Benoit C. St-Antoine

Electroluminescence from single-wall carbon nanotube network transistors.

The electroluminescence (EL) properties from single-wall carbon nanotube network field-effect transistors (NNFETs) and small bundle carbon nanotube field effect transistors (CNFETs) are studied using spectroscopy and imaging in the near-infrared (NIR). At room temperature, NNFETs produce broad (approximately 180 meV) and structured NIR spectra, while they are narrower (approximately 80 meV) for CNFETs. EL emission from NNFETs is located in the vicinity of the minority carrier injecting contact (drain) and the spectrum of the emission is red shifted with respect to the corresponding absorption spectrum. A phenomenological model based on a Fermi-Dirac distribution of carriers in the nanotube network reproduces the spectral features observed. This work supports bipolar (electron-hole) current recombination as the main mechanism of emission and highlights the drastic influence of carrier distribution on the optoelectronic properties of carbon nanotube films.

Single-walled carbon nanotube thermopile for broadband light detection.

We designed a thermopile based on a PN doping profile engineered in a suspended film of single-walled carbon nanotubes (SWNTs). Using estimates of the film local Seebeck coefficients, the SWNT thermopile was optimized in situ through depositions of potassium dopants. The overall performances of the thermopile were found to be comparable to state-of-the-art SWNT bolometers. The device is characterized at room temperature by a time response of 36 ms, typical of thermal detectors, and an optimum spectral detectivity of 2 × 10(6) cm Hz(1/2)/W in the visible and near-infrared. This paper presents the first thermopile made of a suspended SWNT film and paves the way to new applications such as broadband light (including THz) detection and thermoelectric power generation.

Position Sensitive Photothermoelectric Effect in Suspended Single-Walled Carbon Nanotube Films

The photovoltage properties of suspended single-walled carbon nanotube (SWNT) films were measured in high vacuum. Experiments with localized illumination showed significant photovoltage amplitudes of up to 0.36 mV at 1.2 mW intensity. The photoresponse dependence upon the laser position was explained by a thermal mechanism that is independent of the nanotube-metal barrier. The response was also found to depend on doping heterogeneities of the film. A model was developed to deduce from the data the spatial variation of the local Seebeck coefficient for a given photovoltage profile.

Photothermoelectric Effects in Single-Walled Carbon Nanotube Films: Reinterpreting Scanning Photocurrent Experiments

AbstractWe revisit the mechanism leading to the photoresponse of locally illuminated single-walled carbon nanotube (SWNT) films deposited on substrates. Our study examines the impact of multiple device parameters and provides many evidences that the position-dependent photocurrent is dominated by photothermoelectric effects. The photoresponse arises from the temperature variations at the metal-nanotube film interfaces, where mismatches of the Seebeck coefficients are measured. Our work also stresses the impact of the substrates, electrode materials and post-thermal treatments on the amplitude and dynamics of the photoresponse. The knowledge gained should guide the future development of photothermoelectric devices and detectors based on SWNTs.