scholarly journals Critical current fluctuations in graphene Josephson junctions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammad T. Haque ◽  
Marco Will ◽  
Matti Tomi ◽  
Preeti Pandey ◽  
Manohar Kumar ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Critical Current ◽  
Superconducting State ◽  
Dirac Point ◽  
Low Frequency ◽  
Monolayer Graphene ◽  
Current Fluctuations ◽  
Frequency Noise ◽  
Noise Power ◽  
Diffusive Limit

AbstractWe have studied 1/f noise in critical current $$I_c$$ I c in h-BN encapsulated monolayer graphene contacted by NbTiN electrodes. The sample is close to diffusive limit and the switching supercurrent with hysteresis at Dirac point amounts to $$\simeq 5$$ ≃ 5 nA. The low frequency noise in the superconducting state is measured by tracking the variation in magnitude and phase of a reflection carrier signal $$v_{rf}$$ v rf at 600–650 MHz. We find 1/f critical current fluctuations on the order of $$\delta I_c/I_c \simeq 10^{-3}$$ δ I c / I c ≃ 10 - 3 per unit band at 1 Hz. The noise power spectrum of critical current fluctuations $$S_{I_c}$$ S I c measured near the Dirac point at large, sub-critical rf-carrier amplitudes obeys the law $$S_{I_c}/{I{_c}}^2 = a/f^{\beta }$$ S I c / I c 2 = a / f β where $$a\simeq 4\times 10^{-6}$$ a ≃ 4 × 10 - 6 and $$\beta \simeq 1$$ β ≃ 1 at $$f > 0.1$$ f > 0.1  Hz. Our results point towards significant fluctuations in $$I_c$$ I c originating from variation of the proximity induced gap in the graphene junction.

Noise properties of a single ZnO nanowire device

2008 ◽  
Vol 1080 ◽  
Author(s):  
Choi Soo Han ◽  
Dong Wook Kim ◽  
Do Young Jang ◽  
Hyun Jin Ji ◽  
Sang Woo Kim ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Field Effect Transistors ◽  
Electrical Contact ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Power ◽  
Noise Amplitude ◽  
Noise Power Spectrum ◽  
Low Frequency Noise ◽  
Zno Nanowire

ABSTRACTThe low frequency noise of individual ZnO nanowire (NW) field effect transistors (FETs) exposed to air is systematically characterized. The measured noise power spectrum shows a classical 1/f type. The noise amplitude is independent of source-drain current and inversely proportional to gate voltage. The extracted Hooge's constant of ZnO NW is found to be 6.52×10−3. In addition, the low frequency noise of ZnO NW according to NW resistance and contact property are investigated. The noise amplitude is proportional to the square of ZnO NW resistance. If a sample shows a nonlinear current-voltage (I-V) characteristic due to a poor electrical contact, the noise power spectrum is proportional to the third power of current instead of the square of current.

scholarly journals Low Frequency Noise in Tantalum Capacitors

1987 ◽  
Vol 12 (4) ◽  
pp. 215-221 ◽  
Author(s):  
D. T. Smith
Keyword(s):  
Power Spectrum ◽  
Bias Voltage ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Noise Current

Noise has been measured in a number of biased solid tantalum capacitors at frequencies down to 0.01 Hz. The noise current was found to have a 1/f power spectrum, and the amplitude varied with the bias voltage with a law in the range 1st to 4th power. There was a large difference in amplitudes between different capacitors of the same type.

scholarly journals Measurements of Low Frequency Noise of Infrared Photo-Detectors with Transimpedance Detection System

2014 ◽  
Vol 21 (3) ◽  
pp. 461-472 ◽  
Author(s):  
Łukasz Ciura ◽  
Andrzej Kolek ◽  
Waldemar Gawron ◽  
Andrzej Kowalewski ◽  
Dariusz Stanaszek
Keyword(s):  
Dark Current ◽  
Detection System ◽  
Power Spectra ◽  
Low Frequency ◽  
Frequency Noise ◽  
Noise Power ◽  
Low Frequency Noise ◽  
Leakage Resistance ◽  
Noise Measurements ◽  
Hgcdte Detector

Abstract The paper presents the method and results of low-frequency noise measurements of modern mid-wavelength infrared photodetectors. A type-II InAs/GaSb superlattice based detector with nBn barrier architecture is compared with a high operating temperature (HOT) heterojunction HgCdTe detector. All experiments were made in the range 1 Hz - 10 kHz at various temperatures by using a transimpedance detection system, which is examined in detail. The power spectral density of the nBn’s dark current noise includes Lorentzians with different time constants while the HgCdTe photodiode has more uniform 1/f - shaped spectra. For small bias, the low-frequency noise power spectra of both devices were found to scale linearly with bias voltage squared and were connected with the fluctuations of the leakage resistance. Leakage resistance noise defines the lower noise limit of a photodetector. Other dark current components give raise to the increase of low-frequency noise above this limit. For the same voltage biasing devices, the absolute noise power densities at 1 Hz in nBn are 1 to 2 orders of magnitude lower than in a MCT HgCdTe detector. In spite of this, low-frequency performance of the HgCdTe detector at ~ 230K is still better than that of InAs/GaSb superlattice nBn detector.

scholarly journals Noise Analysis of Monolayer Graphene Nanopores

2018 ◽  
Vol 19 (9) ◽  
pp. 2639 ◽  
Author(s):  
Zi-Yin Zhang ◽  
Yun-Sheng Deng ◽  
Hai-Bing Tian ◽  
Han Yan ◽  
Hong-Liang Cui ◽  
...  
Keyword(s):  
Noise Level ◽  
Noise Analysis ◽  
Low Frequency ◽  
Monolayer Graphene ◽  
Frequency Noise ◽  
Membrane Thickness ◽  
Free Standing ◽  
Suspended Graphene ◽  
Noise Characteristics ◽  
Graphene Nanopore

Graphene-based nanopore devices have shown tantalizing potential in single molecule detection for their monoatomic membrane thickness which is roughly equal to the gap between nucleobases. However, high noise level hampers applications of graphene nanopore sensors, especially at low frequencies. In this article, we report on a study of the contribution of suspended graphene area to noise level in full frequency band. Monolayer graphene films are transferred onto SiNx substrates preset with holes in varied diameters and formed self-supported films. After that, the films are perforated with smaller, nanoscale holes. Experimental studies indicate a dependency of low-frequency 1/f noise on the underlying SiNx geometry. The contribution of the suspended graphene area to capacitance which affects the noise level in the high frequency range reveals that the graphene free-standing film area influences noise level over a wide frequency region. In addition, the low-frequency noise demonstrates a weak dependency on salt concentration, in deviation from Hooge’s relation. These findings and attendant analysis provide a systematic understanding of the noise characteristics and can serve as a guide to designing free-standing monolayer graphene nanopore devices.

Measurement of Wiener Spectrum of Radiographic Screen–Film Systems

2012 ◽  
Author(s):  
Wan Muhamad Saridan Wan Hassan
Keyword(s):  
Power Spectrum ◽  
Hospital Setting ◽  
Low Frequency ◽  
Published Data ◽  
Noise Power ◽  
X Rays ◽  
Low Pass ◽  
Density Values ◽  
Data Points ◽  
The Mean

Satu kaedah untuk mengukur spektrum Wiener sistem skrin-filem radiografi dalam persekitaran hospital disajikan. Radiograf yang didedahkan kepada sinar–X seragam, diimbas oleh sebuah mikrodensitometer, dan data turun naik ketumpatan optik di sekitar nilai ketumpatan min diperoleh dengan menolak nilai ketumpatan min daripada nilai ketumpatan optik. Data dituras-laluan-rendahkan dengan mempuratakan pasangan piksel, diikuti dengan penurasan frekuensi rendah untuk menyingkirkan komponen frekuensi yang sangat rendah. Suatu surihan celah disintesis dengan mempuratakan surihan-surihan bersebelahan, dan surihan celah itu dibahagikan kepada segmen-segmen 256 data yang bertindih 128 datanya. Data dalam setiap segmen ditingkapkan dan transformasi–Fourier–pantaskan. Pekali–pekali Fourier dikuasa dua dan dinormalkan untuk menghasilkan spektrum kuasa. Pengukuran di lapangan terhadap skrin Lanex Regular dan Lanex Fine memberikan keputusan yang hampir sama dengan hasil yang telah diterbitkan. Kata kunci: Spektrum kuasa; radiografi; sistem skrin-filem; spektrum Wiener A method to measure the wiener spectrum of radiagraphic screen–film systems in a hospital setting is presented. Radiographs exposed to uniform X–rays are scanned by a microdensitometer, and optical density fluctuation data about the mean density are obtained by subtracting the mean density from the density values. The data are low–pass–filtered by averaging pairs of pixels, followed by low–frequency filtering to eliminate very low–frequency components. A slit trace is synthesised by averaging adjacent traces and the trace is segmented to segments of 256 data points per segment with overlap of 128 data points. Data in each segment are windowed and fast Fourier transformed. The Fourier coefficients are squared and normalized to obtain the power spectrum. On site measurement for Lanex Regular and Lanex Fine screens gives results that are comparable with published data. Key words: Noise power spectrum; radiography; screen-film system; Wiener spectrum

Low-Frequency Noise Characterization in AlGaN/GaN HEMTs with Varying Gate Recess Depths

2004 ◽  
Vol 831 ◽  
Author(s):  
Shrawan. K. Jha ◽  
Bun. H. Leung ◽  
Charles C. Surya ◽  
Heins Schweizer ◽  
Manfred. H. Pilkhuhn
Keyword(s):  
Low Frequency ◽  
Dry Etching ◽  
Frequency Noise ◽  
Noise Power ◽  
Hot Electron ◽  
Low Frequency Noise ◽  
Noise Power Spectral Density ◽  
Noise Measurements ◽  
Gan Hemts ◽  
Gate Recess

ABSTRACTLow-frequency noise measurements were performed on a number of AlGaN/GaN HEMTs with different gate recess depths, which were formed by dry etching. Detailed characterizations of the low-frequency noise properties were performed on the devices as a function of as a function of hot-electron stressing conducted at VD = 10 V and VG = -1.5 V. The room temperature voltage noise power spectral density, SV(ƒ), of the devices were found to show 1/ƒ dependence. A comparison of SV(ƒ) measured from different devices clearly indicate increase in the noise levels for the devices with large recess depths, reflecting the degradation caused by ion-impact induced damage during recess formation. Furthermore, the results of low-frequency noise measurements showed fast degradations for the devices with larger gate recess depths. Our experimental data clearly show that the dry etching process has induced damages in gates.

The Effect of Indium Surfactant on the Optoelectronic and Structural Properties of MBE Grown Gallium Nitride

2000 ◽  
Vol 618 ◽  
Author(s):  
C.F. Zhu ◽  
W.K. Fong ◽  
B.H. Leung ◽  
C.C. Cheng ◽  
C. Surya ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Power Spectra ◽  
Low Frequency ◽  
Rf Plasma ◽  
Frequency Noise ◽  
Noise Power ◽  
Low Frequency Noise ◽  
X Ray Diffraction ◽  
X Ray ◽  
The One

ABSTRACTGallium nitride films were grown by rf-plasma assisted molecular beam epitaxy. A small indium flux was used as surfactant during the growth. The optical and electrical properties of the films grown with and without In surfactant were characterized by investigating the photoluminescence (PL), high resolution x-ray diffraction (HRXRD) and low-frequency noise power spectra. The sample grown in the presence of In surfactant showed a suppressed yellow luminescence (YL) compared to the one grown without In surfactant. Significant reduction in the full width at half maximum of the GaN (0002) x-ray diffraction peak, indicating a better film quality, was obtained when In surfactant was used during growth. Atomic force microscopy studies show that the root mean squared surface roughness for films grown with and without the In surfactant are 5.86 and 6.99 nm respectively indicating significant improvement in surface morphology. This is attributed to the enhanced 2-dimensional growth by In surfactant. A smaller Hooge parameter was obtained from the low-frequency noise measurement for the sample grown with In surfactant indicating that application of In surfactant led to significant reduction in the trap density of the material.

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