Showing papers by "Xiaolei Liu published in 2003"
TL;DR: In this article, an approach to use individual In2O3 nanowire transistors as chemical sensors working at room temperature was presented, which exhibited significantly improved chemical sensing performance compared to existing solid state sensors in many aspects, such as the sensitivity, the selectivity, the response time, and the lowest detectable concentrations.
Abstract: We present an approach to use individual In2O3 nanowire transistors as chemical sensors working at room temperature. Upon exposure to a small amount of NO2 or NH3, the nanowire transistors showed a decrease in conductance up to six or five orders of magnitude and also substantial shifts in the threshold gate voltage. These devices exhibited significantly improved chemical sensing performance compared to existing solid-state sensors in many aspects, such as the sensitivity, the selectivity, the response time, and the lowest detectable concentrations. Furthermore, the recovery time of our devices can be shortened to just 30 s by illuminating the devices with UV light in vacuum.
482 citations
Journal Article•
TL;DR: In this paper, an approach to use individual In2O3 nanowire transistors as chemical sensors working at room temperature was presented, which exhibited significantly improved chemical sensing performance compared to existing solid state sensors in many aspects, such as the sensitivity, the selectivity, the response time, and the lowest detectable concentrations.
Abstract: We present an approach to use individual In2O3 nanowire transistors as chemical sensors working at room temperature. Upon exposure to a small amount of NO2 or NH3, the nanowire transistors showed a decrease in conductance up to six or five orders of magnitude and also substantial shifts in the threshold gate voltage. These devices exhibited significantly improved chemical sensing performance compared to existing solid-state sensors in many aspects, such as the sensitivity, the selectivity, the response time, and the lowest detectable concentrations. Furthermore, the recovery time of our devices can be shortened to just 30 s by illuminating the devices with UV light in vacuum.
421 citations
384 citations
353 citations
Journal Article•
311 citations
TL;DR: In this article, the gate-screening effect was investigated in nanowire chemical sensors at high NH3 concentrations, which is induced by adsorbed NH3 molecules working as charge traps.
Abstract: NH3 gas sensing properties of In2O3 nanowires were carefully studied. Change of conductance in opposite directions was observed with different nanowire sensors. We suggest that this differential response is caused by various doping concentrations in the semiconducting In2O3 nanowires. In addition, we have also investigated a “gate-screening effect” exhibited in our nanowire chemical sensors at high NH3 concentrations, which is induced by adsorbed NH3 molecules working as charge traps. Both the doping-dependent response and the gate-screening effect will be especially valuable and helpful for understanding the detailed sensing mechanism of semiconducting metal oxide materials.
183 citations
TL;DR: In this article, single-crystalline In2O3 nanowires were synthesized and then utilized to construct field effect transistors consisting of individual nanwires. But the performance of these nanowire transistors exhibited nice n-type semiconductor characteristics with well-defined linear and saturation regimes.
Abstract: Single-crystalline In2O3 nanowires were synthesized and then utilized to construct field-effect transistors consisting of individual nanowires. These nanowire transistors exhibited nice n-type semiconductor characteristics with well-defined linear and saturation regimes, and on/off ratios as high as 104 were observed at room temperature. The temperature dependence of the conductance revealed thermal emission as the dominating transport mechanism. Oxygen molecules adsorbed on the nanowire surface were found to have profound effects, as manifested by a substantial improvement of the device performance in high vacuum. Our work paved the way for In2O3 nanowires to be used as nanoelectronic building blocks and nanosensors.
183 citations
TL;DR: In this article, single-crystalline, needle-shaped CdO nanostructures were synthesized using a chemical vapor deposition method and characterized using a variety of techniques.
Abstract: Single-crystalline, needle-shaped CdO nanostructures were synthesized using a chemical vapor deposition method and characterized using a variety of techniques. Devices consisting of individual CdO nanoneedles were fabricated and high conductance as well as high carrier concentrations was observed. The temperature dependence of the conductance revealed thermal excitation as the dominating transport mechanism. Our devices exhibited good sensitivity to both infrared light and diluted NO2 gas, indicating potential applications as infrared photodetectors and toxic gas sensors.
170 citations
Journal Article•
TL;DR: In this paper, single-crystalline In2O3 nanowires were synthesized and then utilized to construct field effect transistors consisting of individual nanwires. But the performance of these nanowire transistors exhibited nice n-type semiconductor characteristics with well-defined linear and saturation regimes.
Abstract: Single-crystalline In2O3 nanowires were synthesized and then utilized to construct field-effect transistors consisting of individual nanowires. These nanowire transistors exhibited nice n-type semiconductor characteristics with well-defined linear and saturation regimes, and on/off ratios as high as 104 were observed at room temperature. The temperature dependence of the conductance revealed thermal emission as the dominating transport mechanism. Oxygen molecules adsorbed on the nanowire surface were found to have profound effects, as manifested by a substantial improvement of the device performance in high vacuum. Our work paved the way for In2O3 nanowires to be used as nanoelectronic building blocks and nanosensors.
169 citations
TL;DR: In this article, an approach to tackle long-standing problems in contacts, thermal damage, pinhole induced short circuits and interconnects in molecular electronic device fabrication and integration is presented.
Abstract: We present an approach to tackle long-standing problems in contacts, thermal damage, pinhole induced short circuits and interconnects in molecular electronic device fabrication and integration. Our approach uses metallic nanowires as top electrodes to connect and interconnect molecular wires assembled on electrode arrays in crossbar architectures. Using this simple and reliable approach, we have revealed intriguing memory effects for several different molecular wires, and demonstrated their applications in molecular memory arrays. Our approach has great potential to be used for fast screening of molecular wire candidates and construction of molecular devices.
155 citations
TL;DR: In this paper, photoconducting properties of In2O3 nanowires were studied and the use of UV light as a gas cleanser was demonstrated for chemical sensors, leading to a recovery time as short as 80 s.
Abstract: Photoconducting properties of In2O3 nanowires were studied. Devices based on individual In2O3 nanowires showed a substantial increase in conductance of up to four orders of magnitude upon exposure to UV light. Such devices also exhibited short response times and significant shifts in the threshold gate voltage. The sensitivity to UV of different wavelengths was studied and compared. We have further demonstrated the use of UV light as a “gas cleanser” for In2O3 nanowire chemical sensors, leading to a recovery time as short as 80 s.
TL;DR: In this article, single-crystalline In2O3 nanowires were used to detect ammonia gas via electrical measurements at room temperature and interesting phenomena have been observed, as the direction of the conductance modulation upon NH3 exposure depends on both the initial state of the nanowire surface and the nanouire doping concentration.
Abstract: Devices based on single-crystalline In2O3 nanowires were used to detect ammonia gas via electrical measurements at room temperature. Interesting phenomena have been observed, as the direction of the conductance modulation upon NH3 exposure depends on both the initial state of the nanowire surface and the nanowire doping concentration. For nanowires with surfaces cleaned via UV illumination in a vacuum, the conductance has been found to increase for lightly doped nanowires and decrease for heavily doped nanowires upon exposure. In contrast, for nanowires residing in ambient atmosphere, i.e., under practical conditions, the conductance has been consistently observed to increase upon NH3 exposure, regardless of the doping concentration. This is explained by considering electron transfer between In2O3 nanowires and NH3. Our work clearly demonstrates the potential of using In2O3 nanowires as NH3 sensors under practical conditions.
TL;DR: Single‐crystalline indium oxide nanowires were synthesized using a laser ablation method and characterized using various techniques, revealing n‐type semiconductors with thermal emission as the dominating transport mechanism, as revealed by temperature‐dependent measurements.
Abstract: Single-crystalline indium oxide nanowires were synthesized using a laser ablation method and characterized using various techniques. Precise control over the nanowire diameter down to 10 nm was achieved by using monodisperse gold clusters as the catalytic nanoparticles. In addition, field effect transistors with on/off ratios as high as 10(4) were fabricated based on these nanowires. Detailed electronic measurements confirmed that our nanowires were n-type semiconductors with thermal emission as the dominating transport mechanism, as revealed by temperature-dependent measurements. Furthermore, we studied the chemical sensing properties of our In(2)O(3) nanowire transistors at room temperature. Upon exposure to a small amount of NO(2) or NH(3), the nanowire transistors showed a decrease in conductance of up to five or six orders of magnitude, in addition to substantial shifts in the threshold gate voltage. Our devices exhibit significantly improved chemical sensing performance compared to existing solid-state sensors in many aspects, such as the sensitivity, the selectivity, the response time and the lowest detectable concentrations. We have also demonstrated the use of UV light as a "gas cleanser" for In(2)O(3) nanowire chemical sensors, leading to a recovery time as short as 80 seconds.
TL;DR: It is confirmed that small amounts of noise help a nanotube transistor detect noisy subthreshold electrical signals and promises applications to signal detection in wideband communication systems and biological and artificial neural networks.
Abstract: Experiments confirm that small amounts of noise help a nanotube transistor detect noisy subthreshold electrical signals. Gaussian, uniform, and impulsive (Cauchy) noise produced this feedforward stochastic-resonance effect by increasing both the nanotube system’s mutual information and its input-output correlation. The noise corrupted a synchronous Bernoulli or random digital sequence that fed into the thresholdlike nanotube transistor and produced a Bernoulli sequence. Both Shannon’s mutual information and correlation measured the performance gain by comparing the input and output sequences. This nanotube SR effect was robust: it persisted even when infinite-variance Cauchy noise corrupted the signal stream. Such noise-enhanced signal processing at the nanolevel promises applications to signal detection in wideband communication systems and biological and artificial neural networks. Noise can help carbon nanotube transistors detect subthreshold electrical signals by increasing the transistor’s input output mutual information or correlation. Several researchers have demonstrated the stochastic resonance (SR) effect for various types of threshold units or neurons. 1-6 Experiments
TL;DR: In this article, the chemical gating effect of organic molecules and biomolecules with amino or nitro groups was investigated and attributed to the amino groups carried by the bio species.
Abstract: In2O3 nanowire transistors were used to investigate the chemical gating effect of organic molecules and biomolecules with amino or nitro groups. The nanowire conductance changed dramatically after adsorption of these molecules. Specifically, amino groups in organic molecules such as butylamine, donated electrons to In2O3 nanowires and thus led to enhanced carrier concentrations and conductance, whereas molecules with nitro groups such as butyl nitrite made In2O3 nanowires less conductive by withdrawing electrons. In addition, intrananowire junctions created by partial exposure of the nanowire device to butyl nitrite were investigated, and pronounced rectifying current–voltage characteristics were obtained. Furthermore, chemical gating by low-density lipoprotein cholesterol, the offending agent in coronary heart diseases, was also observed and attributed to the amino groups carried by the bio species.
Journal Article•
TL;DR: In this paper, the chemical gating effect of organic molecules and biomolecules with amino or nitro groups was investigated and attributed to the amino groups carried by the bio species.
Abstract: In2O3 nanowire transistors were used to investigate the chemical gating effect of organic molecules and biomolecules with amino or nitro groups. The nanowire conductance changed dramatically after adsorption of these molecules. Specifically, amino groups in organic molecules such as butylamine, donated electrons to In2O3 nanowires and thus led to enhanced carrier concentrations and conductance, whereas molecules with nitro groups such as butyl nitrite made In2O3 nanowires less conductive by withdrawing electrons. In addition, intrananowire junctions created by partial exposure of the nanowire device to butyl nitrite were investigated, and pronounced rectifying current–voltage characteristics were obtained. Furthermore, chemical gating by low-density lipoprotein cholesterol, the offending agent in coronary heart diseases, was also observed and attributed to the amino groups carried by the bio species.
TL;DR: In this article, the authors used gold nanoparticles as the catalyst to grow single-crystal gallium nitride (GaN) nanowires, which enabled control over several important aspects of the growth, including control of the nanowire diameter, location, and orientation.
Abstract: Chemical vapor deposition (CVD) using gold nanoparticles as the catalyst to grow high-quality single-crystal gallium nitride nanowires was developed. This method enables control over several important aspects of the growth, including control of the nanowire diameter by using monodispersed gold clusters, control of the nanowire location via e-beam patterning of the catalyst sites, and control of the nanowire orientation via epitaxial growth ona-plane sapphire substrates. Our work opens up new ways to use GaN nanowires as nanobuilding blocks.
15 Sep 2003
TL;DR: In this paper, a two-zone chemical vapor deposition technique was employed to operate the vapor generation and the nanowire growth at differential temperatures, leading to high quality products and growth rates as high as 4-10 /spl mu/m/hour.
Abstract: InN nanowires were synthesized and characterized using a variety of techniques. A two-zone chemical vapor deposition technique was employed to operate the vapor generation and the nanowire growth at differential temperatures, leading to high-quality products and growth rates as high as 4-10 /spl mu/m/hour. The as-grown nanowires showed highly single-crystalline structures and precisely controlled diameters by using monodispersed gold clusters as the catalyst. Devices consisting of single nanowires have been fabricated to explore their electronic transport properties. The temperature dependence of the conductance revealed thermal emission as the dominating transport mechanism.
TL;DR: In this article, field effect transistors consisting of poly(3-hexylthiophene) have been fabricated with high dielectric constant SrBi2Ta2O9 films working as the gate insulator.
Abstract: Field-effect transistors consisting of poly(3-hexylthiophene) have been fabricated with high dielectric constant SrBi2Ta2O9 films working as the gate insulator. Significantly enhanced gate effects were observed in these devices compared to similar transistors with conventional SiO2 gate dielectric. Our devices exhibited operating voltages around 10 V, as compared to about 100 V for devices employing SiO2 as the gate dielectric. Moreover, inverters based on such polymer transistors were demonstrated with nice input–output characteristics.
15 Sep 2003
TL;DR: In this paper, single crystalline In/sub 2/O/sub 3/ nanowires were synthesized and then utilized to construct field effect transistors (FETs) consisting of individual nanometres.
Abstract: Single crystalline In/sub 2/O/sub 3/ nanowires were synthesized and then utilized to construct field effect transistors (FETs) consisting of individual nanowires. Chemical sensors based on these In/sub 2/O/sub 3/ nanowire FETs have been demonstrated. Upon exposure to gaseous molecules such as NO/sub 2/ and NH/sub 3/, the electrical conductance of the In/sub 2/O/sub 3/ nanowire FETs is found to be dramatically modified, accompanied by substantial shifts in the threshold gate voltage. Our In/sub 2/O/sub 3/ nanowire sensors exhibit significantly improved sensitivity to NO/sub 2/ gas, as well as shortened response times compared to most existing solid-state gas sensors. In addition, NH/sub 3/ gas sensing properties of In/sub 2/O/sub 3/ nanowires have also been carefully studied. Change of conductance in opposite directions was observed with different nanowire sensors. We suggest that this differential response is caused by various doping concentrations in the semiconducting In/sub 2/O/sub 3/ nanowires.
Journal Article•
Journal Article•
TL;DR: In this article, a two-zone chemical vapor deposition technique was employed to operate the vapor generation and the nanowire growth at differential temperatures, leading to high quality products and growth rates as high as 4-10 μm/hour.
Abstract: InN nanowires were synthesized and characterized using a variety of techniques. A two-zone chemical vapor deposition technique was employed to operate the vapor generation and the nanowire growth at differential temperatures, leading to high-quality products and growth rates as high as 4–10 μm/hour. The as-grown nanowires showed highly single-crystalline structures and precisely controlled diameters by using monodispersed gold clusters as the catalyst. Devices consisting of single nanowires have been fabricated to explore their electronic transport properties. The temperature dependence of the conductance revealed thermal emission as the dominating transport mechanism.
TL;DR: In this article, single-crystalline needle-shaped CdO nanostructures were synthesized using a chemical vapor deposition method and characterized using a variety of techniques.
Abstract: Single-crystalline needle-shaped CdO nanostructures were synthesized using a chemical vapor deposition method and characterized using a variety of techniques. Devices consisting of individual CdO nanoneedles were fabricated and high conductance as well as high carrier concentrations was observed. The temperature dependence of the conductance revealed thermal excitation as the dominating transport mechanism. Our devices exhibited good sensitivity to both infrared light and diluted NO2 gas, indicating potential applications as infrared photo-detectors and toxic gas sensors.
TL;DR: In this article, single crystalline In2O3 nanowires were synthesized and then utilized to construct field effect transistors (FETs) consisting of individual Nanowires.
Abstract: Single crystalline In2O3 nanowires were synthesized and then utilized to construct field effect transistors (FETs) consisting of individual nanowires. Chemical sensors based on these In2O3 nanowire FETs have been demonstrated. Upon exposure to gaseous molecules such as NO2 and NH3, the electrical conductance of the In2O3 nanowire FETs are found to dramatically decrease rapidly, accompanied by substantial shifts in threshold gate voltage. Our In2O3 nanowire sensors exhibit significantly improved sensitivity, as well as shortened response times compared to most existing solid-state gas sensors. In addition, ultraviolet (UV) light is found to be able to greatly enhance the surface molecular desorption kinetics and serve as a “gas cleanser” for the In2O3 nanowire chemical sensors. It has been demonstrated that the recovery time of our devices can be shortened to ∼30 s by illuminating the devices with UV light in vacuum.
TL;DR: In this paper, single crystalline gallium nitride (GaN) nanowires are synthesized via a chemical vapor deposition (CVD) method using gold nanoparticles as the catalyst.
Abstract: High-quality single crystalline gallium nitride (GaN) nanowires are synthesized via a chemical vapor deposition (CVD) method using gold nanoparticles as the catalyst. This method enables control over several important aspects of the growth, including control of the nanowire diameter by using mono-dispersed gold clusters, control of the nanowire location via e-beam patterning of the catalyst sites, and control of the nanowire orientation via epitaxial growth on aplane sapphire substrates. Transport properties of these GaN nanowires are studied. Our work opens up new ways to use GaN nanowires as nano-building blocks.
TL;DR: In this paper, single crystalline In203 nanowires were successfully synthesized using a laser ablation method using a monodispersed gold clusters as the catalyst, and they can be grown with well-defined diameters around 10 nm.
Abstract: Single crystalline In203 nanowires were successful synthesized using a laser ablation method. Extensive material characterization such as X-ray diffraction (XRD) and selected area electron diffraction (SAED) revealed a cubic crystal structure for these nanowires with [110] as the growth direction. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are used to determine the diameter and length of our nanowires. By using monodispersed gold clusters as the catalyst, these nanowires can be grown with well-defined diameters around 10 nm. Individual In2O3 nanowires have been utilized to construct field effect transistors, which confirmed In2O3 nanowires as n-type semiconductors and exhibited on / off ratios as high as 104 at room temperature. The temperature-dependence of the conductance revealed thermal emission as the dominating transport mechanism. Our work can lead to important applications such as chemical sensing for In2O3 nanowires.