allow for the encapsulation and preservation of the transport properties. While the properties of GNRs with ideal contacts have been studied extensively, little is known about the electronic and transport properties of GNRs with 1D edge MCs, including contact resistance (RC), which is one of the key device parameters. In this work, we employ atomistic quantum transport simulations of GNRs with MCs modeled with the wide-band limit (WBL) approach to explore their metallization effects and contact resistance. By studying density of states (DOS), transmission and conductance, we find that metallization decreases transmission and conductance, and either enlarges or diminishes the transport gap depending on GNR dimensions. We calculate the intrinsic quantum limit of width-normalized RC and find that the limit depends on GNR dimensions, decreasing with width downscaling to ~3 Ω∙µm in 0.4 nm-wide GNRs, and increasing with length downscaling up to ~30 Ω∙µm in 5 nm-long GNRs. The worst-case total RC is only ~40 Ω∙µm, which demonstrates that there is room for RC improvement in comparison to the published experimental data, and that GNRs present a promising channel material for future extremely-scaled electronic nanodevices.

Journal ArticleDOI
TL;DR: In this article, an ultra-thin TiN film is deposited on the surface of LiNi0.8Co0.1O2 (NCM811) particle by atomic layer deposition (ALD) to improve the electrochemical performance.

Journal ArticleDOI
30 Oct 2021-Carbon
TL;DR: In this article, Boron and nitrogen atoms were introduced into the hexagonal carbon lattice of the CNTs through judicious combination of high temperature thermal doping and plasma treatment.