Jianping Zou

Carbon Nanotube Driver Circuit for 6 × 6 Organic Light Emitting Diode Display

Single-walled carbon nanotube (SWNT) is expected to be a very promising material for flexible and transparent driver circuits for active matrix organic light emitting diode (AM OLED) displays due to its high field-effect mobility, excellent current carrying capacity, optical transparency and mechanical flexibility. Although there have been several publications about SWNT driver circuits, none of them have shown static and dynamic images with the AM OLED displays. Here we report on the first successful chemical vapor deposition (CVD)-grown SWNT network thin film transistor (TFT) driver circuits for static and dynamic AM OLED displays with 6 × 6 pixels. The high device mobility of ~45 cm2V−1s−1 and the high channel current on/off ratio of ~105 of the SWNT-TFTs fully guarantee the control capability to the OLED pixels. Our results suggest that SWNT-TFTs are promising backplane building blocks for future OLED displays.

Complementary logic gate arrays based on carbon nanotube network transistors

An efficient technique of fabricating high performance n- and p- type single-walled carbon nanotube (SWNT) network field-effect transistors (NET-FETs) is successfully demonstrated. Complementary inverters, NOR, NAND, OR, AND logic gates have been achieved from integrating these p- and n-type SWNT-NET-FETs. The processing technique described here is fully compatible with conventional silicon microelectronic technologies and it is readily suitable for scalable integration.

Roles of inter-SWCNT junctions in resistive humidity response.

As a promising chemiresistor for gas sensing, the single-walled carbon nanotube (SWCNT) network has not yet been fully utilized for humidity detection. In this work, it is found that as humidity increases from 10% to 85%, the resistance of as-grown SWCNT networks first decreases and then increases. This non-monotonic resistive response to humidity limits their sensing capabilities. The competition between SWCNT resistance and inter-tube junction resistance changes is then found to be responsible for the non-monotonic resistive humidity responses. Moreover, creating sp(3) scattering centers on the SWCNT sidewall by monovalent functionalization of four-bromobenzene diazonium tetrafluoroborate is shown to be capable of eliminating the influence from the inter-tube junctions, resulting in a continuous resistance drop as humidity increases from 10% to 85%. Our results revealed the competing resistive humidity sensing process in as-grown SWCNT networks, which could also be helpful in designing and optimizing as-grown SWCNT networks for humidity sensors and other gas sensors.

Optical-reconfigurable carbon nanotube and indium-tin-oxide complementary thin-film transistor logic gates

Optically transparent thin-film transistors (TFTs) have recently attracted significant attention for a new generation of transparent electronics where p- and n-channel transistors form the basic building block for complementary analog and digital integrated circuits (ICs). This paper reports a hybrid integration of p-channel carbon nanotube (CNT) and n-channel junctionless indium-tin-oxide (ITO) TFTs using a simple and cost-effective shadow mask-assisted fabrication process. The fabricated devices exhibit a high transmittance of ∼90% in the visible light region and function as inverters, NAND and NOR gates. More interestingly, distinct optoelectronic responses of the CNT- and ITO-TFTs to ultraviolet light have been clearly observed. In addition to conventional electrically gated logic operations, simple optical-reconfigurable logic operations have been realized with hybrid CNT/ITO-TFT based logic gates. The results suggest that introducing optical-modulation to the logic gates could increase the functionalities compared with the traditional electrically driven counterparts.

Influences of water molecules on the electronic properties of atomically thin molybdenum disulfide

Although it is well known that the performances of two-dimensional transition metal dichalcogenide (2D-TMD) based devices are strongly affected by humidity, the roles of water molecules in the electronic properties of 2D-TMDs are still unclear. In this work, the influence of water molecules on the electrical properties of monolayer molybdenum disulfide (MoS2) is studied systemically using the dielectric force microscopy (DFM) technique. Taking the advantage of the DFM technique and other nondestructive characterization techniques, the electronic properties (surface potential, dielectrics, and carrier mobility) of atomically thin MoS2 exposed to different levels of humidity are investigated. Furthermore, Raman spectroscopy manifested the correlation between the optical phonon and the mobility drop of MoS2 flakes when subjected to humidity variations. Our results provide an in-depth understanding of the mechanism of water molecules interacting with MoS2.

Single-Walled Carbon Nanotubes based sensors and amplifier circuit integrated on flexible substrates

Single-Walled Carbon Nanotubes (SWCNTs) have been shown to be a promising candidate for flexible electronics, especially logic circuits. However, very little study on SWCNT based analog circuit elements, such as amplifiers and comparators, on flexible substrates has been reported. For practical applications, fully functional flexible electronic devices must have an analog input circuitry to achieve appropriate functionalities. In this work, we demonstrate a resistive SWCNT gas sensor integrated with an amplifier circuit on flexible substrate to detect and amplify the sensing signals.

Giant Humidity Response Using a Chitosan-Based Protonic Conductive Sensor

As a natural biopolymer, chitosan has a very unique protonic conductivity that is highly sensitive to water vapor. However, there has been no report on pure chitosan-based resistive humidity sensors, probably due to the difficulty of direct-current measurement of protonic current in chitosan. Here, a simple and cost-effective chitosan-based protonic conductive humidity sensor is presented. The sensor exhibits a large conductance response of four orders of magnitude when relative humidity is increased from 10% up to 90%. The effects of adsorbed water on proton density and dielectric constant change of chitosan could be responsible for the giant humidity response. More importantly, the sensor shows high stability, repeatability, recoverability, and selectivity to water vapor over ethanol, acetone, and toluene vapors.