Contact and Channel Resistances of Ballistic and Non-ballistic Carbon-nanotube Field-effect Transistors

Jong-Myeon Park,Shin-Nam Hong 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.2

Recently, many research has been conducted on the carbon-nanotube field-effect transistors (CNFETs) in expectation that the CNFETs could replace metal-oxide-semiconductor field-effect transistors (MOSFETs) in the sub-10-nm era. In consideration of both ballistic conduction and nonballistic conduction, including elastic scattering, optical phonon scattering, and acoustic phonon scattering, this paper presents the simulated dependence of the coaxially-gated single-walled semiconducting CNFET characteristics on the contact and the channel lengths. When the contact length was longer than 100 nm, the CNFETs showed a constant minimal value of the contact resistance. In this case, the saturated drain current was higher than that of CNFETs with a shorter contact length. When the channel was longer than 600 nm, the channel resistance was significantly increased due to acoustic phonon scattering. When the channel was shorter than 200 − 250 nm with optical scattering, acoustic scattering or all three scattering mechanisms taken into account, the contact resistance began to become larger than channel resistance.

Efficient compact model for calculating the surface potential of carbon-nanotube field-effect transistors using a curve-fitting method

박종면,홍신남 한국물리학회 2015 Current Applied Physics Vol.15 No.8

This paper presents an analytical method to compute the surface potential of ballistic metal-oxide semiconductor field-effect transistor (MOSFET)-like carbon-nanotube field-effect transistors (CNFETs). The proposed compact model considers the surface potential as functions of the carbon-nanotube diameter, gate insulator thickness, gate voltage and drain voltage. One of the advantages of this model is that there is no need to refer to the numerical model to recalculate the surface potential each time nanotube diameter or insulator thickness is changed. Instead of using a constant smoothing parameter regardless of the device size and applied bias voltages, a parameter calculated for the specific situations is employed to provide the simulation results with higher accuracy. The validity of the proposed model was verified by comparing the simulated output characteristics of three CNFETs with those of the numerical model and the previous compact model.

A Field Effect Transistor Fabricated with Metallic Single-Walled Carbon Nanotubes

Na, Pil Sun,Park, Noejung,Kim, Jinhee,Kim, Hyojin,Kong, Ki-Jeong,Chang, Hyunju,Lee, Jeong-O Taylor Francis 2006 Fullerenes, nanotubes, and carbon nanostructures Vol.14 No.2

<P> We report novel transport properties of the individual single-walled carbon nanotube (SWNT) field effect transistors (FETs) decorated with the protein (streptavidin)-coated nanoparticles. Upon adsorption of the protein-coated nanoparticles at the metal-nanotube contact, the metallic SWNT devices abruptly exhibit a p-type semiconducting behavior. In the case of semiconducting SWNT devices, the adsorptions of protein-coated nanoparticles make the gating more effective, resulting in a far suppressed off-state leakage current as well as an enhanced on-state p-channel current. Through the ab initio electronic structure calculations, it is suggested that such an apparent metal-semiconductor transition may be due to the intervening charged species in the contact area, originated from the surface of the proteins. Noting the separation of the semiconducting nanotubes from metallic ones would be a formidable task; we suggest that the device concept here could be another breakthrough for the nanotube-based electronic devices, in which the nanotubes are not necessarily semi-conducting.</P>

Effect of Polymer Gate Dielectrics on Charge Transport in Carbon Nanotube Network Transistors: Low-<i>k</i> Insulator for Favorable Active Interface

Lee, Seung-Hoon,Xu, Yong,Khim, Dongyoon,Park, Won-Tae,Kim, Dong-Yu,Noh, Yong-Young American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.47

<P>Charge transport in carbon nanotube network transistors strongly depends on the properties of the gate dielectric that is in direct contact with the semiconducting carbon nanotubes. In this work, we investigate the dielectric effects on charge transport in polymer-sorted semiconducting single-walled carbon nanotube field-effect transistors (s-SWNT-FETs) by using three different polymer insulators: A low-permittivity (epsilon(r)) fluoropolymer (CYTOP, epsilon(r) = 1.8), poly(methyl methacrylate) (PMMA, epsilon(r) = 3.3), and a high-epsilon(r) ferroelectric relaxor [P(VDF-TrFE-CTFE), epsilon(r) = 14.2]. The s-SWNT-FETs with polymer dielectrics show typical ambipolar charge transport with high ON/OFF ratios (up to similar to 10(5)) and mobilities (hole mobility up to 6.77 cm(2) V-1 s(-1) for CYTOP). The s-SWNT-FET with the lowest-k dielectric, CYTOP, exhibits the highest mobility owing to formation of a favorable interface for charge transport, which is confirmed by the lowest activation energies, evaluated by the fluctuation-induced tunneling model (FIT) and the traditional Arrhenius model (E-aFIT = 60.2 meV and E-aArr = 10 meV). The operational stability of the devices showed a good agreement with the activation energies trend (drain current decay similar to 14%, threshold voltage shift similar to 0.26 V in p-type regime of CYTOP devices). The poor performance in high-epsilon(r) devices is accounted for by a large energetic disorder caused by the randomly oriented dipoles in high-k dielectrics. In conclusion, the low-k dielectric forms a favorable interface with s-SWNTs for efficient charge transport in s-SWNT-FETs.</P>

전도성 그래핀 페이스트로 제작된 전극을 이용한 완전탄소 기반 플렉시블 전계효과 트랜지스터

김병국,오현수,정수연,정승열,윤영 한국마린엔지니어링학회 2019 한국마린엔지니어링학회지 Vol.43 No.6

탄소나노물질인 탄소나노튜브와 그래핀은 높은 전하 이동도, 화학적 안정성, 훌륭한 유연성 등의 우수한 특성을가지고 있으므로 유연한 전자장치 개발에 활발히 연구되고 있다. 본 논문에서는 전도성 그래핀 페이스트 용액 공정을이용하여 FET의 소스, 드레인 전극을 제작하였으며, 채널층 제작을 위해 SWCNT(Single-walled cabon nanotube)를 사용하였다. 제작된 유연한 전계 효과 트랜지스터는 P형 특성을 나타내며 저전압에서 동작한다. 측정 결과에 의하면 본 논문의FET는 3.73cm2/Vs의 이동도를 보였으며, 이는 기존의 CNT기반 FET의 약 12배 정도의 높은 수치이다. Carbon nanotubes and graphene are nanocarbon materials that possess several properties such as high charge mobility, chemical stability, and excellent flexibility, and they are actively studied for developing flexible electronic devices. In this study, source and drain electrodes were fabricated by employing a conductive graphene paste solution-based process, and single-walled carbon nanotubes were incorporated in the channel layer. The fabricated flexible field effect transistor (FET) indicated p-type characteristics and required a low voltage for operation. Furthermore, evaluation results demonstrated that the fabricated FET had an effective mobility of 3.73cm2/Vs, which is twelve times the effective mobility of a conventional carbon-nanotube-based FET.

Patterned carbon nanotube electrodes for use in high-performance field-effect transistors

강웅기,김남희,이동윤,김민제,장석태,조정호 한국공업화학회 2015 한국공업화학회 연구논문 초록집 Vol.2015 No.1

We demonstrated the solution-processed single-walled carbon nanotube (SWNT) source-drain electrodes patterned using a plasma-enhanced detachment patterning method for high-performance organic transistors and inverters. The high-resolution SWNT electrode patterning began with the formation of highly uniform SWNT thin films on a hydrophobic silanized substrate. The SWNT source-drain patterns were then formed by modulating the interfacial energies of the prepatterned elastomeric mold and the SWNT thin film using oxygen plasma. The SWNT films were subsequently selectively delaminated using a rubber mold. The patterned SWNTs could be used as the source-drain electrodes for both n-type PTCDI-C8 and p-type pentacene field-effect transistors (FETs). The n- and p-type devices exhibited good and exactly matched electrical performances, with a field-effect mobility of around 0.15 cm² V-1 s-1 and an ON/OFF current ratio exceeding 106. The single electrode material was used for both the n and p channels, permitting the successful fabrication of a high-performance complementary inverter by connecting a p-type pentacene FET to an n-type PTCDI-C8 FET. This patterning technique was simple, inexpensive, and easily scaled for the preparation of large-area electrode micropatterns for flexible microelectronic device fabrication.

On/off ratio enhancement in single-walled carbon nanotube field-effect transistor by controlling network density via sonication

Jang, Ho-Kyun,Choi, Jun Hee,Kim, Do-Hyun,Kim, Gyu Tae Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.444 No.-

<P><B>Abstract</B></P> <P>Single-walled carbon nanotube (SWCNT) is generally used as a networked structure in the fabrication of a field-effect transistor (FET) since it is known that one-third of SWCNT is electrically metallic and the remains are semiconducting. In this case, the presence of metallic paths by metallic SWCNT (m-SWCNT) becomes a significant technical barrier which hinders the networks from achieving a semiconducting behavior, resulting in a low on/off ratio. Here, we report on an easy method of controlling the on/off ratio of a FET where semiconducting SWCNT (s-SWCNT) and m-SWCNT constitute networks between source and drain electrodes. A FET with SWCNT networks was simply sonicated under water to control the on/off ratio and network density. As a result, the FET having an almost metallic behavior due to the metallic paths by m-SWCNT exhibited a p-type semiconducting behavior. The on/off ratio ranged from 1 to 9.0 × 10<SUP>4</SUP> along sonication time. In addition, theoretical calculations based on Monte-Carlo method and circuit simulation were performed to understand and explain the phenomenon of a change in the on/off ratio and network density by sonication. On the basis of experimental and theoretical results, we found that metallic paths contributed to a high off-state current which leads to a low on/off ratio and that sonication formed sparse SWCNT networks where metallic paths of m-SWCNT were removed, resulting in a high on/off ratio. This method can open a chance to save the device which has been considered as a failed one due to a metallic behavior by a high network density leading to a low on/off ratio.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The network density of single-walled carbon nanotube was controlled by sonication. </LI> <LI> The on/off ratio of a field-effect transistor was varied by the network densities. </LI> <LI> Sparse network density resulted in an electrically semiconducting behavior. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Design of non-volatile digital circuit with assuming magnetic tunneling junction and carbon nanotubes field-effect transistors devices

Mohsen Naeimi,Mohammd Bagher Tavakoli,Reza Sabbaghi-Nadooshan 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.27 No.6

Power consumption has become the key constraint in electronics design, since the MOSFET threshold and hence the supply voltage can no longer be scaled. This trend calls for new device concepts such as Spintronic devices that are fundamentally different from CMOS. A carbon nanotube field-effect transistor (CNTFET) refers to a field-effect transistor that utilizes a single carbon nanotube or an array of carbon nanotubes as the channel material instead of bulk silicon in the traditional MOSFET structure. Magnetic tunnel junction (MTJ) is an emerging technology which has many advantages when used in logic in memory structures in conjunction with CMOS. In this paper, we present novel designs of hybrid CNTFET-MTJ circuits; AND, XOR and 1-bit full adder. The proposed CNTFET-MTJ full adder design has 20 times lower Power-delay-product (PDP) compared to the previous CMOS- MTJ full adder. Also, the delay in CNTFET-MTJ circuit is reduced 20 times compared to the CMOS- MTJ circuit.

Imaging Ultrafast Carrier Transport in Nanoscale Field-Effect Transistors

Son, Byung Hee,Park, Jae-Ku,Hong, Jung Taek,Park, Ji-Yong,Lee, Soonil,Ahn, Yeong Hwan American Chemical Society 2014 ACS NANO Vol.8 No.11

<P>In the present study, we visualize ultrafast carrier dynamics in one-dimensional nanoscale devices, such as Si nanowire and carbon nanotube transistors using femtosecond photocurrent microscopy. We investigate transit times of ultrashort carriers that are generated near one metallic electrode and subsequently transported toward the opposite electrode based on drift and diffusion motions. Conversely, pure diffusion motion is observed when the pump pulse is located in the middle of the nanowires. Carrier dynamics have been addressed for various working conditions, in which we found that the carrier velocity and pulse width can be manipulated by the external electrodes. In particular, the carrier velocities extracted from transit times increase for a larger negative gate bias because of the increased field strength at the Schottky barrier.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-11/nn5042619/production/images/medium/nn-2014-042619_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn5042619'>ACS Electronic Supporting Info</A></P>

Silencing of Metallic Single-Walled Carbon Nanotubes via Spontaneous Hydrosilylation

Lee, Yoonmi,Jeon, Ki-Seok,Lim, Hyunseob,Shin, Hyeon Suk,Jin, Seung Min,Byon, Hye Ryung,Suh, Yung Doug,Choi, Hee Cheul WILEY-VCH Verlag 2009 Small Vol.5 No.12

<B>Graphic Abstract</B> <P>The sidewalls of metallic single-walled carbon nanotubes (SWNTs) are selectively attacked by triethylsilane through a hydrosilylation reaction. Network-type SWNT field-effect transistor devices (see picture) show increased on/off current ratios after hydrosilylation. <img src='wiley_img/16136810-2009-5-12-SMLL200801763-content.gif' alt='wiley_img/16136810-2009-5-12-SMLL200801763-content'> </P>