Carbon Nanotube Far Infrared Detectors with High Responsivity and Superior Polarization Selectivity Based on Engineered Optical Antennas

Single-wall carbon nanotube (SWCNT) thin films are promising for sensitive uncooled infrared detection based on the photothermoelectric effect. The SWCNT film is usually shaped into a belt and diversely doped to form a p-n junction at the center. Under the illumination of a focused incident light, the temperature gradient from the junction to the contacts leads to photoresponse. When the SWCNTs are aligned in one direction, the photoresponse becomes polarization selective. Although a typical bowtie antenna can improve the responsivity and polarization extinction ratio by deep-subwavelength light focusing, the absolute absorptance of the junction region is only 0.6%. In this work, the antenna was engineered for a higher light coupling efficiency. By integrating a bottom metal plane at a specific distance from the SWCNT film and optimizing the antenna geometries, we achieved ultra-efficient impedance matching between the antenna and the SWCNTs, thus the absorptance of the junction region was further enhanced by 21.3 times and reached 13.5%, which is more than 3 orders of magnitude higher than that of the device without the engineered antenna. The peak responsivity was further enhanced by 19.9 times and responsivity reached 1500 V/W at 1 THz. The resonant frequency can be tuned by changing the size of the antenna. Over the frequency range of 0.5 THz to 1.5 THz, the peak responsivity was further enhanced by 8.1 to 19.9 times, and the polarization extinction ratio was enhanced by 2.7 to 22.3 times. The highest polarization extinction ratio reached 3.04 × 105 at 0.5 THz. The results are based on the numerical simulations of the light and the thermal fields.

Scalable Production of Graphene/Semiconducting Single-Wall Carbon Nanotube Film Schottky Broadband Photodiode Array with Enhanced Photoresponse

A general approach was developed to fabricate graphene/semiconducting single-wall carbon nanotube (graphene/s-SWCNT) film Schottky junctions on a large scale. The graphene/s-SWCNT film photodiodes array based on the vertically stacked Schottky junction were fabricated. The all-carbon cross-shaped structure consisted of multielement graphene/s-SWCNT Schottky photodiodes and presented a rich collection of electronics and photonics. The as-fabricated carbon-based photodiode presented an ultra-broadband photodetection characteristic with a high responsivity of 1.75 A/W at near-infrared wavelengths and a fast response rise time of 15 μs. The as-fabricated device clearly showed gate-tunable and wavelength-dependent photoelectric characteristic. Moreover, the corresponding photocurrent excitation spectrum was also demonstrated. In particular, the Si compatible and high throughput fabrication process for the devices made it conducive for large-area multielement optoelectronics devices.

Directional sensing based on flexible aligned carbon nanotube film nanocomposites

An aligned SWCNT-film with anisotropic mechanical and electrical properties was utilized to prepare directional sensor.

Electrical Transport Properties of Multilayered Single-Walled Carbon Nanotube Films

An improved layer-by-layer vacuum filtration method was adopted for the fabrication of single-walled carbon nanotube (SWCNT) films aiming at a series of SWCNT films with controllable thickness and density. The electrical transport properties of the multilayered SWCNT films have been investigated. With the constant film density, the decrease of the layer number of the SWCNT film results in an increase of the temperature coefficient of resistance (TCR). SWCNT film with 95% metallic nanotubes has shown a lower TCR than that of the SWCNT films with a low percentage of metallic nanotubes. The effect of thermal annealing and subsequent acid (HNO3) treatment on the electrical properties of the SWCNT films has also been investigated.