Growth of Highly Conductive Ga-Doped ZnO Nanoneedles.
The molecular beam epitaxy growth of highly degenerate Ga-doped ZnO (GaZnO) nanoneedles (NNs) based on the vapor-liquid-solid (VLS) growth mode using Ag nanoparticles (NPs) as the growth catalyst is demonstrated. It is shown that when the growth substrate temperature is sufficiently high, a portion of a Ag NP can be melted for serving as the catalyst to precipitate GaZnO on the residual Ag NP and form a GaZnO NN. Record-low turn-on and threshold electric fields in the field emission test of the grown GaZnO NNs are observed. Also, a record-high field enhancement factor in field emission is calibrated. Such superior field emission performances are attributed to a few factors, including (1) the low work function and high conductivity of the grown GaZnO NNs due to highly degenerate Ga doping, (2) the sharp-pointed geometry of the vertically aligned GaZnO NNs, (3) the Ag doping in VLS precipitation of GaZnO for further reducing NN resistivity, and (4) the residual small Ag NP at the NN tip for making the tip even sharper and tip conductivity even higher.
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Yu-Feng
YF
Yao
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Charng-Gan
CG
Tu
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Ta-Wei
TW
Chang
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Hao-Tsung
HT
Chen
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Chi-Ming
CM
Weng
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Chia-Ying
CY
Su
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Chieh
C
Hsieh
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Che-Hao
CH
Liao
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
Yean-Woei
YW
Kiang
Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei 10617, Taiwan.
C C
CC
Yang
Ga-doped ZnO; field emission; growth catalyst; nanoneedle; vapor−liquid−solid mode