Sergey Rumyantsev - Academia.edu (original) (raw)

Papers by Sergey Rumyantsev

arXiv (Cornell University), Mar 6, 2015

We report on the transport and low-frequency noise measurements of MoS 2 thin-film transistors wi... more We report on the transport and low-frequency noise measurements of MoS 2 thin-film transistors with "thin" (2-3 atomic layers) and "thick" (15-18 atomic layers) channels. The back-gated transistors made with the relatively thick MoS 2 channels have advantages of the higher electron mobility and lower noise level. The normalized noise spectral density of the low-frequency 1/f noise in "thick" MoS 2 transistors is of the same level as that in graphene. The MoS 2 transistors with the atomically thin channels have substantially higher noise levels. It was established that, unlike in graphene devices, the noise characteristics of MoS 2 transistors with "thick" channels (15-18 atomic planes) could be described by the McWhorter model. Our results indicate that the channel thickness optimization is crucial for practical applications of MoS 2 thin-film transistors.

Applied Physics Letters, 2022

We report the results of an investigation of low-frequency excess noise in high-current diamond d... more We report the results of an investigation of low-frequency excess noise in high-current diamond diodes. It was found that the electronic excess noise of the diamond diodes is dominated by the 1/f and generation-recombination noise, which reveals itself as Lorentzian spectral features (f is the frequency). The generation-recombination bulges are characteristic of diamond diodes with lower turn-on voltages. The noise spectral density dependence on forward current, I, reveals three distinctive regions in all examined devicesit scales as I 2 at the low (I<10 A) and high (I>10 mA) currents, and, rather unusually, remains nearly constant at the intermediate current range. The characteristic trap time constants, extracted from the noise data, show a uniquely strong dependence on current. Interestingly, the performance of the diamond diodes improves with increasing temperature. The obtained results are important for the development of noise spectroscopy-based approaches for device reliability assessment for high-power diamond electronics.

Journal of Applied Physics, 2015

We report on fabrication of MoS2 thin-film transistors (TFTs) and experimental investigations of ... more We report on fabrication of MoS2 thin-film transistors (TFTs) and experimental investigations of their high-temperature current-voltage characteristics. The measurements show that MoS2 devices remain functional to temperatures of at least as high as 500 K. The temperature increase results in decreased threshold voltage and mobility. The comparison of the direct current (DC) and pulse measurements shows that the direct current sub-linear and super-linear output characteristics of MoS2 thin-films devices result from the Joule heating and the interplay of the threshold voltage and mobility temperature dependences. At temperatures above 450 K, a kink in the drain current occurs at zero gate voltage irrespective of the threshold voltage value. This intriguing phenomenon, referred to as a “memory step,” was attributed to the slow relaxation processes in thin films similar to those in graphene and electron glasses. The fabricated MoS2 thin-film transistors demonstrated stable operation aft...

Journal of Physics: Condensed Matter, 2010

We fabricated a large number of single and bilayer graphene transistors and carried out a systema... more We fabricated a large number of single and bilayer graphene transistors and carried out a systematic experimental study of their low-frequency noise characteristics. A special attention was given to determining the dominant noise sources in these devices and the effect of aging on the current-voltage and noise characteristics. The analysis of the noise spectral density dependence on the area of graphene channel showed that the dominant contributions to the low-frequency electronic noise come from the graphene layer itself rather than from the contacts. Aging of graphene transistors due to exposure to ambient for over a month resulted in substantially increased noise attributed to the decreasing mobility of graphene and increasing contact resistance. The noise spectral density in both single and bilayer graphene transistors either increased with deviation from the charge neutrality point or depended weakly on the gate bias. This observation confirms that the low-frequency noise characteristics of graphene transistors are qualitatively different from those of conventional silicon metal-oxide-semiconductor field-effect transistors.

Journal of Applied Physics, 1999

We report on the results of measurements of low frequency noise in n-type gallium nitride (GaN) g... more We report on the results of measurements of low frequency noise in n-type gallium nitride (GaN) grown on sapphire with 300 K electron mobility of 790 cm2/V s. The noise spectra have the form of 1/f noise with a Hooge parameter α of approximately 5×10−2. This value of α is two orders of magnitude smaller than that observed before in n-GaN. The obtained results show that the level of flicker noise in GaN, just like that in GaAs and Si, strongly depends on the structural perfection of the material (the amplitude of the 1/f noise is much smaller in material with high mobility). The effects of band-to-band illumination on the low-frequency noise show that 1/f noise in GaN might be caused by the occupancy fluctuations of the tail states near the band edges. This mechanism of the 1/f noise is similar to that in GaAs and Si.

Journal of Applied Physics, 2008

Noise in nanostructures is one of the key problems impeding their applications in electronic devi... more Noise in nanostructures is one of the key problems impeding their applications in electronic devices. We show that the level of 1∕f and recombination-generation noise in GaN nanowire field effect transistors can be suppressed by ultraviolet radiation by up to an order of magnitude. This strong suppression of the noise is explained by the illumination changing the occupancy of traps responsible for noise.

Japanese Journal of Applied Physics, 2007

The 1= f noise in insulated gate strained Si n-channel modulation doped field effect transistors ... more The 1= f noise in insulated gate strained Si n-channel modulation doped field effect transistors (MOSMODFETs) and in control Si metal-oxide-semiconductor FETs (MOSFETs) has been studied at gate voltages below and above the threshold. All transistors have a deposited gate oxide of 20 nm and gate length of 0.5 mm. Mobilities extracted from the capacitance-and current-voltage characteristics were found between 580-700 cm 2 V À1 s À1 for the MOSMODFETs, and between 300-400 cm 2 V À1 s À1 for the Si MOSFETs. In spite of the difference in the mobility both FETs demonstrated identical noise characteristics. The 1= f noise was found well described by the model of number of carriers fluctuations equally below and above threshold. The effective density of traps is $5 Â 10 10 eV À1 cm À2 responsible for the noise was within the usual range reported before for regular n-channel Si MOSFETs and somewhat higher than for p-SiGe MODFETs.

Applied Physics Letters, 2013

We investigated experimentally the effect of the electron-beam irradiation on the level of the lo... more We investigated experimentally the effect of the electron-beam irradiation on the level of the low-frequency 1/f noise in graphene devices. It was found that 1/f noise in graphene reduces with increasing concentration of defects induced by irradiation. The increased amount of structural disorder in graphene under irradiation was verified with micro-Raman spectroscopy. The bombardment of graphene devices with 20-keV electrons reduced the noise spectral density, SI/I2 (I is the source-drain current) by an order-of magnitude at the radiation dose of 104 μC/cm2. We analyzed the observed noise reduction in the limiting cases of the mobility and carrier number fluctuation mechanisms. The obtained results are important for the proposed graphene applications in analog, mixed-signal, and radio-frequency systems, integrated circuits and sensors.

Applied Physics Letters, 1996

Low frequency noise in 4H-silicon carbide junction field effect transistors (JFETs) has been inve... more Low frequency noise in 4H-silicon carbide junction field effect transistors (JFETs) has been investigated. JFETs with a buried p+n junction gate were manufactured by CREE Research Inc. Very low noise level has been observed in the JFETs. At 300 K the value of Hooge constant α is as small as α∼10−5 and the α value can be decreased by an appropriate annealing to α∼2×10−6. It has been shown that even these extremely low noise values are determined not by the volume noise sources but by the noise at the SiC–SiO2 interface.

arXiv (Cornell University), Oct 3, 2010

We report results of investigation of the low-frequency excess noise in device channels made from... more We report results of investigation of the low-frequency excess noise in device channels made from topological insulatorsa new class of materials with a bulk insulating gap and conducting surface states. The thin-film Bi 2 Se 3 samples were prepared by the "graphene-like" mechanical exfoliation from bulk crystals. The fabricated four-contact devices had linear currentvoltage characteristics in the low-bias regime |V SD |<0.1 V. The current fluctuations had the noise spectral density S I ~ 1/f for the frequency f <10 kHz. The noise density S I followed the quadratic dependence on the drainsource current and changed from about ~10-22 to 10-18 A 2 /Hz as the current increases from ~10-7 to 10-5 A. The obtained data is important for planning transport experiments with topological insulators. We suggest that achieving the pure topological insulator phase with the current conduction through the "protected" surface states can lead to noise reduction via suppression of certain scattering mechanisms. The latter has important implications for implementing the ultra-low-power and ultra-low-noise electronics.

arXiv: Applied Physics, 2019

The low-frequency amplitude and phase noise spectra of magnetization waves, i.e. magnons, was mea... more The low-frequency amplitude and phase noise spectra of magnetization waves, i.e. magnons, was measured in the yttrium iron garnet (YIG) waveguides. This type of noise, which originates from the fluctuations of the physical properties of the YIG crystals, has to be taken into account in the design of YIG-based RF generators and magnonic devices for data processing, sensing and imaging applications. It was found that the amplitude noise level of magnons depends strongly on the power level, increasing sharply at the on-set of nonlinear dissipation. The noise spectra of both the amplitude and phase noise have the Lorentzian shape with the characteristic frequencies below 100 Hz.

ACS applied materials & interfaces, Jan 19, 2018

Wafer-scale MoS growth at arbitrary integer layer number is demonstrated by a technique based on ... more Wafer-scale MoS growth at arbitrary integer layer number is demonstrated by a technique based on the decomposition of carbon disulfide on a hot molybdenum filament, which yields volatile MoS precursors that precipitate onto a heated wafer substrate. Colorimetric control of the growth process allows precise targeting of any integer layer number. The method is inherently free of particulate contamination, uses inexpensive reactants without the pyrophoricity common to metal-organic precursors, and does not rely on particular gas-flow profiles. Raman mapping and photoluminescence mapping, as well as imaging by electron microscopy, confirm the layer homogeneity and crystalline quality of the resultant material. Electrical characterization revealed microampere output current, outstanding device-to-device consistency, and exceptionally low noise level unparalleled even by the exfoliated material, while other transport properties are obscured by high-resistance contacts typical to MoS devices.

Nano letters, Jan 11, 2017

We report results of investigation of the low-frequency electronic excess noise in quasi-1D nanow... more We report results of investigation of the low-frequency electronic excess noise in quasi-1D nanowires of TaSe3 capped with quasi-2D h-BN layers. Semimetallic TaSe3 is a quasi-1D van der Waals material with exceptionally high breakdown current density. It was found that TaSe3 nanowires have lower levels of the normalized noise spectral density, SI/I(2), compared to carbon nanotubes and graphene (I is the current). The temperature-dependent measurements revealed that the low-frequency electronic 1/f noise becomes the 1/f(2) type as temperature increases to ∼400 K, suggesting the onset of electromigration (f is the frequency). Using the Dutta-Horn random fluctuation model of the electronic noise in metals, we determined that the noise activation energy for quasi-1D TaSe3 nanowires is approximately EP ≈ 1.0 eV. In the framework of the empirical noise model for metallic interconnects, the extracted activation energy, related to electromigration is EA = 0.88 eV, consistent with that for C...

Applied Physics Letters, 2015

We demonstrated selective gas sensing with MoS2 thin-film transistors using the change in the cha... more We demonstrated selective gas sensing with MoS2 thin-film transistors using the change in the channel conductance, characteristic transient time, and low-frequency current fluctuations as the sensing parameters. The back-gated MoS2 thin-film field-effect transistors were fabricated on Si/SiO2 substrates and intentionally aged for a month to verify reliability and achieve better current stability. The same devices with the channel covered by 10 nm of Al2O3 were used as reference samples. The exposure to ethanol, acetonitrile, toluene, chloroform, and methanol vapors results in drastic changes in the source-drain current. The current can increase or decrease by more than two-orders of magnitude depending on the polarity of the analyte. The reference devices with coated channel did not show any response. It was established that transient time of the current change and the normalized spectral density of the low-frequency current fluctuations can be used as additional sensing parameters ...

IEEE Electron Device Letters, 2015

We report on the transport and low-frequency noise measurements of MoS 2 thin-film transistors (T... more We report on the transport and low-frequency noise measurements of MoS 2 thin-film transistors (TFTs) with thin (2-3 atomic layers) and thick (15-18 atomic layers) channels. The back-gated transistors made with the relatively thick MoS 2 channels have advantages of the higher electron mobility and lower noise level. The normalized noise spectral density of the low-frequency 1/ f noise in thick MoS 2 transistors is of the same level as that in graphene. The MoS 2 transistors with the atomically thin channels have substantially higher noise levels. It was established that, unlike in graphene devices, the noise characteristics of MoS 2 transistors with thick channels (15-18 atomic planes) could be described by the McWhorter model. Our results indicate that the channel thickness optimization is crucial for practical applications of MoS 2 TFTs.

SPIE Proceedings, 2007

We report on the low-frequency current and light noise in 515 nm green GaInN/GaN quantum well LED... more We report on the low-frequency current and light noise in 515 nm green GaInN/GaN quantum well LEDs. The current noise was the superposition of the 1/f and the generation-recombination (GR) noise. The characteristic time of the GR process was found to be proportional to the reciprocal current for the entire current range. This dependence is the characteristic for the monomolecular non-radiative recombination .The dominance of the nonradiative recombination is in agreement with the measured low external quantum efficiency (EQE) <10%. Hence, the noise measurements point out that a low EQE is caused by the low internal quantum efficiency and not by an inefficient light extraction. The noise spectra of light intensity fluctuations were close to the 1/f noise and correlated with the LED quantum efficiency and with the recombination current. Higher noise corresponded to a smaller quantum efficiency and to a higher non-radiative recombination current. The relative spectral noise densities of the light intensity fluctuations within the LED spectral line increase with the wavelength decrease. Fluctuations at different wavelengths are found to be correlated.

Solid-State Electronics, 2009

The low frequency (1/f) noise characteristics of Schottky-gated strained-Si n-channel modulation ... more The low frequency (1/f) noise characteristics of Schottky-gated strained-Si n-channel modulation doped field effect transistors have been investigated as a function of Ge concentration for different virtual substrates. The gate voltage dependence of the 1/f noise agrees well with the McWhorter carrier number fluctuations model. The trap density (extracted using a Ge dependent potential barrier height and tunnelling constant) is low in devices on thick virtual substrates (N t = (2-6) Â 10 16 cm À3 eV À1), and does not degrade with the increase of the Ge concentration from 30% to 40%. This trap density is the same for thin Helax virtual substrates (He + ions implanted thin substrate) but increases two orders of magnitude for thin low-temperature grown substrates.

Nano Letters, 2012

We show that vapors of different chemicals produce distinguishably different effects on the low-f... more We show that vapors of different chemicals produce distinguishably different effects on the low-frequency noise spectra of graphene. It was found in a systematic study that some gases change the electrical resistance of graphene devices without changing their low-frequency noise spectra while other gases modify the noise spectra by inducing Lorentzian components with distinctive features. The characteristic frequency f c of the Lorentzian noise bulges in graphene devices is different for different chemicals and varies from f c =10-20 Hz to f c =1300-1600 Hz for tetrahydrofuran and chloroform vapors, respectively. The obtained results indicate that the low-frequency noise in combination with other sensing parameters can allow one to achieve the selective gas sensing with a single pristine graphene transistor. Our method of gas sensing with graphene does not require graphene surface functionalization or fabrication of an array of the devices with each tuned to a certain chemical.

Journal of Applied Physics, 2006

Light intensity low-frequency noise was studied in green GaInN / GaN quantum well light emitting ... more Light intensity low-frequency noise was studied in green GaInN / GaN quantum well light emitting diodes. The light intensity noise was measured as a function of wavelength within the light emitting diode spectral emission line. The spectral noise density is found to increase with decreasing wavelength. Comparing the wavelength-resolved noise with the total light noise, we found that the emission intensity fluctuates synchronously across the entire linewidth. The source of this noise can be ascribed to nonradiative recombination centers.