• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.163-168
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• 2009

Negative differential resistance(NDR) behaviors of Keggin-type and Wells-Dawson-type heteropolyacids with cation, heteroatom, and polyatom substitutions were investigated by scanning tunneling microscopy. A reliable correlation between NDR peak voltage and reduction potential of heteropolyacid catalysts was established. It was found that more reducible heteropolyacid catalyst showed NDR behavior at less negative voltage, regardless of the structural difference. Thus, NDR peak voltage of heteropolyacid catalyst could be utilized as a single correlating parameter for the reduction potential of heteropolyacid catalyst.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.237-237
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• 1999

We have observed that a stable and reproducible Negative Differential Resistance(NDR) is induced by external microwave at low power in Nb/AlO$_x$/Al/Alo$_x$/Nb junctions. To study the erratic and pozzling NDR observations we have simulated Stewart-McCumber model in the region. Experimental results and simulation results will be presented with a discussion to draw a dynamic interpreration of the NDR.

• Journal of Korea Society of Digital Industry and Information Management
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• v.4 no.4
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• pp.21-29
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• 2008

The DC characteristics of GaAS Gunn diode are investigated as a preliminary study on the planar grade gap injector GaAs Gunn diode which is the transferred electron device with high output power and dc-rf conversion efficiency. The Gunn devices we fabricated were confirmed to have the DC characteristics of negative differential resistance(NDR). We discussed the nature of the NDR effect, including the electron intervalley transfer; the NDR effect was examined for six different cathode radii.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.546-550
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• 2013

We propose a novel negative differential resistance (NDR) device with ultra-high peak-to-valley current ratio (PVCR) by combining pn junction diode with depletion mode nanowire (NW) transistor, which suppress the valley current with transistor off-leakage level. Band-to-band tunneling (BTBT) Esaki diode with degenerately doped pn junction can provide multiple switching behavior having multi-peak and valley currents. These multiple NDR characteristics can be controlled by doping concentration of tunnel diode and threshold voltage of NW transistor. By designing our NDR device, PVCR can be over $10^4$ at low operation voltage of 0.5 V in a single peak and valley current.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.811-813
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• 2003

We investigated the electrical properties of self-assembled (4,4'-Di(ethynylphenyl)-2'-nitro-1-thioacetylbenzene), which has been well known as a conducting molecule having possible application to molecular level negative differential resistance(NDR)[1]. Generally, the phenomenon of NDR can be characterized by the decreasing current with the increasing voltage[2]. To deposit the SAM layer onto gold electrode, we transfer the prefabricated nanopores into a 1mM self-assembly molecules in THF solution. Au(111) substrates were prepared by ion beam sputtering method of gold onto the silicon wafer. As a result, we measured the voltage-current properties and confirmed the negative differential resistance properties of self-assembled organic thin film and measured, using Scanning Tunneling Microscopy(STM).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.7 s.361
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• pp.1-8
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• 2007

The DC characteristics of GaAs Gunn diode are investigated as a preliminary study on the planar grade gap injector GaAs Gunn diode which is the transferred electron device with high output power and dc-rf conversion efficiency. The Gunn devices we fabricated were confirmed to have the DC characteristics of negative differential resistance(NDR). We discussed the nature of the NDR effect, including the electron intervalley transfer; the NDR effect was examined for six different cathode radii.

• Journal of Electrical Engineering and Technology
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• v.1 no.3
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• pp.366-370
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• 2006

We investigated the negative differential resistance (NDR) property of self-assembled 4,4-di(ethynylphenyl)-2'-nitro-l-(thioacetyl)benzene ('nitro-benzene'), which has been well known as a conducting molecule [1], Self-assembly monolayers (SAMs) were prepared on Au (111), which had been thermally deposited onto pre-treated $(H_2SO_4: H_2O_2=3:1)$ Si, The Au substrate was exposed to a 1mM solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing of the sample, it was exposed to a $0.1{\mu}M$ solution of nitro-benzene in dimethylformamide (DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. Following the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_2Cl_2$, and finally blown dry with $N_2$. Under these conditions, we measured the electrical properties of SAMs using ultra high vacuum scanning tunneling microscopy (UHV-STM) and scanning tunneling spectroscopy (STS) [2]. As a result, we confirmed the properties of NDR in between the positive and negative region.

• Electronics and Telecommunications Trends
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• v.36 no.3
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• pp.34-40
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• 2021

For developing a switching device of a new concept that cannot be implemented with a semiconductor device, we introduce the Mott insulator-metal transition (IMT) phenomenon occurring out of the semiconductor regime, such as the temperature-driven IMT, the electric-field or voltage-driven IMT, the negative differential resistance (NDR)-IMT switching generated at constant current, and the NDR-based IMT-oscillation. Moreover, the possibilities of new concept IMT switching devices are briefly explained.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.622-627
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• 2005

In this study, electrical properties of self-assembled dipyridinium dithioacetate molecule onto the Au(111) substrate is observed using Scanning Tunneling Microscopy(STM) by vortical structure of STM probe. At first, the Au(111) substrate is cleaned by piranha solution$(H_2SO_4:H_2O_2\;=\;3:1)$. Subsequently, 1 mM/ml of dipyridinium dithioacetate molecule is self-assembled onto the Au(111) surface. Using STM, the images of dipyridinium dithioacetate molecule which is self-assembled onto the Au(111) substrate, can be observed. In addition, the electrical properties(I-V) of dipyridinium dithioacetate can also be examined by using Scanning Tunneling Spectroscopy(STS). From the results of the measurement of the current-voltage(I-V), the property of Negative Differential Resistance(NDR) that shows the decreases of current according to the increases of voltage is observed. We found the NDR voltage of the dipyridinium dithioacetate is -1.42 V(negative region) and 1.30 V(positive region), respectively.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.55 no.1
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• pp.16-19
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• 2006

The characteristic of negative differential resistance(NDR) is decreased current when the applied voltage is increased. The NDR is potentially very useful in molecular electronics device schemes. Here, we investigated the NDR characteristic of self-assembled 4,4'-di(ethynylphenyl)-2'-nitro-1-benzenethiolate, which has been well known as a conducting molecule. Self-assembly monolayers(SAMs) were prepared on Au(111), which had been thermally deposited onto $pre-treatment(H_2SO_4:H_2O_2=3:1)$ Si. The Au substrate was exposed to a 1 mM/1 solution of 1-dodecanethiol in ethanol for 24 hours to form a monolayer. After thorough rinsing the sample, it was exposed to a 0.1 ${\mu}M/l$ solution of 4.4'-di(ethynylphenyl)-2'-nitro-1-(thioacetyl)benzene in dimethylformamide(DMF) for 30 min and kept in the dark during immersion to avoid photo-oxidation. After the assembly, the samples were removed from the solutions, rinsed thoroughly with methanol, acetone, and $CH_2Cl_2,$ and finally blown dry with N_2. Under these conditions, we measured electrical properties of self-assembly monolayers(SAMs) using ultra high vacuum scanning tunneling microscopy(UHV-STM). The applied voltages were from -2 V to +2 V with 298 K temperature. The vacuum condition was $6{\time}10^{-8}$ Torr. As a result, we found the NDR voltage of the 4,4'-di(ethynylphenyl)-2'-nitro-1-benzenethiolate were $-1.61{\pm}0.26$ V(negative region) and $1.84{\pm}0.33$ V(positive region). respectively.