High-Mobility Nanotube Transistor Memory

Fuhrer, Michael S.; Kim, B. M.; Dürkop, T.; Brintlinger, Todd

doi:10.1021/nl025577o

Cited by 498 publications

(461 citation statements)

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“…It is known that large gate voltages applied to the nanotube can inject electrons from the nanotube into SiO 2 . 19 Experimentally, we have observed a variety of singlettriplet gap values; they do not seem to obey a clear pattern as a function of V gate . The random overlap of the nanotube electron with the localized state and the successive filling of different localized states should both cause irregular variations in the exchange interaction with V gate .…”

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confidence: 74%

Two-stage Kondo effect and Kondo-box level spectroscopy in a carbon nanotube

et al. 2010

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The concept of the "Kondo box" describes a single spin, antiferromagnetically coupled to a quantum dot with a finite level spacing. Here, a Kondo box is formed in a carbon nanotube interacting with a localized electron. We investigate the spins of its first few eigenstates and compare them to a recent theory.In an "open" Kondo-box, strongly coupled to the leads, we observe a nonmonotonic temperature dependence of the nanotube conductance, which results from a competition between the Kondo-box singlet and the "conventional" Kondo state that couples the nanotube to the leads. DOI: 10.1103/PhysRevB.82.161411 PACS number͑s͒: 73.23.Ϫb, 72.15.Qm One of the exciting concepts that has emerged in modern condensed-matter physics is that of competing many-body ground states: the existence of states with different symmetries leads, for instance, to distinct phases separated by quantum phase transitions. 1 It was later appreciated that similar physics also occurs in an individual quantum impurity system, 2 where distinct many-body states may, for example, possess different spin. Experimentally, this physics is best studied in nanostructures, in which one can tune the system parameters and create complex set ups with competing many-body states. 3 The quantum impurity system that we study is a carbon nanotube quantum dot exchange coupled to a localized electron ͓schematic in Fig. 1͑b͔͒, thereby forming a Kondo box. [5][6][7][8] We focus on the case of an odd number of electrons in the nanotube and identify the spin of the ground state and several excited states. For a Kondo box strongly coupled to the leads, the nanotube spin can either be Kondo screened by the leads or form a singlet state with the localized electron. We find that the competition between these distinct ground states results in a peculiar nonmonotonic dependence of the nanotube conductance on temperature, where the initial rise in conductance at intermediate temperatures changes into a sharp drop at the lowest temperatures. At these lowest temperatures, a single channel in the leads screens both the localized spin and the spin in the nanotube quantum dot. 9 The nanotubes are grown on a Si/ SiO 2 substrate by chemical vapor deposition using CO as a feedstock gas. 10 This method usually produces nanotubes with diameters of about 2 nm. We present results measured on a single semiconducting nanotube with two metal contacts separated by a distance of 400 nm. Similar results have been observed in other samples. The measurements were performed at the base temperature of 25 mK ͑except for the temperature dependence in Fig. 3͒. Figures 1͑a͒ and 1͑b͒ show the nanotube zero-bias differential conductance as a function of gate voltage ͑V gate ͒. Both graphs correspond to adding four successive electrons to the nanotube, as seen by four single-electron conductance peaks. ͓The feature "B" in Fig. 1͑a͒ is formed by two peaks merged by the conventional Kondo effect; 4 they can be separated by a finite source-drain bias.͔ We will focus most of our attention on valleys "A" a...

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Two-stage Kondo effect and Kondo-box level spectroscopy in a carbon nanotube

et al. 2010

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“…The electrometer can be implemented either by a single electron transistor (SET), as in the original experiments, [2] or by a highly sensitive field effect transistor (FET) [3]. Many kinds of electrometers have been implemented so far, that involve metallic [2], semiconducting [5] and more recently single walled [6,7] or multi walled [8] carbon nanotube as the active channel.…”

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Self‐Assembly of Carbon‐Nanotube‐Based Single‐Electron Memories

Marty

Bonnot

Bonhomme

et al. 2005

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We demonstrate the wafer-scale integration of single electron memories based on carbon nanotube field effect transistors (CNFETs) using a process based entirely on self assembly. First, a "dry" self assembly step based on chemical vapor deposition (CVD) allows the growth and connection of CNFETs. Next, a "wet" self-assembly step is used to attach a single 30 nmdiameter gold bead in the nanotube vicinity via chemical functionalization. The bead is used as the memory storage node while the CNFET operated in the subthreshold regime acts as an electrometer exhibiting exponential gain. Below 60 K, the transfer characteristics of goldCNFETs show highly reproducible hysteretic steps. Evaluation of the capacitance confirms that these current steps originate from the controlled storage of single electrons with a retention time that exceeds 550 s at 4 K.

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“…To date, a number of nanoelectronic devices have been realized with CNTs, such as field effect transistors, [2][3][4] room-temperature single-electron transistors, 5 logic gate circuits, 6 inverters, 7 and electromechanical switches. 8 Very recently, the prototypes of memory devices based on CNT field effect transistors were also reported, [9][10][11][12] demonstrating another significant extension of CNTs applications. From then on, several groups have carried out research on the CNT-based memories.…”

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Memory effects of carbon nanotubes as charge storage nodes for floating gate memory applications

2006

Applied Physics Letters

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A nonvolatile flash memory device has been fabricated using carbon nanotubes ͑CNTs͒ as a floating gate embedded in HfAlO ͑the atomic ratio of Hf/ Al is 1:2͒ high-k tunneling/control oxides and its memory effect has been observed. Capacitance-voltage ͑C-V͒ measurements illustrated a 400 mV memory window during the double C-V sweep from 3 to −3 V performed at room temperature and 1 MHz. Further studies on their programming characteristics revealed that electron is difficult to be written into the CNTs and the memory effect of the structures is mainly due to the holes traps. The memory window width can remain nearly unchanged even after 10 4 s stressing, indicating excellent long term charge retention characteristics. We therefore suggest that the CNTs embedded in HfAlO can be potentially applied to floating gate flash memory devices. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2179374͔Since their discovery in the early 1990s, 1 carbon nanotubes ͑CNTs͒ have attracted much attention, both of scientific and technological interest, for possible nanoelectronic applications. To date, a number of nanoelectronic devices have been realized with CNTs, such as field effect transistors, 2-4 room-temperature single-electron transistors, 5 logic gate circuits, 6 inverters, 7 and electromechanical switches. 8 Very recently, the prototypes of memory devices based on CNT field effect transistors were also reported, 9-12 demonstrating another significant extension of CNTs applications. From then on, several groups have carried out research on the CNT-based memories. [13][14][15][16][17] In these research works, the CNTs were synthesized on a conductive Si substrate capped by several hundred nanometers of SiO 2 . Metal electrodes were evaporated on the CNTs to form source and drain electrical contact to them. The conductive Si substrate actually acts as the gate of the memory device. The function of the CNTs was the current channel, and the memory effect of the devices was attributed to the charges injected from the CNTs to the defects or charge traps in the dielectrics or the interface between the CNTs and the oxides. 15-17 The CNTs were not used as the charge storage nodes.For commonly studied flash memory devices, Si, 18 Ge, 19 and Si 1−x Ge x ͑Ref. 20͒ nanocrystals are widely used as the charge storage nodes and the memory structures are sandwiched with nanocrystals embedded in the SiO 2 or high-k dielectrics. But up to now, there is no report on flash memory devices using CNTs as a floating gate. In terms of electrical properties, CNTs have many unique advantages for the application in memory devices such as tunable band gap, high thermal stability and chemical inertness, perfect sidewall structure, and nearly zero surface states. 21,22 These unique properties are very favorable for their application as the charge storage nodes in the memory devices. In this letter, we report the fabrication of the HfAlO/ CNTs/ HfAlO/ Si memory structures and characterization of the unique memory characteristics of CNTs using as the c...

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High-Mobility Nanotube Transistor Memory

Cited by 498 publications

References 20 publications

Two-stage Kondo effect and Kondo-box level spectroscopy in a carbon nanotube

Two-stage Kondo effect and Kondo-box level spectroscopy in a carbon nanotube

Self‐Assembly of Carbon‐Nanotube‐Based Single‐Electron Memories

Memory effects of carbon nanotubes as charge storage nodes for floating gate memory applications

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