C.C. Hwang

pH-sensing characteristics of hydrothermal Al-doped ZnO nanostructures

Highly sensitive and stable pH-sensing properties of an extended-gate field-effect transistor (EGFET) based on the aluminumdoped ZnO (AZO) nanostructures have been demonstrated. The AZO nanostructures with different Al concentrations were synthesized on AZO/glass substrate via a simple hydrothermal growth method at 85°C. The AZO sensing nanostructures were connected with the metal-oxide-semiconductor field-effect transistor (MOSFET). Afterwards, the current-voltage (I-V) characteristics and the sensing properties of the pH-EGFET sensors were obtained in different buffer solutions, respectively. As a result, the pH-sensing characteristics of AZO nanostructured pH-EGFET sensors with Al dosage of 3 at.% can exhibit the higher sensitivity of 57.95mV/pH, the larger linearity of 0.9998, the smaller deviation of 0.023 in linearity, the lower drift rate of 1.27mV/hour, and the lower threshold voltage of 1.32V with a wider sensing range (pH 1 ∼ pH 13). Hence, the outstanding stability and durability of AZO nanostructured ionic EGFET sensors are attractive for the electrochemical application of flexible and disposable biosensor.

Trench MOS barrier Schottky rectifier formed by counter-doping trench-bottom implantation

Abstract A trench MOS barrier Schottky (TMBS) rectifier has been formed by carrying out trench bottom counter-doping implantation for improving the blocking voltage and the device reliability. By additionally implementing a counter-doped region enclosing the trench bottom, the reverse blocking voltage of the conventional TMBS rectifier can be significantly enhanced without considerable degradation of on-state characteristics. In addition, the device reliability can be significantly improved. The large peak electric field in the corner of trench bottom, which limits the blocking voltage of the conventional TMBS rectifier, can be largely alleviated due to charge compensation. Though the counter-doped region enclosing the trench bottom may partly encroach into the mesa region, no considerable deterioration of on-state characteristics is caused. In addition, a too low-dose trench-bottom implantation cannot provide sufficient charge compensation, and a too high-dose trench-bottom implantation would create a large peak electric field below the trench bottom. As a result, a proper trench-bottom implantation may be employed to significantly enhance the blocking voltage without considerable degradation of on-state characteristics.

A novel density control of carbon nanotubes by partial oxidation of catalyst metal and its field emission enhancement

A novel density control of carbon nanotubes is fabricated using partial oxidation of catalyst metal prior to the CNTs growth. The results show that CNTs are aligned, closely spaced, and divided into two groups with some long nanotubes protruding among short ones. Field emission improvement is achieved due to those long nanotubes are subjected less field screening effect from the surrounding nanotubes. The obtained results show that a low turn-on field (1.9 V/μm) and an ultra high field emission current density (160mA/cm2 at 6 V/μm) can be achieved through this novel morphology of CNTs.

Annealing effect on hydrothermally grown ZnO thin-film transistors

High-performance zinc oxide (ZnO) thin-film transistors (TFTs) with location-controlled lateral grain were fabricated by low-temperature hydrothermal method. The ZnO active channel was laterally grown with aluminum-doped ZnO (AZO) seed layer underneath the Ti/Pt film. The annealed ZnO TFTs reveal high-quality ZnO films with the compensated structural defects in the channel region compared to the unannealed devices. Thus, the superior device performances (i.e. the excellent μFE of 9.07 cm2/V·s, high on/off current ratio of ∼ 106, and low gate leakage current of < 1 nA) of hydrothermal growth (HTG) ZnO TFTs can be achieved after annealing.