Puminun Vasinajindakaw

All ink-jet-printed carbon nanotube thin-film transistor on a polyimide substrate with an ultrahigh operating frequency of over 5 GHz

We report a flexible carbon nanotube (CNT) thin-film transistor (TFT) fabricated solely by ink-jet printing technology. The TFT is top gate configured, consisting of source and drain electrodes, a carrier transport layer based on an ultrapure, high-density (>1000 CNTs/μm2) CNT thin film, an ion-gel gate dielectric layer, and a poly(3,4-ethylenedioxythiophene) top gate electrode. All the TFT elements are ink-jet printed at room temperature on a polyimide substrate without involving any photolithography patterning or surface pretreatment steps. This CNT-TFT exhibits a high operating frequency of over 5 GHz and an on-off ratio of over 100. Such an all-ink-jet-printed process eliminates the need for lithography, vacuum processing, and metallization procedures and thus provides a promising technology for low-cost, high-throughput fabrication of large-area high-speed flexible electronic circuits on virtually any desired flexible substrate.

Optimizing light absorption in quantum dot infrared photodetectors by tuning surface confinement of surface plasmonic waves

In this paper, we measured the transmission of the 2DSHA surface plasmonic structures and its variation with the hole diameters a of the 2DSHA structures. The relationship between the transmission and the hole diameters a is found to be different from the prediction of Bethes diffraction theorem. We also found that the photocurrent of the quantum dot (QD) infrared photodetectors (QDIPs) with different QD active layer thicknesses show different dependence on the hole diameters a of the 2DSHA structures. The photocurrent of the QDIPs with 10 active QD layers (10-QDIPs) saturates and starts to decrease as the hole diameter a is larger than 1.6 µm, whereas that of the QDIPs with 20 active QD layers (20-QDIPs) increases linearly with the hole diameter. The difference in the hole-diameter dependence of the 10-QDIPs and the 20-QDIPs is attributed to the variation of the near-field spreading in the vertical (surface-normal) direction due to the change in the hole diameters. An over 6 time (6×) photocurrent enhancement is obtained by optimizing the hole diameter of the 2DSHA surface plasmonic structure.

A Fano-type interference enhanced quantum dot infrared photodetector

In this letter, we report a quantum dot photodetector enhanced by Fano-type interference in a metallic two-dimensional (2D) subwavelength hole array (2DSHA). The photocurrent enhancement wavelength shows an offset from the plasmonic resonant peak and corresponds to a dip in the transmission spectrum of the 2DSHA structure. The offset is attributed to the Fano-type interference in the 2DSHA structure. The asymmetric line shapes of the plasmonic resonance are analyzed and agree well with the two-peak Fano-type interference model. Over 100% enhancement in photodetectivity and photoresponsivity is achieved at the wavelength of the Fano dip of the first order plasmonic mode.

Surface plasmonic enhanced polarimetric longwave infrared photodetection with band pass spectral filtering

In this paper, we report a surface plasmonic enhanced polarimetric longwave infrared (LWIR) photodetector. Polarization-selective detection of LWIR incidence with different polarizations is achieved at different plasmonic resonant modes. Band-pass spectral filtering is also provided at the plasmonic resonant modes by the plasmonic enhancement. The extinction ratio (ER) of the polarimetric detection and its limiting factor is discussed.

A voltage-tunable multispectral 320 × 256 InAs/GaAs quantum-dot infrared focal plane array

A voltage-tunable multispectral 320 × 256 infrared imaging focal plane array (FPA) is reported. It is based on InAs/GaAs quantum dots infrared phototdetctors (QDIP) with GaAs and In0.20Ga0.80As capping layers, corresponding to the extended middle-wave infrared (5–8 µm) and long-wave infrared (8–12 µm) detection bands, respectively. The FPA shows a noise-equivalent temperature difference of 172 mK at an operating temperature of 67 K. Voltage-tunable multispectral imaging was also achieved. Since each of the detection spectra of the QD FPA can be individually tuned by engineering its QD capping layer, this approach offers great flexibility in designing of a multispectral FPA.

A HIGH OPERATING TEMPERATURE (HOT) MIDDLE WAVE INFRARED (MWIR) QUANTUM-DOT PHOTODETECTOR

In this paper, a high operating temperature (HOT) middle wave infrared (MWIR) InAs/GaAs quantum dot (QD) infrared photodetector (QDIP) is reported. The QDIP covers a wide detection spectrum range from 3 μm to 6 μm. A large photoresponsivity of 6.4 A/W at a low bias voltage of 0.5 V and a high peak specific photodetectivity D* of 6.0 × 107cmHz1/2/W were obtained at a high operating temperature of 230 K.

All-Printed Thin-Film Transistor Based on Purified Single-Walled Carbon Nanotubes with Linear Response

We report an all-printed thin-film transistor (TFT) on a polyimide substrate with linear transconductance response. The TFT is based on our purified single-walled carbon nanotube (SWCNT) solution that is primarily consists of semiconducting carbon nanotubes (CNTs) with low metal impurities. The all-printed TFT exhibits a high ON/OFF ratio of around 103 and bias-independent transconductance over a certain gate bias range. Such bias-independent transconductance property is different from that of conventional metal-oxide-semiconductor field-effect transistors (MOSFETs) due to the special band structure and the one-dimensional (1D) quantum confined density of state (DOS) of CNTs. The bias-independent transconductance promises modulation linearity for analog electronics.

All-printed CNT transistors with high on-off ratio and bias-invariant transconductance

We report an all-printed flexible carbon nanotube (CNT) thin-film transistor (TFT). All the CNT TFT components, including the source and drain electrodes, the TFT transport channel, and the gate electrode, are printed on a flexible substrate at room temperature. A high ON/OFF ratio of over 103 was achieved. The all printed CNT-TFT also exhibits bias-invariant transconductance over a certain gate bias range. This all-printed process avoids the conventional procedures in lithography, vacuum, and metallization, and offers a promising technology for low-cost, high-throughput fabrication of large-area flexible electronics on a variety of substrates, including glass, Si, indium tin oxide and plastics.

Thermo-electrically cooled shortwave infrared and longwave infrared dual-band quantum-dot photodetector

We report a longwave infrared quantum dot infrared photodetector working at room temperature (RT) (298K). A photoresponsivity and photodetectivity of 0.02A/W and 9.0x106 cmHz1/2/W was achieved at 298K with a low bias voltage of -0.1V. The RT QDIP avoids bulk and heavy cryogenic cooling systems and thus enables the development of ultra-compact IR sensing and imaging systems.

High-operating temperature (HOT) broadband quantum-dot infrared photodetector

In this paper, a high operating temperature (HOT) broadband InAs/GaAs quantum dot (QD) infrared photodetector (QDIP) is reported. The QDIP covers a wide detection spectrum range from 3 μm to 10 μm. A large photoresponsivity of 12.0 A/W at a low bias voltage of 0.15V and a high peak specific photodetectivity D* of 1.2×108 cmHz1/2/W are obtained at a high operating temperature of 298 K.