Detecting signals buried in noise via nanowire transistors using stochastic resonance
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Device structure of an SRT. (a) A birds-eye view of an SRT with a double channel. Voltage applied to each electrical contact is also shown. (b) A cross-sectional views along the channel.
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Current characteristics of an SRT. (a) I S1-V LG characteristics of an SRT when V D is changed from 1 to 2.5 V in 0.25-V steps. The slope of the dotted line indicates the SS of 60 mV/dec, which is the minimum theoretically determined at room temperature in conventional MOSFETs. Cyclic measurements of I S1-V LG characteristics at V D of (b) 2.0 and (c) 2.3 V. Triangle waveforms with amplitude of 0.6 V and center voltage of (b) −2.1 and (c) −2.3 V are applied to V LG. Frequencies of triangle waveforms are 1, 10, 100, and 1000 Hz. For clarity, I S1-V LG characteristics during ten periods of triangle waveforms applied to V LG are shown here. Voltages, V on and V off, at which current cut across 10−6 A in positive and negative sweeps of V LG, respectively, are also shown. (d) Histograms of 50 samples of V on and V off at V D of 2.3 V. Solid lines are fitting curves based on Gaussian distribution. Dotted lines indicate shifts of the peaks of Gaussian distributions.
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Signal detection using SR in an SRT. (a) A schematic view for SR demonstration. V offset is the center of the square waveform. (b) Measured signals applied to the LG. Root mean squares of S noise are 0.128 and 0.096 Vrms, respectively. V offset is −2.6 V. For clarity, the top and middle lines are shifted vertically by 2 and 1 V, respectively. I S1-S in characteristics at V D of (c) 2.0 and (d) 2.3 when S noise superimposed on S in is changed. For clarity, each line in (c) and (d) is shifted by 1 and 2.5 μA, respectively. S in is the same as that in (b). (e) C characteristics as a function of S noise at various V D's. Solid lines are guides for the eyes. In the legend, SS at each V D is also shown. Open plots at V D of 2.0 and 2.1 V are theoretical plots8 fitted to the experimental results. Open squares at V D of 2.35 V are fitted to experimental curves at V D of 2.35 V by using MC simulation. (f) C-S noise characteristics simulated by an MC method with the assumption that V off is changed at constant V on of −2.35 V. The dotted arrow indicates the shift of peak values of C when V off is changed from −2.35 to −3.1 V. (g) A Schematic of energy diagram in a non-linear system when S in is “High” value and S out is still “Low” value. Schematics of energy diagrams in bistable systems (h) without and (i) with dynamic hysteresis loops. Closed circles and broken arrows represent S out, and its transition caused by S noise. Since S in is “High,” energy diagrams are modulated. While slope of energy diagram between “Low” and “High” becomes gentle in a non-linear system, energy at “High” becomes the global minima at a bistable system corresponding to hysteresis current characteristics. The dotted curve in (i) represents fluctuation of barrier height in the case of hysteresis characteristics with fluctuation of V on and V off.
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Enhancement of SR in a SRT. (a) Simulated C-S noise characteristics of the multiple SRTs. We assume that each SRT has the same I S1 characteristics and that Von and Voff are without (lower figure) and with (upper figure) fluctuation of 0.06 V rms. The numbers of SRTs are 1, 2, 4, 8, 20, and 40. (b) Change in I D, I S1, and I S2 when S in superimposed on S noise is applied to the LG and S noise is changed. V D is 2.35 V. Each line is shifted by 0.25 μA. S in is the same as that in Fig. 3. (c) Change in C of I D, I S1, and I S2 when S noise is changed at V D of 2.35 V. The solid curves are guides for eyes. (d) Simulated C-S noise characteristics of I D, I S1, and I S2, with the assumption that V on and V off are without (lower graph) and with (upper graph) fluctuation of 0.04 V rms.
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