Quantitative Experimental Analysis of Schottky Barriers and Poole–Frenkel Emission in Carbon Nanotube Devices

Perello, D.,Dong Jae Bae,Kim, M.J.,DongKyu Cha,Seung Yol Jeong,Bo Ram Kang,Woo Jong Yu,He Younge Lee,Minhee Yun IEEE 2009 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol.8 No.3

<P>In this paper, we investigated carbon nanotube FETs (CNT FETs) utilizing semiconducting single-walled CNTs (SWCNTs). Multiple devices, each of different metal source and drain contacts, were fabricated on a single SWCNT. Over specific temperature regimes, transport properties of the devices were found to be consistent with the Bethe theory of thermionic emission for Schottky contacts, and the Poole-Frenkel emission was dependent on the device position. As was expected, transport from thermionic emission over the barrier was found to be the dominant mechanism. Barriers of 25-41 meV were present, as found by activation energy analysis for temperatures ranging from 20 to 300 K for the devices. A Schottky diode was also fabricated on a separate nanotube using an ohmic contact at the Pd source and a Schottky contact for the Ag drain electrode. Assuming the same physical assumptions for an Si semiconductor device, the results indicate an ideality factor greater than 2, Schottky barrier of ~0.37 eV, and image charge lowering of ~0.1 eV.</P>

Analysis of hopping conduction in semiconducting and metallic carbon nanotube devices

Perello, David J.,Yu, Woo Jong,Bae, Dong Jae,Chae, Seung Jin,Kim, M. J.,Lee, Young Hee,Yun, Minhee American Institute of Physics 2009 JOURNAL OF APPLIED PHYSICS - Vol.105 No.12

Anomalous Schottky Barriers and Contact Band-to-Band Tunneling in Carbon Nanotube Transistors

Perello, David J.,ChuLim, Seong,Chae, Seung Jin,Lee, Innam,Kim, Moon. J.,Lee, Young Hee,Yun, Minhee American Chemical Society 2010 ACS NANO Vol.4 No.6

<P>Devices incorporating nanoscale materials, particularly carbon nanotubes (CNTs), offer exceptional electrical performance. Absent, however, is an experimentally backed model explaining contact-metal work function, device layout, and environment effects. To fill the void, this report introduces a surface-inversion channel model based on low temperature and electrical measurements of a distinct single-walled semiconducting CNT contacted by Hf, Cr, Ti, and Pd electrodes. Anomalous barrier heights and metal-contact dependent band-to-band tunneling phenomena are utilized to show that, dependent upon contact work function and gate field, transport occurs either directly between the metal and CNT channel or indirectly <I>via</I> injection of carriers from the metal-covered CNT region to the CNT channel. The model is consistent with previously contradictory experimental results, and the methodology is simple enough to apply in other contact-dominant systems.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2010/ancac3.2010.4.issue-6/nn100328a/production/images/medium/nn-2010-00328a_0002.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn100328a'>ACS Electronic Supporting Info</A></P>

Thermionic Field Emission Transport in Carbon Nanotube Transistors

Perello, David J.,Lim, Seong Chu,Chae, Seung Jin,Lee, Innam,Kim, Moon. J.,Lee, Young Hee,Yun, Minhee American Chemical Society 2011 ACS NANO Vol.5 No.3

<P>With experimental and analytical analysis, we demonstrate a relationship between the metal contact work function and the electrical transport properties saturation current (<I>I</I><SUB>sat</SUB>) and differential conductance (σ<SUB>sd</SUB> = ∂<I>I</I><SUB>sd</SUB>/∂<I>V</I><SUB>sd</SUB>) in ambient exposed carbon nanotubes (CNT). A single chemical vapor deposition (CVD) grown 6 mm long semiconducting single-walled CNT is electrically contacted with a statistically significant number of Hf, Cr, Ti, Pd, and Au electrodes, respectively. The observed exponentially increasing relationship of <I>I</I><SUB>sat</SUB> and σ<SUB>sd</SUB> with metal contact work function is explained by a theoretical model derived from thermionic field emission. Statistical analysis and spread of the data suggest that the conduction variability in same CNT devices results from differences in local surface potential of the metal contact. Based on the theoretical model and methodology, an improved CNT-based gas sensing device layout is suggested. A method to experimentally determine gas-induced work function changes in metals is also examined.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-3/nn102343k/production/images/medium/nn-2010-02343k_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn102343k'>ACS Electronic Supporting Info</A></P>

Through-and-through Nasal Reconstruction with the Bi-Pedicled Forehead Flap

Agostini, Tommaso,Perello, Raffaella,Russo, Giulia Lo,Spinelli, Giuseppe Korean Society of Plastic and Reconstructive Surge 2013 Archives of Plastic Surgery Vol.40 No.6

Background Nasal reconstruction is one of the most difficult challenges for the head and neck surgeon, especially in the case of complex full thickness defects following malignant skin tumor resection. Full-thickness defects require demanding multi-step reconstruction. Methods Seven patients underwent surgical reconstruction of full-thickness nasal defects with a bi-pedicled forehead flap shaped appropriately to the defect. Patients were aged between 58 and 86 years, with a mean age of 63.4 years. All of the tumors were excised using traditional surgery, and in 4 of the patients, reconstruction was performed simultaneously following negativity of fresh frozen sections of the margins under general anesthesia. Results Nasal reconstruction was well accepted by all of the patients suffering non-melanoma skin tumors with acceptable cosmetic outcomes. The heart-shaped forehead flap was harvested in cases of subtotal involvement of the nasal pyramid, while smaller defects were reconstructed with a wing-shaped flap. No cartilaginous or osseous support was necessary. Conclusions This bi-pedicled forehead flap was a valid, versatile, and easy-to-implement alternative to microsurgery or multi-step reconstruction. The flap is the best indication for full-thickness nasal defects but can also be indicated for other complex facial defects in the orbital (exenteratio orbitae), zygomatic, and cheek area, for which the availability of a flap equipped with two thick and hairless lobes can be a valuable resource.

Determining the Fermi level by absorption quenching of monolayer graphene by charge transfer doping

Adhikari, S.,Perello, D.,Biswas, C.,Ghosh, A.,Luan, N.,Park, J.,Yao, F.,Rotkin, S.,Lee, Y. Royal Society of Chemistry 2016 Nanoscale Vol.8 No.44

<P>While optical properties of graphene in the visible region are solely defined by the frequency-independent fine structure constant, an onset of absorption has been observed in the infrared region due to Pauli blocking of interband transitions. Here, we report a complete absorption quenching in the infrared region by coating graphene with bis(trifluoromethanesulfonyl)amine (TFSA), an optically transparent p-type chemical dopant. The Fermi level downshift due to TFSA doping results in enhanced transmission in the infrared region proportional to the doping concentration. An absorption quenching onset method, developed in our work, to extract the Fermi level shift in pristine and doped graphene agrees with values extracted from Raman G-band and 2D-band shifts, Hall measurements and the binding energy shift observed in X-ray photo-electron spectroscopy. Performing simple UV-visible transmittance spectroscopy to obtain the absorption quenching onset of graphene also allows detection of environmental and substrate effects via Fermi level shift. Our method opens up the practical implementation of this unique phenomenon of graphene in future optoelectronic devices.</P>

Chirality-specific transport phenomena of isolated single-walled carbon nanotube

Jeong, Seung Yol,Perello, David,Kim, Sung Jin,Jang, Jin Ho,Kang, Bo Ram,Yu, Woo Jong,Bae, Dong Jae,Yun, Minhee,Lee, Young Hee WILEY-VCH Verlag 2007 Physica Status Solidi. B Vol.244 No.11

<P>Single-walled carbon nanotube-field effect transistors (SWCNT-FETs) have been fabricated using in-situ thermal chemical vapor deposition. For isolated devices, the resonant Raman spectra confirmed that the full width at half maximum (FWHM) of the radial breathing mode (RBM) peaks was about 4 cm<SUP>–1</SUP>, consistent with atomic force microscopy (AFM) images that clearly revealed the individually isolated SWCNTs on the patterned substrate with a diameter of 1.3 nm. Subsequent I –V measurements of the SWCNT-FET revealed a clear gating effect for samples with semiconducting SWCNTs. The transport phenomena of a device with mixed metallic and semiconducting SWCNTs network were governed by the metallic nanotube with severely suppressed gate modulation. Identification of the chirality of SWCNTs by resonant Raman spectroscopy prior to the I –V characteristics guarantees the validity of working FET devices. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>

Through-and-through Nasal Reconstruction with the Bi-Pedicled Forehead Flap

Tommaso Agostini,Raffaella Perello,Giulia Lo Russo,Giuseppe Spinelli 대한성형외과학회 2013 Archives of Plastic Surgery Vol.40 No.6

Background Nasal reconstruction is one of the most difficult challenges for the head and neck surgeon, especially in the case of complex full thickness defects following malignant skin tumor resection. Full-thickness defects require demanding multi-step reconstruction. Methods Seven patients underwent surgical reconstruction of full-thickness nasal defects with a bi-pedicled forehead flap shaped appropriately to the defect. Patients were aged between 58 and 86 years, with a mean age of 63.4 years. All of the tumors were excised using traditional surgery, and in 4 of the patients, reconstruction was performed simultaneously following negativity of fresh frozen sections of the margins under general anesthesia. Results Nasal reconstruction was well accepted by all of the patients suffering non-melanoma skin tumors with acceptable cosmetic outcomes. The heart-shaped forehead flap was harvested in cases of subtotal involvement of the nasal pyramid, while smaller defects were reconstructed with a wing-shaped flap. No cartilaginous or osseous support was necessary. Conclusions This bi-pedicled forehead flap was a valid, versatile, and easy-to-implement alternative to microsurgery or multi-step reconstruction. The flap is the best indication for full-thickness nasal defects but can also be indicated for other complex facial defects in the orbital (exenteratio orbitae), zygomatic, and cheek area, for which the availability of a flap equipped with two thick and hairless lobes can be a valuable resource.

Influence of Concomitant Food Intake on the Excretion of Orally Administered myo-Inositol Hexaphosphate in Humans

F. Grases,A. Costa-Bauza,J. Perello,B. Isern,I. Vucenik,M. Valiente,J.A. Munoz,R.M. Prieto 한국식품영양과학회 2006 Journal of medicinal food Vol.9 No.1

myo-Inositol hexaphosphate (InsP6) widely occurs in plant seeds. At present, some important benefits of InsP6for human health have been described. The purpose of this study was to find the best condition for the optimum absorptionof orally administered InsP6, evaluated by InsP6 urinary excretion. The influence of different stomach conditions (empty,empty with an alkalinizing agent, and full stomach) on the effects of oral administration of InsP6 and its urinary excretionwas investigated in six healthy subjects on an InsP6-poor diet, given 400 mg of calcium/magnesium salt of InsP6 as a singledose. The basal urinary excretion of InsP6 on an InsP6-poor diet (50.91. 15.09 .g) was significantly lower than that foundwhen an InsP6-normal diet was consumed (100.09. 26.42 .g) (P. .05). No differences were observed in the areas underthe curve of accumulated excretion at 8 hours among the three different stomach conditions studied, suggesting that the over-all InsP6 absorption took place independently of the stomach state (full or fasted) and indicating that the InsP6 absorption alsotakes place during the intestinal transit. Thus, if InsP6 supplements of vegetal origin are consumed to maintain the optimumInsP6 levels needed for a healthy status, these supplements can be consumed either during or between meals with the sameefficacy.

Room Temperature Semiconductor-Metal Transition of MoTe₂ Thin Films Engineered by Strain

Song, Seunghyun,Keum, Dong Hoon,Cho, Suyeon,Perello, David,Kim, Yunseok,Lee, Young Hee American Chemical Society 2016 NANO LETTERS Vol.16 No.1

<P>We demonstrate a room temperature semiconductor-metal transition in thin film MoTe2 engineered by strain. Reduction of the 2H-1T' phase transition temperature of MoTe2 to room temperature was realized by introducing a tensile strain of 0.2%. The observed first-order SM transition improved conductance similar to 10 000 times and was made possible by an unusually large temperature-stress coefficient, which results from a large volume change and small latent heat. The demonstrated strain-modulation of the phase transition temperature is expected to be compatible with other TMDs enabling the 2D electronics utilizing polymorphism of TMDs along with the established materials.</P>