SnO2Nanowire Arrays and Electrical Properties Synthesized by Fast Heating a Mixture of SnO2and CNTs Waste Soot
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SnO2nanowire arrays were synthesized by fast heating a mixture of SnO2and the carbon nanotubes waste soot by high-frequency induction heating. The resultant SnO2nanowires possess diameters from 50 to 100 nm and lengths up to tens of mircrometers. The field-effect transistors based on single SnO2nanowire exhibit that as-synthesized nanowires have better transistor performance in terms of transconductance and on/off ratio. This work demonstrates a simple technique to the growth of nanomaterials for application in future nanoelectronic devices.
KeywordsSnO2nanowires Semiconducting Field-effect transistor
One-dimensional semiconductor nanowires and nanotubes have stimulated increasing attention in the last few years and are expected to lead to novel device application due to their intriguing properties and potential applications in constructing nanoscaled electronic and optoelectronic devices [1–12]. Among semiconducting oxide nanostructure, SnO2 nanowires, nanobelts, and nanowires are very important n-type semiconductors for applications as transparent conducting electrodes , gas sensors , and lithium-ion batteries , which utilize the unique characteristics of SnO2 nanostructures including a wide band gap (Eg = 3.6 eV at 300 K) and large surface-to-volume ratios. A precondition for SnO2 nanostructures based on the applications is an easy and lager-scale synthesis of SnO2 nanostructures. Several methods have been reported for the synthesis of SnO2 nanowires/nanobelts, including thermal decomposition , electrospinning [16, 17], solution-based crystal growth [18, 19], laser ablation, and template-based approaches . However, those methods always required long time for heating and cooling, which hinder the mass production of SnO2 nanostructures. Due to its versatility and simplicity, the synthesis method of SnO2 nanowires is still investigated .
The electrical properties of SnO2 nanowires and nanobelts are also reported [22, 23]. Field-effect transistors (FETs) based on single carbon nanotube, Si nanowire, ZnO nanowire and others are with excellent properties superior to their bulk counterparts [24, 25]. SnO2 nanowires are one of the potential semiconducting materials for nanoelectronic devices due to their excellent electronic properties. In the present study, we report a novel method to synthesize aligned SnO2 nanowires by using high-frequency inductive heating furnace. A mixture of SnO2 and the carbon nanotubes (CNTs) waste soot which was a main by-product in the production of CNTs by arc-discharge. The electrical properties including application in FETs of SnO2 nanowires were also studied.
The as-grown SnO2nanowires were characterized by scanning electron microscopy (SEM, FEI SIRION 200) equipped with energy-dispersive X-ray spectroscopy (EDX, INCA OXFORD) and transmission electron microscopy (TEM, JEM-2010). The electronic measurements were made using an Agilent 4156C semiconductor characterization system under an ambient condition at room temperature.
Results and Discussions
These peaks confirm that SnO2nanowires possess the crystalline structure of the tetragonal rutile structure, which is corresponding to the results of XRD.
After growth, the SnO2nanowires were transferred from silicon substrates, and a number of FETs device structures were fabricated. Devices were fabricated by thermally growing SiO2film with 500 nm thickness on the top of n-type Si wafers, followed by deposition of an Au layer with sputtering and standard photolithography. Parallel Au electrode pairs, with ~1 μm in length and 80 nm in thickness, were patterned. The parallel Au electrodes will be used as source and drain electrodes. An n-type silicon layer serves as the back gate. The as-prepared SnO2nanowires were sonicated into a suspension in ethanol, followed by solution casting the slightly dispersed SnO2nanowires between the drain and the source of Au electrodes to form a single SnO2nanowire FET (SnO2-FET). The SnO2-FET samples were quickly transferred to a stove to anneal in Ar at 973 K for 5 min in order to improve the quality of Au–SnO2contacts. The inset in Fig. 3is the SEM image of the as-fabricated single SnO2nanowire with a channel width of ~200 nm.
This value is consistent with those obtained in planar single-crystalline SnO2nanowire and other metal oxide nanowires. The performance of SnO2-FET devices depends to a large extent on the source and drain contacts. In our cases, we find that it is effective to improve the quality of Au–SnO2contacts by annealing the SnO2-FET devices in Ar at 973 K for 5 min. Therefore, the value of effective mobility, transconductance, and on/off ratio has also been significantly improved.
We present a simple, fast, and a low-cost method to synthesize SnO2nanowire arrays by using fast heating furnace. A ball-milled mixture of SnO2and CNTs waste soot was used as source materials. SEM and TEM images show nanowire diameters of 50–100 nm and lengths up to tens of mircrometers. The electrical properties of the as-synthesized single SnO2nanowire in FETs devices show that the n-type SnO2nanowires have larger on/off ratio (>105) and higher carrier mobility at room temperature. This method provides a promising candidate for large-scale preparation of SnO2nanostructures.
We acknowledge that this work is supported by National Natural Science Foundation of China (No. 50730008), Shanghai Science and Technology Grant (No. 0752nm015), and National Basic Research Program of China (No. 2006CB300406).