SEM images of MWNT forest on Si substrate taken at (a) low and (b) high magnifications.
(a) Dependences of dc photovoltage VP (top) and differential photoresistance dVP/dI (bottom) on bias current I taken at different temperatures; (b) Dependences of differential resistances of forest in dark (dVD/dI, black) and irradiated (dVL/dI, red) states on bias current I taken at different temperatures; (c) Dependences of amplitudes of first (VH 1, top) and second (VH 2, bottom) lock-in harmonics of ac photovoltage on bias current at sinusoidal 25 Hz laser excitation taken at different temperatures; (d) Dependences of photovoltage VP on power of incident radiation at several bias currents taken at 114 K using triangular laser excitation.
(a) Temperature dependences of first (VH 1), second (VH 2), and third (VH 3) lock-in harmonics of ac photovoltage at sinusoidal 25 Hz laser excitation recorded at bias current I = 1.5 mA; (b) Dependences of average dc forest resistance R and numerically evaluated temperature coefficient of resistance (TCR) α = −1/R * dR/dT; (c) Temperature dependences of forest resistance in dark (RD ) and irradiated (RL ) states as well voltage responsivity ℜV estimated from time traces of bolometric signal at triangular laser excitation; bias current I = 1.5 mA.
(a) Frequency dependences of first (VH 1) lock-in harmonic of ac photovoltage at sinusoidal laser excitation recorded at different temperatures; (b) Time traces of photovoltage induced by triangular laser excitation of variable frequency recorded at 114 K. Time scale was multiplied by excitation frequency; bias current I = 1.5 mA.
(a) Time traces of photovoltage at sinusoidal 25 Hz laser excitation taken at different temperatures; bias current I = 1.5 mA. Red lines corresponding to noise-free signal were obtained by digital smoothing the time traces. (b) Temperature dependences of root mean square noise (VN ), signal (VS ) voltages, and signal-to-noise ratio (SNR) evaluated from time traces.
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