Displacement current detection of photoconduction in carbon nanotubes

Abstract

Using a capacitive photocurrent measurement technique, we demonstrate the ability of both semiconducting and metallic single wall nanotubes to function as photodetectors over a wide spectral range. We observe clear peaks in the photo induced displacement current of a nanotube-plated capacitor that correspond directly to the semiconducting and metallic transitions in the nanotube absorbance spectrum. The signal increases substantially as the carrier drift velocity is raised with applied bias. A large increase in the photocurrent observed below temperatures of 100 K suggests that the nanotube hot carrier relaxation rate decreases substantially at low temperatures.

Uncooled Carbon Nanotube Photodetectors

“…Later, numerous studies put attention on the spatially-and spectrally-resolved photocurrent of individual CNT devices to explore the electron-hole pair generation and separation in semiconducting SWCNTs [46,47,48,49] and the nanophysics of individual CNT devices such as the formation of Shottky barriers at the CNT-metal electrode interfaces. [50,51,52] Although photoconductors based on individual CNTs are a useful platform to investigate the photophysics of nanodevices, the signal is too weak for practical photodetection due to the small absorption cross section.…”

“…The photoresponse mechanism of these detectors was predominantly thermal effects, such as the bolometric effect [54] and the photothermolelectric effect, [55] as we will discuss in later sections. However, a technique known as capacitive photocurrent spectroscopy was adopted to study the photocurrent spectrum in individual CNTs [48] and in pure CNT films, [47] which can distinguish the photoconductive effect from the thermal effect. Results showed that in CNT films electronhole pairs can be dissociated into free carriers under large external electrical fields.…”

Terahertz detection in single wall carbon nanotubes

“…2 Photoconductive detection is apparently very weak, 3 but Itkis et al 4 have reported a sensitive bolometric Near Infrared detector based on a carbon nanotube ͑CNT͒ film. Microwave detection using SWCNTs has been extended to 110 GHz.…”

Photoexcitation of the triplet exciton in single wall carbon nanotubes

“…Optical characterization is performed using a recently developed capacitive photocurrent technique [14][15][16][17][18] . The sample is fixed to a copper block within an optical flow cryostat which is placed between the poles of an electromagnet.…”