Graphene single crystals with dimensions of up to 0.5 mm on a side were grown by low-pressure chemical vapor deposition in copper-foil enclosures using methane as a precursor. Low-energy electron ...microscopy analysis showed that the large graphene domains had a single crystallographic orientation, with an occasional domain having two orientations. Raman spectroscopy revealed the graphene single crystals to be uniform monolayers with a low D-band intensity. The electron mobility of graphene films extracted from field-effect transistor measurements was found to be higher than 4000 cm2 V−1 s−1 at room temperature.
Field-effect transistors fabricated on graphene grown by chemical vapor deposition (CVD) often exhibit large hysteresis accompanied by low mobility, high positive backgate voltage corresponding to ...the minimum conductivity point (V min), and high intrinsic carrier concentration (n 0). In this report, we show that the mobility reported to date for CVD graphene devices on SiO2 is limited by trapped water between the graphene and SiO2 substrate, impurities introduced during the transfer process and adsorbates acquired from the ambient. We systematically study the origin of the scattering impurities and report on a process which achieves the highest mobility (μ) reported to date on large-area devices for CVD graphene on SiO2: maximum mobility (μmax) of 7800 cm2/(V·s) measured at room temperature and 12 700 cm2/(V·s) at 77 K. These mobility values are close to those reported for exfoliated graphene on SiO2 and can be obtained through the careful control of device fabrication steps including minimizing resist residue and non-aqueous transfer combined with annealing. It is also observed that CVD graphene is prone to adsorption of atmospheric species, and annealing at elevated temperature in vacuum helps remove these species.
Oral potentially malignant disorders (OPMD) are oral mucosal disorders which have a high potential to turn into malignancy. A recent report suggests that 16%-62% of epithelial dysplasia cases of OPMD ...undergo malignant transformation, showing the need for early detection of malignancy in these disorders. Micro RNA (miRNA) plays an important role in cellular growth, differentiation, apoptosis, and immune response, and hence, deregulation of miRNA is considered a signature of oral carcinogenesis. A search was done using MeSH terms in the PubMed, ScienceDirect databases, hand search, and finally, six studies were included in this systematic review. A total of 167 patients with oral cancer, 78 with OPMDs, 147 healthy controls, and 20 disease controls were analyzed for the expression of salivary miRNAs. Quality assessment based on the Quality Assessment of Diagnostic Accuracy Studies 2 tool was used to obtain a risk of bias chart using Revman 5.3 software and it was proved that the study done by Zahran et al. in 2015 had a low risk of bias. The results of this study revealed upregulated miRNA 184 with an area under the curve (AUC) of 0.86 and miRNA 21 with an AUC of 0.73 and downregulated miRNA 145 with an AUC of 0.68, which proved that these miRNAs are significant in detecting early malignancy in OPMD and should be further analyzed in various populations. This systematic review explored the potential of expression of salivary miRNA in OPMD for future studies. This could pave the way to utilize saliva as a surrogate marker in diagnosing early malignant changes in OPMD.
Hexagonal boron nitride (h-BN) has been considered a promising dielectric for two-dimensional (2D) material-based electronics due to its atomically smooth and charge-free interface with an in-plane ...lattice constant similar to that of graphene. Here, we report atomic layer deposition of boron nitride (ALD-BN) using BCl3 and NH3 precursors directly on thermal SiO2 substrates at a relatively low temperature of 600 °C. The films were characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron microscopy wherein the uniform, atomically smooth, and nanocrystalline layered-BN thin film growth is observed. The growth rate is ∼0.042 nm/cycle at 600 °C, a temperature significantly lower than that of h-BN grown by chemical vapor deposition. The dielectric properties of the ALD-BN measured from Metal Oxide Semiconductor Capacitors are comparable with that of SiO2. Moreover, the ALD-BN exhibits a 2-fold increase in carrier mobility of graphene field effect transistors (G-FETs/ALD-BN/SiO2) due to the lower surface charge density and inert surface of ALD-BN in comparison to that of G-FETs fabricated on bare SiO2. Therefore, this work suggests that the transfer-free deposition of ALD-BN on SiO2 may be a promising candidate as a substrate for high performance graphene devices.
Controlled synthesis of graphite at low temperatures is a desirable process for a number of applications. Here, we present a study on the growth of thin graphite films on polycrystalline Ni films at ...low temperatures, about 380 °C, using inductively coupled plasma enhanced chemical vapor deposition. Raman analysis shows that the grown graphite films are of good quality as determined by a low I D / I G ratio, ∼0.43, for thicknesses ranging from a few layers of graphene to several nanometer thick graphitic films. The growth of graphite films was also studied as a function of time, precursor gas pressure, hydrogen concentration, substrate temperature and plasma power. We found that graphitic films can be synthesized on polycrystalline thin Ni films on SiO 2 /Si substrates after only 10 seconds at a substrate temperature as low as 200 °C. The amount of hydrogen radicals, adjusted by changing the hydrogen to methane gas ratio and pressure, was found to dramatically affect the quality of graphite films due to their dual role as a catalyst and an etchant. We also find that a plasma power of about 50 W is preferred in order to minimize plasma induced graphite degradation.
Silicon-on-insulator (SOI) technology offers many advantages for transistors while also presenting significant challenges in thermal management. The buried oxide (BOX) layer impedes vertical heat ...dissipation, rendering conventional cooling solutions based on air and liquid coolers inefficient. In this study, we propose a novel theoretical design of a holey silicon-based lateral thermoelectric cooler (TEC) that provides a unique cooling solution for SOI transistors. By redistributing heat laterally, this TEC overcomes the limitation of poor vertical heat dissipation caused by the BOX layer, meanwhile taking advantage of the sustained temperature gradient in the device layer. In addition, we present a novel precooling strategy which utilizes a long-time, optimal-voltage TEC cooling pulse to cool down a short-time, high-power-density heating pulse. We evaluate the cooling performance through simulation of two devices: an SOI transistor-TEC device and a <inline-formula> <tex-math notation="LaTeX">5\times5 </tex-math></inline-formula> SOI transistor-TEC array device. Under a 10 <inline-formula> <tex-math notation="LaTeX">\mu \text{s} </tex-math></inline-formula> transient heat pulse with high-power density of 11000 W/cm2 (1.6 W), the SOI transistor-TEC device with a 10 <inline-formula> <tex-math notation="LaTeX">\mu \text{m} </tex-math></inline-formula> thick BOX layer can be cooled from 465.7 °C down to 407.4 °C (<inline-formula> <tex-math notation="LaTeX">\Delta {T} </tex-math></inline-formula> = 58.3 °C) in peak hotspot temperature when precooled with a 1000 <inline-formula> <tex-math notation="LaTeX">\mu \text{s} </tex-math></inline-formula> TEC pulse, consuming 0.20 W of TEC power. Furthermore, the SOI transistor-TEC array device provides spatial temperature control by incorporating multiple coolers which enable selective cooling for individual transistor units without significant loss of cooling performance. In summary, our TEC design exhibits great potential in offering dynamic thermal management for a wide range of advanced SOI devices.
The fundamental properties of graphene are making it an attractive material for a wide variety of applications. Various techniques have been developed to produce graphene and recently we discovered ...the synthesis of large area graphene by chemical vapor deposition (CVD) of methane on Cu foils. We also showed that graphene growth on Cu is a surface-mediated process and the films were polycrystalline with domains having an area of tens of square micrometers. In this paper, we report on the effect of growth parameters such as temperature, and methane flow rate and partial pressure on the growth rate, domain size, and surface coverage of graphene as determined by Raman spectroscopy, and transmission and scanning electron microscopy. On the basis of the results, we developed a two-step CVD process to synthesize graphene films with domains having an area of hundreds of square micrometers. Scanning electron microscopy and Raman spectroscopy clearly show an increase in domain size by changing the growth parameters. Transmission electron microscopy further shows that the domains are crystallographically rotated with respect to each other with a range of angles from about 13 to nearly 30°. Electrical transport measurements performed on back-gated FETs show that overall films with larger domains tend to have higher carrier mobility up to about 16 000 cm2 V−1 s−1 at room temperature.
Phishing is a fraudulent scheme to steal a user's personal and confidential information by masking as a trustworthy entity in the electronic commerce. Phishers lure online users to visit their fake ...webpages and capture the user's sensitive financial information. The current anti-phishing technique focuses on determining the legitimacy of the webpages that the user visits, and it alerts users with a phishing label when a webpage is found to have suspicious activity. Most of the times, however, these warnings are ignored by the users as there is no significant information present in the alerts except for the phishing label. The method proposed in this paper addresses the aforementioned lacunae by generating a coherent and complete explanation in the natural language text for the anti-phishing system's decision. The explanation includes the phishing label along with information to establish why such a decision has been taken. This would, in turn, contribute to the user's enhanced understanding of the threat and also strengthens the user's trust in the system. It is quite evident from the pilot evaluation, which involved 50 users, that the proposed methodology significantly improves the user's understanding of the phishing label and strengthens their trust in the system.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Matrix metalloproteinase-9 (MMP-9) is an inducible enzyme. Oral potentially malignant disorders (OPMDs) are considered as the early tissue changes that happen due to various habits such as smoking ...tobacco, chewing tobacco or stress. This alteration in the tissues alters the expression of MMP-9. The rationale of the review is to know the expression of MMP-9 in OPMDs. Hand searching and electronic databases such as PubMed and ScienceDirect were done for mesh terms such as OPMDs and MMP-9. Eight articles were obtained, after applying inclusion and exclusion criteria. These articles were assessed with QUADAS and data were extracted and evaluated. The included eight studies were done in 182 oral squamous cell carcinoma cases, 430 OPMDs (146 oral lichen planus, 264 leukoplakia and 20 oral submucous fibrosis) and 352 healthy controls evaluated for MMP-9. MMP-9 expression was found to be elevated in tissue, serum and saliva samples of OPMDs than in healthy controls. There is only one study in each serum and saliva samples to evaluate MMP-9. Saliva being noninvasive and serum being minimally invasive, more studies need to be done in both serum and saliva to establish MMP-9 as an early diagnostic marker in OPMDs to know its potential in malignant transformation.
The transport properties of graphene field effect transistors are typically characterized using a conventional test structure consisting of graphene on silicon dioxide with deposited metal contacts. ...Two of the primary parameters affecting the total resistance of this structure are the channel mobility and contact resistance. A simple model is used to describe the impact of these parameters on total device resistance and experimentally extract them. Important issues related to characterizing the transport properties of graphene field effect transistors are presented and discussed.
► Issues related to characterizing transport of graphene transistors are presented. ► The maximum resistance of a graphene device cannot be strongly changed. ► The minimum resistance for quality graphene is limited by the contact resistance. ► An explanation for the length and width dependence of mobility is presented. ► The saturated resistance of a graphene device is the contact resistance.
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